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Question and Flour Problems (Flour Components; Lipids, Dietary Fibres, and Mineral)



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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