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Wheat is the second largest crop cultivated around the world and constitutes a major part of the daily diet in Europe. During the course of improving the baking quality of wheat cultivar, most of the nutritional attributes have been underestimated. It is therefore unfortunate that most of wheat-based food products are mostly produced from refined white flour from which peripheral tissues (germ and envelopes) are removed. However, these tissues, which are eliminated and serve mainly for animal feeding, contain most of the vitamins, minerals, fiber and phytochemicals of the grain. It is becoming evident that many of the health benefits associated with the consumption of whole grain cereal products, relate to the enhanced intake of micronutrients, phytochemicals and dietary fiber. In the context of consuming wheat derived foods with enhanced nutritional value,  as part of a healthy diet, this thesis provide results which strengthen the knowledge of vitamins accumulation in  common wheat and in wheat-based food products.

Firstly, we have developed a simple and rapid method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) for the simultaneous screening of seven water soluble vitamins in various wheat-based food materials. The vitamins present in the test materials were separated in less than 15 min by using a reverse-phase C18 column, and analyzed by positive ion electrospray selected reaction monitoring MS/MS.  The MS response for all the vitamins was linear over the working range (0.05 to 9 µg/mL) with correlation coefficients ranging between 0.991 and 1. Limits of quantification in the different food materials ranged from 0.09 to 3.5 μg/g. Intra-day and inter-day precision was found satisfactory.

The  second part of our research, have focused on monitoring the levels of vitamins upon the wheat-based foods processing operations, such as production of new wheat milling fraction (consisting in enriched fraction) and breadmaking toasted bread. In order to achieve this goal, the developed method was applied for the simultaneous analysis of the water-soluble vitamin natural content of different semi-coarse wheat flours and in their corresponding baking products. In addition the vitamin E, Lutein and β-sitosterol natural content was also measured in the same materials. It was shown that the concentration of nicotinic acid, pyridoxal, pyridoxine, pantothenic acid were significantly higher in the coarse bran than in the other milling fractions, while the concentration of β-sitosterol, lutein, α-tocotrienol, α-tocopherol and thiamin (20.87 μg/g DM) were the highest in the enriched fraction. The toasting step induced a significant increased of α-tocopherol (+216%), β-γ-tocopherol (+52%), α-tocotrienol (+83%), β-γ-tocotrienol (+32%), nicotinic acid (+55%), nicotinamide (+97%) and of pyridoxine (+77%). Furthermore, it was demonstrated that the enriched fraction could be a functional ingredient in order to enrich wheat-based products in fat soluble vitamins and that the toasting process could release bound bioactive compounds and led to enhance the nutritional quality of bread.

This thesis also addressed the influence of genetic and environmental variability on the nutritional status of bread wheat varieties of a large international bread wheat core collection grown in two contrasting growing location. The results presented indicate that genotype had a significant impact on the variations of nicotinamide, riboflavin and pantothenic acid contents for the B-vitamins and significant impact on the variations of α-tocotrienol, β-sitosterol and lutein contents for the fat-soluble bioactive compounds. In addition, the growing environment may significantly affect the vitamin compositions and, it was suggested that within the core collection used in this study, the variation in B and lipid-soluble bioactive componds was highly heritable. The evaluation of the relationship between the contents of vitamins and the release dates or geographical origins of wheat accessions in the core collection, has led to the conclusion that the contents of vitamins have not decreased with modern plant breeding.

Finally, relevant genomic regions involved in the genetic control of wheat vitamins composition have been reported. Thus, the current analyses provides innovative and relevant genetic data to develop new molecular markers to accelerate genetic gain for vitamin content in bread wheat.