17C-3 |
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M. I. SALEH, J.-F. Meullenet, W. K. Chung, and A. Han. Department of Food Science, University of Arkansas, 2650 N Young Avenue, Fayetteville, AR 72704 Rice is a heterogeneous structure composed of three major constituents, starch, protein and lipids. Changes in rice starch, protein and lipids during storage are considered as important factors in determining rice functional properties. The objective of this study is to investigate the participation of each rice constituents in determining rice functional properties during aging. Rice cultivars (Wells and Bengal) were stored at 4°C, 21°C and 38°C for up to 48 weeks. Rice sample functionality was assessed at three-week intervals. Starch was extracted using an alkaline steeping method. Free lipids were removed from rice flour using chloroform: methanol. Bound lipids were removed by propanol: water using a Soxhtec method (55oC for 3h). Protease treatment was performed on rice flour. Rheological properties were determined using a TA Advanced Rheometer AR 2000 in combination with a starch pasting cell. The removal of the lipid fraction from the flour resulted in a significant increase of the slurry viscosity (4.72 and 4.09 Pa.s for Bengal and Wells, respectively) and a more rapid swelling of the starch granules. This increase in viscosity (a 20% increase over rice flour) was attributed to the release of proteins from lipid rich protein bodies. This was confirmed by the lower viscosity of protease treated defatted rice flour. Protease treated rice flour had the lowest trough, peak and final viscosities of all treatments showing the predominant role of proteins in determining rice pasting properties. Lipid removal contributed to a more rapid starch granule swelling while protein removal contributed to slowing starch swelling. Preliminary results indicate that the minor components of rice (i.e. proteins and lipids) play a major role in determining pasting properties of rice flour. It is expected that the role of the rice constituents in determining rice functionality changes during aging will be established.
Session 17C, Food Chemistry: Cereals, grains, legumes and their products
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