Fermenting

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Fermenting

Summary

Ferment the mash/wash at a constant 25^oC, using 1.5g/L of good yeast suited to the wash.

Use an airlock to let CO₂ out but not let air in.

Let the yeast settle out, and possibly even filter the wash before putting it into the still.

Introduction

Fermentation is the conversion of sugar to ethanol and carbon dioxide by yeasts (wort to wash). Whilst doing this, it can create a range of flavours beyond what the wort started with. During fermentation yeast converts sugar into alcohol and carbon dioxide by feeding on a series of increasingly complex sugars, essentially breaking the sugar down into other compounds which enable it to grow. First on the menu is glucose, before moving onto maltose, then maltotriose. Depending on the strain of yeast, these sugars may be tackled at different rates, and not always strictly in sequence. Although sugars account for the majority of flavours, yeast works on various other compounds, including amino acids and fatty acids, which also contribute flavours.

Theoretically 10 kg of sugar will produce 6.5 L (5.1 kg) of ethanol and 4.9 kg (4900L) of carbon dioxide. In doing so, some energy is released too (about 2.6 MJ/kg of ethanol).

Yeasts are single-cell fungi organisms. The most important ones used for making ethanol are members of the Saccharomyces genus, bred to give uniform, rapid fermentation and high ethanol yields, and be tollerant to wide ranges of temperature, pH levels, and high ethanol concentrations. Yeasts are facultative organisms - which means that they can live with or without oxygen. In a normal fermentation cycle they use oxygen at the start, then continue to thrive once it has all been used up. It is only during the anaerobic (without oxygen) period that they produce ethanol.

Gil explains ....

More correctly, in the absence of free dissolved oxygen the yeast will continue to breath by scavenging oxygen from the sugar molecules, and by doing so will continue to exhale carbon dioxide but leave the remnant sugar molecule behind in the form of ethyl alcohol.

The yeast does not consume sugar as food, but the other nutrients added to the wort. Mead making is an interesting experiment in this respect since unlike grape juice honey water will not in itself sustain yeast, and any half-decent distiller will do themselves a favour by mastering the technique of making such an environment more friendly.

Over the years I have learned to sustain the yeast in mead batches on a mixture of Vegemite and Epsom Salts, then aerate the wort thoroughly before activating the yeast and pitching. You can experiment with any number of nutrients and aerating systems to breed as much yeast as you want, but I have found the above mix avoids an off-taste in the finished mead and is easy to introduce to the colony.

The process implies two distinct fermentation phases. The primary fermentation takes place as the yeast breeds rapidly in the initially aerobic environment and the colony comes up to strength. Then the secondary fermentation takes place in the anaerobic environment thus generated, as the yeast strips oxygen from the sugar molecules in order to avoid suffocating.

Fermentation does not mean that alcoholic is being produced, only that the wort is in a ferment; that is, bubbling merrily.

Throughout both stages there is an abundance of carbon dioxide being exhaled which assists in maintain the anaerobic environment conductive to the production of ethyl alcohol. It does need to be kept in mind that it is not the yeast colony's intention to produce the alcohol, but ours.

All the yeast is trying to do is avoid suffocating in anaerobic conditions.

Beyond that it is fundamentally misleading to suppose that yeast is much interested in sugar, which can kill it the same as alcohol does, and here we must also recall that we are merely exploiting its ability to adapt to what are essentially hostile conditions.

My reference is A.J. Salle, "Fundamental Principles of Bacteriology", 3rd Edition, New York: McGraw-Hill, 1948.

Another book that must be read is Bill Mollison, "The Permaculture Book of Ferment and Human Nutrition", Tyalgum: Tagari Publications, 1993.

The influence of the yeast depends on the sugar concentration in the wort, the pitching temperature, and the rate of fermentation.

There are three phases to fermentation once the yeast has been added:

an initial lag phase, where little appears to be happening, but the yeast is adjusting to its new environment, and begining to grow in size
after about 30 minutes, the yeast begins to reproduce rapidly and the number of yeast cells increases exponentially (thus known as the exponential growth phase). Carbon dioxide is released in large quantities, bubbling up through the liquor. As the fermentation proceeds, the yeast cells tend to cluster together (flocculate).
The last phase is a stationary phase during which nutrients are becoming scarce, and the growth rates slow down. The evolution of carbon dioxide slows down, and the yeast settles to the bottom of the fermentor.

Under optimal conditions, a yeast cell is able to split its own mass of glucose (ie about 200 million million molecules) into alcohol and carbon dioxide every second.

For more information about fermentation, see Fermented Fruits and Vegetables - A Global Perspective, and Brewing Yeasts.

Yeast produces 33 times more alcohol while reproducing than when resting (so most of the gains are in the first couple of days, then you're just relying on the large numbers of yeast finally present to slowly work their way through the remaining sugars)

Once the nutrients have run out, and the fermentation has become "stuck" or sluggish, it is then too late to provide either nutrients or new yeash. If this happens really early during the fermentation, then you're in trouble.This is because when a yeast is deprived of a nutrient, it grows as best as it can with what is available, and then growth comes to a halt. Those cells are then put together with less than satisfactory levels of (lets say) protein due to deficient nitrogen. Their enzyme content is less than adequate, and they don't metabolize well at all. Growing cells are ~33 x faster at ethanol production than non-growing cells. Supplementation at that point does not reinitiate growth in the older cells. By that time the medium is higher in alcohol and still deficient in some nutrients. Some cells may even have died. Even supplying the combination of BOTH nutrients and new yeast won't get the activity restarted again. So the trick is to ensure you have enough nutrients available at the start of the fermentation.

You end up with having grown about 2g per litre of yeast (eg 40g in a 20L wash) This is why you don't get the full 51.1% conversion of sugar to ethanol, and gives some idea of the amount of nutrients - particularly nitrogen - that you need to supply.

Bakers yeast will produce a maximum of around 14% alcohol, whereas the "turbos" can generate up to 20% alcohol. Obviously you'd use different amounts of sugar for either case. Its not that the Turbo makes a higher % from less sugar, its advantage is that it can handle the higher concentrations (first of heaps of sugar, then later, the high alcohol %), and hence you need proportionally less water. Hence you end up with more alcohol in your 20L wash, because you are able to put more sugar in. Only use the Turbo's if you're after a "neutral" alcohol. If you're trying to make a flavoured spirit, (eg corn whisky, brandy, rum, etc) then use a yeast which will help give you the flavour profile that you desire.

While making the ethanol, the yeasts will also make very small amounts of other organic compounds - including other alcohols, aldehydes, esters, etc. These are known as the "cogeners" or the "fusel oils". It is the presence of these that give the alcohol its flavour. So when trying to make a neutral spirit, we'd try to minimise their presence, but if making a whisky, rum, brandy etc, then we need a very small proportion of them present.

Fusel oil concentration in the wash can be up to around 0.24 g per Litre from 20% sugar (eg about 3.2 mL from a 20L wash)

Fusels increase depending on ...
* yeast strain (eg Saccharomysce cerevisia makes more than S.carlsbergensis)
* temperature (higher temp = more fusels)
* increased aeration and agitation (news to me ! so don't over-stirr it !)
* wort composition (nitrogen sources and readily metabolised sugars)

The most common limiting factor for yeast growth is a lack of nitrogen. Nitrogen is approx 9% of the cell mass. Most common form to add it is as the ammonium ion, as the sulphate and phosphate salts (phosphorus is approx 1-2% of the cell mass, and sulfur 0.3-0.5% so these are needed too - this is a nice way of getting all three in there). Add the ammonium phosphate at a rate of 25-50 gramms for a 25L wash.

The second most common limiting factor is a lack of oxygen, but it only needs it until high cell numbers are present (eg during the first day) (so make sure that you've aerated the wash well just prior to adding the yeast, but don't do this too much later in the game) "Splash filling" is enough to do the job.

Bacteria can double in number every 20-30 minutes, but yeast takes 3 hours (so guess which one will win the race if an infection gets started and you don't deal to it). Another technique to help with this is to use a lot of yeast - when using Bakers yeast, use at least 150g for a 20L wash. Note that using more yeast wont make the yeast work through to a higher % alcohol, but just enable it to get where its going, faster.

Theres a fair bit of choice available as to which yeast to use. I'm personally inclined to use the "Turbo" yeasts, which are pre-packaged with all the nutrients etc necessary. Thats because I'm only ever doing sugar-water washes for pure neutral spirits, and I find it easy, convienient, and reliable. I don't try and reuse it a second time, as I only distill every couple of months, and can't be bothered storing it for that long. If however you are doing more of a grain or fruit based mash, and interested in flavours, then consider some of the other yeasts.

How do you know when fermentation has finished ? Alex tells ..

You determine the end of fermentation with these signs:
1. There is no more bubbles coming to the surface.
2. There is no more hissing noise inside the vessel.
3. Gravity of the mash sinks equal or below 1.00
4. The mash does not tast sweet anymore.
5. It has been sitting in the bathroom for three weeks.

Hector writes ...

Yeast, as simple a living organism as it is, has some complex nutritional needs, certainly more than just sucrose. However there’s a wide variety of yeast strains who’s needs differ widely. Alcohol producing strains fall always under the Saccharomyces family, and they, and their metabolic needs and environment adaptation pathways have been the subject of much study. There are “usual” metabolic mechanisms for the fermentation of grape juice, beer wort, et all, by specific members of the Saccharomyces family (e.g. bayanus or capensis in wine, cerevisae and carlsbergensis / uvarum in beer). All of those mechanisms require the presence of their specific sugar and nutrient carrying mediums (grape or apple juice, malt wort, etc.) because their specific yeasts are perfectly adapted to this environments. There’s no such thing as an alcohol producing yeast strain that can thrive in such a nutrient deprived medium as a sugar (sucrose) wash. Saccharomyces family strains are all adapted to nutrient rich environments as those cited before, but being that there’s no other organism in earth that adapts and mutates as readily and fast as yeast (that’s a fact, and it’s why yeast is the natural “guinea pig” in cellular death studies that are being advanced right now in the hope of learning to fight cancer), it always finds a way to survive as long as some type of nourishment can be found. This “ways” almost certainly imply a certain loss in the edible qualities of the fermented product because the chemical compounds generated by starving and abused yeasts usually form azeotropic bonds with the ethanol molecule, which is the product you concentrate when you distill an alcohol carrying substance. This compounds are mainly fusel alcohols, esters like amyl and ethyl acetate; diacetyl, acetaldehyde and sulfur compounds like ethyl mercaptin and dimethyl sulfide and disulfide, just to mention the beer (my specialty) pertinent, but universal in this scenario, by-products.

