Esterification Of Starches With Octenyl Succinic From Different Rice Cultivars

Octenyl succinic starch esters were prepared in aqueous suspension systems from 12 strains of native indica rice starches with amylose contents (AC) of 1.65-27.15%. The paste properties, amylopectin chain length distribution, emulsification and in vitro digestion were also investigated to evaluate the effect of ACs on starch properties.The effect of AC on rice pasting properties was evaluated by means of rapid viscosity analyzer (RVA). The results showed significant difference in rice cultivars with different AC. With the increase of AC, the cultivars had higher hot paste viscosity (HPV), cool paste viscosity (CPV) and the setback (SBV). Among the seven RVA parameters, HPV had significant positive correlation with CPV, SBV, and the peak time (PT) (P<0.01). Moreover, CPV had positive correlation with SBV and PT (P<0.05); AC had significant positive correlation with HPV, CPV, SBV,and PT(P<0.01).The research of chain length distribution before and after esterification showed that different rice starch had roughly the same distribution trend of amylopectin chain length distribution. However, the peak time was changed for the rice starch with different AC. The highest peak appeared between DP (9-12). We found that the content of DP> 20 are rarely less than 1%.This emulsification of rice starches with different AC before and after OSA modification was also analyzed. The emulsification experiment showed that amylose content and emulsifying properties showed a negative correlation. The droplet size distribution of emulsions was in the range of 0.1～50μm obtained by a laser particle size analyzer.The digestibilities of indica rice starch with different cultivaties before and after OSA modification were also studied using an in vitro method. The results revealed that the esterification of starch with OSA could impair effect of a-amylase. Because amylase enzyme quickly broke into smaller molecules, the digestion rate decreased with the time. The higher amylose content in the starch, the lower starch was hydrolyzed.