I ONLY SHIP TO THE U.S.
The following information is provided by www.homedistiller.org
IntroductionFermentation 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 ....
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:
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 ..
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.
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 UseTed recommends
The yeast selection pretty much depends on what you are making -
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 ...
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 !
[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.
You can make your own Turbo yeasts. Jack wrote ..
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 YeastsIt 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 ..
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 UseJack advises ...
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.
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.)
Here are a few guidelines for proper yeast use in any ferment:
Nutrients & AcidityA 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 ...
One recipe for nutrient ale salts is
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 ...
Concerning the use of Urea in nutrients, Des writes :
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.
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.
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)
OxygenDuring 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 ..
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.
So how do you put O2 in your wash?
Cooling the WortBefore 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 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.
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 HydraulicsJack writes ...
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:
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 YeastsWhen 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 ..
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
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 ControlTemperature 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 ..
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).
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 ..
SettlingSettling 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 ..
The settling/clearing behaviour of yeast depends on the type of yeast you've used. From Brewing Yeasts (rehashed a bit)...
Jack writes ..
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
Ian writes ...
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 WashYou 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 YeastIt is possible to reuse the yeast several time. Ted Palmer advises :
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.
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).
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.
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...
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' BackRe-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 ..
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 ...
Freezing Yeast CulturesMatt reports
High Gravity FermentsIf 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 ....
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.
If your fermentation peters out early in the story, it could be due to a couple of reasons.
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 ..
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:
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: