The influence of starch structure and anthocyanin content on the digestibility of Thai pigmented rice.

Starch digestibility and polyphenol content were investigated in six (white, red and purple) Thai rice varieties. Total phenolic content (TPC), total anthocyanin content (TAC), amylose content, gelatinization parameters and in vitro digestibility were determined. Purple and red rice varieties were found to have the highest levels of TPC, TAC and amylose content. TAC was not detected in white rice, while purple rice had the highest values. Gelatinization parameters were determined using differential scanning calorimetry. Red rice (Sung Yod) showed the highest gelatinization enthalpy. Non-pigmented rice (Hom Mali) in both purified starch and flour showed the highest starch digestibility, with a total starch digestibility of 76.85% and a digestion rate of 0.25 min-1. In contrast pigmented rice varieties showed lower starch digestibility. These results suggest that pigmented rice varieties are a source of phenolics and anthocyanin and also a possible good source of low digestible starch to develop as functional food products.