Chemistry Reference
In-Depth Information
9.1.1.6
α
-Glucosidase
As can be expected, malt also contains an enzyme which forms, in a similar way as microbial
glucoamylase, glucose from maltose and isomaltose. It is called
α
-glucosidase and it has an
isomaltose effect.
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The pH-optimum is at 4.6, the temperature optimum at 45
◦
C.
9.1.1.7
Transglucosidase
A transglucosidase, belonging to the main class of transferases, is a microbial enzyme, from
for example
A. niger.
This enzyme is able to build up unfermentable dextrins from maltose,
as opposed to the starch decomposing enzymes discussed so far. From experience the process
of mashing and fermentation in distilleries is not affected yet by this enzyme, since in the
presence of yeast during the fermentation, there is no dextrin synthesis from sugar.
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9.1.2 Cellulases
Cellulases also have to be mentioned among the important technical enzymes for distilleries.
In fact this group of enzymes does not belong to the common distillery enzymes yet, but
it can be expected that cellulases will achieve an important position in this area in the
future. Exploratory tests have shown that the enzymatic decomposition of cellulose provides
a possibility means to increase alcohol recovery.
The interaction of several single enzymes is needed for the enzymatic hydrolysis of
cellulose. However, cellulose breakdown is as yet incompletely clarified.
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Several groups of
enzymes involved are defined and must be called 'cellulolytic systems' instead of 'cellulases'.
The C
1
-component of these systems does not have a hydrolytic effect but reduces hydrogen
bonds which stabilize the crystal structure of the cellulose in and between the β-1,4-glucan
chains. This creates additional reaction areas for the hydrolytic acting β-1,4-glucanases.
As a third component in a cellulolytic system, β-glucosidases are involved in cellulose
breakdown. β-Glucosidases widely differ in their preference for certain chain lengths of the
molecules. The final product of enzymatic cellulose hydrolysis is glucose.
Technical enzymes for saccharification of cellulose can be derived from several moulds.
The activities of those preparations in relation to native (crystalline) cellulose are, however,
relatively low. The optimum effects of these enzyme systems are achieved at pH 4-6 and at
60
◦
C,
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which is a convenient area for the mashing in distilleries.
9.2
ENZYMES IN WINEMAKING
9.2.1 Introduction
Wine is an alcoholic beverage made from the fermentation of fresh grapes or fresh grape juice.
Although other fruits such as apples and berries can be fermented, the resultant 'wines' are
normally named after the fruit from which they are produced (e.g. apple wine or elderberry
wine) and are generically known as fruit wines. The commercial use of the word 'wine'
(and its equivalent in other languages) is protected by law in many jurisdictions. According
to the 'Organization Internationale de la Vigne et du Vin' (OIV) 2005,
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worldwide wine
production, excluding grape juices and musts, is estimated to be 282 million hectoliters with
Europe accounting for 191 million hectoliters. More and more wine is being produced in
