Wheat Bran: overwiew part I

Research regarding the composition and characteristics of wheat bran

1 – Wheat Bran
“Wheat bran includes the outer layers of the grain including the pericarp, head and aleurone layer (millers definition). Bran is an important by-product of milling wheat, when white flour is produced (see Section 3.3). The chemical composition (Table 5.4) is characterized by the high content (ò45%) of non-starch polysaccharides (food fibre) consisting mainly of arabinoxylans (ò60%) and cellulose (ò30%). Further characteristics are the relatively high content of minerals (potassium and phosphorus), unsaturated fatty acids (linoleic and oleic acids) and vitamins (nicotinamide, pantothenic acid and a-tocopherol). A disadvantage of bran is that the high lipid content can cause rancidity. Therefore bran is often heat treated (stabilized) to prevent enzymatic oxidation of fat.

Table 5.4. Chemical composition of wheat bran [18]

Due to the valuable nutritional composition, wheat bran has been widely used as component for animal feed (see Section 4.6), in particular for livestock like horses, cattle, goats, pigs, and rabbits. In recent years, wheat bran has increasingly been in the limelight as dietary supplement for human nutrition. Many studies have shown that the consumption of wheat bran, containing a unique mixture of valuable bioactive components, improves bowel functions and reduces the risk of colon cancer, type 2 diabetes, and cardiovascular diseases (see Section 6.4). Due to valuable antioxidants, its intake can prevent the onset of various oxidative stress-related diseases. Wheat bran is therefore frequently used as food additive, for example for bread, other baked products, and breakfast cereals [19]. It has been introduced into various further market segments including functional foods, nutraceuticals, and pharmaceuticals. Increased consumer awareness of the health benefits of bran induced great demand and food-grade bran can now easily be purchased in drugstores, health food shops, and supermarkets. Taken together, wheat bran is no longer a useless waste product but can be used in many areas of applications. Wheat-based raw materials Herbert Wieser, Katharina A. Scherf, in Wheat – An Exceptional Crop, 2020.”

2 – Wheat Bran
“Wheat bran is a by-product of wheat grain milling and grinding. The physiological effects of wheat bran can be split into the following: nutritional effects from its constituent nutrients; mechanical effects in the gastrointestinal tract due to its fiber content; and antioxidant effects arising from its phytochemical constituents. Wheat bran has higher antioxidant activity than other milled fractions, and contains various components such as phytic acid, polyphenols (including lignans and phenolic acids), vitamins, and minerals. These components of wheat bran possess health benefits for humans, including preventative effects against cancer and type 2 diabetes. Various studies have reported that these compounds exhibit significant antioxidant capabilities, including scavenging free radicals, chelating metal ions, and activating antioxidant enzymes, suggesting antioxidant properties of wheat bran. This chapter includes an overview of stress and oxidative stress and a discussion of the antioxidant properties of wheat bran. Chapter 15 – Antioxidant Properties of Wheat Bran against Oxidative Stress. Masashi Higuchi. https://doi.org/10.1016/B978-0-12-401716-0.00015-5.”

4 – Wheat bran
“Antioxidants (in bran) can interact with gluten proteins by reducing disulfide-sulfhydryl interchange reactions, thus impacting gluten protein aggregation. (Huang et al., 2018).”

