Fanny Leenhardt

Parameters controlling the glycaemic response to breads.

Bread is one of the most widely consumed staple foods worldwide. White-wheat bread, largely consumed in France, is made from highly refined flour, which leads to a low nutrient density. Due to a highly porous structure and gelatinised starch, it is easily broken down during digestion, leading to a rapid increase of glucose released into the bloodstream. Low glycaemic responses are considered favourable to health, especially against a background of diabetes. Literature reports show that selection of raw material is an essential factor in decreasing the glycaemic index (GI) of white bread. There are two means of decreasing the rate of starch degradation: either (i) slowing gastric emptying rate and/or glucose diffusion-absorption through the intestinal mucosa, which can be achieved by incorporating soluble fibre or organic acid in bread, or (ii) limiting starch accessibility to alpha-amylase by using high-amylose cereal varieties and/or incorporating intact cereal grains. Studies on cereal products show that preservation of the food structure during digestion seems to be a more important GI-reducing factor than the degree of starch crystallinity or the presence of soluble fibre. Thus, we should look to produce bread with a more compact food structure or higher density, which is the case in leavened wholewheat bread or bread with intact cereal grains. The baking process should also be improved to achieve this goal, by using, for example, a reduced kneading time or less yeast than usual.

Wheat Germ Supplementation of a Low Vitamin E Diet in Rats Affords Effective Antioxidant Protection in Tissues

Background: Oxidative stress is implicated in the etiology of many diseases, but most of clinical trials failed to demonstrate beneficial effects of antioxidant supplementation. Methods: In the present experiment, we assessed the mean-term effect of wheat germ supplementation, as a dietary source of vitamin E, on antioxidant protection in rat. Results: Feeding rats a 20% wheat germ diet significantly increased plasma and liver vitamin E levels, compared to the low vitamin E basal diet. Concurrently, wheat germ diet consumption strongly decreased the susceptibility of heart and liver lipids to oxidation, as well as the plasma. Wheat germ feeding did not change triglycerides (TG) nor total cholesterol concentrations in plasma or liver, resulting in higher vitamin E/ TG ratio compared to controls. Similar results were found with a diet in which wheat germ oil provided the same amount of vitamin E. Conclusions: Wheat germ appears thus very effective to improve antioxidant defense status, especially in tissues, irrespective of modifications of lipids status.

Improving the yellow pigment content of bread wheat flour by selecting the three homoeologous copies of Psy1

The yellow pigment content (YPC) of endosperm affects the quality and nutritional value of wheat grain products. Major quantitative trait loci (QTL) for endosperm YPC have been repeatedly mapped on chromosomes 7A and 7B in durum and bread wheats. The genes coding for phytoene synthase (PSY1), which is involved in the biosynthesis of carotenoids, generally co-segregate with these QTL, indicating their role in determining YPC. Here, to study the genetic factors underlying endosperm YPC in bread wheat, the sequence polymorphism of the homoeologous A, B and D copies of genes coding for PSY1, Psy-A1, Psy-B1, and Psy-D1, was studied in a worldwide core collection, which was also phenotyped for flour YPC. Seven novel alleles of Psy-A1 and two novel alleles of Psy-B1 were detected, which confirms the high level of polymorphism of these genes. Two major QTL with respective candidate genes Psy-A1 and Psy-B1 were identified in the distal region of chromosomes 7A and 7B using progeny of a cross between Apache and Ornicar, high and low YPC cultivars, respectively. Association mapping confirms the role of these genes in YPC and shows that the D copy also significantly influences this trait. These results indicate that breeders need to consider all three Psy1 copies when seeking to improve the YPC of wheat endosperm.

AN INTEGRATED APPROACH TO IMPROVE BREAD NUTRITIONAL QUALITY

ABSTRACT A post-genomic program was initiated to study the potential improvement of the micronutrient content of wheat and their bioavailability in derived food products. To do so we chose an integrated approach most adapted to the European market and consumers. We were interested in increasing the overall nutritional value of wheat and wheat-based products by a synergy between plant breeding, production schemes and adapted transformation processes. The originality was to take each and every step within the cereal chain into consideration. The aimed targets were the vitamin (B especially) and mineral concentration (Mg) and bioaccessibility. The first objective of this inter-disciplinary project was to explore the genetic basis of targeted nutritional wheat traits. Despite the impact of growing conditions on micronutrient content we showed there is a strong potential for nutritional trait improvement in European wheat by traditional breeding. Rare alleles have been identified by systematic study of germplasm diversity. They are now used in the genetic identification of relevant molecular markers, necessary for efficient introduction of nutritionally correlated chromosome segments in a genetic base of good agronomic and end-use criteria. Wheat is rarely consumed as whole grain products and most of the time goes through fractionation steps (e.g. milling) and transformation processes (e.g. bread-making) Variability in cereal raw material micro-nutrients impact on the nutritional density of final products. A strong interaction between process and variety was observed. New fractionation processes, based on the mechanical properties of the aleurone layer, and product concepts have been derived from this understanding.