Characterization of Lebanese bread wheat : agronomic, biochemical and technological approach ; Caractérisation des variétés de blé tendre libanaises : approches agronomique, biochimique et technologique

In order to support the introduction of local varieties of common wheat, the Lebanese State has recently implemented an improvement program aimed to select the plant material with good productivity in semi-arid conditions and which can give a national production that meets the best the needs expressed by Lebanese processors. In the framework of this project, agronomic criteria, biochemical components and rheological behaviors were characterized on selected local varieties of common wheat. During the two consecutive years of cultivation, the inter-annual variability and the irregular distribution of precipitation induced a non-satisfaction of the water needs of the crops resulting in a limiting growing conditions during the vegetative phase and more seriously during the flowering phase. Which affected the formation of the grain and the grain weight respectively. In addition, the rise in temperatures during grain development penalized the grain yield of crops by impacting the main filling mechanisms (i.e. modification of the kinetics of accumulation of the main constituents of the grain thus reducing the PMG of the grain). At the same time, the level of polymerization/aggregation [i.e., gliadin/glutenin ratio, non-extractable protein polymers (UPP), mean molar mass of glutenins] were impacted (very significant increase in all these indicators). The reduction in starch levels was accompanied by a significant change in the amylopectin/amylose ratio. Significantly different distributions of starch granules were noted ; the percentage of volume occupied by starch granules of type A and type B varied between genotypes for the two years of cultivation. These changes in the composition of wheat grains induced changes in rheological behavior. Thus, the studied flours showed high levels of wet and dry gluten, strong Zeleny index and low gluten index. Similarly, these flours were characterized by high extensibility (alveograph and extensograph), high dough resistance (farinograph), as well as high water absorption. Finally, ...