Encapsulation of β-carotene in high internal phase Pickering emulsions stabilized by soy protein isolate – epigallocatechin-3-gallate covalent composite microgel particles

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• Covalently conjugated SPI-EGCG microgel particles were used to stabilize HIPPEs. • EGCG addition improved the functional properties of β-carotene-loaded HIPPEs. • Thick particle layer and gel network jointly promoted the stability of HIPPEs. • Encapsulation of β-carotene enhanced the chemical stability and bioaccessibility. In the current study, soy protein isolate (SPI) and epigallocatechin-3-gallate (EGCG) covalent composite microgel particles with antioxidant capacity were prepared and the particles was used as β-carotene-loaded high internal phase Pickering emulsions (HIPPEs) stabilizers. The covalent binding of SPI-EGCG altered the structures of the SPI through an unfolding of the polypeptide chain. Moreover, compared to HIPPEs stabilized by SPI alone, HIPPEs stabilized by SPI-EGCG microgel particles showed smaller particle size, higher apparent viscosity, and better stability. Microstructure of the fabricated HIPPEs results revealed that SPI-EGCG covalent conjugates promoted the formation of a thick and dense protective layer on the surfaces of oil droplets. Furthermore, β-carotene-loaded HIPPEs stabilized by SPI-2% EGCG microgel particles exhibited a higher retention rate after 42 days of storage and better bioaccessibility (86.64 ± 0.27% and 54.43 ± 0.50%, respectively) compared to HIPPEs stabilized by SPI (75.80 ± 0.49% and 38.31 ± 0.93%, respectively). The current study illustrated that the design of HIPPEs stabilized with protein–polyphenol composite particles were of great importance for the delivery of lipophilic bioactive compounds.