Covalent modification of soy protein isolate with tea polyphenols: A potential strategy for enhancing flaxseed oil emulsion stability and sustained delivery of α-linolenic acid

The adaptability of soybean protein isolate (SPI) modified with tea polyphenols (TP) for emulsion delivery systems was investigated. This study fabricated the SPI-TP non-covalent complex (NC) and covalent complex (C) and flaxseed oil emulsions stabilized by NC (NC-E) and C (C-E). The differences in the solubility, antioxidant activity, and particle size of NC and C were discussed first. And the emulsions’ resistance to storage, pH, temperature, and ionic strength was further evaluated. The C-E exhibited superior antioxidant capacity and environmental stability compared to the NC-E. This might be attributed to TP conjugation differences in NC and C and SPI property changes modified via two approaches. Moreover, the bioaccessibility of α-linolenic acid (ALA) in flaxseed oil emulsions stabilized by SPI, NC, and C was 58.38 ± 0.13 %, 42.84 ± 0.03 %, and 45.89 ± 0.03 % as evidenced by INFOGEST 2.0, indicating covalent modification would be a promising strategy for delivering functional lipids.