Yeast and beer

Chlup, P. L., Bernard, D., Stewart, G. G. (2007). The disc stack centrifuge and its impact on yeast and beer quality. Journal of the American Society of Brewing Chemists, 65, 29-37. 

Primitive people very likely encountered vinegar-like Hquids in hoUows in rocks or downed timber into which berries or fmit had fallen. Wild yeasts and bacteria would convert the natural sugars to alcohol and acetic acid. Later, when eady peoples had learned to make wines and beers, they certainly would have found that these Hquids, unprotected from air, would turn to vinegar. One can postulate that such eady vinegars were frequendy sweet, because the fmit sugars would have been acted on simultaneously by both bacteria and yeast. Only since the middle 1800s has it been known that yeast and bacteria are the cause of fermentation and vinegar formation. 

Fermentation is carded out in two different, very distinct ways top fermentation and bottom fermentation. The governing principles are the same in both processes the chief differences are in the type of yeast and temperature employed, and consequently the method used for collecting the yeast after fermentation is finished. The alcohol content and, to a higher degree, the taste and stabiUty of the beer, are directly dependent on the normal progress of the fermentation. 

The "cheese effect" is a well-established phenomenon whereby an amine-rich food is consumed while the patient is being treated with an irreversible MAOI. Foods which cause such an effect include cheeses, pickled fish, yeast products (red wines and beers, including non-alcoholic varieties), chocolate and pulses such as broad beans (which contain dopa). It appears that foods containing more than 10 mg of tyramine must be consumed in order to produce a significant rise in blood pressure. Furthermore, it is now apparent that there is considerable variation in the tyramine content of many of these foods even when they are produced by the same manufacturer. Therefore it is essential that all patients on MAOIs should be provided with a list of foods and drinks that should be avoided. 

Well over 85,000 tons (76.500 metric tons) of yeast dry matter are produced in the United States alone each year. About 75% of this is in the form of bakers yeast, the remaining 25% represents about equal amounts of food yeast and feed yeast. This production issues from four types of manufacture (1) Bakers yeast is grown batchvvise in aerated molasses solutions. (2) Candida, utilis is obtained from wood pulp mill spent liquid. (3) K. fragiH.r is grown batchwise in cottage cheese whey, (4) Dried yeast is recovered as spent beer yeast. Worldwide production of all types of food and feed yeast is estimated at more than 450,000 dry tons (405.000 metric tons) per year. 

Malt Beer Grain Bed Yeast and Trub Total... 

The most important yeasts are strains of Saccharomyces cerevisiae, which are used in the manufacture of wine and beer and in the leavening of bread. 

Biomass (e.g., living micro-organisms such as lactic acid bacteria, wine and beer yeast, as well as extracts of these) ... 

Some yeasts and bacteria are able to produce different alcohols like ethanol and butanol as well as polyols like glycerin and 2,3-butandiol. These compounds- are used in drinks such as beer and wines, and also may be used in or as solvents, drugs, chemicals, oils, waxes, lacquers, antifreezing and antifoaming agents, precipitants, dyestuff, pomades, raw materials for chemical syntheses, motor fuels, and carbon sources for SCP production. These products are mainly synthesized from petroleum — derived materials like ethylene and acetaldehyde. However, because of the insufficient availability and high prices of the raw materials, the microbial production of alcohols has become an interesting area for many researchers. 

---