Brewing with enzymes - Enzymes in Food Technology - page 180

The first step is mashing at 50 ◦ C. At this mashing temperature, the proteolytic enzymes
(carboxypeptidase, amino peptidase and dipeptidase) together with endo-β-1,4-glucanases
and pentosanases are most active. With an increase in mash temperature from 50 ◦ Cto63 ◦ C,
the viscosity increases rapidly at 58 ◦ C. This temperature of viscosity increase is noted

as being the point of the gelatinization of the barley starch (gelatinization temperature).
The most frequently reported gelatinization temperatures for many bulk samples of normal
barley starch lie in the range 53-58 ◦ C. During gelatinization, the starch granules take up
warm water, soak and swell, causing a rapid increase in viscosity. Amylolytic enzymes
(α- and β-amylase) can therefore act on this accessible starch substrate. Heating causes
inactivation of the proteases and β-glucanases. Following this, the mash temperature is
maintained at 63 ◦ C. Due to the action of β-amylase, maltose production continues. Further,
enzymatic breakdown of the gelatinized starch occurs due to the combined action of the α-
and β-amylases. The mash temperature is then raised to 70 ◦ C; β-amylase is less active at this
point. Enzyme inactivation is an interaction between time and temperature. With an increase
in time at temperatures

∼

70 ◦ C, β-amylase is inactivated. The α-amylases further break down
the gelatinized starch and high molecular weight dextrins into low molecular weight dextrins
and glucose. The temperature is then raised to 78 ◦ C where α-amylase inactivation is reported
to occur.

≥

8.3.3 Biological acidification during mashing
Studies have also shown that biological acidification of mash and wort can result in improved
mash and wort characteristics. Some reports even claim that ultimately a smoother tasting
beer can be produced. More importantly, it has been shown that when employed in high
adjunct mashes it can compensate for decreased endogenous grain enzyme activities. It has
been shown that at a barley adjunct level of 20%, biological acidification of the mash with
Lactobacillus amylovorus stock wort resulted in improved extraction, fermentability, FAN
and reduced wort β-glucan levels. This could be attributed not only to a lowering of mash-in
pH to 5.4, but also to the additional proteolytic and amylolytic enzyme activities that the
biologically acidified stock brought into the mash. Thus, biological acidification can offer
the adjunct brewer an alternative natural way of bringing additional enzyme activities into
the mash. It is commonly applied in countries operating under Rheinheitsgebot (beer purity
laws), which specifies that beer can only be made from malted barley, malted wheat, yeast,
hops and water. Because the acidified stock is malted barley-derived and the inoculated
strains have been isolated from the natural micro flora present on the surface of malt, a
biologically acidified stock is therefore considered a natural malt-derived ingredient.

8.3.4 Enzymes in lautering/mash filtration
Lautering and other forms of mash filtration are performed at mashing-off temperatures of
75-78 ◦ C. Almost all malt enzymes are already inactivated at these temperatures. A small
amount of residual α-amylase activity will be present when a relatively low mash filtration
temperature is used. During sparging of the spent grains in the filter bed, water with a
temperature of 75-78 ◦ C is used. Higher water temperatures are preferred for the reasons
of reduced wort viscosity, increased rate of wort separation and to some extent increased
extract recovery. Temperatures in excess of 80 ◦ C are not advised as these may lead to
extraction of excess polyphenols, leading to astringency in flavour and potential shelf life
stability problems with the final product. If large quantities of adjunct or under-modified