Digestibility and physicochemical properties of starch-galactomannan complexes by heat-moisture treatment

Native maize starch blended with galactomannan (NS-GM) was used to produce starch-galactomannan complex with heat-moisture treatment (HMT). In-vitro digestibility and physicochemical properties of starch and starch-galactomannan complexes were investigated. It was found in this research that the resistant starch content in the HMT NS-GM composite particles was related to the ratio of galactose/mannose residues in the galactomannan. The resistant starch content was presented in the order of HMT starch-locust bean gum complex, HMT starch-Tara gum complex, HMT starch-Guar gum complex, and the resistant starch content of HMT starch-Tara/Guar composite significantly increased with the amount of gum increased. Moreover, the resistant fragment in the resulting composites was more than that in the native and HMT starches. Scanning electron microscopy (SEM) showed that the degree of attachment of galactomannan to starch was also positively correlated with the galactose/mannose residue ratio of galactomannan and the phenomena became more obvious with the increase in the addition amount of the gums. X-ray diffraction results showed that the crystal forms of HMT starch and HMT NS-GM were the same as the maize starch. Differential scanning calorimetry (DSC) determination showed that the crystal structure of starch become stabler after heat-moisture treatment and the addition of galactomannan, but the double helix structure and the crystallization area was reduced. HMT NS-GM formed relatively looser recrystallization structure after refrigerated storage. (C) 2017 Published by Elsevier Ltd.