Abstract: The purpose of this study was to evaluate the effect of ultrasonic field on the relative molecular mass of starch. We examined the changes in the relative molecular mass of potato starch as affected by different ultrasonic treatment conditions and different concentrations of starch paste by gel permeation chromatography. The results showed that the number-average relative molecular mass (Mn), weight-average relative molecular mass (MW) and peak-average relative molecular mass (Mp) of potato starch paste were decreased by ultrasonic treatment, indicating that the degradation of starch molecules was increased with irradiation time and decreased with ultrasonic intensity. The effect of ultrasonic field on the starch paste was increased with the decrease in starch paste concentration. The initial stage of the ultrasonic degradation of the starch paste was a random process and then the relative molecular mass distribution became wider. However, the middle stage was a non-random process and the relative molecular mass distribution became narrower. The relative molecular mass distribution tended to a limit valu e in the final stage.

Key words: ultrasonic, potato starch, relative molecular mass