29-2 |
Pasting properties of starch isolated from rice flours as influenced by added lipids and b-cyclodextrin (b-CD) |
J. M. KING1, X. Liang1, and F. F. Shih2. (1) Department of Food Science, Louisiana State University Agricultural Center, 111 Food Science Bldg., Louisiana State University, Baton Rouge, LA 70803, (2) USDA-ARS-SRRC, New Orleans, LA 70124 It is well know that lipids can generally affect starch properties, but pasting properties of starches isolated from different rice flours and the effects of lipid structure and b-CD have not been compared. The objective of this study was to compare the effects of isolation from different flour sources, and of lipid- and b-CD-starch interactions on the pasting properties of isolated rice starch. Two saturated and 3 unsaturated fatty acids, as well as monopalmitin(MP) and tripalmitin(TP), lysophosphatidylcholine(LC) and lysophophatidylethanolamine(LE), and b-CD were tested on rice starch isolated from white rice flour only. Lipids were added at 0.2 and 0.6%, and b-CD was added at 2 and 6% of the starch. Flours were defatted by soxhlet extraction and de-proteinated by alkaline protease digestion. Defatting reduced final viscosity(FV), total setback(TSB) and pasting temperature(PT), while de-proteination decreased all pasting parameters compared to the native white flour. TSB decreased from 177 to 64 RVU, peak viscosity(PV) from 250 to 198 RVU and BKD from 118 to 78 RVU. For brown rice flour PV, FV, TSB and BKD all increased after each isolation step. The largest increase was for BKD, which changed from 1.67 (defatted) to 37 RVU (de-proteinated). None of the lipids affected PT, except for a 3°C increase by LE at 0.6% addition. BKD was mainly affected and increased up to 39 RVU for fatty acids while decreasing up to 80 RVU for other lipids. TSB was doubled by the addition of 0.6% MP, but decreased to 1/3 by 0.6% LE or LC. The addition of b-CD decreased MV and FV, while increasing BKD. This study showed that brown rice flour isolate has different pasting properties from white rice flour isolate, which is also affected by type of lipid added. This information may be useful in the development of modified rice starch products.
Session 29, Carbohydrate
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