Abstract: This study investigated the effect of adding oxidized tannic acid (OTA) to oil-in-water (O/W) emulsions prepared with porcine plasma protein hydrolysates (PPPH) as an emulsifier on improving their physical stability during storage. The changes in emulsion droplet size, zeta potential, flocculation index, creaming index and protein partition coefficient during storage were determined, and the microstructure was visualized via confocal laser scanning microscopy (CLSM). The results showed that compared with the control group, D[3,2], D[4,3], flocculation index and coagulation index were decreased significantly with the increase in OTA concentration (P < 0.05), whereas zeta potential value was obviously increased (P < 0.05), reaching its maximum when 1% OTA was added, during the period from 1 to 10 d of storage. Meanwhile, OTA slightly induced cross-linking of PPPH, significantly increasing their distribution at the emulsion interface (P < 0.05). The CLSM micrographs also revealed that the interfacial membrane in emulsions with the addition of 1% OTA was more compact and more massive than other groups. The results indicated that the addition of OTA significantly improved the physical stability of O/W emulsions containing PPPH during storage, which will lay a theoretical foundation for the application of OTA in food emulsions.

Key words: oxidized tannic acid, porcine plasma protein hydrolysates, oil-in-water emulsion, cross-linking, physical stability