Nanoemulsification of epigallocatechin gallate for debitterization, antibrowning, and inhibition of intracellular lipid accumulation

Abstract

This study addressed the instability of epigallocatechin gallate (EGCG), a green tea-derived polyphenol, by developing a robust EGCG oil-in-water nanoemulsion. The nanoemulsion comprised lecithin (dispersed phase), pectin (continuous phase), and gallic acid (antibrowning agent). Using a blend of phases via high-energy ultrasonication, we achieved an 88.9% encapsulation efficiency. The nanoemulsion's physical properties improved, yielding a small droplet size (diameter: 169.3 nm) and low polydispersity index (0.16). The nanoemulsion exhibited long-term stability, 82% DPPH radical scavenging activity and 63% browning prevention compared with EGCG. Upon expressing the human taste receptor TAS2R16 + GIRK1/4 in Xenopus oocytes, the nanoemulsion elicited a 50% decrease in bitterness compared with EGCG, as quantified by the oocytes' membrane potential using the two-electrode voltage clamp method. Treating 3T3-L1 cells with the nanoemulsion resulted in a 49% reduction in lipid accumulation and 58% enhancement of triglyceride degradation, as confirmed via Oil Red O staining and lipolysis studies, respectively. This study provides insights into establishing an effective emulsification system for EGCG, enhancing its role as a functional food ingredient.