Effects of interaction between rice glutelin and starch on starch gelatinization in a simulated storage system

Abstract

Starch and protein are the two major components of rice and interaction between them will occur during storage. However, whether the interaction between starch and protein impacts rice starch gelatinization is still unclear. In this study, the effects of starch-protein interaction on starch gelatinization (japonica rice) were investigated using a glutelin–starch simulation system under high temperature and humidity storage conditions. A glutelin–starch ratio of 1:4 was used in the simulation system and stored in an artificial climate chamber (40 °C, 60% humidity) for 60 d. The interaction had a significant effect on starch gelatinization. Starch granule particles were broken down, and the bonds of starch granules weakened during interaction with glutelin. The secondary structure of glutelin loosened, as the starch disintegrated the α-helix structure. Correlation analyses revealed that peak viscosity (PV), trough viscosity (TV), and final viscosity (FV) had a significant negative correlation with carbonyl content, and disulfide bonds (P < 0.01), as well as a significant positive correlation with the active thiol content (P < 0.01). Moreover, setback (SB) had a significant positive correlation with the α-helix and a negative correlation with the β-turn content (P < 0.05). PV, TV, breakdown (BD), and FV were significantly related to β-sheet in glutelin (P < 0.05). These results suggest that glutelin and starch can interact and affect starch gelatinization.