15D-32 |
Effect of ohmic heating on amylose leaching from rice starch and flours |
H. J. AN and J. M. King. Department of Food Science, Louisiana State University Agricultural Center, 111 Food Science Bldg., Louisiana State University, Baton Rouge, LA 70803 Research has shown ohmic heating's usefulness in the pasteurization, drying rate improvement, and increased extractability of foods as well as influencing surimi gelation. No research has been done to determine the effect of ohmic heating on amylose leaching from rice starch granules. Our objective was to determine how ohmic heating affected amylose leaching from rice starch and flour. Twenty grams of pure rice starch, two different white rice flours or brown rice flour were placed in 100 mL water. The slurries were placed in the ohmic heating cell with electrodes at each end. Samples were heated to 100°C. Three frequencies were tested at 1 Hz, 60 Hz and 90 Hz with varying voltages from 20 V/cm to 120 V/cm. Proximate analysis showed that the two white rice flours were very similar in their constituent levels (on wet basis) with a range of 0.69 to 0.71 % fat, 6.52 to 7.77 % protein and 80.14 to 80.88 % carbohydrate. The brown rice flour was different from the white rice flours in that it had 3.03 % fat, 9.12 % protein and 77.14 % carbohydrate. The control pure rice starch was 0.01 % fat, 0.56 % protein and 88.03 % carbohydrate. There was a decrease in apparent amylose content with increased fat and protein content of the rice starch and flours. This indicated that these non-starch constituents may inhibit the release of amylose during ohmic heating. There was a trend for lower apparent amylose contents with an increase in frequency at the same voltage for voltages above 70 V/cm. Processing rice flours or starch at higher frequencies may help to produce a starch product that will have less retrogradation potential. This information may be useful for starch ingredient development.
Session 15D, Food Engineering: Processing Technologies
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