In this episode, we're going to cover yeast. I'll describe to you what yeast is, and what it does. I'll describe the two forms that yeast is sold in. I'll review how best to use yeast, and we'll go over some basic controls of fermentation. I won't be covering the use of starters, re-hydrating dry yeast, any trouble-shooting, or the production of sour beers in this video. We'll save those topics for a later installment. This video is intended to be an introduction to yeast.
I want to begin by quickly describing what yeast is. Yeast is a living organism called Saccharomyces cerevisiae. This name means ''sugar eating fungus for beer,'' and that's exactly what yeast does, it eats sugars, and spits out alcohol and some by products. Yeast can only eat sugars found in wort, including simple sugars, maltose and maltotriose. The by products are sources of flavor in your finished beer. Once alcohol levels are too high, or sugar levels are too low, the yeast cells go to sleep, clump together, and fall to the bottom. This is called flocculation.
There are two main types of yeast in the world. The first type have been selected for by people for thousands of years, and are used specifically for beer. These are called brewer's yeasts, and include the two varieties of ale and lager yeasts. The second type is wild yeast. This is all the other varieties of yeast. Wild yeasts are everywhere. They are in dust, soil, fabrics, and carpets. Wild yeasts can create strange flavors, cloudy beer, and extremely dry beers. Sanitary practices will protect you against wild yeasts.
Brewer's yeast is available to you in one of two forms, either dry or liquid. Dry yeast obviously has very little water, and is much better suited for long periods of storage. Dry yeast can resist high and low temperatures. Unfortunately, there is not as good of a selection of dry yeast, and there are dead yeast cells present from the drying process. Liquid yeast comes suspended in a little bit of wort. This form is not intended for long storage, and must be used as soon as possible. It must be stored cool in your refrigerator. There are lots of varieties to choose from, and you can really flex your creative muscles by experimenting with different yeasts.
Now I want to share some keys to success when adding your yeast to wort, which we call pitching. First off, always pitch yeast into cool wort. You can cool your wort down in any number of ways, but never pitch yeast into wort that is warmer than 80 F. Always sanitize the yeast package by dipping in into sanitizer before opening it. After pitching, gently roll, or rock your sealed fermenter to mix the yeast and wort, and introduce air into the mixture. Because yeast is alive, it needs air to grow and work. Always use an airlock on your fermenter to keep unwanted wild yeasts and bacteria out of your beer.
To help keep wild yeast and bacteria under control, close any windows and turn off any fans to make sure nothing blows into your exposed wort. Don't vacuum or sweep the floor before you pitch any yeast, because this will also kick up critters that you don't want in your beer. Try to keep any pets away from the area that you brew in.
One package of yeast is usually enough yeast to ferment your beer. However, we recommend increasing the amount of yeast you pitch into beers that are above 1.050 starting gravity to two packages of either liquid or dry yeast. This will ensure a faster start to your fermentation, a more vigorous fermentation, and a cleaner, less sweet finished beer.
Let's move on now, and talk about how to use dry yeast. Re-hydration is a way of waking-up your dry yeast. We don't recommend that you re-hydrate your dry yeast. This is an easy opportunity for critters to get in, and its also really easy to kill your yeast if you don't control the temperature carefully. Sprinkle your yeast on top of your cool wort and cover it. Come back in 15 minutes and give your sealed fermenter a good rocking to mix the yeast up and add air.
Liquid yeast is the easiest of the two forms to pitch into your wort. The two main liquid yeast companies, Wyeast and White Labs, both suggest that you add their yeast directly to your wort. Be sure to let the yeast warm up to room temperature before pitching. Follow the directions on Wyeast packages on how to break-open the enclosed nutrient pouch. Be sure to check the expiration dates on the packages, and never use old yeast. Store your liquid yeast in a refrigerator before your brew-day.
Because yeast is alive, it has specific tolerances for it to survive. Yeast is somewhat tolerant to the wonderful toxin known as alcohol. Some yeast varieties are more tolerant, and can make beers that are stronger. Some yeasts can't handle very much alcohol, and they wimp out, making a sweeter beer. Keeping the temperature controlled during fermentation will keep your yeast happy, and they will make clean, good tasting beer for you. Warmer temperatures, above 75 F, will make beers that have more fruity, spicy, or solvent-like aromas. Cooler temperatures, below 60 F for ales and below 50 F for lagers, can make beers that are not fully fermented, or have vegetable and buttered popcorn aromas. In the most general terms, ales should be fermented at 65 F, and lagers should be fermented at 50 F. You can place an inexpensive liquid crystal thermometer on your fermenters to keep track of your temperature.
The best way to control temperature is with a refrigerator equipped with a temperature controller. This is expensive and is a bit more advanced. Always place your fermenter in a room in your house that does not have wild swings in temperature, such as a basement or bathroom. Try to use a room in the center of your house. An easy way to keep fermentations cool is to wrap your fermenter in a wet old t-shirt or towel. As the water evaporates, it cools the fermenter. Be sure to check the t-shirt or towel to make sure they stay wet. This can drop the temp of your fermenter by at most ten degrees F. If your fermentation is too cool, the best way to warm it is with an electric fermentation heater, such as one of these pictured here. You can also simply move the fermenter to a warmer spot. Do not expose your fermentations to sunlight to warm them.
Looking back on what we've covered, you should now have an understanding of what yeast is and what it does. You know what types of yeast are out there, and how they are available to you to purchase. You know how to use yeast, and how to keep it happy during your fermentation.