Physicochemical and digestion properties of starches from sweet potato mutants obtained with gamma irradiation

Abstract

The physicochemical, digestion, and pasting characteristics of starches isolated from Korean sweet potato cultivar (Shingeonmi) mutants were investigated. The sweet potato stems were irradiated with 0.1 kGy dose of a 60Co source with a rate of 5 Gy/h (0 Gy as a control), and seven plant lines (MS1-7) were examined. The yields of 100 g or more storage roots of control and MS1-7 were 44.71, 52.94, 46.44, 38.80, 52.81, 32.12, 25.90 and 50.41%, respectively. The mean volume diameter (d4,3) of the mutant starch granules had a wide range of between 12.98 and 43.91 μm, while there was no change in the granule shapes. Amylose contents and branch chain length distributions of the starches were not significant different. All the starches exhibited a Ca-type of X-ray diffraction pattern. The relative crystallinities varied from 44.70 to 51.03%, and MS5 and MS1 had the lowest and highest crystallinity, respectively. The higher To and Tp of MS1 implied that the starch had a higher degree of structural stability as well as the higher crystallinity. MS1 showed the lower swelling and pasting behaviors, which are most likely due to the higher relative crystallinity and the smaller granule size. The storage modulus (G) and loss modulus (G) of all the starches increased with an increase in angular frequency, but the G was greatly higher than the G, a characteristic of gel, showing solid-like behavior. MS1 showed the lower viscoelastic behavior than the other starches. Both the raw and cooked starches of MS1 showed the lower digestibility, but the digestibilities of other mutant starches were not significantly different compared to the control. In conclusion, these results suggested that gamma irradiation had an influence on the morphological, pasting, rheological, and digestion properties of starches and the potential applicability of the mutant starches in food industry.