Fabrication of whey protein–pectin conjugate particles through laccase-induced gelation of microemulsified nanodroplets

A mixed solution of whey protein isolate, sugar beet pectin and laccase was microemulsified as nanodroplets in a mixture of sunflower oil and span 80. The droplets were transformed into nanoparticles through laccase-induced cross-linking and in situ gelation of biopolymers. Entrapment of caffeine within the conjugate bulk gel of biopolymers postponed the gelation time indexed by dynamic rheometry and decreased the strength of the final gel. The mean size of conjugate particles was 109 nm. Scanning electron microscopy images revealed an almost spherical morphology for uniformly shaped particles. Fourier transform infrared spectroscopy suggested the cross-linking of protein and pectin with participation of ferulic acid groups of pectin. Heat scanning experiments carried out by differential scanning calorimetry indicated the transition of conjugate particles from glassy to rubbery state at lower temperatures than their parent biopolymers.