I understand that the much popular ... “turbo” yeast products are no more than specially packaged Saccharomyces strains that include the bare necessities (in nutritional terms) that yeast will need to barely ferment just one sucrose based batch. That’s why you guys find the notion of re-pitching your yeast so alien. I believe turbos are a very good thing for the yeast industry and truly they deserved a break. But I find they could try to strike a more consumer wise equilibrium on pricing (IMO they’re obscenely expensive). However there’s a notion that I believe would make this group improve exponentially their distilled products (and that I haven’t read about in any post so far) and it’s that whatever you can do to enhance your wash’s quality as a fermented product brings by itself a better spirit. I’m no fanatic on this. I don’t drink my molasses wines, for instance (though my whiskey’s beers are just as good as the product I sell commercially, sans the hops, of course). It’s just little things you need to do to avoid the basic problems, like always boiling and quickly cooling the wash, aerating the cooled wash prior to inoculation, keeping the fermentation temp below 23 deg. centigrade, and the original sugar concentration below 17-19º Brix (1.070-1.079 s.g.), and of course, work sanitarily. That’s all.

Which Yeast to Use

Ted recommends

I have a yeast that can ferment to 17% with greater than 80% attenuation in less than 4 days at 75 degrees F. It has a slight H₂SO₄ nose to it but it clears bright in 2 days and then you can't smell the H₂SO₄. Esters and phenols are slight to none. No breadiness, sour or vegemite aromas from the yeast that has been stored for 2 weeks and its viability is 94% after 34 generations. This yeast is a work horse! www.whitelabs.com - California Ale Yeast This isn't the only one out there that is fantastic either.

Jack recommends ...

Types of Yeast
The yeast selection pretty much depends on what you are making -

For whiskey (corn or malt) the best bet is a dry ale yeast - Doric brnad ale is my favorite (ask your homebrew shop owner what his most attenuative, alcohol tolerant dry ale yeast is and use that).

For wine and mead the best choice is Lalvin's K1V-1116 - it has a 16% alcohol tolerance and is very fast (it also has the ability to fight off bacterial contamination).

For plain sugar mashes (to be made into vodka) the best bet is Lalvin's EC-1118 - it has an 18% alcohol tolerance and is faster than the K1V-1116 - but it tends to result in a stale, brackish flavor in the wine and the distillate - making it a bad choice for a wine yeast (by overpitching this yeast - 100grams in 20 liters and about 100 grams of yeast nutrient with 6-8 kilos of sugar you can make your own Turbo- style yeast) - carbon polishing will take care of the stale taste from this yeast- making it a good vodka yeast.

For making rum out of molasses I like to use plain old bread yeast- it has a nice flavor when it's distilled, and while it's fermenting the house smells like cookies.

NEVER use Montrachet yeast. I have had many recipes for wine taste horrible becuase this yeast was what the recipe said to use- it always ended up tasting (reeking) of sulfur- even when no sulfite was used to make the wine. The sulfur smell it makes is more than capable of carrying over into the distilled product (rotten egg schnaps was not what I was trying for). If you find a recipe that uses this yeast- use the K1V-1116 instead. I later found out that Montrachet was prone (genetically) to producing hydrogen sulfide gas, hence the sulfur taste/smell whenever I used this yeast. Avoid it at all costs.

Ken recommends ..."SAF-DISTIL.B-28" from D.C.L.Yeast

For more on EC-1118 see http://consumer.lallemand.com/.

See also http://www.hambletonbard.com.

A new White Labs strain WLP099 claims to do up to 25% EtOH : http://www.whitelabs.com/

Donald advises ...

Distillers' yeast is now sold in slurry form in the major homebrewer's yeast banks. Unless you are making neutral spirits, do not use a distiller's "fuel yeast". The Tennessee whisky yeast, Highland Scotish yeast, Fruit Brandy/Eau de Vie yeast, ect. all add extra oganoliptics that fuel yeast cannot.

Ryzopus derived Ryzozyme (Alltech Biotechnology) is a "cold mash" koji (not aspergillis as used in Sake) now for sale from Alltech, Inc. Ryzozyme step converts starch to sugar at room temp. I achieved a yield of 23.6% alcohol (yes that's right) in 40 hours with 100% corn mash this fall at the Alltech Alcohol School. (1 week for $950.00 US$). The entire Alltech Biotechnology line is sold through Crosby & Baker in the USA. Alltech, Inc. products are sold world wide, so check the web. if your local suppliers don't carry this yet. They also have great distillers yeast, yeast nutrient and other biotech fermentation supplies. The brave new worlds' bright side is here at last !

Patrick writes ..

For those of you not using turbos in the US. Check out this site, you can purchase 500g packets of wine yeast at HUGE discount! There is a Red Star yeast, same strain as Lalvin EC-1118 for $8.95 US for 500g! Thats just over a pound! Presque Isle Wine Supplies http://www.piwine.com.

M writes ...

I recently purchased a pound of "SuperStart" Distillers Yeast by Alltech from Crosby & Baker. (http://www.crosby-baker.com) According to the spec. sheet the optimal fermentation temperature is 90F +/-2F. So for those of you in hotter climates this may be just the ticket. Also, Seth from C&B reported that it is very possible to get a 21-22% yield from this yeast.Pricewise - 1lb. - $3.15 US (label states that 1/2lb will ferment 1000gal.

Baker writes about Red Star Ethanol Red (ER) :

From the product sheet ...Ethanol Red is a specially selected strain of saccharomyces Cerevisiae that has been developed for the Fuel Alcohol Industry. ER is a fast acting, temperature tolerant dry yeast that displays higher alcohol yields and maintains higher cell viability during fermentation as compared with standard distiller's yeast. Designed for producing alcohol at elevated temperatures, ER is capable of maximizing alcohol yields under a wide range of temperatures. Yields of 48g ethanol/ 100g sugar at 35C have been reported. Lower cooling costs, higher ethanol levels, and increased fermenter through put can be expected using ER. Industrial fermentation for the production of fuel alcohol from grain mashes is the primary application for this strain. this strain performs well for the production of ethanol from a variety of carbohydrate sources including molasses, citrus pulp and corn syrup. Pitching levels between 25 - 50 g per hectoliter will give an initial yeast density of approximately 5 - 10 million yeast cells per mL. Prior to inoculation, yeast should be rehydrated in 4 -5 times its weight in clean 40 C water.

[in comparison ..] Alltech SuperStart is a superstarter, but rapidly peters out. It performs better with a protease to provide FAN, but even with a protease does not perform as well as Red Star without. Red Star performs equally well with or without a protease except in a milo mash where adding the protease improves its performance.

Mike cautions though ...

Just an aside for "newbies", please don't get the idea that some yeasts produce more alcohol from a given amount of sugar than others. The "higher alcohol yield" bit refers to the tolerance of this yeast to alcohol during fermentation. For example, the strains of yeast used by bakers cannot tolerate concentrations of alcohol higher than around 8%, so any sugar left in the wash once this level is reached remains unfermented. Other strains are more tolerant to the alcohol they produce, and are therefore more efficient if the aim is to process as much sugar as you can in the shortest possible time ... which is what cost-effective production of fuel alcohol is all about. The downside for us, trying to produce potable alcohol, is that the hotter (and faster) the fermentation, and the higher the alcohol tolerance of the yeast, the more likely it is that other compounds will be produced with the ethanol, so we will have more heads and tails to deal with. For example, the new "24 hour" turbos perform as claimed (stand well back!), but the downside is that the concentration of ethyl acetate is very much higher than their slower cousins. In their defence, they are much "cleaner" than the Zippo yeasts favored by the Fuel Industry which, to be fair, is not concerned about how the product tastes so long as it burns well.

You can make your own Turbo yeasts. Jack wrote ..

Use large amounts of the wine yeasts called "prisse de mousse" (by the Red Star company), or EC-1118 (by the Lavlin company) - these are the yeasts used in the Turbo yeast packs- you just need to buy 100 grams (4 ounces) of it and pitch it all at once to get the turbo yeast performance (this also requires 100 grams of citric acid and about 100grams of yeast nutrient). Both these yeasts are common winemaking yeasts in the U.S

Mike adds ...

It is very easy to stretch a turbo (or any yeast, for that matter), but the process is a tradeoff - more work and time spent.

The procedure is similar to that spelled out as "the Cone Protocol" in The Compleat Distiller - you manage the stresses that the yeast sees during the ferment.

What are those stresses? Osmotic potential (sugar concentration), temperature and alcohol concentration. One of the reasons that turbo yeast packets contain so much yeast is that up to 80% of the yeast cells are killed or severely damaged when they are put into the wash - too high a sugar concentration and too low a temperature slow down the entry of water into the cells and allow a lot of damage to occur. Lowering the initial sugar concentration allows a lot more of these cells to survive, meaning that they can do more work.

Temperature - the active and rapid fermentation produces a lot of heat. Gert has published tables of yeast viability by temperature and alcohol concentration, and the higher the alcohol concentration, the lower the temperature that will kill them off. Lowering the initial sugar concentration will reduce the heat production and temperature rise in the wash. External temperature control is also very useful for extending a turbo.

Alcohol concentration - Alcohol is a yeast waste product. The more of it that is present, the harder is is for yeast to produce more, and the more stressed the yeast is, making them even more sensitive to osmotic and temperature effects. Sugar should be added in decreasing amounts throughout the fermentation as the alcohol concentration rises.

WARNING!! Active ferments are supersaturated with CO2!! If you just dump in some more sugar, you will see foam like you could not believe, and will lose several liters of wash to the surrounding environment. When you add sugar, begin stirring the wash, and trickle a spoonful of sugar into it. It will foam semi-violently, but will not overflow. Repeat a few times until it quits foaming when you add a little sugar. Now you can add it more rapidly.

Here is one way to stretch a turbo (based on the "20%" regular speed turbos out there). This method takes two weeks to complete. It is designed to completely use a standard (American) 25 pound sack of sugar. The Final volume is 8 US gallons instead of 25 liters. Pour 13 pounds of the sugar into the fermenter, and make up to just under seven gallons with warm water to end up at 30 deg C. Stir to make sure the sugar is all dissolved, then stir in the turbo and vigorously stir for a couple of minutes. You probably want the fermenter set into a tub of water to avoid a sharp temperature rise when fermentation takes off. (This is for two reasons - one to preserve the yeast, second, because a cooler fermentation is a cleaner one!) Control the temperature of the water jacket to about 18 deg C.

