30D-17 |
Effect of ohmic heating on pasting characteristics of rice starch and flours using rapid visco-analysis (RVA) |
H. 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 Ohmic heating was studied for the purposes of extracting specific components or improving drying rate of fruits or vegetables. No research has been done to determine the effect of ohmic heating on pasting characteristics of rice starch. Our objective was to determine ohmic heating affects on the pasting characteristics of rice starch/flours with varying lipid and protein levels, as compared to native samples. Thirty grams of pure rice starch, two white rice flours or brown rice flour were dispersed in 100mL-distilled water and placed in an ohmic heater. Samples were heated to 100°C at 1, 60, and 90 Hz with varying voltages from 20 V/cm to 70 V/cm. Three grams of ohmically heated starch and 25g of added water were heated from 50 to 95°C, and then cooled to 50°C by RVA. Brown rice flour with greatest fat and protein showed the greatest cooking stability and least retrogradation potential as shown by lower breakdown and total setback. Brown rice flour showed the greatest pasting temperature and lowest peak viscosity, while pure starch had the lowest pasting temperature. Ohmic heating decreased pasting temperature for pure rice starch, resulting in a starch that swelled faster. This was not observed in the flours. This indicated that non-starch constituents might act as a stabilizer and barrier to water access into the granules. At higher voltage, ohmic heating produced less cooking stability resulting from a faster heating rate since the electrical conductivity of ohmic heating increases with higher voltage. Low frequencies are correlated with greater electrical conductivities, and breakdown as well as total setback was greatest at 1Hz resulting in a less stable starch. Ohmic heating has been shown to alter rice starch pasting characteristics with an added influence of lipids and proteins. This information might useful for modified rice starch and flour ingredient development.
Session 30D, Food Engineering: Physical and chemical properties
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