88C-9 |
The characterization of chemical gelatinization of corn starches using spin-spin relaxation time changes |
Y. LEE1, M. J. McCarthy, and K. L. McCarthy. (1) Food Science and Technology, University of California Davis, One shields Ave., Davis, CA 95616 Starch is one of the most abundant and widely used natural polymers. Because of its functionality, starch has been used for variety of applications in the food, paper and textile industries. To meet diverse purposes, the physical properties of starches have been changed through modification. The characterization of different types of starch is critical for its proper application. The objective of this work is to determine the potential for monitoring gelatinization using spin-spin relaxation time measurements. Unmodified, acid-thin, and oxidized corn starches were gelatinized with 0.2 mol NaOH. A 10% (w/w) starch dispersion was prepared for each starch at a temperature of 40 °C. The spin-spin relaxation time (T2) throughout the gelatinization process was monitored using a Bruker Minispec PC 110. The relaxation time was fitted with a bi-exponential model. The spin-spin relaxation times for all three starches varied with time. During the first 6 minutes the relaxation times changed only slightly. After 6 minutes the spin-spin relaxation times changed significantly reaching a constant value after 7 hours. Each of the corn starches studied displayed similar behavior, however the value of the spin-spin relaxation times are different for each corn starch. For example, 3 hours after the start of gelatinization T2 values were 480 ms, 366 ms, and 871 ms for unmodified, acid-thin, and oxidized starch samples respectively. Spin-spin relaxation times are sensitive to the changes during chemical gelatinization of corn starch.
Session 88C, Food Engineering: Physical and Chemical Properties
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