TECHNOLOGY AND MICROBIOLOGY OF HOME BREW

Spread the love

Generally, brewed products including beer and other beverages are made from malted grains or other starches and distilled spirits are made by the distillation of fermented products such as brews and wines. Commodity alcohol is used as a gasoline additive and industrial solvent. The amateur brewer can make many kinds of beer at home, from English bitters and India pale ale to German bock and Russian Imperial stout. The necessary equipment and supplies, including yeast, can be purchased from a local beer and winemakers shop.

The brewing process can be divided into three basic stages: (1) making the wort, (2) carrying out the fermentation, and (3) bottling and aging. The character of a brew depends on many factors: the proportion of malt, sugar, hops, and grain; the kind of yeast; the temperature and duration of the fermentation; and how the aging process is carried out. The fermentor (i.e., the vessel in which the fermentation takes place, usually made of stainless steel) itself consists of a 20-liter (5-gallon) narrow-necked glass jar that can be fitted with a tightly fitting closure. To brew a good quality beer, it is essential that everything be sterilized that comes in contact with the wort. This includes the fermentor (i.e., the fermentation vessel), tubing, stirring spoon, and bottles. An easy procedure is to use a sterilizing rinse consisting of 50-60 ml of liquid bleach in 20 liters of water. Soak the items for 15 minutes and then rinse lightly with hot water or dry air.

  1. Making the wort: In commercial brewing, the wort is made by extracting fermentable sugars and yeast nutrients from malt, sugar, and hops. Many home brewers make their own wort from malt, but a reasonably satisfactory beer can be made with hop-flavoured malt extract purchased ready-made. Malt extracts come in a variety of flavours and colours, and the kind of beer depends on the type of malt extract used. A simple recipe for making the wort uses 2.25-2.75 kg (5-6 lb) of hop-flavoured malt extract and 20 liters of water. The malt extract and 5-6 liters of water are brought to a boil for 15 minutes in an enamel or stainless steel container. The hot wort is then poured into 14-15 liters of clean, cold water that has already been added to the fermentor. After the temperature has dropped below 30oC, the yeast is added to initiate the fermentation.
  2. Carrying out the fermentation: Add two packs of fresh beer yeast to the cooled wort and cover the fermentor with a rubber stopper into which a plastic hose has been inserted. The hose is directed into a bucket containing water. During the initial 2-3 days of the fermentation, large amounts of CO2will be given off,which will exit through the hose. The water trap is to prevent wild yeasts or bacteria from the air from getting back into the fermentor. After about 3 days, the activity will diminish as the fermentable sugars are used up. At this time, the rubber stopper and hose are replaced with an inexpensive fermentation lock. The fermentation lock, which can be purchased at the home brew store, prevents contamination while permitting the small amount of gas still being produced to escape. Allow the beer to ferment for 7-10 days at 10-15oC or higher.
  3. Bottling and aging: The fermentation should be allowed to proceed for the full 7-10 days, even if the vigorous fermentation action ceases earlier. By this time, most of the yeast should have settled to the bottom of the fermentor. Carefully siphon the beer off the yeast layer, allowing the beer but not the sediment to run into sanitized glass beer bottles. The bottles used should accept standard crown caps, and new, clean caps should be used. Before capping, add three-quarters of a teaspoon (but no more) of corn syrup to each 350- to 465-ml (12- to 16-ounce) bottle. Once the bottles are capped, turn each one upside down once to mix the syrup and then allow the beer to age upright at room temperature for at least 7-10 days. After this aging period, the beer may be stored at a cooler temperature.

All homemade beer will improve if it is allowed to age for several weeks. Aging tends to make beer smoother and remove bitter components. Using the same basic production equipment, several different types of beer can be made, each with its own distinctive taste and character. Dark beers, which typically contain more alcohol than lighter beers, require more malt for their production and are usually brewed from a combination of different malts such as those obtained from darker varieties of grain or those that have been roasted to caramelize the sugars and yield a darker colour. A typical American-style light lager contains about 3.5% alcohol (by volume), whereas a Munich-style dark contains 4.25% alcohol, and bock beers contain about 5% alcohol.

The trend towards “individuality” in beer is evident not only by the growing number of home brewers, but also by the fact that major brewers in the United States are feeling more and more competition from new, usually very small, breweries called microbreweries. Although total production by a microbrewery may pale by comparison to that of a major brewer, the products themselves often have their own distinctive character and local appeal. Part of these differences has to do with the smaller scale on which the brewing takes place but also with the use of different sources of ingredients, water, yeast strains, and brewing procedures.

Further reading

Madigan M.T., Martinko J.M., Dunlap P.V and Clark D.P (2009). Brock Biology of Microorganisms, 12th edition. Pearson Benjamin Cummings Inc, USA.

Be the first to comment

Leave a Reply

Your email address will not be published.


*