Brewing beer involves microbial activity at every stage, from raw material production and malting to stability in the package. Most of these activities are desirable, as beer is the result of a traditional food fermentation, but others represent threats to the quality of the final product and must be controlled actively through careful management, the daily task of maltsters and brewers globally.
The purpose of brewing is to convert a starch source into a sugary liquid called wort and to convert the wort through the fermentation process effected by yeast into the alcoholic beverage. There are several steps in the brewing process, which include malting, milling, mashing, lautering, boiling, fermenting, conditioning, filtering, and packaging.
Brewing begins by crushing the malted grain between iron rollers. The grist is then mixed with warm water until it forms a mash of porridge-like consistency. Then supplementary grains are added, and the temperature of the mash is raised from 38 °C to 77 °C, at a rate that allows time for the various enzymes to act.
There are three main fermentation methods, warm, cool and wild or spontaneous. During fermentation, the wort becomes beer in a process where the yeast converts sugar into alcohol and carbon dioxide. This requires a week to months depending on the type of yeast and strength of the beer.
Larger brewing companies, tend to manage their own in-house strains of yeast, including the storage of master cultures. Back-ups of these organisms are deposited with third parties. Storage of cultures in liquid nitrogen is deemed preferable in terms of survival, shelf life, and genetic stability compared to storage on agar, in broth, or by lyophilization.
Brewing process
