42-8 |
Prediction of long-grain rice texture and pasting properties from starch and protein fractions |
J. F. C. MEULLENET1, A. Brun, and W. K. Chung1. (1) Dept. of Food Science, Univ. of Arkansas, 2650 N. Young Ave., Fayetteville, AR 72704-5585 There is abundant literature dealing with the effects of postharvest handling (i.e., drying, storage and milling) on functional characteristics of rice. However, there is little information on the variability in the functionality of specific rice cultivars within a field or between fields and what its physico-chemical determinants may be. The objective of this study was to determine predictive models of rice functionality from protein and starch chemistry data. One long-grain rice variety (Cocodrie) was harvested from two fields in Arkansas. Rice was harvested from 8 locations in each field. Samples were then stored at 21oC/50% RH until equilibrated to a storage moisture content of 12%. Texture properties were measured using a TPA test on ten cooked rice kernels in conjunction with a Texture Analyzer (TAXT2i, Texture Technologies, Scarsdale, NY) while pasting properties were measured with a Rapid Visco-Analyzer. Rice chemical properties measured included amylose and protein contents, starch molecular weight profiles and protein molecular weight distribution. Rice harvested from a single rice field was quite variable in physicochemical properties. For example, the protein contents of rice flour samples ranged from 6.62 to 8.44% and peak viscosity of the rice flours ranged from 184.7 to 217 cp. This implies that small changes in water or nutrient availability can have a significant impact on rice quality. It was also established that functional characteristics can be predicted from both starch and protein chemistry. Peak viscosity (Rc=0.98, Rp=0.72) was well predicted by protein and starch data. Overall, data indicate that starch was more important in predicting peak viscosity than were proteins. These results are not necessarily new findings as many studies have demonstrated the role of starch and to some extent proteins in determining functional characteristics such as cooked rice texture. However, this study illustrates the fact that the same general principles apply to variations in functionality within a single cultivar.
Session 42, Food Chemistry: Proteins II
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