Float a hydrometer in the wash. Intial reading will be about 1.080. When it has dropped to about 1.010 - 1.020, add seven pounds of sugar. When it has dropped back to 1.10, add another three pounds. When it drops to 1.005, add the final two pounds. If done properly, the terminal gravity will be about 0.9.

Mixing Different Yeasts

It is sometimes useful to use two different stains of yeast at the same time; one strain for flavor and another for the alcohol content. Sometimes distilleries will mix brewers yeast with distillers yeast - thinking that the brewers yeast will add a heavier, fatter, mealier quality to new spirit. Others reckon it makes no difference.

Ray writes ..

It is quite a common practise to use a combination of yeast strains to acheive the desired result e.g. I have seen a good general purpose type yeast which is designed to go to around 13% mixed with a high alcohol yeast strain which is designed to go to 18% or higher, the idea being that the general purpose yeast does the majority of the work converting the sugar to alcohol then the high alcohol yeast kicks in and takes the percentage up to the next level. I haven't used that method for a long time but it seemed to work fine at the time.

Ted suggests ..

Use the low alcohol tolerent yeast to ferment first to get as much of that yeasts "flavor " as is possible. Then add more of the first strain to your ferment to push it along a bit further. The reason for this is that most yeast can withstand high levels of alcohol for a while before they go into stasis (they aren't really dieing off). then go for the tolerent yeast. Be aware that in high gravity ferments that the number of yeast cells must be increased a lot!!! (High gravity is anything over 1.060) Most yeast producers won't tell you this but, many strains are mixtures of yeasts that have different profiles and variing flocculation habits. On your recipe, you could try two seperate ferments one at a low gravity and one high then combine for distillation.

The Omnipresent Mecakyrios does similar ..

I like the "Two Fermentations" idea. I brew my batches (a hard Cider and Mead mix. Some call it a Melomel, but the taste is not like a Melomel at all) then use the following fermentation method: primary fermenter for about a month, rack into a secondary for about two months, rack into another secondary for about a month or two (depending on how the brew is doing), and if everything looks good I let it age for about a month and then distill it. After I distil it, I let it age for about three to six months.

If I were to do the "Two Fermentations" idea, I could use the "flavor yeast" in the primary, and the "strength yeast" in the first racking of the secondary. Then I could shorten the first racking time and lengthen the second to even things out.

How Much Yeast to Use

Jack advises ...

To use the best brewing guidelines- use 2 to 4 grams of dried yeast per gallon of mash.

If the alcohol is in the 5% or less range - use 2 grams per gallon.
in the 5 to 7%abv range; use 3 grams per gallon.
In the 8 to 10%abv range use 4 grams per gallon.

You will know when you have pitched the right amount of yeast because the high kraeusen stage (the tall foamy cap) will have formed in four hours or less. If it takes longer than 4 hours- don't worry too much. If it takes longer than 24 hours to form- you aren't using enough yeast.

Higher than 4 grams per gallon will get you some sulfur flavors that can be hard to get rid of, so only use the 100 grams of dry yeast per 5 gallons (20 litres) rule for a pure sugar mash that is destined to be carbon polished and turned into vodka or a "base spirit" for liqueurs, etc.

If buying that much dry yeast is a problem, you can make a starter. Make a small "mini batch" of your mash - using the same ingredients at the same concentration (no less than 500ml no more than 2,000ml for a 5 gal/20liter batch) and put it into a sanitized glass flask, bottle, jug, etc. Do this one or two days before you plan to make the main (5 gal/20L) batch. Add the small (typically 5 gram) packet of yeast to the starter, and when it is at high kraeusen, add it to the main batch. Yeast "learns" to feed on sugars when it wakes up from that little packet- it takes yeast seven generations to learn how to digest a different kind of sugar- therefore you MUST make your starter out of the same stuff you are going to make the main mash out of (this is why waking up your yeast in orange juice is a bad idea). Also, yeast is sensitive to sugar concentrations- so the starter MUST be the same strength or weaker than the main batch in order to prevent osmotic pressure from causing the formation of mutant yeast cells (a big cause of off flavors).

The temperature the yeast is used at also can cause the flavor to degrade. Most whiskey mashes use an ale yeast- the ideal temperature range is 60 to 70 degrees F. Lower temps will slow down the yeast- if sanitation is good- this is not a problem. If a higher temp is reached - the yeast will undergo "stress" reactions that cause excessive ester and higher alcohol formation- this will result in a solvent- like flavor that can carry over into the finished spirit. Lager yeasts tend to form a lot of sulfur compounds at the begining of the ferment- during the lagering stage the yeast reabsorbs these sulfur compounds, leaving a crisp clean lager flavor in the beer- since you don't want to store a whiskey mash for 2 months in the fridge- it's best to use an ale yeast.

When you are fermenting wine (for brandy or drinking)- it is best to use 2 grams of dry yeast per gallon and no more (two of the five gram packets per 5gal/20L batch). It's true that you would think to use 4 grams per gallon since the alcohol is so high (typically 10% or more)- but, with wine, in order to preserve the delicate aroma of the fruit you are fermenting, you need to have a slow, cool (60-70F) ferment to prevent the CO2 from driving off all of the more delicate flavors. A fast ferment in a wine will find the CO2 "scrubbing" the delicate flavors out, leaving you with a bland acidic wine that tastes pretty rough.

Note though that you can over-pitch a wort with too much yeast. Jack warns ..

when used at a rate over 4 grams per gallon (with ale yeast and a potential alcohol of less than 9%), dry yeast will give off some excessive ester/ sulfur compounds that are almost impossible to get rid of through cold storage (lagering). If the stuff is to be distilled, and you "overpitch" your yeast- just make sure you have a LOT of copper to get rid of the extra sulfur compounds.

The very high cell concentrations typically cause a reduction in yeast growth. This makes the yeast that is pitched is the yeast that is responsible for the ferment- if the yeast viability is below 90%, stuck ferments may occur. Otherwise, the profile of the flavors that yeast makes is typically a mix of compounds made during both the aerobic and anaerobic phases- with the aerobic phase suddenly gone- some very odd smells occur (sulfur compounds), that, thanks to the stress of fermenting without any time to adapt (the lag phase), the yeast is damaged, and unable to reabsorb any of the esters and sulfur compounds when they go dormant (during the settling out and lagering phase-if any). The high cell count also makes fining and filtering more difficult.

Overall, underpitching is more of a concern than overpitching. Underpitching causes a long lag time that can allow bacterial infection to take hold, overpitching can cause off flavors to develop that can be removed with a long lagering/secondary ferment, and alot of copper exposure.

As a general rule, you use 400ml of yeast solids per hectoliter of wort (for a lager yeast), and half of that for ale yeast (granted, this is at 12degrees plato). For dry yeast, 2 to 4 grams per gallon of wort is best- 2 grams for standard beer, 4 rgams for doppelbocks, barleywines, etc. For an active yeast starter, the actively fermenting starter should comprise 10% of the volume of the mash/wort. It should also be of the same sugars/composition and at the same concentration (err on the side of a weaker starter, rather than a stronger one- yeast can go from "rags to riches", but not the reverse.)

Ted Palmer writes ...

Many if not most commercial distilleries use some form of brewers yeast. What should determine the type and AMOUNT of yeast is the make-up of your wash. A common problem isn't the type of yeast that you are using but rather how you are using it. A 1.060sg wash will be reduced just fine by any yeast so long as there are enough yeast cells per ml. and enough nitrogen to keep the cells healthy. In fact by repitching more activly fermenting yeast several times into a high gravity wash, a "beer yeast" can ferment up to 16 to 18 percent alc. If you use a packet of dry yeast then there are too few cells let alone heathy ones.

Here are a few guidelines for proper yeast use in any ferment:

You will need 10 X 10^6 cells per ml for any wash up to 1.050sg and 1 X 10^6 cells more for each 1.004sg above 1.050.

Always use a rigorously fermenting pitch of yeast, ie: never use yeast straight from a package, always grow up enough cells for the SG you are using (called a yeast starter). Say you are going to make 10 liters of wash at 1.050, open the package and grow the cells in 10 ml. of 1.050 wash. When fermentation passes the most rigorous point pitch the 10 ml. into 100 ml. of 1.050 wash, repeat this into 1 liter and then pitch into the 10 liters. with higher gravities use 2 or more seperate yeast starters.

Yeast need proper nutrition, nitrogen must be present. If using only sugar put 2 ml. of ammonia per 1 liter of wash. If using fruit juice or grain mash 0.5 ml. per liter. Yeast also need more than just sucrose for food, add some fructose, dextrose, maltose or any other simple sugar. An acid isomerization of sucrose(invert sugar) will also work if other sugars aren't available.

Reuse the yeast from the last batch you made! This is the easiest way to make sure there are enough cells for your wash, keep any eye out for infections though and only reuse yeast that fermented properly in the last batch.

Nutrients & Acidity

A slightly acidic environment is enjoyed by yeast, and also inhibits the development of bacterial contaminants. The pH of the brew should be adjusted to between 4.0 and 4.5 prior to fermentation, using citric or lactic acids. You can also use lemon juice rather than citric acid - it works great in distilling, but is bad in winemaking. Just use it on an equal volume basis- 1TBSP of acid blend = 1TBSP of lemon juice.

This calculation seems on the low side practically - it must be that the citric acid sold in supermarkets / brewshops isn't 100% pure. Always double-check the pH using pH papers or some other test.

Nutrients also need to be present. Yeast cells require phosphorus, nitrogen and potassium, as well as amino acids and vitamins, for metabolic processes. The extent to how much is required depends on the feedstock being used. The nitrogen requirement may be supplied in the form of amino acids, ammonia, or ammonium salts. If the solids are separated from the sugar solution prior to fermentation (or say starting only with sugar) the bulk of the protein will be removed, and hence a potential nitrogen source lost. Ammonia or ammonium salts are the preferred source of of additional nitrogen if its needed, however avoid using excessive amounts because it can kill the yeast. Both nitrogen and phosphorus can be supplied by ammonium phosphate (commonly available as a fertilizer). Many fermentations will proceed satisfactorly without vitamin suppliments because the fermentation medium contains sufficient of these nutrients, however in most cases, cell growth is enhanced when B-vitamins are added.

Jack adds ...

