The effect of the endogenous protein on the rheological and digestive properties of rice starch

The effects of the endogenous protein on the rheology and digestibility of rice starch were investigated. The protein augments the apparent morphology of the protein-starch mixture from smooth and dense to a uniform porous structure and finally a flaky and loose structure. Low protein content will assist the dispersibility of the starch granule, increasing the storage modulus (G′) of the protein-starch mixture. However, the elevated protein content will subsequently reduce the storage modulus of the mixture. In contrast, the loss modulus (G″) did not significantly change with different protein contents. From in vitro starch digestion analysis, when the amount of protein was varied, there was no significant difference in the slowly digestible starch. The level of rapidly digestible starch, however, increased at low protein content but subsequently decreased at the higher protein level. At the other end of the spectrum, resistant starch gradually increased with the increase in protein content.