Physicochemical and nutritional properties of reduced-caloric density high-fibre breads

The influence of some physicochemical properties (chemical and nutritional composition, particle size, colour, dynamic viscosity, viscoelastic moduli) of associated binary mixtures of structuring hydrocolloids (cellulose derivatives, galactomannans) and prebiotic oligosaccharides (fructo- and gluco-oligosaccharides) in diluted hydrated wheat flour matrixes is discussed in terms of nutritional (higher resistant starch, lower digestible starch and lower in vitro Glycaemic Index) and technological functional profiles (higher sensory scores and longer keepability) of reduced-caloric density (−20%) high-fibre (>6 g/100 g) breads. Few technological functional (sensory firmness and overall acceptability) and most nutritional bread properties (protein digestibility, rapidly digestible starch, slowly digestible starch, in vitro expected Glycaemic Index, total digestible starch and resistant starch) were found to depend on dietary fibre molecular characteristics (mean particle diameter (D[4, 3]), storage modulus (G′), loss modulus (G″), complex viscosity (η*), and lactic acid solvent retention capacity. Dietary fibres with larger particle size resulted in highly sensory acceptable breads with higher amounts of resistant starch and slightly lower protein digestibility. Fibres exhibiting high viscoelasticity -G′, G″- and complex viscosity -η*- in concentrated solutions yielded breads with better sensory perception, lower digestible starch and higher resistant starch contents bringing to lower in vitro expected Glycaemic Index.