Structural characterizations and in vitro digestibility of acid-treated wrinkled and smooth pea starch (Pisum sativum L.)

In this study, the molecular structure of acid-treated wrinkled and smooth pea starch residues was investigated, and the in vitro digestibility of the residues with 2.2 M HCl at 35°C for different time periods (1, 3, 5, 8, and 15 days) was assessed. After acid treatment, the amounts of rapidly digestible and slowly digestible starches increased, whereas the amount of resistant starch decreased. The granular appearance of the two pea starches was destroyed and small fractions formed aggregates. The changes in the ratio of absorbance at 1047 cm to that at 1022 cm, the intensities of major peaks, relative crystallinity, and thermodynamic parameters from DSC were observed during acid hydrolysis. These properties of wrinkled pea starches were significantly different from those of smooth pea starches. The crystallinity of acid-hydrolyzed starches increased slightly with increased acid-treatment time. From the entire hydrolysis process, the B polymorph of acid treated pea starch has a higher hydrolysis than that of A polymorph. A reduced tendency in chain-length distribution occurred with the degradation of chains in amylose and amylopectin. These results demonstrated that the slow digestion and resistance properties of wrinkled and smooth pea starches were affected by both the structure of the amorphous and crystalline regions of starch granules