Accelerated fermentation of lager beer

#In the specification that follows, attention is directed to various references by number. A list of the references is included at the end of the specification.

#Historically, there are two general methods of fermenting malt beverages. For the production of ale-type beers, a top-fermentation process is used which utilizes a species of yeast which tends to rise to the top surface of the fermenting wort. The temperature during top-fermentation is conventionally regulated at about 15.degree.-20.degree. C (58.degree.-68.degree. F) throughout the most active period of fermentation. For the production of lager-type beers, a bottom-fermentation process is used which utilizes a species of yeast that remains more or less uniformly suspended throughout the fermenting wort during active fermentation, by natural agitation created by ascending CO.sub.2 bubbles (25), then settles to a more or less compact layer on the bottom of the fermentation vessel as fermentation reaches completion. The temperature during a bottom-fermentation is conventionally regulated at about 10.degree.-15.degree. C (50.degree.-58.degree. F) during active fermentation (1, 2).

#It is well known that if the temperature during bottom-fermentation is increased, the fermentation can be accelerated and the fermentation time substantially shortened. However, it is also known that the beer so obtained has an undesirable winey flavor which is not typical of a lager-type beer (3-5).

#This example is a control. In it, conventional fermentation conditions are used. These conditions give an acceptable raw beer. Note that a total of 196 hours were required to complete the fermentation.

#One hundred liters of the conventional wort, aerated and pitched at about 10 million cells/cc, were fermented at a constant 57.degree. F with low level agitation (33 rpm) and no CO.sub.2 overpressure. The yeast concentration reached a maximum of 5.77 grams/liter (dry weight basis) and 60 million cells/cc. About 160 hours were required to ferment the available carbohydrates and an additional 36 hours (approximately) were required to reduce diacetyl to 0.10 ppm. The volatiles concentration expressed as the total area of the component peaks from the gas-liquid-chromatographic (GLC) analyses, relative to the peak area of an internal standard taken as 100, was 904 (by analyzing CS.sub.2 extract of the beer) and 648 (by analyzing headspace vapors over the beer).

#This example is another control. It is like Example 1, except that the temperature was increased to 72.degree. F, to determine whether the increased temperature would shorten fermentation time while giving an acceptable product. As shown, the time was decreased, but the product was unacceptable.