Reinforcement of bovine serum albumin-based interfaces by the addition of genipin and carboxymethyl cellulose: Effect of pH

Protein based interfacial films are a vital component of encapsulated functional food. Hypothesis: The stability and mechanical performance of bovine serum albumin (BSA) films can be significantly enhanced through two complementary strategies: (i) electrostatic complexation for example with carboxymethyl cellulose (CMC), and (ii) interfacial covalent cross linking of BSA by genipin (GNP). Approach: Quartz crystal microbalance (QCM), interfacial small amplitude oscillatory shear rheology (iSAOS), and atomic force microscopy (AFM) were combined to quantify mass adsorption, viscoelastic film development, and interfacial morphology of BSA, both alone and in mixtures with CMC and/or GNP at pH 3.0 and 7.0. Results: Attractive electrostatic interactions between BSA and CMC led to interfaces with the highest viscoelastic shear moduli (G' = 0.069 ± 0.004 N/m for BSA + CMC at pH 3.0). At neutral pH genepin enhanced the properties of a BSA film from predominantly liquid like to predominantly solid-like. These findings demonstrate that electrostatic complexation and interfacial cross-linking provide two complementary pathways for the reinforcement of protein-based interfacial films and reveal new routes for enhancing mechanical stability of encapsulated ingredients.