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February 24, 2014

Fermentation and Yeast - Beer, Wine, Spirits and Fuel Alcohol

Yeast is the single most important ingredient in the process of making beer, wine, spirits, and even fuel alcohol. Why? Well, remember, the process of distillation does not make alcohol, it only concentrates alcohol to increase the proof. Alcohol is made during the fermentation process, and fermentation is made possible by combining two critical ingredients: sugar and yeast. So without yeast, there would be no beer, there would be no wine, and there would be no whiskey. 

Aside from making the very existence of distilled spirits and other types of alcohol possible, yeast have a big impact the flavor. Much of the aroma and the taste of these products results from the fermentation process. In this article we'll discuss the different types of yeast that brewers and distillers use to make their products. We'll also talk about the fermentation process itself.

What is Yeast, Why is It Important?

Yeast is a single-celled fungus, technically speaking. The cells are egg-shaped and can only be seen with a microscope. Yeast is a critical ingredient in most types of bread, beer, cheese, wine, and whiskey (basically all of the food and drinks that make life worth living). Yeast is more or less one of God's greatest gifts to humanity.

How Does Yeast Make Alcohol? 

Yeast cells eat simple sugars found in whiskey mash and produce carbon dioxide and alcohol as waste products. That's right, the glass of beer next to your keyboard is somewhere in the neighborhood of 5-10% yeast piss. Your glass of whiskey, it's more like 40-50%. Yummy, huh!

    What basic conditions do yeast need to thrive? 

    • Proper pH - The pH of the mash should be adjusted to between 4.0 and 4.5 prior to fermentation.

    • Correct and Even Temperature - Temperature will depend on the yeast strain that you are using. Try and ferment in the recommend temperature range suggested by the manufacturer and keep the temperature as steady as possible.

    • Nutrients - Yeast is a living organism and all living organisms need nutrients. All grain batches made with malted barley, rye, or wheat, geared to produce a starting wash alcohol of 5-10% should contain enough nutrients to allow yeast to do their thing without producing any nasty smelling or tasting byproducts. However, if you're not using much malted grain and/or are shooting for a starting alcohol higher than 10%, you might want to add fermentation nutrients.

    • Oxygen - Yeast also need plenty of oxygen to get things moving at the beginning of the fermentation process. Always aerate your mash before adding yeast. Some folks use aquarium stones and air pumps, while other folks just dump the mash back and forth between 2 buckets (so it foams and bubbles up) a dozen times or so. We prefer the latter method because it's simple, although somewhat messy.

    What defects can result when yeast are stressed?

    Yeast creates two major byproducts during fermentation - ethanol (alcohol) and carbon dioxide. In general, when yeast is treated well and is given good conditions to work in, it will produce good results. However, if yeast gets stressed, it can produce an excessive amount of undesirable chemical compounds and flavors, such as the following:

    • Fusel Alcohols - This group of chemical compounds provide nothing beneficial in terms of aroma or taste, but they will give you a hell of a hangover. Although fusel alcohols can be removed during distillation by making a good tails cut (see our article on making cuts), distillers try to keep the overall amount of fusel oil produced during fermentation to a minimum. To do this, they ferment their mash as close as possible to the temperature recommended by the yeast manufacturer. They also, keep the temperature as steady as possible. Even slight temperature swings can cause large differences in production of "metabolic by-products" (AKA: the nasty stuff).

    • Sulfur - Unless distillers want their whiskey to taste like rotten eggs (which they don't), they try to reduce / remove as much sulfur from their wash and final product as possible. Sulfur gets naturally scrubbed out of the wash by CO2. The more vigorous the fermentation, the more sulfur gets removed. So, they make a yeast starter to help your yeast get moving. Also, they make sure to keep fermentation from dropping too low and see to it that your little yeasties have enough nutrients to do their thing. Copper is also great at removing sulfur.

