Effects of rutin incorporation on the physical and oxidative stability of soy protein-stabilized emulsions

• Rutin could bind with soy protein to form a protein–rutin complex.
• The addition of rutin reduced interfacial tension of native SPI.
• The addition of rutin enhanced physical and oxidative stability of SPI emulsions.
• The rutin-native SPI mixed emulsion showed more obvious improvement than heated SPI.

We investigated the effects of rutin additive on the physical (droplet size, zeta potential, and interfacial adsorption) and oxidative stability of emulsions stabilized by native soybean protein isolate (SPI) and heat-denatured SPI. The fluorescence spectra and interfacial tension of SPI–rutin mixture were also measured. The formation of SPI–rutin complex mainly driven by hydrophobic interactions was verified. The addition of rutin reduced interfacial tension of native SPI at the oil–water interface, while that of HSP was less influenced. In the case of native SPI emulsion, rutin particles could competitively adsorb into the oil–droplet interface with high interfacial accumulation. The formation of native SPI–rutin mixed interfacial layers resulted in the reductions in oil droplet size of emulsions and evident improvement of physical and oxidative stability. However, the stability of heated SPI emulsions showed no remarkable improvement due to lower interfacial accumulation and physical location of rutin. Rutin particles were believed to mainly adsorb outside protein layer. These findings showed that rutin can be used as a native stabilizer for protein emulsions to enhance its physical and oxidative stability.

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