Abstract:

In order to explore the difference in starch composition content and the change of rice digestion rate in rice lines. In this study, the contents of amylose (AC), total starch (TS), rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS)in 126 indica rice strains were analyzed by enzyme digestion method in vitro. And then detected the digestion rate of the cooked rice and estimated the glycemic index (eGI) of 18 rice lines with significant differences in AC,SDS and RS. The results indicated that the starch contents of these lines differ greatly, AC was 4.29%—25.58% with an average of 10.43%, TS was 71.69%—82.45% with an average of 77.73%, RDS was 43.31%—57.47% with an average of 50.07%, SDS was 18.96%—32.56% with an average of 25.26%, and RS was 0.59%—4.87%with an average of 2.39%. There was a certain correlation between eGI values and starch content in different rice lines. The eGI values of high AC were significantly lower than low AC, but it was also found that the eGI values of Diangu 2030 with low AC and Dianpan 3429 with low SDS were also low. The eGI values of high SDS were lower than low SDS, but there were also cases where the eGI values of low SDS were also low. The eGI value of high RS was significantly lower than low RS. The rice digestion rate was fast and the sugar release was the highest of all the rice stains within 30 min after the meal, which continued to decrease after 60 min. The eGI values of the lines with high AC, SDS or RS content were generally lower than those with low starch content. The grain digestion rates were different among the tested rice lines, and it suggested that the digestion rates of rice grain could be affected by other factors except the AC, SDS and RS. These results can offer valuable references for the development of low-GI rice varieties.

Key words: Rice, Starch component, Enzyme digestion in vitro, Estimated glycemic index, Digestible sugar content