Contribution of protein hydrophobicity to its functionality

HANSCH analysis for quantitative structure‐activity relationship (QSAR) was applied to aspartyl proteinases and it was found that higher hydrophobicity, tighter molecular structure, and lower charge are required for milk clotting enzymes compared to proteolytic enzymes. For simplicity in analysis of food proteins, the use of fluorescence hydrophobicity, solubility and steric relating parameters, e. g., SH‐SS content and viscosity, are used instead of hydrophobic, electrical and steric parameters in the original QSAR concept. Solubility of milk and soy proteins after different heat treatments was investigated and it was found that aromatic hydrophobicity measured by anilinonaphthalenesulfonate fluorometry and by phenyl‐Sepharose chromatography showed better correlation than aliphatic cis‐parinarate (CPA) hydrophobicity. The use of CPA hydrophobicity in conjunction with solubility is, therefore, justified in an attempt to avoid multicollinearity in regression study. Significant correlations were found for emulsifying and fat binding capacity of both unheated and heated food proteins when the apparent hydrophobicity with CPA was used as a predictor variable. For foaming property, CPA hydrophobicity measured for unfolded protein ( S e ) and viscosity played important roles. S e and SH‐group content showed good correlation with thermal functionality of proteins. Emulsifying and fat binding properties of crude salt extracts of meat proteins from beef and fish which had been subjected to different processing conditions were explained by using CPA hydrophobicity, solubility and SH‐group content.