5 – Wheat bran
“Bran is the most prominent co-product of the wheat milling process. In this process, the largest part of the endosperm tissue, i.e. the flour, is separated from the germ and bran after consecutive grinding, sieving and purification steps (Hemdane et al., 2016). From a botanical point of view, bran is a collection of multiple histological layers (i.e. outer and inner pericarp, seed coat and nucellar epidermis) of the outer part of the wheat kernel. However, wheat bran obtained as a milling fraction (referred as miller’s bran) also includes the aleurone layer and some residual endosperm tissue attached to it. Its yield varies between 13 to 19% of the total kernel weight (Deroover et al., 2020; Hemdane et al., 2016; Onipe et al., 2015). In this review, the term wheat bran refers to the miller’s bran.
Wheat bran mainly consists of arabinoxylan (17-33%), cellulose (9-14%) and fl-D-glucan (1-3%), but also starch (6-30%), proteins (14-26%), lipids (3-4%), lignin (3-10%), minerals (5-7%), phytic acid (4.5-5.5%), fructans (3-4%), and phenolic compounds (0.4-0.8%) (Hemdane et al., 2016). The pericarp is the main source of the kernel’s dietary fiber (mainly cross-linked arabinoxylans, cellulose and lignin). The aleurone layer is rich in arabinoxylan but also in lignan, phytic acid, minerals and vitamins (Deroover et al., 2020; Onipe et al., 2015).
Wheat minerals which are important for human health include iron, zinc, calcium, manganese, magnesium and copper. They are mainly located in the aleurone cells. Magnesium plays an important role in blood glucose homeostasis and insulin sensitivity (Veronese et al., 2016). However, minerals in wheat have low bioavailability because they are chelated by mainly phytic acid and/or because they are physically entrapped into rigid aleurone cells (Lemmens et al., 2019).
Bran is the main source of the phenolic compounds in wheat. Ferulic acid is the most abundant C6 – C3 phenolic acid. It is esterified to some of the arabinoses in the arabinoxylan chains. Arabinoxylan chains are cross-linked by formation of ferulic acid dimers and higher oligomers which are esterified to the arabinoxylan chains. Bran also contains the C6 – C3 phenolic acids sinapic and p-coumaric acid and the C6 – C1 phenolic acids p-hydroxybenzoic, vanillic, syringic, and gallic acid (Laddomada et al., 2015). Components of wheat and their modifications for modulating starch digestion: Evidence from in vitro and in vivo studies. Konstantinos Korompokis, Jan A. Delcour, in Journal of Cereal Science, 2023.”

5 – Wheat bran

“Wheat bran is a rich source of dietary fiber and other healthy components, which are biologically active, such as alkylresorcinol, ferulic acid, fl-glucan, arabinoxylan, lignans, and sterols (Pr¸ckler et al., 2014). Besides nonstarch carbohydrates (arabinoxylan, cellulose, fructan, and mixed-linkage fl-glucan), wheat bran contains starch, protein, lipids, and significant quantities of B vitamins and minerals (Hemdane et al., 2016a). The composition of wheat bran is presented in Table10.1 (USDA, 2015).”

6 – Wheat bran

“Wheat bran is a by-product of flour milling and frequently used as ingredient in diets for pigs (Huang et al., 1999; Hassan et al., 2008). It is composed of the pericarp and the outermost tissues of the seed, including the aleurone layer with variable amounts of remaining starchy endosperm (Jondreville et al., 2000; Hassan et al., 2008). Wheat bran constitutes almost 10% of the total weight of wheat milled for flour (Hassan et al., 2008). It is characterized by a high level of insoluble lignified fiber which is known to be extremely resistant to degradation in the gastrointestinal tract (Noblet and Le Goff, 2001). Molist et al. (2011) concluded that incorporation of WB in diets for piglets improved gut health by beneficially modulating the activity and composition of the intestinal microbiota.”

7 – Wheat bran
“Wheat bran is a by-product of the milling process of wheat. It usually contains 14-19% of total grain weight. As a rich source of dietary fibre, wheat bran contains 46% of non-starch polysaccharides, including arabinoxylan (70%), cellulose (24%) and beta-glucan (6%), and it also contains minor amounts of glucoglucomannan and arabinogalactan (Carre and Brillouet, 1986; Bertrand et al., 1981).
Depending on composition and particle size, wheat bran fractions may have negative effects on product quality, such as textural properties and loaf volume for bread. Reducing the particle size of wheat bran can influence product quality by increasing interaction surface and releasing reactive intracellular components (Noort et al., 2010).”