Cereal whole grain for human nutrition. Influence of genetic, environmental and technological factors on content and composition of specific bioactive compounds

Cereal whole grains contain significant amounts of bioactive compounds which may provide health benefits to the consumers. These substances include: vitamins (B and E group and folate, etc), minerals (selenium, iron, zinc and magnesium, etc.), fiber (lignans, beta-glucan, soluble pentosans, arabinoxylans, etc.), phytosterols, sphingolipids, polyphenols and phenolics (hydroxycinnamic, ferulic, vanillic p-coumaric acids, alkylresorcinols, etc), carotenoids (alpha- and beta-carotene, lutein, zeaxanthin, etc.) and phytate. Total dietary fiber comprises mainly complex carbohydrates which are resistant to digestion and absorption in the small intestine although some of them could be at least partly used as substrates for micro-organisms in the large intestine. Arabinoxylan (AX) is one of the most important dietary fiber component in cereal grains and of particular interest for its positive effects on health related to its ability to slow down the passage of food in the upper intestinal tract and to increase the rate of transit in the large intestine. AX are classified as water extractable (WEAX) and water unextractable (WUAX) fractions, hence, an important source of both soluble and insoluble dietary fiber. Both forms (WE-WU AX) affect flour functionality during cereal processing or/and the quality of end products in different way. Among phenolic compounds alkylresorcinols (ARs) are members of a family of phenolic lipids, which have been identified in numerous plants, fungi and bacteria. In Triticum species, 5-n-alkylresorcinols typically occur as mixtures of homologues with side chains of 17 to 25 carbons with varying degrees of saturation. These polyketides exert a wide spectrum of biological activities (i.e. antimicrobial, interaction with protein, biological membranes and enzymatic activities) which may be associated with their amphiphilic structure. Considering the health promoting effects of these bioactive compounds, the objective of this thesis is to allow a better knowledge of main factors influencing the production of whole grain based products nutritionally improved for increased levels of dietary fiber and/or antioxidant compounds. In detail, this research was focused on: • to determine the AX, ARs, free phenols (STP) content and relative antiradical activity (AA) in a wide range of durum wheat cultivars growing in different location in order to select genotypes for breeding program and to study the effects of genetic (G) and environmental (E) factors on the accumulation and composition of these bioactive compounds; • to explore the variation of ARs, STP and AA between ancient and modern diploid, tetraploid and hexaploid Triticum species; • to follow up the bioactive compounds throughout the whole grain pasta production from the seed trough the innovative milling process (micronization and air separation), up to the final product. The results highlight that genotype (G) and environment (E) are the main factors influencing the phytochemical content of durum wheat whole grain and significant E and G effects were found for all analyzed traits (p< 0.001 and p< 0.01 respectively). Considerable differences in the bioactive compounds content were observed among cultivars. In fact, many varieties appeared to accumulate the highest TOAX content in the environments which were characterized by the highest rainfall level. Conversely, the highest AR concentrations were associated to lowest mean temperatures and rainfall level. The high water availability during grain filling appeared to increase the accumulation of STP. A great variation in the phytochemical profiles between ancient and modern wheat crops was observed, while their scavenging capacity of DPPH radical is very similar. The ARs homologues compositions, in particular C19:0 and C21:0 chains, showed high discriminating power among different Triticum species analysed. The use of an innovative milling system and hydrothermal treatment allowed us to obtain wheat flour fractions naturally enriched with bioactive compounds, thus increasing the nutritional value of whole grain foodstuffs. In fact the innovative technological process favored the availability of phenolic compounds (AR) and dietary fiber (AX) in durum wheat raw material for pasta making improving nutritional profile of the products.