Introduction to Alcohol Production
From the pages of HomeDistiller.org
Selections by CS
Words of Wisdom
How do I get or make a still?
How do I run a Reflux / Fractionating Still?
Can I run my car on it?
How do I convert between gallons and litres and ....
Distillation - Introduction
Distillation is simply the collection of the ethanol (alcohol) that was made during fermentation. It is the process of heating up the liquid so that it becomes a vapour, then condensing the vapour on a cold surface & collecting it. This works due to the fact that the vapour will contain more alcohol than the liquid it is boil off, because of the different physical properties of water and ethanol. We can then make the vapour more pure by letting it be "stripped" of its water content by passing it up through a packed column which has some condensed vapour running back down through it as liquid. When the two pass each other, the vapour will absorb alcohol from the falling liquid, and the liquid will take some of the water from the vapour. Distilling doesn't "make" the alcohol, nor turn some of it "bad", or into something that will blind you; its only collecting the alcohol that was made during fermentation.
Fermentation - 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 beginning 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. [Latter url corrected via Wayback Machine 4/1/14 CS]
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 yeast. 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 re-initiate 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.
[snip re fusels - CS]
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 grams 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.
There's 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. That's because I'm only ever doing sugar-water washes for pure neutral spirits, and I find it easy, convenient, 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:
- There is no more bubbles coming to the surface.
- There is no more hissing noise inside the vessel.
- Gravity of the mash sinks equal or below 1.00
- The mash does not tast sweet anymore.
- 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 17-19° Brix (1.070-1.079 s.g.), and of course, work sanitarily. That's all.
Words of Wisdom
An interesting topic on the newsgroup was one of "if there were just three bits of advice to pass onto someone starting distilling, what would they be ?" [Selected – CS]
Patience + Persistence = Results
- read every word of "homedistiller.org" at least three times.
- wait till the enthusiasm wears off a little prior to getting confused/asking questions.
- ease into it slow & take notes (just like your building your first customized harley)
Fermentation. Sanitize everything involved in the fermentation process. Boil all of the water used to make a mash. Perform aeration (aquarium pump & stone) prior to adding yeast. Use enough yeast. Keep fermenting wash below 30 C, 20 to 25 is better yet.
- Develop a plan to accomplish your goals.
- Ask questions from people who have done it before. Then ask some more questions. 3 people can read a question written by somebody else and see three whole different ways to answer it.
- Avoid buying a whole bunch of expensive fancy equipment until you know that this hobby is what you expected it to be. Lots of equipment can be substituted with less expensive (or free) items. Ask what equipment is absolutely necessary.
Do quite a few sugar washes before attempting grain/mollasses type washes.
Read as much as you can from a wide variety of sources. Get a good book or two with illustrations of how to build and operate a still. Build a small one first, not too large. You can practice your workshop skills. Join a club or news group and LISTEN to all opinions, ask questions, and after awhile, filter out the stuff that you don't believe fits in with the your accumulated experience. Believe in your own abilities, and get on and do it.
How do I get or make a still ?
Reflux stills can be made from plans on the net, or bought from several manufacturers. For reflux still plans see
- There are 100's of designs in the reflux section, of the forums:
- The photos section for Offset head designs, and this section for general reflux stills.
- Alex's designs at http://groups.yahoo.com/group/Distillers/files/OFTS/
- Ian Smileys "Making Pure Corn Whisky" at http://www.home-distilling.com , with full design details.
- For an excellent book on all aspects of still design, see "The Compleat Distiller" at http://www.amphora-society.com
- See the list of "web resources" below for links to sites selling ready-made stills.
- For fuel alcohol stills see the Mother Earth Alcohol Fuel Manual at http://journeytoforever.org/biofuel_library/ethanol_motherearth/meToC.html, and the The Manual for the Home and Farm Production of Alcohol Fuel by S.W. Mathewson at http://journeytoforever.org/biofuel_library/ethanol_manual/manual_ToC.html. Regarding the choice of heating for the still - if you have 240V available it is usually easiest to control & safer (particularly with internal elements). Gas can be used, but more care is needed to keep the collection container further away and not letting it overfill.
- For more details on design, see Designs and Reflux Design
How do I run a Reflux / Fractionating Still?
See How to Use a Reflux Still for details +/or variations. Also, see this post from the HD forum: LM Still running instructions and a very good how to thread on running an older CM type still is found at: Running a brewshop CM still
Can I run my car on it?
You can run your car on alcohol over about 80% purity. Because any water present will seperate out in the presence of the gasoline (and become a problem), you either need to exclusively use the alcohol, or dry it right out (eg 99%+ purity) if using it to mix with gasoline. See Steve Spences site for more details, the Mother Earth Alcohol Fuel manual, or the The Manual for the Home and Farm Production of Alcohol Fuel. In addition, in the USA, you can get a "small fuel producer" permit, which allows small scale distilling for "motor fuel" purposes. A nice advantage is that they don't require denaturing for "fuel" used on the premises. [Editor's note: This is out of date; see further on this site. CS]
How do I convert between gallons and litres and ....
To convert between SI & Imperial units, multiply the first unit by the conversion factor to get the second. Divide back to do it in reverse .eg 1L = 0.264 US gal, so 20 L = 20 x 0.264 = 5.28 US gal, and 20 US gal / 0.264 = 75.76 L
1 L = 0.264 US gal = 0.221 UK gal
1 L = 1.057 US qt = 0.880 UK qt
1 kg = 2.204 lbm = 32.15 oz (troy) = 35.27 oz (av)
deg F = ((9/5) x deg C )+ 32
1m = 1000 mm = 39.37 inch = 3.28 ft = 1.09 yd