18A-18 |
|
H.-W. CHOI, Starches and Sweetener Division/R&D Center, Daesang Corp., 125-8, Pyokyo-ri, Majang-myun, Ichon, 467-813, South Korea, D.-S. Kim, Dept. of Food Science, Milyang National Univ., 1025-1 Nae 2 Dong, Miryang, 627-130, South Korea, N.-Y. Hur, Dept.of Food and Culinary Art, Osan College, 17, Chunghak-dong, Osan, 447-749, South Korea, B.-Y. Kim, Dept. of Food Science & Technology, Kyung Hee Univ., Seochun 1, Yongin, South Korea, and M.-Y. Baik, Dept. of Food Science and Technology, KyungHee Univ., Seochun 1, Yongin, 449-701, South Korea. Chemical modification would improve the functional properties of starch. Cross-linking and substitution are two major modification methods. Cross-linking reinforces the hydrogen bonds in the granule with chemical bonds, which act as bridges between molecules. Hydroxypropylation, one of popular substitution methods of starches, weaken the internal bond strength between starch molecules. Although physicochemical properties of modified starch are well established, they are focused on single modification and limited information is available on cross-modified starches. The objective of this work is to investigate the physicochemical properties of cross-modified starch, which focused on the effect of cross-linking on hydroxypropylated rice starch. Rice starch was hydroxypropylated using propylene oxide (2%, 6%, 12%). Hydroxypropylated rice starches were then cross-linked using phosphorous oxychloride (0.005%, 0.02%). Physicochemical properties of cross-modified (Hydroxypropylated and cross-linked, HPCL) rice starches were investigated using RVA and DSC. Swelling power of HPCL rice starch increased at relatively lower temperature than native rice starch. HPCL rice starch showed lower solubility than native rice starch and solubility increased with increasing propylene oxide. For RVA pasting properties, pasting temperature and peak viscosity of HPCL rice starches were lower than native starch, but holding strength and final viscosity were higher than native starch. It is interesting to note that RVA pasting properties were categorized as the degree of hydroxypropylation suggesting hydroxypopylation is predominant in this case. DSC thermal transitions of HPCL rice starches were shifted to lower temperature than native rice starch as the degree of hydroxypropylation increased and cross-linking decreased. This work showed the importance of reaction order in cross-modification and provides the basic and scientific information on the physicochemical properties of cross-modified (HPCL) rice starch.
Session 18A, Carbohydrate: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |