Surface Hydrophobicity in Protein–Polysaccharide Conjugates: A Critical Review of Analytical Methods, Structural Determinants, and Implications for Emulsification and Foaming

Protein–polysaccharide conjugates have attracted increasing interest as functional hydrocolloid ingredients because they can modulate protein structure, interfacial behavior, and colloidal stability in complex food systems. Among the structural parameters commonly reported for these conjugates, surface hydrophobicity is one of the most frequently measured, yet its interpretation remains inconsistent across studies. This review examines surface hydrophobicity as a system-dependent parameter in protein–polysaccharide conjugates, with emphasis on its analytical determination, particularly by the widely used ANS (8-anilinonaphthalene-1-sulfonic acid) fluorescence method, and on the principal limitations of current approaches. Key factors affecting measured surface hydrophobicity are discussed, including protein source, polysaccharide type and structure, conjugation route, protein-to-polysaccharide ratio, pH, and ionic strength. The review also evaluates the relationship of surface hydrophobicity with hydrocolloid functionality, especially emulsification and foaming. Available evidence shows that increased surface hydrophobicity does not necessarily result in improved functional performance, because hydration, steric stabilization, solubility, and aggregation state also strongly influence interfacial behavior. Overall, this review highlights the need for more rigorous interpretation and standardized reporting of surface hydrophobicity in food hydrocolloid conjugates.