DAP (Diammonium phosphate) is also known as "yeast nutrient" among wine/beer makers. Yeast energizer is typically a yeast hull extract- an all-natural version of yeast nutrient- it doesn't work as well, because there just isn't enough free-amino nitrogen in it. Most homebrew shops (who know what they are doing) sell the DAP salt- it should look just like any other chemical salt (like table salt, but with bigger crystals)- if it's off-white, brown, or any other color- it's likely a mix of yeast nutrient, yeast energizer, some B vitamins and other assorted junk (ie trace minerals, folic acid). If your local homebrew shop has it's head up it's arse, try checking online for a domestic home-brew shop that sells it online. Most homebrew magazines have dozens of adds for places like this- just find the closest one to save on shipping.

One recipe for nutrient ale salts is

58 g sodium chloride (common table salt)
170 g citric acid
7 g ammonium sulphate
6 g magnesium sulphate
2.5 g grape tannin

This mixture is hygroscopic (attracts water), so keep it in a cool dry place with a good lid.

The "Great New Zealand Home Wine Making Book" suggests to ... "buy some ammonium sulphate or ammonium phosphate, and some pottassium phosphate or potassium sulphate and add 2g (1/2 teaspoon) of each to every 4.5 L. Another valuable addition is vitamin B1. You can buy these as tiny 3 milligram tablets from your local chemist or pharmacy and add one of these each 4.5 L" ...
Darryl offers ...

Before turbo yeasts came along, I would use a champagne yeast and my own nutient mix to ferement a sugar wash. For a 20 litre wash I would use 5 kg sugar plus the following nutrient mix:

4 tsp winemakers' yeast nutrient salts

4 tsp citric acid

1/3 small jar molasses

1 tsp marmite

Concerning the use of Urea in nutrients, Des writes :

According to 'The Food Regulations 1984, Amendment No. 5' dated 2nd December 1991 regulation 235, General alcoholic drinks, subclause 3 says "General alcoholic drinks may contain any of the following:", paragraph (i) "Yeast nutrients, except urea"

Which is what has been quoted in past correspondence and always referred to when discussing the issue, however: 'The Food Regulations 1984, Amendment No. 9' dated 10th of October 1994 regulation 101, (3) states "Regulation 235 of the principal regulations is hereby further amended by revoking paragraph (i) of subclause (3)." ie the exception to urea above is now revoked.

On seeing this I contacted the New Zealand Health Department and requested, under the Official Information Act, all the paper work as to why the original banning and why the lifting of that ban. Of course, I got screeds of paper but the story is that the ban was instigated because of research done in England that pointed health risks of urea as an ingredient for fermentation. Thus it was banned.

It was later realised that although these chemicals were present in the fermented wash, they were not present once the wash had been distilled. It appears that they are not carried over in the distillation process, thus the ban for this type of alcoholic product was lifted.

Mike adds ...

Nothing wrong with urea in modest quantities... the human body excretes it daily, and in some quantity, so it is not a killer. However, only drawback with its use as a nutrient is that it encourages production of ammonia compounds, and that can taint a brew. This was a common complaint from people who had problems with early turbo mixes that used excessive urea. Current mixes appear to have overcome this problem, but addition of urea yourself should be governed by caution. A little goes a long way. DAP is a better nutrient to use as the ammonium radical is more tightly bound.

Also, don't use too much nutrient. It won't make the yeast work any faster, once you've supplied its needs ... but it can make your spirit turn blue. Mike explains ...

... alkaline washes that hold a lot of nitrogen-containing compounds that have been put in as nutrients will liberate ammonia and that, being a gas, will get to the top condenser and form an aqueous ammonia solution, which is alkaline. Normal oxidation of copper under heat forms cupric hydroxide in an alkaline solution. This turns black when boiled with water, and is commonly seen on copper components in stills. This, in turn, reacts with ammonia solution to form Schweitzer's solution, containing the tetrammino-cupric ion Cu[4NH3]++, which is deep blue. Don't worry ... it won't hurt you, and you might even think the colour attractive!

Answer is to ensure that your wash is not alkaline, but acidic. This is the normal condition after a fermentation, as yeasts tend to acidify the wash with their by-products. You say that you added yeast nutrients, and I suspect that you were a bit too enthusiastic, as this can tipp the balnace the other way. Addition of citric acid is usually enough to neutralise and then acidify a solution made too alkaline by overdosing with nutrients, but without acid buffers to control the pH. In an acidic solution, those nitrogen-containing compounds will react with the acid to form salts, and so will not ne carried up to the top condenser.

If this happens, make sure you strip down your tower, and clean it well. The blue alcohol can be cleaned up by adding some citric acid (50g per 5L) (which will react with the ammonia to produce ammonium citrate which will precipitate out along with the copper leaving hydrogen sulphyte and or sulphide), and then filtering it through some coffee filters to collect the flocculant; the alcohol will then be ok to redistil.

Matt suggests

The White Labs site (http://www.whitelabs.com/) mentions that they are now distributing Servomyces a nutrient which apparently even conforms with the Reinheitsgebot! It was developed in Europe, and seems aimed more at the beer brewing market, but it might still give interesting results for those doing a low-nutrient wash ferment.

Wyeast Labs of Oregon, USA also offers a yeast nutrient: http://www.wyeastlab.com/nutrient/nunutrie.htm

Brians recommendation re nutrients is lallemand fermaid k; use at a d/r of circa 60/100 g /20 litres ( http://www.lallemand.com)

Oxygen

During fermentation, yeast has a couple of choices. If it has oxygen available to it, it will be able to reproduce quite rapidly (doubling every 3 hours). If there is only limited oxygen available, it will turn its task to producing ethanol and other products (about 1300 in all), like higher alcohols (sometimes called fusel oils), esters, organic acids, and carbonyl compounds. To get good initial growth of the yeasts, you want to have a bit of oxygen available - but you can do this simply by stirring the wash vigorously when disolving the sugar. Once you have added the yeast, it is critical to seal the container such that air cant get in, but you can still let the CO₂ out, by using an airlock. To minimise the amount of other volitiles produced, make sure that you are using a yeast designed for the job, and keeping it happy with nutrients & with a stable temperature.

Fizz writes ..

..for those of us who have heard about the need for oxygenating the water prior to pitching the yeast and (like me) cannot afford extra equipment to do this I would recommend (if you have one) a kitchen stick blender, like what you use to make soups or sauces etc. 2 minutes in that baby and the water had that much O2 in it, it turned milky !

If you're going to use an airstone to aerate the wash, Mecakyrios recommends ..

1.) I HIGHLY recommend for you to use an in-line HEPA air filter. This will allow for the air going through it to be essentially sterile when it comes out through the air stone. This aids in protecting your wash from becoming infected with unwanted nasties.

2.) I would recommend using a racking cane with a small piece of tubing connected to your air stone. Let me try to explain better: You have you air pump connected to the correct length of tubing to get to your wash. You connect that tubing to your racking cane. To the other end of the raking cane you add a small piece of tubing, and to that tubing you put on your air stone. Then you submerge the air stone by placing the raking cane into the wash. What this will do for you is allow you to position the air stone where ever you may need to, but more importantly it will keep the stone from floating to the top of the wash. By using the raking cane (or similar device) method you now have more control over the air stone while making sure that it remains submerged.

There are brew shops that sell both of these products. Some even sell special "air wands" that come with both the filter and a special "wand" that keeps the air stone submerged.

If you would like more information, or at least a look at some products for this topic, I would recommend going to http://www.williamsbrewing.com/. Go to the fermenting equipment section and then go to "Wort Aeration" section to look at some products that deal with this issue.

Ted Palmer writes ..

In order to properly "grow up" a series of yeast starters you must aerate the wash with sterile air or pressurized oxygen (O2). The reason for this is that yeast cells bud or reproduce only when there is enough oxygen present to grow. During fermentation yeast cells will still bud, but at a slower rate since it has to pull oxygen out of chemicals. The amount of O2 required is small, on the order of 20 microliters per ml. to support the budding phase.

So how do you put O2 in your wash?

Sterile air:
Pump air through a 0.02 micron filter and then a stone (fish tank bubblers work well) into the wash. If you can't get a filter use a jar setup like a thump barrel only put a stone on the inlet pipe, fill this with hydrogen peroxide halfway full. pump air through this jar and then a stone into the wash. Run this setup 20 - 30 seconds for each liter of wash.

Pressurized O2:
Use any tank of pure oxygen fitted to a stone on a length of tubing, run for 5 - 10 seconds for each liter of wash.
Aerating a fermenting wash will result in one hell of a lot of yeast and very little alcohol. Aerating a fermenting wash for even a short time will oxidize flavor components including ethanol !!!

Cooling the Wort

Before you pitch the yeast, you need to cool the wort down below 26 ° C. You could leave it overnight to cool, but then you risk letting an infection get started. Its often better to force-cool the brew down. The rate and length of fermentation is adjusted by the pitching temperature, which in turn can influence the flavours.

Jack writes ...

If it's a pure sugar/molasses wash- your only concern is with the temperature. If you add the yeast when the temperature is still above 70F you are going to stress the yeast- and it's going to produce more higher alcohols (methanol, for example) than it normally would.

If you are making a mash using grain (corn, rye, malt, etc) you should try and cool the mash down to 70F in under one hour. Otherwise, you are allowing the production of a chemical called DMS (dimethyl sulfide)- this is a chemical compound that gives beer/mash a buttery/ butterscotch flavor- in some dark beers, it's okay- in light beers and whiskey mashes it's a problem. Over time DMS is reduced into various other sulfur compounds- some will form a rancid butter flavor/oder, others will be estery (solvent flavor). By cooling the beer/mash quickly, you inhibit the formation of this compound. And, yes, the nasty flavors DMS can make will transfer over into the finished spirit.

And, that's the prime time for an infection to take over. The rule is: cool to 70F as quickly as possible, and add your yeast as soon as you get to that temp.

Tim writes ...

I have a counterflow wort chiller for my beer brewing. It's a 20' piece of 1/2" ID copper tubing inserted inside a 19 1/2' piece of 3/4" ID rubber hose. This whole thing is wound into a coil around a beer keg (then the beer keg is removed...)

The inside of the chiller has to be spotless and sanitized to keep from contaminating the (then cooled) wort on its way to the fermenters.

I've been using and cleaning this thing for 10 years and have NEVER had a contaminated batch.

The vinegar/water mix makes it shine like a new penny!

This method was told to me by a PhD Brewing Chemist who'd been doing this for years. It really works!

Fermentation Tank Hydraulics

Jack writes ...

