In addition to clarification (i.e., removing yeast), beer must display physical stability with respect to haze. Colloidal instability in beer is caused mainly by interactions between polypeptides and polyphenols. Amino acids make up polypeptides which, in turn, make up proteins. Polypeptides and polyphenols combine to produce visible haze that reduces a product's physical shelf life. Reducing the levels of one or both of the precursors using suitable stabilizing treatments will extend physical stability.
Over the years a number of chillproofing agents have been used to enhance beer haze stability (i.e., reduction of beer proteins and/or polyphenols). Each agent has its pros and cons, and many are used in combination, to suit the brewers own requirements and plant constraints.
Proteolytic enzymes are prepared from papain or pepsin and act on proteins by degrading them to smaller molecules.
Tannic acid is traditionally used to remove haze material and is still employed in Germany.
Hydrolysable tannins are also used to precipitate proteins. Beers treated with hydrolysable tannins show excellent colloidal stability as well as acceptable clarity values (47).
Silica gels are effective chillproofers in that they remove high-molecular-weight proteins responsible for haze formation without detriment to foam stability.
Bentonite, an insoluble alumino-silicate, can also be used as a protein adsorbent, but it is beset with many disadvantages.
Polyvinylpolypyrrolidone (PVPP) is used to absorb polyphenolic materials. Part of PVPP's success as a beer stabilizer stems from the fact that it mimics the action of proteins by combining with polyphenols at a greater magnitude than proteins (41).
Brewhouse Procedures Used for Stabilizing Beer
It should be noted that neither, stabilization or clarification or for that matter filtration are end-all measures for correcting mistakes made in the production process. Therefore, from the very beginning, it is necessary to perform stringent quality control paying attention from the selection of raw materials all the way through to conditioning, filtration, and packaging. Some of the techniques that a brewer can employ to achieve colloidal stability are as follows:
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