Parboiling Alters Protein and Lipid and Impacts In Vitro Rice Digestibility and Glucose Release

ABSTRACT Parboiling is a hydrothermal processing of paddy grain applied to 20% of all rice consumed. Parboiling can alter rice biochemical composition, starch properties, and subsequent starch digestibility. In this experiment, glucose release on in vitro digestion of nonparboiled and parboiled rice was examined, and the protein and lipid content of rice was analyzed. Glucose release on in vitro digestion was decreased in nine parboiled rice samples but increased in six samples. There was little change in lipid and total protein content in parboiled rice samples. Extractable globulin, glutelin, and prolamin proteins were significantly reduced in all parboiled rice may be due to a stronger protein–starch matrix induced by parboiling. Acetic acid extracted globulin had a negative correlation with glucose release upon in vitro digestion in parboiled rice samples, and correlation was significant at 120 min digestion ( r = −0.67, p < 0.01). Changes in glucose release upon in vitro digestion due to parboiling had weak negative correlations with changes in lysophospholipid content ( r = −0.69) and lipid‐bound amylose content ( r = −0.57). In conclusion, parboiling has little effects on the total lipid and total protein content, however, can change the interaction between starch and nonstarch components (protein and lipid) in rice impacting glucose release upon in vitro rice digestion.