Traditionally, shallow, open, "wading pool" shaped fermenters were the most common found in old breweries/distilleries. Due to space concerns, "unitanks" (sealed on top, with a conical bottom and a valve to separate trub and yeast) have taken over, as they provide a more sheltered enviroment that, being tall rather than wide, allows companies to expand production at a fraction of usual expansion costs. After testing various fermenter shapes, it was found that the effective height (that which is actually filled) of the fermenter should be less than the fermenter's diameter. A few industrial studies show why this is so. In 1978 it was found that carbon dioxide gradients were present- the largest values being at the bottom of the fermenter. This caused s heterogeneous flow field that included isolated vortices. The maximum vortex formation was found at the top of the fermenter, which influenced temperature, sugar concentration, and Ph- effectively, tall fermenters have not one, but several fermentations taking place in parallel.

In order to counter this effect, the best method is to use a stirring device within the fermenter, or to recirculate a small amount of the mash (maybe 5 to 7% of the total volume).

Why was this done? Because short/wide fermenters work markedly better than tall ones. Check the numbers:

Tall fermenter Short/wide fermenter

Fermentation time: 10 days 8 days

Final gravity: 1.010 1.011

Diacetyl (mg/L) 0.350 0.060

Clearing poor excellent

pH at end point 4.6 4.4

The lower pH will provede a greater stability in the mash/beer during storage/secondary fermentation/ clarifying procedures. Blind tastings have also shown that the short fermenter in an "open fermenter" form (a large stainless steel stockpot with the lid on instead of an airlock) made for a cleaner, better tasting beer/mash. For large industrial concerns, closed unitank fermenters are a good business idea. For home brewers/distillers using a large (7 gallon) stainless steel stockpot with a lid gives you a great fermenter (even compared to carboys- just watch the sanitation in the surrounding area), that will give a faster ferment and a faster clearing time. That alone reccomends it for distiller-only hobbyists, but the flavor improvementsalso make it worthwhile. Remember, a still will not make a bad mash taste good- it will only make it taste stronger. As a result of this info, I now brew my beer (and bourbon) in an open fermenter. And I'm drinking/distilling it 2 days faster as a result.

Pitching Yeasts

When the temperature of the wash has dropped below 26 °C, add the yeast. Do not add the yeast too soon - if the temperature is above about 34 °C, it will kill the yeast.

You're aiming for around 10 million yeast cells per mL of wash. A 25L wash at 1.080 will therefore need about 3 cups of slurry. Get this amount by using the slurry left over from the previous run. See the comments below in the Reusing Yeast section.

If using dried yeast, it can be helped along by letting it soak in about 1C of warm (24 °C) water for about an hour beforehand. Use a high alcohol yeast such as for champagne, or the new proprietary alcohbase or "turbo" yeasts which can generate up to 21% alcohol (who needs distillation ?). If the pack you're using is one of those small ones, it will pay to grow it up to a suitable size before using it (see Teds comments below).

Close the fermentor, and use an airlock. Keep the temperature around 28 C, and the specific gravity should drop to approx 0.980 - 0.990 g/mL and have ceased bubbling within 5 days.

Jack H recommends ..

Try using cling wrap over the top of your fermenting vessel. Secure with a rubber band(I cut mine from an old tyre inner tube) Then prick about 6 holes in the wrap to allow the gas pressure to escape.You can see when the fermentation is over and I have found that I have never had a failure with this method as opposed to using a fermentation lock .

MeadMaker suggests a method of making a simple airlock ...

while most people go out and buy a one way valve, it is realy quite easy to make at home. all you need is: (1) the lid of the bottle you will be fermenting in, (2) 2 straws, (3) something to seal with, (e.g. bluetac, wax (just melt a candle), glue (might make it smell though) and/or sticky tape), and (4) a glass of water.

Now... make a hole in the lid using a hammer and nail, and then widen it using sissors to the diameter of the straw. Then insert the straw so that the end of it is just in the hoke in the lid. Wax/bluetac/glue so that it is sealed. Then make the straw so that it is on a right angle (I'm assuming ur using one of those "bendy ones". Insert the second straw into this, then sticky tape and wax/bluetac/glue so that it is sealed. Make THAT straw on a right angle, so that the end of it is inserted into a glass of water. Test by adding some baking soda and vinigar to the bottle. If the gas seems to ONLY be coming out through the glass of water, it works.

Also, this is better for SMALL bottles, if ur making a big brew, i recomend u use a rubber pipe or something instead of straws

Bill writes ...

Open (barrel) fermenters, Found the plastic used to cover windows, shrink wrap works well its nice and clear lets you check the temp. and specific g. without removing the cover and letting air into the fermenter. if its cut about two in. larger than the top it can be held in place with a bit of twine attached to an elastic band, then heated for a couple of seconds with a hair dryer, this makes it nice and tight and clear.

If the fermenter doesn't bubble, check that the lid is sealing well. If you squeeze the container when you put the lid & airlock on, the water should move up in the airlock, then drop again when you let go. If it doesn't, then the lid isn't on correctly.

Another way of knowing how far the fermentation has progressed is to measure the weight of your fermentor & contents. Half the sugar is expected to convert to CO2 gas and bubble away. Theoretically the yield is 48.9%, but practically this is 40% because some of the gas dissolves in the wort. So if you have added 5 kg of sugar, and the weight has only dropped by 1 kg, keep it going for a while longer (you expect 5 x 0.4 = 2kg weight loss).

For excellent discussions about yeast, and how to get the best out of it, see the Turbo yeast and AllTech web pages.

Temperature Control

Temperature control is very important during fermentation. Yeast is a living organism, and will die if too stressed. Both alcohol and temperature stress it. With no alcohol around, it won't die until about 40 °C. At 14% alcohol, it will die at 33 °C, and at 25 °C if in 20% alcohol. So keep it below 25 °C at ALL times. Lower temperatures will also result in less volitiles. When the temperature has been kept below 30 °C the production of fusel oils is minimal, and is extremely small if kept below a maximum of 25 °C. This is where you get into a bit of a trade-off; if you keep it too cool, it will take heaps longer, with greater time for the risk of infection etc to set in. At 25 °C, it will take 3 days to ferment 0.24 kg/L sugar, but at 15 °C it will take nearly 2 weeks.

Higher fermentation temperatures will result in more fusels being formed. Jack advises ..

This is for the Wyeast1056/s001 strain that is used for Sierra Nevada's pale ale:

Temperature Ethyl acetate(mg/l) Amyl acetate(mg/l)

60F (15.5C) 16 0.5

68F (20C) 26 2.0

75F (24C) 53 4.0

Technically, ethyl acetate and amyl acetate are considered esters, not fusels, but they act the same in the still. Fusel oils are formed by the ferment of amino acids- not sugars. There are two types of fusel oils; aliphatic and phenol. The aliphatic have a straight line structure and are volatile- they have a warming alcoholic/solvent note with fruity tones. They lead to definate harshness. Phenol types are involatile, aromatic alcohols with a madicinal flavor.

Lager yeasts fermented at the right temperature (cold) form less than half the fusel oils an ale yeast does at normal temp. (25mg/l against 70mg/l for an ale).

All yeast start to increase fusel oil production when sugar concentrations above 16% (sp.gr.1.065) are used.

Mutated and first generation (air-bubbled "lab-grown" yeast) tend to make more than recycled yeasts do- hence the Scotch distillers use of second hand yeast from the Dublin breweries).

Ian Smiley adds ..

However, when fermenting straight sugar-and-water with turbo yeast one is typically making grain neutral (i.e. vodka), and such congener production is not really relevant if using a high-separation still like a full-reflux fractionating still. Virtually all such congeners are stripped out during a double distillation anyway, so the distiller need not worry about off flavours and is typically better off with the faster turnaround of a hotter fermentation. Also, commercial distilleries have no problem separating comparatively high concentrations of congeners given the sophistication of their stills.

The temperatures that I refer to, BTW, for the fast turbo yeast fermentations are between 80 and 90F (27 and 33C). And, in Making Pure Corn Whiskey I recommend a fermentation temperature range between 70 and 90F (21 and 33C) for the production of whiskey.

Now, the production of beer, wine, and whiskey (or any other flavour-positive spirit, for that matter) is a different story, because the congener profile formed during fermentation will pervade through to the finished beverage. This is clearly true of beer or wine where no distillation is done, so whatever is formed is with the substrate for the duration of its life cycle. Flavour-positive spirits undergo distillation but since certain families of congeners are retained this makes such spirits sensitive to the congener make-up of the mash, unlike grain neutral where everything but the alcohol is stripped out.

I have done extensive experimentation with whiskey-mash fermentation, including numerous different temperature regimens. I've even lagered whiskey mashes with bottom-fermenting lager yeasts for as long as 13 weeks. It produced an unhopped corn/rye all-grain lager that I swear I could have bottled and conditioned and consumed as a very light (and cheap) lager, and I'm confident that it would have been delicious and refreshing. However, when I distilled it, it was completely insipid. It simply didn't have enough esters to give it a significant flavour. It was pleasant enough, but it just wasn't whiskey, although when I rectified it into grain neutral it was very clean.

All of this would have been due to the long lager fermentation where the yeast literally consumes esters, aldehydes, and fusel alcohols during the late-phase fermentation cycle.

I have found that the best whiskey and schnapps flavours are in fact formed during a hot, fast, brisk fermentation, and that long languishing fermentations (i.e. other than lagering) are the ones that produce the less desirable flavours. Of course, this point would be subject to personal preference.

In another experiment, I fermented a corn mash with a wine yeast and let it ferment for over four months. The mash actually formed a sherry flor on top and oxidized and darkened and took on a very unusual but pleasant smell. When I distilled it, it had a distinct fruity/sweet fragrance and flavour that could only be described as a delicious liqueur. I haven't had time to return to this line of experimentation, but when I do I'd like to explore this further.

Just to clear up my use of the term "secondary fermentation", what I mean by that is the fermentation phase that takes place immediately following the high krausen phase. Wine and beer makers will recognize the pattern whereby their fermentations start out with a lag phase followed by a vigorous bubbling phase, often with foaming, then it settles down to just spurious bubbling. This vigorous fermentation is the high krausen phase, or primary fermentation. After that, the mash or must settles down to a spurious bubbling, this is the "secondary fermentation" in my parlance, and it usually takes one or two weeks for beer and one or two months for wine. After this, the beer or wine is left to age or lager (German for, "store in the cold"). In my terminology, the fermentation that naturally carbonates a beverage is called the "conditioning fermentation".

