Master of Science (MS)
School of Nutrition and Food Sciences
This study assessed the effects of amino acid additives, aspartic acid, leucine, lysine, and methionine, on the pasting and thermal characteristics of white-fleshed and orange-fleshed Beauregard sweet potato starches. Also, the white-fleshed and the orange-fleshed sweet potato starches were compared for any differences in their resistant starch and crystalline properties. This study was performed using Differential Scanning Calorimetery (DSC), Rapid Visco Analysis (RVA), X-ray Diffraction (XRD), and Resistant Starch Determination. The orange-fleshed starch granules began to gelatinize at a lower temperature (56.8°C) than the white-fleshed starch (70.1°C), but the two starches needed the same amount of energy to gelatinize. Lysine increased the gelatinization temperature of the orange-fleshed starch. The addition of lysine and aspartic acid increased the gelatinization temperatures of the white-fleshed starch. In comparing pasting characteristics, the orange-fleshed starch was found to be easier to cook, had a lower potential for retrogradation, and was less stable during heating than the white-fleshed starch. The RVA analysis showed that the charged amino acids, aspartic acid and lysine, had more of an affect on the two starches than did the neutral amino acids, leucine and methionine. Aspartic acid had similar effects on both starches, making them less stable during cooking and lowering the potential for retrogradation. Lysine, when added to the orange-fleshed sweet potato starch, decreased the breakdown, allowing for more stability during cooking. The results of the resistant starch determination revealed that the white-fleshed sweet potato starch had significantly more resistant starch than the orange-fleshed starch in gelatinized and ungelatinized forms. Lysine increased the amount of resistant starch in the orange-fleshed starch, while leucine and methionine decreased the resistant starch in the orange-fleshed and the white-fleshed starches, respectively. The crystallinity patterns of the white-fleshed and orange-fleshed sweet potato starches were found to be the A-type pattern before gelatinization, and the B-type pattern after gelatinization. The addition of aspartic acid and methionine did not alter the crystalline pattern of either of the starches and caused a decrease in crystallinity, while the addition of leucine and lysine increased the crystallinity of the white-fleshed sweet potatoes.
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Lockwood, Stephanie Helen, "Effects of amino acids on the properties of white-fleshed and orange-fleshed Beauregard sweet potato starch" (2007). LSU Master's Theses. 1550.