Effect of heating on formation of curdlan gels

Abstract

The characteristics of curdlan preparations that were dehydrated after heating at various temperatures in water were examined by X-ray diffraction, differential scanning calorimetry and electron microscopy. X-Ray diffraction patterns showed that crystallinity was higher in preparations heated to above 80°C, with heated preparations at 170°C having the highest crystallinity. Differential scanning calorimetry showed that the temperature of the endothermic peak caused by swelling decreased and that the peak area became smaller with increasing heating temperatures. Moreover, preparations of (1 → 3)-β- d-glucans of low molecular mass, DPn 131 and 49, with and without heating at 120°C gave similar X-ray diffraction patterns and differential scanning calorimetry curves to those of the original curdlan. The crystallinity was particularly high without heating in the preparation of DP n 49 though the endotherm associated with the breakage of hydrogen bonds was lower and the enthalpy smaller than found for the original curdlan. Electron microscopic studies showed that longer and wider microfibrils were formed in curdlan gels, while shorter microfibrils or crystals were formed with the lower molecular mass samples of (1 → 3)-β- d-glucan, which are incapable of forming gels.