Physicochemical and Structural Properties of Starch Isolated from Apios americana Medikus

Abstract

Physicochemical and structural properties of starch isolated from tuberous roots of apios (Apios americana Medikus) were examined and these features were compared with those from arrowroot starch, potato starch and normal maize starch. The results obtained from the examination of apios starch were similar to those of arrowroot starch in X-ray diffraction pattern, solubility and swelling power, their behavior in the RVA, the susceptibility of starch granules to pancreatin digestion and the FE-SEM appearance as the digestion proceeded. The starch granules from apios showed Ca type in the X-ray diffractogram and had significantly lower swelling power at 70 and 80 °C than starch granules from potato. Apios starch granules had a rapid increase in solubility from 70 to 80 °C, and at 80 °C, it was higher than those of potato and normal maize starch granules. The susceptibility of apios starch granules to pancreatin digestion was higher than that of potato starch granules and lower than that of normal maize starch granules. The elution patterns of isoamylase debranched materials of the apios starch granules were similar to arrowroot and normal maize starch granules. The amount of amylose present in the apios starch granules (25.7%) was similar to the levels found in potato starch granules. Digestion of the granules was monitored by FE-SEM and varied between the different plant species. The differences in the structure of the starches lead to different susceptibilities to pancreatin digestion and the observed changes in the structural appearance of the granules as the digestion proceeds.