Beer Adjuncts(selected excerpts)
Adjuncts are nothing more than unmalted grains such as corn, rice, rye, oats, barley, and wheat. Although adjuncts are used mainly because they provide extract at a lower cost (a cheaper form of carbohydrate) than is available from malted barley and because they are readily available, other definite advantages are also achieved.
Adjunct use results in beers with enhanced physical stability, superior chill-proof qualities, and greater brilliancy. The greater physical stability has to do with the fact that adjuncts contribute very little proteinaceous material to wort and beer, which is advantageous in terms of colloidal stability. Rice and corn adjuncts contribute little or no soluble protein to the wort, while other adjunct materials, such as wheat and barley, have higher levels of soluble protein. Except for barley, adjuncts also contribute little or no polyphenolic substances.
Adjuncts can be used to adjust fermentability of a wort. Many brewers add sugar and/or syrup directly to the kettle as an effective way of adjusting fermentability, rather than trying to alter mash rest times and temperatures.
Adjuncts are often used for their flavor contribution. For example, rice has a very neutral aroma and taste, while corn tends to impart a fuller flavor to beer. Wheat tends to impart a dryness to beer. Semi-refined sugars add flavor to ales that has been described as imparting a luscious character. Adjuncts will also alter the carbohydrate and nitrogen ratio of the wort, thereby affecting for formation of byproducts, such as esters and higher alcohols.
Adjuncts are used for color adjustment, as in the case with dark sugars. On the other hand, adjuncts such as rice and pure starches and sugars are used to dilute malt colors to produce lighter colored beers.
Some adjuncts are used for their chemical properties; e.g., raw barley and wheat, which contribute glyco-proteins to enhance foam stability (24). Other adjuncts, low in protein, are used to improve colloidal stability since they will dilute the amount of potential haze-forming proteins.
Finally, the use of adjuncts can result in increased brewing capacity, reduced labor costs, improved hot and cold breaks, and shorter brewing cycles.
As is so often the case, benefits in one area are offset by problems in another. If the level of adjuncts used is too high, the brewer runs the risk of producing wort with insufficient insoluble nitrogen for yeast growth.
The proportion of adjuncts used varies from 10 to 30% in Europe, to 40 to 50% for some U.S. brewers, to as high as 50 to 75% in certain African countries (22). Although not usually practiced by brewers, adjunct levels up to 100% of total grist composition can be used, but will require the addition of exogenous enzymes (24). However, in certain countries, for example Germany, malt is the only permitted source of fermentable extract because of the German purity law or "Reinheitsgebot."
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