Enhancement Of Porcine Plasma Protein Hydrolysates On The Stability Of Oil-in-water Emulsions

In this study,porcine plasma protein was used as main raw material.First of all,the influence of enzyme type and hydrolysis time on the antioxidant activities and emulsifying properties were investigated.In order to find the porcine plasma protein hydrolysates(PPPH)which simultaneously showed stronger antioxidant activities and higher emulsifying activities,the changes of reducing power,radicals scavenging activities,emulsifying activity index,emulsion stability index and molecular weight distribution of PPPH were determined.Secondly,the potential effect of PPPH coupled with Tween 20 on the physical and oxidative stability of canola oil-in-water emulsions(10 % wt.lipid,pH 7.0)were evaluated.The mean particle size,?-potential,conjugated diene(CD),thiobarbituric acid-reactive substances(TBARS),the distribution of peptides at the interface,as well as the microstructure of the emulsion were measured to explore the possible mechanism.Finally,the influence of different processing conditions(pH values,heating temperatures,ion concentrations)on the physical and oxidative stability of emulsions were systematically illustrated.Through this research,we could build a good theoretical basis for potential application of PPPH in high-stable emulsions.The main results are as follows:(1)Compared with neutral protease and papain,the PPPH which hydrolyzed by alcalase rendered the highest reducing capacity and free radical scavenging ability(P < 0.05).At the same time,the PPPH obtained via limited alcalase-hydrolysis(60 min)possessed the highest emulsifying activity index and emulsion stability index(P < 0.05).In addition,size exclusion chromatography showed that the moderately hydrolyzed PPPH contained high content of high molecular weight peptide(molecular weight greater than 50 KDa or between 10-50KDa).(2)Emulsions stabilized with the PPPH obtained via limited alcalase-hydrolysis(60 min)coupled with Tween-20.The results indicated that the PPPH and Tween 20 prepared emulsions displayed higher emulsifying stability than PPPH alone(P < 0.05).At the same time,a lower concentration of PPPH(2.5 mg/mL)combined with Tween 20 formed the most stable emulsions,which is mainly due to competitive adsorption present at the interface.Additionally,compared with PPPH-free emulsions,the addition of PPPH was able to retard lipid oxidation,showing up to an 8.51% decrease in the formation of conjugated dienes and a 22.08% decrease in thiobarbituric acid-reactive substances after 10 days of storage(P < 0.05).This is mainly attributed to distinctantioxidant amino acid profiles and the distribution of peptides at the interface.(3)The O/W emulsions stabilized with the 2.5 mg/mL PPPH coupled with Tween-20 was placed under different environmental conditions.The results of the study show that H 5.0(near the isoelectric point),heating at 80 ? and higher concentration of NaCl(600 mM)was obviously increased with the particle size,flocculation index and coagulation index of the emulsion during storage(P < 0.05).At the same time,the CD and TBARS values of the emulsions notably increased(P < 0.05).On the contrary,neutral or weak alkaline(pH 7.0 or 8.0),lower heating temperature(40 or 60 ?)and lower NaCl concentration(200 mM to 400mM)had little effect on the stability of the emulsion.In this study,the mechanism of PPPH and Tween 20 inhibiting lipid oxidation and improving the stability of the whole system in rapeseed oil pre-emulsion were studied.It provides a theoretical basis for improving the quality of emulsions.The effect of different processing conditions on rapeseed oil pre-emulsion was also understood.It lays a good theoretical foundation for providing the best environment for O/W emulsion.