No abstract available.
Normal all malt wort carbohydrate composition (c. 12% monosaccharides, 5% sucrose, 47% maltose, 15% maltotriose and 25% higher saccharides) can be obtained from grists containing up to 50% of adjuncts (rice, corn grits, wheat starch, sorghum, barley meal): above 50%, added enzymes are needed. Little is known of the consequence of variations in the composition of fermentable carbohydrates of wort, but the pattern of flavour volatiles is little affected whether the main wort sugar is maltose, sucrose, glucose or fructose. The unfermentable dextrins may not be important wort constituents, except that they represent a loss of raw materials, although they may contribute to the foam, body and carbon dioxide retention of beer and act as flavour carriers and protective colloids. The adverse effects of beta glucans in worts and beers may be enhanced by using cereal adjuncts, especially barley, since the beta glucanase activity in the mash is diminished and added beta glucanase may be beneficial. Different adjuncts cause little change in the amino acid composition of worts: this and the total content of alpha amino N depends on the proportion of malt in the grist and yeast growth suffers only when the wort contains less than 150 mg of alpha amino N/litre. Worts from grists with high proportions of adjuncts yield beers with high contents of vicinal diketones and acetohydroxy acids, but warm storage for 1 to 3 days after fermentation in the presence of yeast reduces these compounds to acceptable levels. The use of low protein adjuncts (pure starch, refined grits) dilutes all malt derived nitrogen compounds, including those of higher MW, so that the resultant beers may be less prone to throw haze, but have poorer foaming properties and a lighter flavour. Wheat and barley contribute some protein to beer and so improve its foam, while adversely affecting its colloidal stability. Too little material of high MW may be extracted from corn grits and rice with 8 to 10% protein appreciably to supplement the contribution made to this fraction by malt. In adjunct brewing, worts may be richer in lipids because they clarify less well. Thus, yeast viability problems associated with lipid deficiency are only likely to occur when sugars and syrups are used. Low wort lipid contents can also lead to estery flavours and gushing, while high contents can cause instability of foam and flavour. Little is known of the influence of brewing with adjuncts on the polyphenols, nucleic acid derivatives, vitamins and mineral constituents of worts and beers.
Keywords: adjunct brewing composition survey wort