Improved water resistance of soy protein adhesive at isoelectric point.

摘要

The effects of protein surface charge on the adhesive performance of soya protein isolates (SPI) were investigated. A laboratory-prepared, freeze-dried SPI was used and achieved positive, neutral and negative net charges on the surface of protein bodies by adjusting the pH. The adhesive performance was evaluated as indicated by bond strength, water resistance, thermal denaturation and rheological properties. Results indicated that a neutral surface charge of protein at isoelectric point (pI) was critical in increasing water resistance of SPI. The highest wet strength of SPI was reached at pI. Dry and soaked strengths were high in the pH range of 3.6-7.6. Differential scanning calorimetry results showed that SPI were more thermally stable at pI than at other pH values. Soya protein became insoluble at pI; xanthan gum, dextrin D2006, dextrin D2256 and pectin were used as suspension additives to increase the homogeneity of the adhesive at pI. Xanthan gum solution had the highest viscosity among the 4 suspensions. The addition of xanthan gum could mimic the rheological properties of SPI at the expense of adhesion strength.