Effects Of High Pressure Homogenization On The Structural And Emulsifying Properties Of Peony Seeds Protein

As a by-product of oil extraction,peony seed dregs are of high protein content and variety bioactive components,but they have not been taking fully use of due to lack of research.Emulsions have a wide range of applications in food industry,and they play an irreplaceable role in people's diet.In the construction of emulsion-type food,choosing a suitable emulsifier is a very important issue.In addition to certain nutritional value,protein molecules also have good oil-water amphiphilicity and film-forming ability.Therefore,they can be used as a kind of natural emulsifier to construct emulsions in food.In this paper,peony seeds protein was used as the research object to explore the effect of high pressure on the structure of peony seed protein and the functional properties of its emulsion.The rheological properties of peony seed protein-based high internal phase emulsion and mayonnaise were compared,which provided a theoretical basis for development of substitute for mayonnaise in functional foods.The results are as follows:(1)Compared with PSP without HPH,PSP was treated with high pressure of 30-120 MPa to explore the effect of high pressure treatment on the protein structure and emulsification properties.The results showed that with the homogenization pressure increasing,the content of?-sheets decreased,and the content of?-helices and random coils increased.HPH treatment increased the surface hydrophobicity and free sulfhydryl content of protein molecules,while reducing turbidity of PSP and the d_4,3 of PSP-based emulsions.The high-speed shear force,turbulent flow and cavitation effect generated by the HPH changed the conformation of PSP,which leading the protein molecular to unfolding to some extent.With the increase of the homogenization pressure,the particle size of the emulsion droplets decreased significantly,and the emulsifying activity and emulsifying stability of the emulsion increased accordingly.(2)To explore the effects of different pressure treatments on the structure and rheological behavior of the PSP stabilized HIPE.The results showed that with the increase of the homogenization pressure(30?120 MPa),the molecular structure of the protein was further unfolded.And more molecules transferred from the bulk phase to the oil-water interface,while making the droplet size of the HIPE smaller and even.The rheological test showed that under small amplitude oscillatory shear,HIPE was elastic gel-like,and the gel strength increased with the increase of homogeneous pressure.As the strain amplitude increased in the nonlinear viscoelastic region,HIPE began to flow.Due to the reduction of protein molecules in the bulk phase,the mechanical deformation resistance of HIPE decreased with the increase of the homogenization pressure.Due to the decrease of particle size of the droplets,the contact area between the droplets increased and the interaction was enhanced.As a result,the apparent viscosity increased as well.The HIPE stabilized by PSP treated at 120 MPa performed the best in terms of emulsification functional properties and rheological behavior.(3)Taking PSP under high pressure of 120 MPa as the research object,the effects of protein concentration on the structure and rheological behavior of HIPE were studied.The results showed that with the increase of the protein concentration(1%?3%),the oil-water interfacial tension decreased significantly(13.5?10.85 m N/m)when reaching equilibrium,as the amount of protein molecules increased which were used to stabilize the oil droplets at the oil-water interface.And the interfacial layer formed on the surface of the oil droplets became thicker,with the structural strength of the protein network increased.As a result,the resistance to mechanical deformation was enhanced.The greater the protein concentration was,the smaller the droplet sizes of the HIPE were,and the closer oil droplets packed,and the greater the strength of the protein network would form,which appeared as the storage modulus G?and the loss modulus G?increased with the protein concentration.The thixotropic recovery performance also increased with the protein concentration.Through the comparative study with mayonnaise,it was found that the rheological behavior of the HIPE with 3%protein concentration was very similar to that of mayonnaise.Therefore,this HIPE has potential application value as a substitute for mayonnaise.