Abstract: In this study, the enhancing effect of adding different amounts of oxidized tannic acid (OTA) on the oxidative stability of oil-in-water (O/W) emulsions prepared using porcine plasma protein hydrolysates (PPPH) as an emulsifier was investigated. Changes in peroxidation value (POV), conjugated diene (CD) value and thiobarbituric acid reactive substances (TBARS) value in the emulsions during storage were measured. We also determined changes in tryptophan fluorescence intensity and fluorescent protein oxidation products (FP) by fluorescence spectroscopy. The results showed that compared with the control group, the POV, CD and TBARS values significantly decreased with increasing addition of OTA from day 1 to 10 of storage (P < 0.05). This effect was positively correlated with OTA addition. Additionally, the tryptophan fluorescence intensity significantly decreased during storage (P < 0.05), while the FP significantly increased (P < 0.05). The changes in both parameters were dependent upon OTA concentration. Our results indicated that the quinine compounds of OTA could react with sulfhydryl and amino groups on peptide chains to form C—N and C—S bonds, promoting the cross-linking of peptide chains. The cross-linked peptides could be effectively wrapped around the surface of oil droplets, significantly improving the oxidation stability of the emulsions during the entire storage period. This study can lay a theoretical foundation for the application of OTA in food emulsion systems.

Key words: oxidized tannic acid, porcine plasma protein hydrolysates, lipid oxidation, protein oxidation, stability