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KMID : 0380620070390050584
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Korean Journal of Food Science and Technology
2007 Volume.39 No. 5 p.584 ~ p.587
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Dynamic Rheological Properties of Hydroxypropylated Rice Starches during the Aging Process
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Choi Hye-Mi
Yoo Byoung-Seung
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Abstract
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The effect of molar substitution (MS, 0.030-0.118) on the dynamic rheological properties of hydroxypropylated rice starch pastes (5%, w/w) was investigated by small-deformation oscillatory measurements during aging. The magnitudes of storage (G′) and loss (G″) moduli measured at 4°C before aging increased with an increase in MS in the range of 0.030-0.118, while those of tan δ (the ratio of G″/G′) decreased. The G′ values of hydroxypropylated rice starches, as a function of aging time (10 hr) at 4°C, increased rapidly at the initial stage, and then reached a plateau region at shorter aging times. However, for the native starch, the plateau values were not observed for G′ after a long aging time. Increasing the MS resulted in a decrease in plateau values. The rate constant (K) for structure development during aging was described by first-order kinetics. The K values of hydroxypropylated rice starches at 0.086 and 0.118 MS were much lower than the K value at 0.030 MS.
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KEYWORD
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Hydroxypropylation, rice starch, rheology, storage modulus
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