Abstract: Potential effects of porcine plasma protein hydrolysates ( PPPH) on oxidative stability of oil-in-water type ( O/W) emulsions were investigated during the storage. Different concentration of PPPH ( 0 ~ 20 mg/m L) were added to rapeseed O/W emulsions which used Tween-20 as the emulsifier.The changes of tryptophan fluorescence spectroscopy, conjugated diene ( CD) and thiobarbituric acid-reactive substances ( TBARS) values of the emulsions were determined during 0¹0 days which storage at 37 ℃.The results showed that the oxidative degradation of tryptophan residues occurred as an early event in protein oxidation whereas fluorescent protein oxidation product ( FP) formed later as secondary protein oxidation products. In addition, compared with the control group, the treatment group with the addition of 2.5 mg/m L PPPH had the highest tryptophan fluorescence intensity and FP ( p < 0.05) , while having the lowest CD and TBARS values ( p < 0.05) . At the same time, the significant negative correlations were found between tryptophan fluorescence and CD. In conclusion, PPPH could significant increase the stability of oil-in-water type emulsions, the antioxidant properties of PPPH at the interface of emulsion droplets would render them suitable as natural antioxidants in some food products.