Influence of Small Amphiphiles on Aqueous Dispersions of <i>β</i>-Lactoglobulin A and Bovine Serum Albumin: (1) Intermolecular Interactions

Abstract

Hydrophilic and hydrophobic ( φ ) interactions among amphiphiles play critical roles in interfacial properties of proteins and other smaller amphiphiles and affect the creation and stability of foams and emulsions in food systems. Contribution of small amphiphiles on H-bonding and hydrophobic ( φ ) interactions at a model interface comprising of a water-hydrophobized surface interface as reflected by contact angle ( θ ) of fatty acid free bovine serum albumin (FAF-BSA), bovine serum albumin (BSA), and β -lactoglobulin variant A ( β -LGA) was investigated. Amphiphiles were used with either protein in neutral water or α -bromonaphtalene ( α -BrN) (22 ° C) to obtain θ -H 2 O and θ - α -BrN measurements, respectively. θ - α -BrN reflected influence of φ -interactions on θ since α -BrN molecules do not partake significantly in H-bonding. Ionic nature of the amphiphiles had no significant effect. Dramatic difference was between zwitterionic Z8 and Z12. At 1%, Z8 significantly increased H-bonding in BSA and β -LGA by 26% and 55%, respectively, whereas Z12, which is more hydrophobic, decreased it by 50% and 21%. At the same concentration, φ -interactions were enhanced by Z8 for BSA by 37% and by all amphiphiles except Z12 for FAF-BSA.