Processing of Wheat Non-Starch Polysaccharides for the Optimization of Their Functional and Nutritional Characteristics
Traitement des polysaccharides non amylacées du blé pour l'optimisation de leurs caractéristiques fonctionnelles et nutritionnelles
Résumé
Wheat grain is mainly composed of starchy endosperm surrounded by multiple layers, from the aleurone to the pericarp, that have different histological compositions; those outer layers are called bran in the milling industry. The major molecular family of bran is dietary fiber (DF), making cereals the main source of fiber intake in the human diet. DF are non-starch polysaccharides (NSP) with at least 10 monomeric units, linked with lignin and other non-glucuronic compounds (i.e. polyphenols). They have beneficial physiological effects such as laxation, fermentation, cholesterol and glucose regulation [1]. However, wheat bran is little valorized in bread industry due to processing difficulties and low consumer acceptability [2]. Biological, physical and chemical treatments exist in order to modify DF physico-chemical properties in raw material. They improve DF processing and functional properties but few studies investigate nutritional and health effects [3]. Our aim is to assess whether ozone can be a good candidate to optimize wheat bran characteristics. Ozone has been recognized as safe and is used to reduce microbial charge of food products for storage and processing. Structural impact on the main constituents of wheat grain following ozone treatment are well documented [4]. Effects on DF have been less studied, but data indicate an increased yield of soluble DF and reduced β-glucans molecular weight. Whilst rheological properties can be modified after wheat grain ozone treatment, high ozone concentration can decrease flour properties [5]. Hence, we chose to work on isolated wheat bran (WB) and investigate the effect of ozone on structure, functional and physico-chemical properties. Our results indicate significant increase of fiber solubility and reduction of their molecular weight. In addition, ozone treatment significantly changes some functional and physico-chemical parameters (i.e. polyphenol content, oil holding capacity, sodium cholate binding capacity and α-amylase inhibitory activity). We also investigated nutritional, rheological and health effects on breads made from ozonated grain and bran. Ozonation significantly reduced white bread glycemic index and improved some rheological properties. This indicates that ozonation of grains or WB could be a potential interesting tool for optimization of functional properties.
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