Guide to Yeast

Guide to Yeast

Yeast is the magical living organism that converts sugars into alcohol and makes beer what it is. Yeast can be purchased in various forms, two of the most common being dry packets and liquid "smack-packs". Brewer's yeast comes in two basic varieties, ale and lager yeast. Ale yeast is a top fermenting yeast and likes to live in temperatures ranging from 60°F to 75°F. Lager yeast are bottom fermenters and like to live in the cooler temperature range of 40-58°F. (When yeast is stored before and in between uses, it should be stored in a refrigerator.) Besides being an "ale" or a "lager" yeast, yeast come in many different "strains". Each strain has it's own characteristic of alcohol tolerance, flavor characteristic, optimal fermentation temperatures as well as a tendency to settle to the bottom of the fermenter after fermentation. Examples of different strains available from Wyeast include Kolsch, Scottish, German, British and Irish Ales, Czech Pilsner, American and Bavarian Lagers

Dry Yeast Assortment On the left can be seen several samples of dried yeast packets. (Note: Bread yeast should not be used for making beer.) Dried yeast is only suitable for beginner brewers as the yeast in dried packs is often old and may even be contaminated with wild yeast. Dried yeast costs less than a tenth of the price of liquid yeast, but as the old saying goes, you get what you pay for. To use dried yeast, hydrate it in 70°F water. Use of a yeast starter is recommended for all yeast prior to pitching into the wort. See below for instruction on using yeast starters.

Activated Liquid Yeast Pack On the right we have photos of a liquid yeast "smack-pack". The left photo shows a pack before activation with the right photo showing a side view of a fully activated pack. Liquid yeast packs contain pure strains of yeast. This purity insures a quality fermentation and is what make liquid yeast so much more expensive than the dried variety. A liquid yeast smack pack consists of a pure yeast strain isolated in a plastic bubble from a small quantity of malt extract. When the yeast bubble is burst by "smacking" the pack, yeast and malt mix, beginning the fermentation process. Smack packs tend to take about 2 days before swelling to about 2 inches thick. Once fully swelled, the yeast is ready to be pitched into a starter wort. For an excellent reference on yeast strains offered by Wyeast Laboratories check out their beer yeast list.

Use of a yeast starter prior to pitching the yeast into your beer's wort is highly recommended. An increased pitching rate leads to a more efficient fermentation and hence a better beer. For a 5 gallon batch of beer, a minimal 1 liter yeast starter should be pitched into the wort . Lee's Brewery uses a 1 liter flask with stopper and air lock for its yeast starters. (See photo, left.) To make a yeast starter, boil 1 liter of water and add to it 2 cups of light dry malt. Boil for 2-3 minutes longer and let the starter wort cool to 70-75°F. Once the starter wort has cooled, pitch the fully activated liquid yeast or hydrated dry yeast into the flask and agitate heavily. (Note: This also applies for pitching yeast into your beer's wort. Heavy agitation oxygenates the wort, providing the yeast cells with a source of oxygen they need for a healthy fermentation.) Fill air lock with vodka and seal flask. When the starter is actively fermenting, usually within 24-48 hours, it should be pitched into your beer's wort. You should try to pitch the yeast during the height of fermentation activity, don't wait until the activity has subsided.

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