Effect of pH-shifting treatment on the gel properties of pumpkin seed protein isolate

Abstract

pH-shifting treatment is a novel method to modify protein, which can improve the functional properties and application of protein in food products. In the present study, the influence of pH-shifting method on heat induced gel properties of pumpkin seed protein isolate (PSPI) was investigated. PSPI, treated under different pH values (pH 2, pH 4, pH 6, pH 8, pH 10, and pH 12) were labeled as PSPI 2, PSPI 4, PSPI 6, PSPI 8, PSPI 10, and PSPI 12, respectively. The water-absorbing ability, textural analysis (hardness, adhesiveness, and cohesiveness) of the gels formed by different pH-shifting treated PSPI were investigated. Compared with that of control, the water-absorbing ability of PSPI 2, PSPI4, and PSPI 12 showed increased (p<0.05) value significantly. The textural analysis of PSPI gels showed that only the hardness of PSPI 6 showed increased (p<0.05) value. The cohesiveness of PSPI samples after treating at pH 2, pH 4, pH 6, pH 8, pH 10, and pH 12 showed no significant (p > 0.05) difference compared to control. The adhesiveness of PSPI 2, PSPI 4, and PSPI 10 showed significant (p < 0.05) decreasement while the adhesiveness of PSPI 6, PSPI 8 and PSPI 12 didn’t show any significant (p > 0.05) difference compared to control. These results indicated that pH- shifting treatment might be a convenient and economical method to change the gel properties of PSPI, which would provide a fundamental knowledge for further utilization of PSPI in food products.