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

The hydrothermal treatment of starch, either in excess water (annealing) or in limiting moisture conditions (heat moisture treatment; HMT), affects its gelatinization properties. The implications of these physical treatments on the starch structure and the starch-lipid interactions are still not completely understood. In this study, these aspects were investigated for hydrothermally treated rice starches with varying lipid contents. Starches were isolated out of rice brokens by steeping for 3 to 24 h in 0.1N NaOH. Starch crystallinity (WAXS) and gelatinization properties (DSC) were only slightly affected by the isolation procedure. The endotherm associated with the dissociation of amorphous amylose-lipid complexes, and the lipid content both increased as a function of steeping time. The native starches were annealed (55 C; 33% w/w starch) or heat moisture treated (100 C; 80% w/w starch) for 24 h. Both treatments caused the gelatinization endotherm to shift to higher temperatures, and the gelatinization range to become smaller (with the latter being more pronounced for the annealed starches). For the HMT samples, DSC measurements showed an endotherm near 120 C, which appeared at the expense of the amorphous amylose-lipid dissociation endotherm. This endotherm was ascribed to the melting of crystalline amylose-lipid complexes formed during DSC analyses. The in situ formation was deduced from the fact that WAXS could not confirm the existence of crystalline amylose-lipid complexes in granular HMT starch, and that slowing down the DSC heating rate caused the 120 C-endotherm to increase.