Chemistry Reference
In-Depth Information
the native starch as well. These lipids are therefore effectively unavailable before most of the
starch is gelatinized.
The non-starch lipids consist of similar levels of polar and non-polar lipids. Part of this
fraction is most likely bound to proteins.
45
Polar lipids are known to play a role in dough stability and processing tolerance of yeast-
leavened baked products. The ability of the polar flour lipids to form lipid monolayers at
the gas/liquid interface is believed to positively influence the gas retention in the dough.
Furthermore, polar flour lipids and gluten proteins interact as well. This interaction is also
believed to positively affect gas retention.
46, 47
6.2
ENZYMES IN BREAD MAKING
Bakery products have undergone radical improvements in quality over the past 10 years in
terms of flavour, texture and shelf life. The usage of enzymes is the biggest contributor to
these improvements. Among the enzymes used in food applications, those used in bakery
industry constitute nearly one-third of the market.
Baking enzymes are used as flour additives and they are used in dough conditioners to
replace chemical ingredients and to perform other functions in a label-friendly way.
The baking industry predominantly makes use of five types of enzymes (Table 6.2).
Amylases are used to convert starch to sugar and to produce dextrins. For strengthening
and bleaching of the dough, oxidases are used. Hemicellulases and proteases are the en-
zymes which have an effect on wheat gluten. While hemicellulases improve gluten strength,
proteases reduce gluten elasticity. All these enzymes together play an important role in main-
taining bread volume, crumb softness, crust crispiness, crust colouring or browning and in
maintaining freshness.
6.2.1
Amylases
-amylases (
EC 3.2.1.1
) are the enzymes which are most frequently used in bakeries.
48
The
reasons for this are their positive influence on bread volume, crumb grain, crust and crumb
colour, flavour development and anti-staling effect.
49, 50
There is also evidence that amylases
have an effect on dough development.
51
α
6.2.2 Classification
Amylases belong to the family of glycohydrolases (GH), based on structural and amino acid
similarities.
52
Various amylases are found in GH families 13, 14 and 15. Besides
α
-amylases
Table 6.2
General effect of enzymes in bread making.
Improved
gluten
network
Gas retention/
increased
volume
Improved
colour and
flavour
Improved
crumb
structure
Improved
shelf life
properties
Amylase
X
X
X
X
Protease
X
Xylanase
X
X
X
Oxidase
X
X
X
Lipase
X
X
X
X