    • Acetaldehyde - In beer it smells like green apples. In general, it contributes to hangovers! Acetaldehyde exists in high concentrations when mash is not allowed to finish fermentation and when a wash is oxygenated and allowed to sit after fermentation is finished. Either way, Acetaldehyde has a very low boiling point and it is very unlikely that you'll ingest it...unless you drink the foreshots...which you should NOT do.

    • Phenols - Phenols introduce a plastic / band-aid / medicinal taste to the wash. To avoid, Avoid using overly chlorinated water (by using filtered water or bottled water for your mash). Also, be careful to sterilize your mashing and fermentation equipment and to cover your mash and use an air-lock during fermentation. Wild yeast contamination can contribute to the presence of phenolic compounds.

    • Overly Sweet - If your wash is overly sweet, may have ended up with a high concentration of non-fermentable sugars after mashing due to an incorrect mash temperature. You may not have let the mash sit long enough during fermentation, meaning that the yeast did have enough time to convert all of the fermentable sugars in to alcohol. This will result in a low alcohol yield, overall.

    • Overly Dry - If your wash has no sweetness or taste at all, your yeast might have powered through the mash and eaten all of the good stuff themselves. We've noticed that champagne yeast and distillers yeasts have a tendency to do this. 

    What Types Of Yeast Are Used To Ferment Mash? 

    Yeast selection is very important as it will greatly impact your final results. You want to make sure you are getting a complete fermentation without any off flavors. Select a yeast that can handle the amount of alcohol in the mash as well ferment in the appropriate temperature range of your mash. There are plenty of distillers yeasts out there, but theyr'e not always easy to get your hands on. Here is a list of more common yeasts that we have had good luck with over the years.

    • Ale Yeast - Danstar Nottingham ferments well between 57 to 70. This is a great yeast strain for winter fermenting especially those who ferment in their basements. We have had great results using this with our rye whiskey mash recipe.

    • Wine Yeast - Lavlin EC-1118 ferments well between 50 and 86F and has a high alcohol tolerance. This strain is great for sugar shine with a high starting ABV.

    • Turbo Yeast - We don't recommend using any type of turbo yeast with added nutrients. The nutrient content is generally way too high and the yeast end up dying off before eating all of the nutrient chemicals (meaning that there will still be chemicals present in your final product). The one advantage of turbo yeasts is that they ferment very quickly. So, if you want to make a BAD whiskey FAST, this is the way to do it. If you want to make GOOD whiskey, don't use turbo yeasts. 

    • Generic Distillers Yeast - Generic distillers yeasts such as Super Start work well, but don't always produce great results. Moving forward, we will be testing additional yeasts, but for the time being we actually prefer even bread yeast to generic distillers yeasts. You can find a lot more info on this topic in the article we did on The Best Yeasts For Distilling.

    • Bread Yeast - .This has been our favorite over the years especially with our corn whiskey and our rum mash recipes. Bread yeast leaves a nice flavor behind with these recipes because it does not (in theory) ferment as low as the other yeast strains. Please read our article on how commercial spirits are made for more information on bread yeast.

    • Yeast Nutrients - These can be purchased at any home-brew shop. They provides the yeast with necessary nutrients to help yeast cells bud and multiply to get fermentation underway. These are extremely useful when making a high gravity sugar wash, but be aware, excessive use of nutrients may contribute off smells and taste to your final product.

    How To Tell When Fermentation Has Finished?

    Read the following articles on this subject for more information:

    How To Know When Fermentation Is Finished Part 1

    How To Know When Fermentation Is Finished Part 2

    How To Use a Hydrometer

    • I have read and listened to a lot of videos trying to find out how much yeast to add to lets say a 4 gal. mash sugar mix , still do not know. I have used highly active bread yeast and distillers yeast. Can you help with each?

      Posted by jim Spradlin on April 28, 2014
    • Lot of info. Solid read making good food for thought, also your links are great, thanks.

      Posted by Terry on February 28, 2014

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