Chemical stability of β-carotene composite or bilayer emulsions coated with pea protein isolate and γ-polyglutamic acid compared to monolayer emulsion

The integration of β-carotene into functional foods is limited due to its limited hydrophilicity and chemical stability. To address this issue, emulsion was encouraged to be utilized. Monolayer, composite, and bilayer emulsions were prepared using pea protein isolate (PPI) alone or in combination with poly-γ-glutamic acid (γ-PGA). Our findings indicate that the bilayer emulsion utilizing γ-PGA as an external emulsifier exhibited the smallest droplet size (737.61 nm) and highest zeta potential (−35.23 mV). Under various environmental stresses, the chemical stability of the composite emulsion surpassed that of the monolayer emulsion but was inferior to that of the bilayer emulsion. Moreover, following simulated gastrointestinal digestion, the β-carotene bioaccessibility in the composite emulsion (12.76 %) exceeded that in the monolayer emulsion (6.57 %) but was less than that in the bilayer emulsion (20.01 %). Therefore, the emulsion preparation method or the sequence of γ-PGA addition significantly affects emulsion stability. Among the studied emulsions, the bilayer emulsion demonstrated the most stable structure, enhancing the stability of β-carotene within the oil droplets.