Just to recap, a mash intended for distillation only needs to undergo the high krausen phase in my standard processes.

The familiar rotten-egg smell ... is due to the formation of hydrogen sulphide, mercaptans, and dimethyl sulphide. All of these compounds are usually consumed later in the fermentation in the case of beers and wines, but with distilled mashes, any amount of contact with copper in the construction of the still will instantly remove it.

An easy way to maintain the temperature in cooler climates is to wrap a water bed heating pad around the fermentor, and tape the thermostat to the side of it before wrapping it all in a blanket. Other people just keep their fermenter in the hot water cupboard. Another way is to keep it in a small cupboard or box with a light wattage lightbulb to supply a lttle heat (but shield the bulb so that the beer doesn't become light-struck). Some even use immersion heaters like those for tropical aquariums - but these can be tricky to sterilise, you need to get the wires through the lid in an airtight manner, and if you lift them out of the brew without turning the power off, they can quickly overheat and burn-out (an expensive exercise in forgetfullness). Others yet put their fermentor into a larger drum/container, fill the gap with warm water & then use an immersion heater to keep the outer water warm.

If using the Turbo yeasts, pay particular attention to the temperature. These babies can raise the temperature of the wash by 5-8 °C, so don't add them until the wash has cooled to about 18-20 °C.

If you are fermenting large volumes, you may need to actually cool the wash, either by dropping in frozen 2L softdrink bottles of water, or getting fancy like big brewers, and running cooling water pipes through the fermentor. The larger the amount you are trying to ferment, the harder it wil become to control, yet it is critical that you try to keep it all at 25 °C plus/minus only 1 °C. You may find washes larger than 200L difficult to control & keep cool.

Ian writes ..

I have made "double" batches of wash - 50 and 60 litres. If you are in a warm climate be careful of the temperature. A double batch will heat up quite a bit more than a 25 - 30 litre batch. During the summer I used ice packs (the chemical that is sealed in little plastic bags - that you freeze for use in your cooler.)

Jack writes ...

To heat up the batch- ferment in a glass carboy, set the carboy in a plastic bucket, fill the space between the two with water, and use a small immersible aquarium heater to keep it warm. To keep it cold, do the same as above, but, instead of the heater, toss a couple of those reusable ice packs in the water covering the fermentor, and switch them out with a couple more kept in the freezer when they finally melt. If you ferment in a bucket, freeze some water in a plastic jug, sanitize the outside of it and float it in the mash. To heat up a bucket, just sit it on a heating pad- start with the lowest temp- that usually is good enough. Putting an immersion pump in the mash also keeps the yeast from "retiring early" when it gets cold.

Settling

Settling is probabaly THE best kept secret for getting really neutral spirits such as those used for gin. If you can really let your wash settle well, maybe even decanting it into another fermentor to let it settle a second time, then the distillate will be so much cleaner when distilled.

Once fermentation has finished (eg final specific gravity of 0.990-0.980 reached), turn off the heat, and let the finished yeast settle over a couple of days to the bottom of the container. Siphon the clear wash into the still, and you're ready to go. Be careful to not disturb the yeast layer, because if it gets into the still it can result in bad smells and flavours. If in a hurry, you can use finings (eg gelatin - 2g in 100mL to settle 25L) to help settle/clear the yeast, or try placing the wash in the freezer, to chill it fast & knock the yeast down. Passing the wash through a simple filter, or even a couple of paper towels to clear out the remaining yeast will also help improve the quality you later get. The simplest (& often most effective) technique though is just time.

There is also a new product available, called "Turbo Clear" which is said to help : http://www.aquavitae.co.nz/spotlight.html.
Jack recommends not to use gelatin ..

Gelatin doesn't work as well in sugar mashes - it works by binding to tannin- which sugar doesn't have. The best bet is Polyclar AT. It can be done in as little as a few hours.

The settling/clearing behaviour of yeast depends on the type of yeast you've used. From Brewing Yeasts (rehashed a bit)...

Yeast normally reproduces by "budding". During budding a small bubble like protuberance from the mother cell is formed into which part of the cytoplasm as well as a daughter nucleus, formed by division, passes. In some yeast strains the mother and daughter cells separate from one another completely, in other strains the cells remain connected to one another and form chains. Bottom fermenting yeasts occur mainly as single cells or pairs of cells, whereas top fermenting yeasts form chains of budding cells. In the case of top fermenting yeasts the mother and daughter cells remain attached to one another for a longer time and as a result branched chains are formed. Top fermenting yeasts can be categorised as powdery and flocculent yeasts. In the case of powdery yeasts the cells remain very finely divided in the fermentation medium and sink slowly to the bottom only at the end of fermentation. The cells of flocculent yeast, clump together after a short timeto form large flocs and then settle rapidly. Bottom fermenting yeasts do not form flocs. Another difference is their ability to fermet the trisaccharide raffinose. Bottom fermenting yeasts can ferment raffinose completely, whereas top fermenting yeasts can ferment only a third of the trisacchride. So... flocculent yeasts produce a clear but less fully fermented beer, whereas powdery yeasts and bottom fermenting yeasts produce a turbid beer with a high degree of attenuation. They also differ in regard to fermentation temperatures .. bottom fermenting yeasts are performed between 4-12 °C, whereas top fermenting yeasts use 14-25 °C.

Jack writes ..

It's very easy to clarify in the primary fermentor - just fine it with some bentonite or some Sparkalloid. Dropping the temperature also helps- say, down into the 50-60F (10-15C) range. The larger yeast volume in the mash may also (if you're lucky) may cause the yeast to re-absorb some of the esters they produced during the ferment as they go dormant- just like in beer brewing with a long lagering phase.

AuntyEthyl describes his technique ...

The process i use for my turbos at the moment is that I ferment only in the primary fermentor. When the spec. gravity hits .990. I rack the wash from the sediment, into a clean fermentor. I then clean my first fermentor and over the period of the next 3 -4 hours. (depending on how lazy I feel) I continuously pour the wash from one fermentor to the other for 3 or 4 times then let it sit for 30mins, and repeat.

This degasses the wash and aids clearing. I then follow the directions for Turbo Clear and add the first of the two part clearing agent let stand for an hour then add second part leave 24hrs. Result, nice clear wash

If you have to split the wash (say you've made more than the still can hold), just pour the remaining wash into a container that will hold the remains and be full. That is, ensure that the air in the container is minimalised. By eliminating the air in your container you will lessen the oxygen thereby lessening the chance of oxidation. This way you will be able to do the remains in a second run any time. The wash should be quite safe for weeks. Keep it sealed.
Ian writes ...

Please don't "run" your wash while it is still cloudy - when I started this gratifying hobby I did just that. The result of distilling all that yeast is you get a lot of nasties that you could avoid by clearing the wash! Yes, the carbon polishing removed all the nasties over a period of time - but as we are striving for excellence - please clarify your wash! I have found a tremendous difference in the result since I started clarifying my wash. Filtering it is NOT the way to go - I use Sparkeloid - it clears the whole batch in 24 hours. Also, just placing the wash in a carboy in a cool place will do the same job over a longer period of time. When your wash is in a carboy - preferably glass - you can see the yeast settle to the bottom . After it has settled, siphon it off - you don't want to suck up the stuff at the bottom - so put the tip of your siphon hose an inch or two above the crud at the bottom. You will have a crystal clear wash. With the stuff remaining in the carboy - I pour or siphon all the loose crap above the almost firm layer of expired yeast into clear 2 litre soda pop bottles - let it settle, and use it in the next batch - the clear stuff of course - not the crud in the bottom.

You should be able to keep your wash happily for weeks or months after its settled, before distilling it. Mike writes ..

The question was recently raised about storing sugar washes. Almost any alcohol solution over about 5% ABV can be stored for long times if oxygen is kept away from them. This means store it in glass or stainless steel; plastic fermenters will allow oxygen to get in and your wash will turn into vinegar! The higher the alcohol content, the easier storage is because the solution will be self sanitizing from the alcohol.

For longer term storage, the yeast present in the wash may present a problem. After the sugar is used up in a wash, the yeast initially will start to process some of the higher molecular weight compounds that it made during the primary fermentation, and the brew will actually get cleaner! Both beers and wines often benefit from some period of "sur lees" (on the yeast)storage. If you are planning a pot distillation for a flavored beverage, this may be a good step to take. Experiment and find out!

As time goes on, the yeast do die and split open, changing the flavor strongly for the worse. For storage longer than a few weeks, the wash should be "racked" (siphoned)off of the yeast cake that will have settled out in the bottom and sealed in an air tight glass or stainless container.It can then be stored for months without problems.

Plastics are not 'impermeable to anything'. They may be considered so for liquids that don't attack them, but their structure makes them relatively porous to gases compared to the dense, amorphous structure of glass. Even steel is very porous to hydrogen! Plastics may therefore be used for long-term storage of chemicals that are not adversely affected by oxidation, but not for sugar washes, where even very small amounts of oxygen can have significant impact. Commercial PET in pop bottle thickness transmits 1.5 to 8 ml of oxygen per square meter per day at room temperature. 'Artificial' corks are made out of carefully selected plastics to have uniform oxygen transmission rates, and are being used because they are more uniform than 'natural' corks, not because they don't allow oxygen in. They have the further advantage of being moisture repellent, unlike 'natural' corks which can soak up wine and so provide a nutrient-rich path for fly or airborne bacteria.

The most common bacterium responsible for production of acetic acid from ethanol is not a member of the lactobacillus family, but is mycoderma aceti, commonly known as Mother of Vinegar. When present in wines, members of the lactobacillus family are responsible for malolactic fermentation, which produces many flavorsome by-products. Far from 'being held in check by the alcohol content', they are responsible for secondary fermentation of new wines that are naturally too high in malic acid, as in Germany, or when particular nuances of taste and flavor are desired, as in the red wines of Burgundy and Bordeaux in France. When present in milk, they produce yoghurt. In contrast, mycoderma aceti, which may be bought in any good brewing shop by those wanting to make their own vinegars, primarily produces acetic acid. In the presence of oxygen, this bacterium oxidises ethanol to acetaldehyde and then to acetic acid. This process can and does occur over long storage times in the best of wines should mycoderma aceti permeate 'natural' corks, in which they can find sustenance and so thrive, resulting in the common complaint that a particularly expensive wine has been 'corked'.

