The Impact of Processing on Potentially Beneficial Wheat Grain Components for Human Health

Wheat based foods, mainly in the form of bread and pasta, are staples in many countries around the world and as such contribute substantially to nutrient intake of human beings. The mature wheat grain is composed for over 70-75% of its dry weight of starch and for around 10-14 % of protein, which has led to the widely spread perception of wheat foods as providers mainly of energy and protein to the human diet. Nonetheless, whole grains are also an important source of dietary fibers, vitamins and minerals and contain notable levels of bioactive compounds of health benefit as for examples lignans, phenolic acids, alkylresorcinols, phytosterols, folates and tocols. Processing is a pre-requisite for using cereal grains as food and obtaining a safe to consume and appealing final product for the consumer. It can help reducing potential hazardous molecules as pesticides, mycotoxins and heavy metals and allows to obtain products with varied and unique properties. Indeed, most of the importance of wheat grain in the human diet is due to its versatility to be processed into various end products like flour, semolina, and other bakery products. Processing of wheat grain involves different regulated steps each impacting either or both on the composition and physical-chemical properties of its different components, which in turn define the technological quality and the nutritional and health promoting properties of the end product. While the unique textural properties of wheat foods are largely determined by starch and gluten proteins present in the starchy endosperm, and therefore associated with white flour or semolina, health effects of wheat-based products are mainly associated with their dietary fibers and bioactive compounds. These compounds are enriched in the grain peripheral layers, mainly in the aleurone layer which is generally driven in the bran fraction upon milling. Milling fractionation and the way the different milling streams are subsequently recombined has, therefore, a profound impact on the relative abundance of the different grain components in the wheat flour/semolina and, consequently, in the end products. Further processing steps, as dough making, microbial fermentation, extrusion, and baking can also have an impact on relative amount of grain components, and are also known to affect their bioavailability. Some examples of the effect of grain processing procedures on bioavailability of important grain components in the wheat products will be presented in this chapter. Suggestions of how to improve these processes in light of their implication for human health will also be discussed.