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Effects of Ice Structuring Proteins on Freeze-Thaw Stability of Corn and Wheat Starch Gels

¹State Key Laboratory of Food Science and Technology, School of Food Science and Technology, International Exchange and Cooperation Program, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, China. ²Corresponding authors. Phone/fax: 86-510-8591-9139. E-mail: yskksu@gmail.com (Y. Kim); wnhuang@jiangnan.edu.cn (W. Huang) ³The China Yuren Food Group, 10 Yurun Road, Jianye District, Nanjing, Jiangsu 210041, China.

The effect of ice structuring proteins (ISP, 0.5%, starch weight basis) on the freeze-thaw stability of corn and wheat starch gels (CS and WS, respectively) was studied. Syneresis measurement, hardness, thermal properties using differential scanning calorimetry (DSC), X-ray diffractions, and scanning electron microscopy (SEM) were determined with starch gels (SG) subjected up to nine freeze-thaw cycles (FTC). The gelatinized SG were stored at –20°C for 22 hr and thawed at 30°C for 2 hr. As the number of FTC increased, syneresis was increased; however, ISP significantly (P < 0.05) reduced the syneresis for all FTC except at FTC 1. Hardness was increased up to FTC 4, then decreased for both SG. ISP significantly lowered the hardness of both SG. The ice melting enthalpy (ΔH_{ice sample}) of SG increased as FTC increased but SG with ISP had significantly lower enthalpy. The retrogradation ratio (RR) from DSC was significantly increased as the number of FTC increased. ISP reduced RR but most of RR was not significantly different for the corresponding FTC. The X-ray diffraction patterns showed less recrystallization of WS with addition of ISP. The microstructures from SEM showed that the addition of ISP reduced the size of ice cell cavities.