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KMID : 0380620070390050534
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Korean Journal of Food Science and Technology
2007 Volume.39 No. 5 p.534 ~ p.540
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Physicochemical Properties of Cross-Linked Waxy Rice Starches and Its Application to Yukwa
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Yu Chul
Choi Hyun-Wook
Kim Chong-Tai
Ahn Soon-Cheol
Choi Sung-Won
Kim Byung-Yong
Baik Moo-Yeol
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Abstract
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In this study, waxy rice starch was chemically modified using phosphorous oxychloride (POCl3, 0.002-0.008%). Then the physicochemical properties of resulting cross-linked waxy rice starches were investigated in order to reduce the steeping time of Yukwa (a Korean oil-puffed rice snack) processing. The swelling powers of the cross-linked waxy rice starch samples were higher than the native waxy rice starch at temperatures above 60°C, and their increases were proportional to the POCl3 concentration. The solubility of the cross-linked waxy rice starch was lower (1.6-3.4%) than the native waxy rice starch (2.7-6.1%). However, the moisture sorption isotherm of the cross-linked waxy rice starch was not significantly different from the native waxy rice starch. The rapid visco analyzer (RVA) pasting temperatures (65.4-67°C) of the cross-linked waxy rice starch were lower than those of the native starch (67°C). The RVA peak viscosities (287-337 RVU) of the cross-linked waxy rice starch were higher than that of native starch (179 rapid visco units (RVU)), and increased with increasing POCl3 concentration. For the differential scornning calorimeter thermal characteristics, although Tc shifted toward higher temperatures with cross-linking, the To, Tp, and amylopectin melting enthalpy of the cross-linked waxy rice starch showed no differences compared to the native waxy rice starch. The X-ray diffraction patterns of both the native and cross-linked waxy rice starches showed typical A-type crystal patterns, suggesting that cross-linking mainly occurs in the amorphous regions of starch granules. Therefore, the cross-linking reaction did not change the crystalline region, but altered the amorphous region of the waxy rice starch molecules, resulting in changes of solubility and RVA pasting properties in the cross-linked waxy rice starch. In summary, since cross-linked waxy rice starch has a high puffing efficiency and no browning reaction, it may be applicable for Yukwa processing without a long steeping process.
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KEYWORD
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Yukwa, cross-Linked waxy rice starch, physicochemical properties, phosphorus content, RVA, DSC, X-ray
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