Agriculture Reference
In-Depth Information
mash of many beers, especially American Pilsner types. They are used mainly for
reasons of economics (cheaper material for fermentation) or for fl avour
moderation, but are not known to infl uence foam stability to any great extent.
Other cereal adjuncts, used to produce certain European beers, are more fl avour-
active and are defi nite foam enhancers. Examples include unmalted triticale (a
wheat x rye hybrid), when used as 25% of the grain bill (Glatthar et al. 2003),
malted or unmalted wheat (Depraetere et al. 2004) and malted rye (Hornsey
1999). In contrast, other adjuncts, such as oats, have a defi nite negative effect
on foam retention, probably because of higher levels of lipids compared with
other cereals. Apart from cereal adjuncts, hops and hop products (see Section
16.2.2) have a positive infl uence on beer head retention, although the synthetic
reduced α-iso acid products are superior in this respect to natural iso acid products
(Wallin et al. 2010). The use of isinglass fi nings (see Section 16.3.1) is also
benefi cial.
16.3.4 Enzymes
Enzyme preparations are widely used throughout the alcoholic drinks industry,
particularly in brewing (Table 16.19). They are either extracted from the industrial-
scale fermentation broth of fungi or bacteria, or are extracted from higher plant
materials (e.g. bromelain from pineapples). Their use falls into three major
categories, with a certain amount of overlap:
Starch liquefaction/saccharifi cation agents
Clarifi cation agents
Flavour/colour enhancement agents.
Starch liquefaction/saccharifi cation agents cleave α (1→4) and/or α (1→6)
glycosidic linkages of starch polysaccharides or oligosaccharides to give smaller
soluble oligosaccharides or fully fermentable sugars, such as maltose or glucose
(Fig. 16.13). These enzymes ( α -amylase, β -amylase, pullulanase and glucoamylase
from a variety of fungal or bacterial sources) are used extensively in brewing,
particularly in the production of low carbohydrate beers and beers from low malt
(high adjunct) wort such as that with high maize or sorghum content (Urias-Lugo
et al. 2005). A highly fermentable cereal wort is also attractive to distillers because
of the increased ethanol yield.
Clarifi cation enzymes include β -glucanase, xylanase and proteases, which
hydrolyse β (1→4) and β (1→3) glucosidic, β (1→4) xylosidic and peptide linkages,
respectively, thus removing hazes caused by β -glucans, arabinoxylans and xylans in
beer (and those caused by β -glucans in wines made from grapes infected with
Botrytis cinerea ) and protein or protein-polyphenol hazes in beer and wine. The
proteases are of bacterial, fungal or higher plant origin and are generally
endoproteases, which break up large proteins into smaller peptides and amino acids.
Pectin methylesterase (see next paragraph) is a clarifying agent used in the
keeving (défécation) process of cidermaking, especially in France. The pectic
acid formed from the hydrolysis of the methyl ester groups of pectin forms a gel
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