Whey protein isolate was hydrolyzed to an in vitro antioxidative hydrolysate, followed by transglutaminase-induced cross-linking and microemulsification in an oil phase. The obtained microemulsion was then dispersed in a gallic acid-rich model wastewater which caused gallic acid transportation into internal nanodroplets. Whey peptides were consequently gelled, yielding nanoparticles. Electrophoresis showed that β-lactoglobulin and low molecular weight peptides were cross-linked by transglutaminase. Protein hydrolysis and subsequent enzymatic cross-linking increased the ζ-potential value. Microscopic investigation indicated that most particles were non-spherical. Non-cross-linked and cross-linked peptides underwent a form of heat-triggered self-assembly in the dry state, while nanoparticles did not show such behavior. Peptide crystallites size was increased by cross-linking and acid-induced particle formation. The latter also caused a reduction in intensity of C-H stretching and C-N bending peaks in infra-red spectrum. Gallic acid release from particles to simulated gastrointestinal fluids was through diffusion from swollen particles, and reached almost 70% release.
Keywords: Cold gelation; Encapsulation; Enzymatic cross-linking; Microemulsion; Whey protein hydrolysate.
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