Partial Leaching of Granule-Associated Proteins from Rice Starch during Alkaline Extraction and Subsequent Gelatinization

Abstract

Starch granule-associated proteins, including granule-bound starch synthase (GBSS), were found to be partially lost during alkaline extraction of rice starch. Variability in amount of loss of GBSS and other granule proteins was found among different rice lines. Also, part of the GBSS and other granule proteins leached out during gelatinization of the alkali-extracted rice starch. Confocal laser scanning microscopy revealed that some protein still existed in gelatinized starch granules prepared from starch isolated using alkaline extraction. The starch that retained more GBSS and other granule proteins after alkaline extraction tended to have more protein in the isolated gelatinized starch granules, indicating that proteins resistant to alkaline extraction also tended to resist leaching during gelatinization. The study suggests that leaching of granule-associated proteins may contribute to variations in paste properties of alkali-extracted starches.