2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Alkali-extracted starches have often been shown to have higher paste viscosities than starches isolated using other methods. Objectives of this study were to examine the effect of alkaline extraction on the amounts and profiles of granule-associated proteins, and to determine its influence in different rice lines. Starch granule proteins, including granule-bound starch synthase (GBSS), were found to be partially lost during alkaline extraction of rice starch. Variability in amount of loss in GBSS and other granule proteins was found among different rice lines. Additionally, part of the GBSS and other granule proteins leached out during starch pasting of alkali-extracted rice starch. The degree of leaching of GBSS from the raw starch during alkaline extraction, and in the gelatinized starch granules during pasting, was proportional to leaching of low molecular weight starch granule proteins. Confocal laser scanning microscopy revealed that protein was widely distributed in the gelatinized starch granules prepared from the starch isolated using alkaline extraction. Starch of rice lines 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 tend to be resistant to leaching during pasting. The study showed that GBSS can be leached out during alkali-extraction, and variation of leaching in GBSS and other granule-associated proteins among different rice lines may partially account for the differences in their pasting properties.