Renewed interest has been raised in maximising the commercial benefit from the polyphenolics in wheat and carbohydrates which are often lost when milling this cereal, especially if the bran and aleurone component is discarded.  The main dietary benefit in wheat is this bran, which not only provides dietary fibre but also contains powerful antioxidants, the polyphenols, especially hydroxycinnamic acids whilst the germ is mainly the storage carbohydrate, starch.  The aleurone layer though is actually the fraction with the highest antioxidant activity (Liyana-Pathirana and Shahidi, 2007) but is only available nutritionally if whole-grains are ingested. The bound antioxidants in the fibre survive intestinal digestion to reach the colon where that are thought to protect it by mopping up free radicals (Fardet et al., 2008). It is conjectured that diets based on whole-grain consumption may help to reduce colon cancer because of these fibre-bound polyphenols (Perez-Jimenez and Saura-Calixto, 2005).

The most abundant polyphenolic component is ferulic acid (approx. 5mg/kg) which is esterified in a variety of linkages to the hemicellulose (Kroon et al., 1997; Gallardo et al., 2006). It’s also found in triticale and rye (Wang et al., 2007). The other significant polyphenols are caffeic acid, syringic acid, p-coumaric acid, vanillic acid and sinapic acid  (Yadav et al., 2007). There are small amounts of colour components provided by the lipid soluble carotenoids and some lutein.   New uses for these traditionally discarded components of wheat include the fibre serving as a functional antioxidant in formulations. There is evidence that the polyphenols attached to the fibre components retain there  antioxidant potential, in which case they might be added to beverages for example to protect colour systems and vitamins.

References

Fardet, A., Rock, E., Rémésy, C. (2008) Is the in vitro antioxidant potential of wholegrain cereals and cereal products well reflected in vivo? J. Cereal Chem.  48, pp. 258-276

Gallardo, C., Jimenez, L., Garcia-Conesa, M. T. (2006). Hydroxycinnamic acid composition and in vitro antioxidant activity of selected grain fractions. Food Chem., 99, pp. 455-463

Kroon, P. A., Faulds, C. B., Ryden, P., Robertson, J. A., Williamson, G. (1997) Release of covalently bound ferulic acid from fiber in the human colon. J. Agric. Food Chem. 45 pp. 661-667.

Liyana-Pathirana, C.M., Shahidi, F., 2007. The antioxidant potential of milling fractions from bread wheat and durum. J.  Cereal Sci., 45, pp. 238-247.

Perez-Jimenez, J., Saura-Calixto, F.(2005). Literature data may underestimate the actual antioxidant capacity of cereals. J. Agric. Food Chem., 53, pp. 5036-5040.

Wang, F., Yang, L.X., Huang, K.X., Li, X.K., Hao, X.J., Stockigt, J., Zhao, Y. (2007): Preparation of ferulic acid derivatives and evaluation of their xanthine oxidase  inhibition activity. Nat. Product Res., 21 pp. 196–202.

Yadav,  M. P., Moreau, R. A., Hicks, K. B. (2007). Phenolic acids, lipids, and proteins associated with purified corn fiber arabinoxylans. J. Agric. Food Chem., 55, pp. 943-947