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HEALTHGRAIN Background
What is whole grain? |
Due to the American Association of Cereal Chemists (AACC) "whole grains shall consist of the intact, ground, cracked or flaked caryopsis, whose principal anatomical components - the starchy endosperm, germ and bran - are in the same relative proportion as they exist in the intact caryopsis."
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Kernel of wheat - Click here to enlarge this picture
(Izydorczyk et al., 2002) |
Whole grain is an important source of dietary fibre, minerals, vitamins, phyto-oestrogens, antioxidants and other components and is low in saturated fatty acids. The nutrients are not uniformly distributed throughout the grain kernel. The highest concentration of nutrients is located in the germ and bran layer. The main nutrients of the three parts are listed below:
- Bran: rich in B vitamins, phytonutrients (flavonoids, indoles), fibre, minerals; small amount of protein
- Endosperm: predominantly carbohydrate, also proteins, small amounts of B vitamins
- Germ: rich in minerals (Fe, Zn), B vitamins, phytonutrients and antioxidant vitamin E
During the milling (or refining) process of grains the bran and germ is removed resulting in a substantial loss of important nutrients.
NOTE: Whole grain products contain the whole package of nutrients from the entire grain kernel!
Dietary fibre
Dietary fibre is made up of the edible parts of the plant that can not be digested or absorbed in the small intestine. It can be found especially in whole grain products like bran and oat bran cereals, whole and mixed grain breads or wholegrain breakfast cereals for example.
- Dietary fibre includes:
- Non-starch polysaccharides: e.g. cellulose, hemicellulose, gums, pectins
- Oligosaccharides: inulin
- Lignin
- Associated plant substances: e.g. lignin and waxes
- Resistant starch: found in pulses, partly-milled seeds and grains as well as in processed cereals. It resists digestion in
the small intestine.
- Dietary fibre is divided into soluble and insoluble fibre:
- Soluble fibre: in oats, barley, rye, fruits, vegetables and pulses. Soluble fibre may slow digestion and absorption of
carbohydrates and therefore help people with diabetes and high blood cholesterol levels improve control their blood
glucose and blood lipid levels. Whole grain products provide 20-50 % of their fibre in the soluble (or viscous) form.
- Insoluble fibre: in whole grain cereals and wholemeal bread, is important for bowel function and regularity
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