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-H2O 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.

Influence of Small Amphiphiles on Aqueous Dispersions of <i>β</i>-Lactoglobulin A and Bovine Serum Albumin: (2) Surface Energy and Emulsifying Properties

“…However, their hydrophobic moiety are different; Z8 is smaller (280 compared to 615 Dalton) with a straight chain octyl-chain whereas CHAPS has a myristoyl-chain with a bile-salt-like aromatic moiety attached to it. As seen earlier, the contribution of short-range interaction in the FAF-BSA dispersion (via H-bonding) was the highest for Z8 followed by CHAPS [9] and this indicated increased structuring of water [20]. In BSA dispersions, γ of control was higher than for FAF-BSA (62 compared to 55.5 mJ•m 2 ).…”

“…All materials and their sources were as listed in the previous article in this series [9]. Commercially available peanut oil was used for preparation of emulsions.…”

“…The previous paper in this series investigated the contribution of various amphiphiles on short range (Hbonding) and Lifshitz Van der Waals long range interactions (hydrophobic interactions) in protein dispersionsrevealed that the smallest peptide-like zwitterionic surfactant used, N-octyl-N, N-dimethyl-3-ammonio-1-propanesulfonate, contributed most to water structuring via H-bonding [9]. This part of the study investigates the influence of the same set of cationic, anionic, nonionic and peptide-like straight chain and aromatic zwitterionic amphiphiles on surface energy (γ) and emulsifying properties of the same proteins that are primary contributors to whey protein functionality [10] [11]; β-lactoglobulin (variant A) (β-LGA) and bovine serum albumin (BSA).…”

Generation and Stabilization of Whey-Based Monodisperse Nanoemulsions Using Ultra-High-Pressure Homogenization and Small Amphipathic Co-emulsifier Combinations

“…However, without GPC, as is the case of β-lactoglobulin in WPC, the associated state of the native protein showed a ubiquitous aggregate size range of 100–599 nm showing a dramatic bulk-phase impact of small amphiphiles on the association tendency of this major protein in WPC . Using a model O/W interface, we recently reported the effect of small ionic, nonionic, and zwitterionic amphiphiles on short- and long-range interactions in whey proteins and how this affects oil-in-water emulsion formation and stability. , All surfactants adversely affected emulsion activity index and stability, except anionic tetradodecyltrimethylammonium bromide, which significantly enhanced stability . According to the “oriented wedge” theory described by Kabalnov and Wennerström, single-tailed surfactants with large polar heads (such as sulfobetaine) tend to stabilize O/W emulsions due to packing constraints at the oil–water interface of an emulsion globule.…”