Wheat flour lipids

Most bread wheat is milled into flour and bran for human consumption, but substantial quantities are also used to feed livestock and poultry. The major components of wheat flour are protein (approximately 10%–12%) and starch (approximately 70–75%), and the minor components are polysaccharides (approximately 2-3%) and lipids (approximately 2 – 2.5%%)

Lipid is the component of wheat flour which, when varied, produces the greatest changes, on a weight basis, in characteristics such as loaf volume and texture. The majority of the lipids in wheat are fatty acid (FA) esters of glycerol, and the remainder include free (unesterified) fatty acids (FFA) and several types of sterol-based lipids and glycosphingolipids.

The total lipid content in the whole grain and in its parts is uniform and is not characteristic of particular wheat varieties. The sum of polar and non-polar lipids content in flour is almost equal to the total lipid content, but the differences are greater in bran, sieving by-products and germs.

Wheat flour lipid, although only constituting about 2 – 2.5% by weight of flour makes important contributions to dough properties, baking behavior and bread staling. They are considered to have significant impacts on flour and dough functionality, by interacting with gluten proteins and starch and by stabilizing gas cells in breadmaking.
Wheat flour lipids

Lipid content of cereal grains

Lipids present in cereals are complex as they consist of a large number of chemical classes and individuals compounds. The distribution of the classes and compounds varies with not only cereal species but also structural parts. 

Lipids –fats and oil makes up approximately 1-7% of a kernel, depending on the grain.

Wheat, rice, corn, rye and barley contain 1-2% lipids. Oats contain higher content of lipids: 4-7%, one-third of which are polar (phospholipids and galactolipids). Most lipids are concentrated in germ and aleurone. 

Maize lipids are predominantly acyltriglycerides in cultivars having a high total lipid content.

The main components of lipid is 72-85% unsaturated fatty acids, primarily, oleic acid, and linolenic acid. 

Phospholipids and glycolipids are also significantly present. Minor components include free fatty acids, tocopherols, tocotrienols, and phytosterol.
 Lipid content of cereal grains

Lipid in Wheat

The lipid fraction is a minor component of the wheat grain, constituting about 3%-4% of whole grain weight, and even less (1%-2.5% by weight) in the endosperm.

A wheat kernel weigh 30-42 mg and contains 0.92-1.24 ug of lipid. The germ and the aleurone cells are rich in triglycerides which are present as spherosomes, while phospholipids and glycolipids predominate in the endosperm.

The lipids are a useful source on n-6 and n-3 types of polyunsaturated fatty acids, a wheat germ is exceptionally rich in vitamin E tocopherols.

Free fatty acids, simple glycerides, galactosyglycerides, phosphoglycerides, sterol lipids, sphingolipids, diol lipids, tocopherol, carotenoids, wax esters and hydrocarbons are among the lipids found in wheat kernels.

The principle glyceride in wheat is triglyceride, with minor amounts of diglyceride and monoglyceride.

Flour lipids play an important role in the dough-mixing and baking processes. They interact and form complexes with gluten protein and contribute to the stabilization of gas-cell structure, thus having significant effects on loaf and on final texture.

Some oxidation of lipids by wheat lipoxygenase occurs in dough, but more important oxidations resulting in dough improvement require soya lipoxygenase, and both contribute to the oxygen requirement of the dough.
Lipid in Wheat