Alcohol Content of the Wash

You can easily calculate the strength of your wash, if you know your starting & final specific gravities (SG) - measure these with a hydrometer. The % alcohol is (Starting - Final) x 129. eg: if your sugar/water mix of SG=1.120 drops to 0.980, then you have a wash with (1.120-0.980)x129=18.1%.

Some winemakers use the Ebulliometer degree table for their wines - it estimates the difference between the boiling point of their wine & distilled water (eg if your distilled water boils at 100C, and the wine boils at 93C, then it has 8.8% alcohol). I've created the following calc based on data from Churchward (ACI Jnrl & Proc, Jan 1940), supplied by Duncan. Note that some correction may required if there is still residual sugar present. This calc is only good for % alcohol less than 25%.

Reusing Yeast

It is possible to reuse the yeast several time. Ted Palmer advises :

You can "re-pitch" yeast more than 10 times in most cases, the biggest factor in determining if the yeast is still healthy would be its viability. Viability is the percentage of live cells in a given sample. To test for this you will need a microscope, a hemocytometer and some methylene blue stain. Here is a good link written by a friend of mine that explains this method in detail http://www.brewingtechniques.com/library/backissues/issue2.4/allen.html.

Another important factor is the genetic strength of the yeast, some yeasts are very stable genetically others aren't. What this means is that genetic mutations change the profile of the cells to the point that they no longer resemble the parent strain. Some yeast strains mutate in less than 4 generations where others are stable for hundreds. Turbo yeast being a highly hybridized yeast falls into the former, I can't tell you how well it will perform or for how many generations, you will have to figure that one out on your own through experimentation. Many packaged yeasts are mixtures of 2, 3 even 4 different yeasts, so if one doesn't crop yeast at the right moment during a ferment one or more of the strains could wind up missing in action. Also be aware that the pitching rate or the number of cells added per ml is an important factor in any ferment . The right # is 10 X 10^6 cells per ml up to 12 degree Plato and you must add 1 x 10^6 per degree Plato above 12. That can be allot of yeast in a high gravity wort. The caveat in yeast pitching is more is better than less.

See also The Microbrewery Laboratory Manual:

Jack comments ....

I've been doing some fermentation speed/alcohol-sugar tolerance experiments. The Canadian wine yeast called Lalvin EC-1118 (champagne-saccharomyces bayanus), when pitched at a massive rate (I made up a starter of 10 lbs of sugar, 5 teaspoons of yeast nutrient, in 5 gal of water, then when this was done fermenting, I repitched the thick yeast cake at the bottom of the carboy into only 2.5 gallons of 15% potential alcohol sugar water), with what seems like excessive yeast nutrients, it acted the same as the Turbo yeasts I hear you guys in NZ talk about, plus, with the competative factor (it's a "killer" yeast strain) no boiling or campden tablets had to be used. Anyone who can't get a turbo yeast can make one by "overpitching " this wine yeast! Fun experiment, but I tested every wine yeast in the store, and I went through over 120 lbs of sugar. EC-1118 was the clear winner by a long shot. Hope this can help someone. (by the way, fermentation took less than a week)

David Lamotte writes (to CraftBrewing@egroups.com (a brewing group for Australians/Kiwis at YahooGroups)) ...

Now repitching is a great way to get huge amounts of yeast working for you quickly, but you can also get the same amount of bugs doing nasty things. Bacteria grow much more quickly than yeast, but are usually killed off as the yeast get going making alcohol and lowering the pH (both are kryptonite to bacteria). But the few that survive from the first brew quickly grow to millions in the second and trillions in the third .... So it can often take a few batches before you have to dump one down the drain.

You can just save some of the slurry from the bottom of the fermenter, but it can only be repitched a few times as the 'gunk' builds up and coats the yeast. The information that you were looking for comes from Wyeast's home page (http://wyeastlab.com/hbrew/hbyewash.htm) and tells you how to wash and store your slurry. You can replace the plain water with an Acid wash which will kill any bacteria (but not wild yeast).

Donald advises ...

For yeast re-pitching & yeast washing applications the alcohol should not go above 6%. This is so the yeast will not become stressed and start to reproduce sexually (causing off flavors & mutations) rather than asexually.

Please note that at the end of primary fermentation there is enough yeast for four re-pitches. So, one can harvest 1/4 for re-pitch unstressed yeast before stepping up with the remaining 3/4. Also if you want to change your yeast strain by harvesting: Repitch of the bottom 1/3 will be more flocculent, repitch of the middle will be moderate 1/3 and re-pitch of the top 1/3 will be hardley flocculent. It is suggested to take 1/3 top, 1/3 middle & 1/3 bottom to assure yeast character. What you want the yeast to do now is up to you.

Turbo yeasts are not recommended to be reused. Mike explains "ul> You can easily re-use beer yeast for two reasons - beer generally is not fermented to high alcohol levels, so most of the yeast in the cake at the bottom is still alive, and beer wort is a nearly perfect growth medium to make more new yeast cells.

Turbos are designed with a LOT of live yeast cells and enough nutrients to grow more - but by the end of a fermentation, the nutrients (should be)nearly all gone, and most of the yeast in the cake is dead - from the combined effects of heat and high alcohol levels.

If you pitched a new sugar wash onto a turbo yeast cake, I would expect it to ferment - but MUCH more slowly than when the turbo was new, and would not expect it to reach the same alcohol levels.

Jack divulges his method for preserving yeast cultures...

Most home brew shops sell syringes (about 10cc sizes) without needles- these can be used to collect yeast in a perfectly clean manner. Fill up a measuring cup full of hot water and microwave it until it's boiling, then stick the tip of the syringe into the water and fill the syringe totally with boiling water, wait one minute, then repeat twice more with boiling water. On the last draw-up of the boiling water, instead of squirting it out, leave it in the syringe, put the cap on and allow the syringe/water to cool in a draft free place. When you brew your next batch of whatever, pour off all of the beer/wine/mash until you just have the yeast layer covered with liquid (the yeast layer sould never have been exposed to open air). Un cap the syringe and wipe down the tip with alcohol, then stick it under the surface of the fermented liquid near what looks like a healthy yeast colony, squirt out the water into the general area to stir the yeast up a little bit (don't wash it away, just unpack it from it's settled state- squirt the rest of the water away from the yeast you are aiming for to prevent from scattering it to the wind-the amount of water needed to blast the yeast loose depends on what kind of settling properties it has)- then draw back the syringe plunger to collect the 10cc of yeast slurry. The inside of the syringe has not been exposed to the contaminating air, neither has the yeast (due to the protective blanket of beer/wine/mash that you did not pour off), using standard beer "yeast starter" techniques you can use the syringe to make ten "sub-cultures" (about 50 to 100ml), which can then be used to make a one litre starter for your next batch- This technique will not work well for the Turbo yeasts designed for nothing but sugar- but for expensive (liquid) yeast cultures for fancy styles of beer/ wine/ whiskey mash- this system works wonders - I store my syringes in the 'fridge- no acid washing no HEPA filter no extra food- they last at least a month this way. Just make sure that if your mom house-sits for you while your on holiday, that you show her what they are so she doesn't think your a junkie and pours your trappist ale culture down the toilet. By the way- special blends of various beer and bread yeasts work great for fermenting whiskey mashes.

Magnetic Stirrers

You can make a magnetic stirrir out of an old tape player- epoxy a bar magnet to the spindle that turns when you push play and fast forward, mount a piece of thin aluminum above it, buy the stir bars at a science shop, or make one by sealing another bar magnet in a length of tubing cut out of the stem inside a Windex spray bottle, then seal it with the hot edge of a knife- very handy for yeast propagation

Sloppin' Back

Re-use of yeast is an old moonshiners trick also known as "sloppin' back". This refers to adding the mash that was strained out of the wash just prior to distilling, or the sludge left in the bottom of the fermentor, to the next batch of mash.

As Sam explains ..

I did't strain mine so to speak. I pumped out beer from the barrel and left the grain. I used about half old and half new grain. NO YEAST. It is already there. I added water and the same amount of sugar as when I would start a fresh batch. Stir like crazy and you only have to wait for 3 days max for the cap to form and fall and you are ready for a good run. Like I mentioned, third time is the best as far as taste and quantity in my opinion.

This can be a good source of infection for the next batch, but if it goes well, it will help boost the yeast count heaps, act as a bit of a source of nutrients (though its still best to add more of the real stuff like ammonia), and should help buffer the pH a touch (dropping it a few 10 ths). The yeast that you're reusing by this technique are those that have already shown themselves to be quite happy in that type of mash, and are ready to go for the next lot.

It appears that the "Turbo" yeasts are only designed to be used once, and not reused. Ola Norrman writes ...

Turbo Yeast (a mixture of yeast and nutrients) - shall never be reused. There are 2 main reasons for this:

Yeast condition. During the manufacture of dried yeast, very high levels of phospholipids are accumulated within the plasma membrane because the yeast is grown aerobically (with oxygen). The yeast population which exists at the end of fermentation has depleted levels making yeast cells more sensitive during subsequent fermentations and fermentation more likely to stick.

So the yeast produce and accumulates lipids during its growth in the yeast factory. Then, during anaerobic fermentation (without oxygen) in the wash, each new generation of yeast contains less and less lipids. Lipids are needed for alcohol tolerance which make this important to 14% Turbos and far more important to 18% Turbos. If to many generations have passed (because of reuse of yeast or to little yeast to start with) the yeast have low "lipid protection" and alcohol tolerance decrease.

Dried yeast also contains typically 15% Trehalose which is a "protectant sugar". It gives the yeast cell internal strength and also is an excellent "start sugar" for the yeast to use at the start of fermentation. Cells at the end of fermentation will typically contain only 2 or 3% Trehalose. Trehalose protect against the shock when the yeast are mixed in the wash.

Nutrient depletion. Not relevant for beer, partly relevant for wine but totally relevant for Turbo. So for Turbo, because the sugar offers no nutritional value, re-using the yeast a second time will result in a stuck.

Turbos also contains pH-buffer to give the yeast perfect pH conditions. Nutrients not only work as nutrients, they also keep the production of volatiles down to a minimum. Nutrients are consumed by the yeast. Re-use of a Good Turbo yeast will also result in a lot more volatiles in the wash. pH-buffer will not work in the second batch. There are other ingredients making the CO2 leave faster, giving the yeast cells something to claim to and move around in the fermentation, assist clearing after fermentation etc. Those functions will also be spoiled as they are a part of the nutrients.

