Lipids
1.Do the lipids present in wheat
play an important role in the processing of wheat flour?
Wheat flour lipids are mostly
unsaturated lipids. When the kernel is milled, the lipids are exposed to
endogenous enzymes and to oxygen, which results in rancidity. More than 50% of
the lipids are located in the bran and the germ. So thorough separation is a
prerequisite for a long shelf-life of the flour with unimpaired sensory
properties. Flour lipids, and galactolipids, improve the volume yield of baked
goods.
2. What is the composition of the
wheat lipids?
The wheat lipids are composed of roughly 1/3 non-polar lipids (oil)
and 2/3 polar lipids (lechitin, galactolipids and others). They contain mainly
unsaturated fatty acids.
3. Do the phospholipids contained
in the wheat fats have any technological significance?
They most probably contribute to
volume yield.
4. Are there interactions between
the constituents of flour improvers/ baking agents and the lipids present in
the wheat?
Lipolytic enzymes hydrolyse polar
and non-polar lipids into more hydrophilic molecules; oxidizing agents react
with the unsaturated parts of the lipids causing off-flavour of colour losses
(bleaching); emulsifiers probably also interfere with lipids, but the
consequences are not known.
Dietary Fibres
1.What dietary fibres do the
outer layers of the wheat kernel contain?
Cellulose, hemicelluloses
(xylans, arabinoxylans and glucans) and lignins.
2. What effects do the outer
layers have on the behaviour of flours during preparation of the dough and
baking?
In particular the water-insoluble
pentosans or more precisely the water-insoluble xylans reduce the volume yield
by interacting with protein and absorbing water. Furthermore, the aleuron layer
contains soluble protein which does not contribute to gluten formation but rather
dilutes the function of gluten proteins.
3. What effect do flour improvers
and baking agents have on the dietary fibres in flours?
Enzymes from the class of
hemicellulases are able to break down some of the non-starch polysaccharides. Oxidative
gelation of the pentosans is induced by oxidizing agents or amylases.
Minerals
1.What is the connection between
the flour yield and the mineral content?
Since the outer layers of the
grain have a higher mineral content than the endosperm, the ash content of the
flour increases with the yield.
2. What role do minerals play in
the processing of flour to make bread, small baked products (e.g. rolls) and
pastry goods?
The minerals contained in the
flour have little effect on processing. However, the proportion of
(water-insoluble) non-gluten proteins, pentosans and enzymes increases along
with the ash content; this permits greater water absorption but also results in
weak doughs and a lower volume yield.
3. Can flour improvers and baking
agents reduce or compensate for the technical disadvantages of mineral-rich
flours?
Flour improvers and baking agents
improve the processing characteristics of mineral-rich flours, making them
superior to those of light coloured, untreated flours. But when fully treated,
the light-coloured flour has better baking properties than dark flour.
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