Whey proteins-folic acid complexes: Formation, isolation and bioavailability in a Lactobacillus casei model

Abstract

The objective of this work was to explore the complexation of a whey protein (β-lactoglobulin, β-lg) and a whey protein isolate (WPI) with folic acid (FA) at pH 3.0. Complexes were formed through non-covalent interactions, mainly electrostatic, as showed by ƺ-potential determination. Whey protein aggregation induced by the FA linkage was achieved, with particle sizes within the nano and microscales. Particle size distribution in aqueous solution was determined by dynamic light scattering (DLS) obtaining values between 15−200 nm. Complexes isolation was achieved by spontaneous phase separation and subsequent lyophilization, obtaining a glassy powder. Particles sizes increased upon both complexation and powder rehydration. The interactions between FA and proteins were corroborated by FTIR. Confocal laser microscopy revealed the heterogeneity and extensive aggregation of the complexation. The bioavailability of the WPI-FA and β-lg-FA complexes, evaluated by Lactobacillus casei BL23 model, was similar to that of FA alone demonstrating that these complexes can be potentially used as a new functional protein-based ingredient.