Nutrient composition are the manufacturers secrets. One can not simply add some DAP (diammoniumphosphate) or similar and expect it to work the same. The first Turbo in the world was made in Sweden. They are sold under the name Prestige and are extremely good. At http://www.turbo-yeast.com/intro.html there is a lot of info about quality Turbos including a "recipe" telling how "Bad Turbos" are made.

There is also info about yeast strains at: http://www.lallemand.com/ It is a bit surprising that they not have some never information here, only old basics.

One could talk about genetic drift and bacterial risks too, but it is not so important.

Freezing Yeast Cultures

Matt reports

Noonan's book does mention freezing as a viable way of culture storage. It seems that yeast cultures that have been refrigerated are allowed to warm up to around 50F/10C for about a week. This causes a sedimentation and the liquid above the yeast layer is decanted off and the bottom layer is harvested. This layer is squeezed of excess water and then tightly rolled into a ball, stored in plastic wrap and then moved to a freezer. It apparently can be stored for several months. To re-animate this yeast, it needs to be thrown into a starter culture of aerated wort before pitching.

High Gravity Ferments

If you want to use high concentrations of sugar, in order to realise final high alcohol, you need to take special steps.
From the Whitelabs site, the instructions for using their WLP099 Super High Gravity Yeast are as follows ....

Aerate very heavily, 4 times as much as with a normal gravity beer. Less oxygen dissolves into solution at high gravity.

Pitch 3-4 times as much yeast as normal.

Consider aerating intermittently during the first 5 days of fermentation. This will help yeast cells during a very difficult fermentation. Aerate with oxygen for 30 seconds or air for 5-10 minutes.

Higher nutrient levels can allow yeast to tolerate higher alcohol levels. Use 2 times the normal nutrient level. This is especially important when using WLP099 to make wine and mead, which have almost no nutrient level to begin with.

Do not start with the entire wort sugar at once. Begin fermentation with a wort that would produce a 6-8% beer, and add wort (it can be concentrated) each day during the first 5 days. This can be done together with aeration. This is mandatory if the reported 25% ABV is to be achieved.

Dr Clayton Cone writes..

Here is a brief protocol for the production of high alcohol fermentations. You can down size to your needs. EC 1118 is a good choice up to 16 - 18 % alcohol. K1 and L2226 seem to work better at 18 - 20+% alcohol. The key to the success of fermenting to these high levels of alcohol is management of the yeast: lots of nutrients, pH control, small amount of aeration and occasional stirring to keep the yeast in suspension.

High Alcohol Fermentation 15-20 +% v/w

K-1or L 2226 Yeast Strain 6# / 1000 gallons

Vi-A-Dry Inactive Yeast 2133 2# / 1000 gallons

Fermaid K 2# / 1000 gallons

Di Ammonium Phosphate (DAP) 4# / 1000 gallons

Sprinkle the 6# K1 or L2226 yeast into 6 gallons of 105 F. water. While gently stirring ,to prevent lumping. Allow to set for a maximum of 30 minutes. Stir to disperse.

To minimize cold temperature shock, cool the warm rehydrated yeast slowly , in stages, by adding equal volumes of juice to the slurry. The attemperating stage is important to prevent the formation of unhealthy yeast cells (petite mutants) which form when the yeast is suddenly exposed to greater than 20 F drop.

Add the yeast inoculum to the bottom of the fermenter after a few gallons of the juice has been pumped in. This allows the yeast added time to get through its lag phase and exposes it to the necessary oxygen that it requires for healthy , alcohol resistant cells after the growth phase.

Divide the nutrients into several portions and add in increments throughout the first 72 - 96 hours.

Start the fermentation in juice that is below 24 brix, preferably 16-20 brix. The lower the initial brix the better the yeast will grow to achieve the necessary population required to complete the last stage of the high alcohol production.

Aerate or circulate gently for the first 24-48 hours. Do not put air cap on for first 48 hours. Oxygen during the yeast growth phase is necessary to produce the cell wall protection that is required towards the end of the fermentation.

Monitor the pH carefully during the first 24 hours. Do not let it drop below 3.4. Adjust with potassium carbonate or other suitable alkaline material.

Monitor the fermentation closely. When the sugar drops to 4 brix, add fermentable sugars to bring it back to 6 brix. Repeat this 4-6 brix. cycle until you reach the desired alcohol level, allowing the last cycle to go to completion (dry).

Comments:
The temperature should be 80 - 85F. for the first 48 hours and 70 - 80F. for the remainder of the fermentation.

pH below 3.1 places an added stress on the yeast cell as the % alcohol increases. It is best to maintain a 3.4+ pH. Use carbonates such as potassium carbonate to keep the pH above 3.4. It is especially important to monitor the pH during the early hours of fermentation when you are using sugar, honey and some concentrates to increase the alcohol level. There is little or no buffering capacity in these sources of sugar.

High levels of nutrients are absolutely essential for the yeast to produce high levels alcohol.

100% fructose sugar is not recommended as a source of added fermentable sugars. Most wine yeast ferment fructose at a slower rate and often times have trouble fermenting to dryness.

You can expect 0.58 - 0.60 % alcohol by volume for each 1% sugar. Thus the total brix or % sugar should be 33 -35.

With experience you may be able to adjust the brix between 4 and 10 rather than 4 and 6 to minimize the number of sugar additions.

Every juice ferments differently You may have to increase the yeast and nutrient levels or you may even be able to decrease one or more of them. If you are using sugar, honey or concentrate to increase the alcohol level, there are little to no nutrients present in these so you will have to add all that the yeast need for a healthy fermentation. .

You should obtain a Clinitest Kit from your local drug store and use it to monitor the sugar level near the end of the fermentation. It cost about $0.10 per test. It is an ultra simple test normally used to test your urine for sugar. 3 drops fermenting wine + 10 drops water in a test tube + 1 tablet, wait about thirty seconds. Read color compared to a chart.

One step, high gravity , 25-40 brix, fermentation:
High nutrient and yeast inoculum levels are necessary..
3-5X the above recommended yeast and nutrients are required.

Sugar is just as toxic to yeast as alcohol. Yeast growth decreases as the brix increases. Above 25 brix the growth drops dramatically and has to be compensated by increasing the inoculum. A general rule of thumb-1x10 6th yeast cells / ml./degree brix; 1/2 # K-1 / degree brix/1000 gallons juice; i.e., 1000 gallons of 30 brix juice would require 15# K-1 yeast.

There is usually very little suspended matter in the high gravity juice and as a result the yeast tends to settle rapidly. The yeast on the bottom of the fermenter participate very little in the sugar to alcohol process. Therefore, stirring and or circulating constantly or frequently throughout the fermentation is recommended.

Stuck Ferments

If your fermentation peters out early in the story, it could be due to a couple of reasons.

Nutrients. This will be the biggie. These are necessary if just using sugar/water. If this is why its become "stuck", then there will be little chance of reviving it (sorry). See the discussion above for more details.
I sometimes suspect that I haven't diligently rinsed all the bleach from my fermenter, and that this has killed the yeast. Repitching with more yeast gets it going again (and remember to rinse better next time).
Sometimes you haven't added enough yeast (there almost is no such thing as "too much" yeast). Use a couple of packets if you are using those little 5-7g sachets.
Temperature problems - too hot will kill the yeast, to cold will make it dormant. Keep the temperature between 26-34 °C, and keep it constant - varying the temperature will jepardise its run.

Do not add more sugar to a stuck ferment. It won't help.

You can still distill a wash which hasn't fully fermented out, but be prepared for some fun. It is likely to foam up heaps, and possibly block the column if you don't give it enough headspace, or use the "anti-foaming" silicon emulsions (wash conditioner) available in brewshops. Also, because not all the sugar has fermented, you're likely to get less alcohol out, and you may caramelise a bit of it on the element or the base of the pot (clean it well afterwards).

Heres a couple of emails between Steve & Dr Clayton Cone that are hugely informative ..

Below is the reply to my enquiry re turbo yeasts and stuck ferments. Dr. Clayton Cone is a microbiologist and consultant at Lallemand which is the manufacturer of the Lallevin EC1118 yeast which is good for up to 18% alc/vol. He provides a protocol for the production of high alc wines/washes below. You may wish to put the following links on your site, www.lallemand.com and www.redstaryeast.com The latter has an interesting text on the history of yeasts.

Regards, Steve

Steve,
I hope that you had a chance to read my articles in the Lalvin Home Wine Making section of the Lallemand.com. I try to cover the role of yeast rehydration, nutrients, oxygen, stirring, pH and other factors that are involved in a healthy fermentation that should assure you of a complete fermentation.

Most stuck fermentations today are caused by:

Mishandling at rehydration. Follow instructions very carefully.

Allow the temperature to rise too high.

No oxygen (aeration) during the first 36 - 48 hours.

No stirring or agitation during the first days of the fermentation and near the end. The yeast settle out and are not up in the must where all the sugar is.

Lack of yeast nutrients.

Too low pH

Toxic effect of Octanoic and decanoic fatty acids

I would first try to reactivate the yeast by adding Vi A Dry yeast residue and stirring, allowing a little air to get into the must. Stir several times for several days. If no activity is observed then you need to do one of the following:

There will be no yeast growth with all of the alcohol present so you must add a large number of live yeast to finish the job. Add 10lbs of properly rehydrated EC 1118, K1 or L2226 directly to the stuck wine and aerate and stir.
or

Calculate the right amount of EC 1118, K1 or L2226 required for the total volume of stuck wine at 5lbs/1000 gallons. Rehydrate the yeast in 10 time its weight in 105F tap water. Add the dry yeast slowly to the water while stirring to avoid lumping and allow to stand for a maximum of 30 minutes.

Add the rehydrated yeast to the following initial mixture which is 5% of the total stuck wine volume:

2.5% of volume of stuck wine (25 gallons/1000 gallons)

2.5 % of volume as water (25 gals./1000 gal.)

2.0 lbs. Fermaid K & 2 lbs DAP /1000 gals. Of wine/water mix

Adjust sugar level of this mixture to 5% with juice concentrate or sugar (40 lbs sugar/100 gals)

Maintain temperature at 70 - 75F

When the sugar level has dropped by 1/2 (<2.5%), begin to add the stuck wine to this starter. Add 2lbs Vi A Dry yeast residue/1000 gallons of stuck wine before starting to add to the starter*. Add in batches of 20% of stuck wine volume. When the sugar has again reduced half add the next batch. Continue untill the fermentation has completed.

* This will adsorb the octonic and decanoic fatty acids that might be present and also furnish nutrients for the yeast.