Interfacial Stability Of Sweet Potato Protein Peptides Emulsion Influenced By Ultrasound Microwave And High Hydrostatic Pressure

Protein hydrolysates used as functional food ingredients have recently gathered attention majorly due to their functional activities displayed in model systems,such as food emulsion.Compared with the natural protein,protein hydrolysates possess exposed free amino groups capable of enhancing peptide diffusion into emulsion interface to reduce interfacial tension,and form consistence emulsion.However,protein hydrolysate emulsions are unstable under long time storage due to their poor adsorption at emulsion interface.Thus,it is of great significance to improve the emulsifying properties of hydrolysates by different enzymatic hydrolysis or treatment methods.Sweet potato protein hydrolysates(SPPH)by enzymatic hydrolysis present remarkable free radical scavenging activities.Ultrasound and microwave has been reported to enhance enzymatic hydrolysis of protein to generate novel peptides with improved functionality.High hydrostatic pressure(HHP)could modify the structure of biopolymers,and improve the microstructure and stability of the emulsion at specific amount of pressure.However,there is no report on effects of ultrasound microwave(UM)-assisted enzymatic hydrolysis and HHP on emulsifying,rheological,interfacial and antioxidant characteristics of SPPH.In this study,the effects of UM-assisted enzymatic hydrolysis and HHP(300,400 and 500 MPa) treatment on emulsifying,rheological,interfacial and antioxidant characteristics of SPPH were examined to provide theoretical basis for the potential use of SPPH as natural functional ingredients in food.The specific research results are as follows:(1)UM assisted enzymatic hydrolysis significantly improve degree of hydrolysis,surface hydrophobicity and emulsifying properties of SPPH.Emulsion stabilized with SPPH by UM at 400MPa was the most physically stable with emulsifying stability index(ESI)of 43.16%compared with other emulsions,which showed lower particle size(239.25 nm)but higher zeta potential(26.75 m V).All emulsions with HHP treatment displayed shear thinning behavior with noticeable increase in viscosity,and the highest viscosity was recorded for UM-SPPH500MPa.(2)HHP significantly increased adsorption and antioxidant activity of SPPH at interfacial layer of emulsion.Emulsion stabilized with UM-SPPH400MPa presented the highest adsorbed peptides at interface(23.79%)with a high ORAC value of 100.49?g TE m L^-1,from which diverse peptides with potential antioxidant activities were obtained by LC-MS/MS.Additionally,changes in peptide conformation and position of some specific amino acids were revealed by structure-activity relationship analysis.Therefore,ultrasound-microwave and HHP have great potential in peptides production with enhanced functionality.The results of this study will deepen the basic theoretical understanding of UM-assisted enzymatic hydrolysis and HHP in improving functional properties of peptides,and provide theoretical basis for promoting the efficient development of sweet potato peptides and innovative design of functional foods.