Beer - The Right Yeast Is Critical
Yeast cultures found in clay pots dating back thousands of years have been revived and have allowed some gourmands to experience the very unique tastes of the beers and breads of ancient history. Some yeasts in common everyday use date back more than a century, such as the famous San Francisco sourdough yeast which was started in the Gold Rush days.
In the past, dry yeast was the only type available to home brewers. Today, yeast is available in several forms. In general, you can buy dry yeast, liquid cultures, or slants. Although the quality of dry yeast is much improved today, liquid cultures offer some advantages over dry. Dry yeast often contains wild yeast and bacteria. Also, it is typically only available in two different varieties, ale and lager. Liquid yeast is not only cleaner, it allows for more variety. Liquid cultures offer the brewer the chance to choose a strain with characteristics suited to a particular beer style. Cultures on slant also offer variety, but should only be obtained from a reputable source to be certain they are free of contaminants. Slant cultures also require at least some knowledge of microbiological techniques. Thus, their use is a bit more involved.
Yeast in any form should be clearly labeled as to the type of yeast and should also include an expiration date. It should always be stored in the refrigerator. For best results, only buy yeast that has been stored properly and is within date. Often, liquid cultures that are beyond their expiration dates can be obtained for a reduced price. These can give good results for experienced brewers if handled properly but, beginning brewers would be better off using the freshest cultures they can get.
Unless you plan to brew within a few days, store yeast in the refrigerator and don't open the package until needed. Liquid cultures typically don't contain a sufficient amount of yeast for fermenting 5 gallon batches and thus, you will need to prepare a starter for best results. Starting with an insufficient amount of yeast can lead to long lag times, incomplete attenuation, contamination, and flavor problems in the finished beer. Some suppliers now carry larger packages that do contain the proper amount of yeast for a 5-gallon batch. If you want to use liquid cultures but don't know how or don't want to bother with preparing a starter, these are an excellent choice.
Because ingredient quality can greatly influence your finished beer, selecting good quality ingredients and maintaining their integrity throughout storage is of the utmost importance. When you buy from a reputable supplier, heed the advice of knowledgeable people whom you trust, and know what to look for, you are off to a good start. The other part of the equation is to maintain the quality of your ingredients once you get them home. Store your brewing ingredients properly to get the most for your money and the best tasting beer. Giving some attention to ingredient quality will pay big dividends in better quality beer.