DETERMINATION OF SURFACE HYDROPHOBICITY OF MILK-PROTEINS - COMPARISONBETWEEN A NEW DETERGENT BINDING METHOD AND HYDROPHOBIC INTERACTION FPLC

A previously published method for the determination of the surface hyd rophobicity of proteins using BIO-RAD protein assay combined with Twee n 80 was adopted to various milk proteins. The relative retention time s obtained by HI-FPLC at Phenyl-Superose for casein and whey protein w ere compared with results of the proposed method and expanded by the a verage hydrophobicity calculated according to BIGELOW. Detergent bindi ng showed good correlation with calculated average hydrophobicities fo r all milk proteins, whereas HI-FPLC results were found to be accurate only for caseins. The relative order of hydrophobicity for single cas eins was pH dependent. In contrast, HI-FPLC was found to be not select ive for separation of whey proteins according to their hydrophobicity, but selective for the solubility characteristics related from the use d buffer system. Evidence is given that this proposed method can be ea sily performed, is highly reliable and adaptable to a rapid quantitati ve differentiation between hydrophobic and hydrophilic areas on protei n surfaces.