61A-14 |
Effects of amino acids on thermal properties of rice starch using differential scanning calorimetry (DSC) |
S. Y. TAN, X. Liang, and J. M. King. Department of Food Science, Louisiana State University Agricultural Center, 111 Food Science Bldg., Louisiana State University, Baton Rouge, LA 70803 Studies have shown that proteins can have an effect on starch gelatinization properties. Protein content has been shown to negatively correlate with water absorption and positively correlate with cooking time. Protein removal was shown to result in decreased gelatinization temperature of flour, indicating that rice protein can inhibit starch granule swelling. The influence of amino acid structure and type on the thermal properties of rice starch has not yet been studied. Our objective was to determine individual amino acids effects on the gelatinization properties of rice starch. Aspartic acid, glutamic acid, arginine, and lysine were added at 6% of the dry weight of commercial rice starch into pans. Water was added to 70% moisture. Duplicate analyses were carried out using DSC with a temperature ramp of 5°C/min from 20 to 130°C and additive influences were compared. Rice starch without additives was used as the control. Two peaks were observed around 67°C and 100°C. Peak and completion temperatures of gelatinization were increased up to 2.1°C and 3.5°C, respectively, by all of the amino acids tested as compared to the control, but enthalpy was not affected. All amino acids except aspartic acid caused an increase in onset temperature up to 1.9°C. In the amylose-lipid complex transition, aspartic and glutamic acids affected enthalpy only, with decreases of 1.4 J/g and 1.8 J/g compared to the control. Although onset, peak and completion temperatures of gelatinization were increased in the presence of arginine or lysine, no amylose-lipid complex transition was detected. These results indicated that presence of acidic or basic charged amino acids can increase the gelatinization temperatures and reduce the enthalpy of amylose-lipid complex melting. Therefore, amino acids somehow inhibit amylose-lipid complex formation. This information may be useful in the development of modified rice starch products.
Session 61A, Carbohydrate
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