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Bran: A deeper look into the layers of wheat

The wheat kernel or caryopsis consists of a different number of tissues: germ, endosperm, aleurone layer and pericarp.

The bran fractions consist of the pericarp, testa, and hyaline and aleurone layers.

If you are not familiar with these layers, check out our blog on structure of a wheat kernel.

In weighing terms, endosperm makes up for 81-84%, bran makes up for 14-16%, and germ makes up for 2-3% of the wheat kernel depending upon the wheat subspecies and variety.

As per this study, the physiological effects of wheat bran can be split into nutritional effects (from the nutrients present), mechanical effects (mainly on the gastrointestinal tract, due to the fibre content) and antioxidant effects (arising from the phytonutrients present such as phenolic acid and alkylresorcinols).

Both wheat variety and growing conditions can significantly alter the antioxidant profiles, concentrations and properties of compounds such as phenolic acids, carotenoids and tocopherols found in wheat bran. Additional work has shown that it is the aleurone layer (wheat bran fraction) that consistently has the highest antioxidant capacity among wheat fractions and that ferulic acid in particular (a derivative of the phenolic acid cinnamic acid) accounts for up to 60% of this antioxidant capacity.

Now that we know that wheat bran is nutritionally so rich, and is what would provide the distinct flavour and aroma to wheat bread upon long fermentation and baking or cooking, it is also important to know it must go through either of the following processes (depending upon the end product) to be bioavailable to the human body:

Phytic acid is a naturally occurring organic compound present in cereals, usually as myoinositol hexaphosphate. It is concentrated in the external covers in the pericarp and aleurone layer of the grain as well as, at lower levels, in the germ; 90% of the phytic acid in grain is in the aleurone layer with 10% in the embryo.

Most of the minerals in wheat kernels are present as complexes with phytic acid. Mature wheat grain has high phytase activity, hydrolysing phytates and making the minerals nutritionally available.

Phytase is a naturally enzyme in the wheat grain, which when properly activated, works to break down the phytic acid, and increase the bioavailability of the minerals.

The ways to activate phytase in the bran is:

  1. While Cooking: If you are using bran to add to make Indian unleavened flatbreads (chapati), then it is recommended to soak the bran in a slightly acidic (add a few drops of lemon juice or apple cider vinegar) water for a few hours before adding that bran to your dough while kneading.

  2. While Baking: If you are using whole wheat flours, then it is extremely important to follow a long fermentation sourdough baking process. Not only will this break down the phytic acid, but this will also bring out the real flavour and aroma of the wheat. The deeper you go, more you will realise that it is as delicate, complex, and nuanced as wine or coffee making.

One of the most common reasons why people add bran to their diet is to get that extra fiber. Wheat bran is a source of concentrated insoluble fiber.

In terms of digestive health, wheat bran can offer several beneficial effects. Wheat bran has an effect on faecal bulking, delays gastric emptying and accelerates small bowel transit. Faecal bulk is a result of multiple interactions between the food, the host and the gut ecosystem. The bulking effects of fibre are greatest with cereal fibre, especially products high in insoluble non-starch polysaccharides such as wheat bran.

Wheat bran is also considered as a prebiotic, which are defined as non-digestible food ingredients that beneficially affect host health by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon. Prebiotic components of dietary fiber in wheat bran (including beta-glucans) may be fermented by colonic microflora to bring about a host of health benefits.

Studies have shown that wheat bran may have a beneficial effect on the prevention of diseases, including some cancers (in particular colorectal cancer), cardiovascular diseases, obesity and some gastrointestinal diseases, including diverticular disease, constipation and irritable bowel syndrome (IBS).

If you are looking to add wheat bran to your diet, you may check it out here.

We hope this was helpful, and you could learn something new about specialty wheat. If you have further questions and would love to know anything in specific, please carry on the discussion on our discord channel in #wheatywednesdays thread.


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