61A-11 |
Effect of ohmic heating on thermal properties of rice starch and flours using differential scanning calorimetry (DSC) |
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 Almost no research has been done on ohmic heating effects on starch functionality. One study found a direct relationship between electrical conductivity and DSC gelatinization curves of starches. However, no research has used various frequencies and voltages to determine the effect of ohmic heating on thermal properties of rice starch. Our objective was to determine if various ohmic heating conditions could alter thermal properties of rice starch and flours, with various levels of lipids and proteins, as compared to native samples. Thirty grams of pure rice starch, two white rice flours or brown rice flour were mixed with 100mL water and placed in an ohmic heater with electrodes paddles. Samples were heated to 100°C at 1, 60, and 90 Hz with varying voltages from 20 V/cm to 70 V/cm. DSC analyses were carried out at a 1:2 starch to water ratio with a 2°C /min ramp to 100°C. The starch granules became more stable after ohmic heating as indicated by increases in onset and peak temperature, especially for samples with the lowest lipid and protein contents. Pure rice starch thermal characteristics became similar to that of brown rice flour after ohmic heating. Enthalpy of gelatinization was lower for ohmically heated samples, which was most likely due to pregelatinization effects. Brown rice flour showed the greatest onset and peak temperatures, indicating an influence of lipid and protein on starch thermal properties. There were no major differences in thermal properties with varying frequencies, but lower voltage resulted in lower enthalpy. This was most likely due to the lower voltage resulting in a more complete pregelatinization due to longer heating time required to reach 100°C. This research shows that ohmic heating can change the thermal properties of rice starch. This information might useful for modified rice starch and flour ingredient development.
Session 61A, Carbohydrate
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