Correlation between Physical Properties and Shear Adhesion Strength of Enzymatically Modified Soy Protein-Based Adhesives

This work was to correlate physical properties with adhesion properties of soy protein‐based adhesives. By building such a correlation, the adhesion properties can be predicted by measuring physical properties of soy protein‐based adhesives. In this context, three important physical properties, viscosity, tacky force, and water resistance, were selected to correlate with adhesion strength of enzymatically modified soy protein‐based adhesives (ESP). Response surface methodology, specifically central composite design, was used with three independent variables to prepare ESP: trypsin concentration (X₁), incubation time (X₂), and glutaraldehyde (GA) concentration (X₃). The three physical properties measured were all greatly affected by our three independent variables with significance at the 95 % confidence level. The responses were then correlated with the adhesion properties of ESP. In conclusion, viscosity can be used to predict the dry adhesion strength of ESP based on the coefficient of determination (R²) of 0.8558. In addition, tacky force and water resistance can be used to represent wet adhesion strength of ESP based on R² of 0.7082 and 0.6930, respectively (P < 0.05). This work preliminarily identified the significant physical properties that can predict the adhesion strength of the ESP system crosslinked with GA, but the results need to be further confirmed by another protein modification system to give a generic conclusion.