Physicochemical and in vitro digestibility properties on complexes of fermented wheat starches with konjac gum

Abstract

In this study, the wheat starch with natural fermentation for 72 h was combined with konjac gum (KGM) at different concentrations (0, 0.1, 0.3, 0.5%, w/w), and the changes in physicochemical and digestible characteristics of the complexes were investigated. The results showed that KGM clumped fermented starch (FS) granules together and caused the FS gels to form a close network structure. The addition of KGM significantly decreased the amylose content and swelling power, and reduced peak viscosity, final viscosity, and setback value (SB), which indicated that FS-KGM complexes possessed soft gel structure and could resist the short-term retrogradation. KGM impeded the increase of relative crystallinity, retrogradation enthalpy and gel firmness of FS during storage, suggesting the long-term retrogradation of FS was retarded by KGM. All starch pastes had a weak gel-like structure, and higher storage modulus (G') and loss tangent (tan δ) values obtained after the addition of KGM. In vitro digestion results showed that KGM could slow the hydrolysis of FS, resulting in the increase of slowly digested starch (SDS) and resistant starch (RS). In particularly, the FS-0.3KGM showed the ideal structure, the best anti-retrogradation effected, and slowest the hydrolysis.

Keywords: Fermented wheat starch; In vitro digestibility; Konjac gum; Physicochemical characteristics.