Preparation Of Whey Protein Isolate-Polyphenol Particles And Its Stabilization Effect On Acer Truncatum Seeds Oil Emulsion

In recent years,with the changes in people’s lifestyles and worsening environmental pollution,people suffering from sub-healthy and chronic non-communicable diseases are rapidly increasing,which greatly stimulates the demand for food’s health functions.Therefore,the research and de velopment of functional food has become a research hotspot for food searchers and companies.Emulsion is a common food delivery system,among which Pickering emulsion has received widespread attention due to its non-toxic,environmentally friendly,and stable advantages.Various natural food macromolecule particles have been used as stabilizers for food-grade Pickering emulsions,such as chitosan,zein,whey protein,microcrystalline cellulose,solid lipids.Whey protein is a widely used emulsifier and stabilizer,but its strong hydrophobicity limits its broader application.Acer truncatum seeds oil is a new resource of woody edible oil in China,with unsaturated fatty acid content as high as 92%.Particularly,it is rich in neuro acid,a dual-effect functional substance that promotes nerve cell regeneration by repairing damaged nerve fibers in the brain.In this study,firstly,free radical grafting was used to four polyphenols(chlorogenic acid,EGCG,gallic acid,and rutin)and whey protein isolate(WPI)to construct composite WPI-polyphenol particles.Secondly,the composite particles were used as stabilizers to prepare Acer truncatum seeds oil,based Pickering emulsion.The effects of po WPI-polyphenol composite particles on emulsion stability under different conditions were compared.Last,WPI-polyphenol particles-stabilized Acer truncatum seeds oil emulsion was used for loading resveratrol.The main research contents and obtained results are summarized as follows:(1)Construction and characterization of WPI-polyphenol covalent composite particles.Using free-radical grafting,polyphenolic compounds(chlorogenic acid,EGCG,gallic acid,and rutin)were covalently combined with whey protein isolate(WPI)to form composite particles.Sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE),Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),three-phase contact angle,graft ratio,and particle size analysis all confirmed that polyphenols successfully covalently grafted with WPI.The covalently complexed particles shifted in the position of the amide II bond,the C-N or C-S bond changed,and the particle morphology also changed with the successful covalently complexed protein aggregation state.(2)Determination of antioxidant activity of WPI-polyphenol composite particles.WPI-polyphenol composite particles were examined for antioxidant activity by DPPH radical scavenging and iron reducing power assays.Results showed that the antioxidant activity of composite particles was significantly higher compared with the WPI,indicating that the successful combination of the two gave WPI higher antioxidant capacity.When WPI was 4mg/m L,the DPPH free radical scavenging rate was 13%.After grafting,the WPI-polyphenol particles had a high radical scavenging rate of 88% at high concentrations.Among them,WPI-EGCG covalent composite particles have stronger antioxidant activity.A similar result was also observed for iron reducing power test.(3)The emulsion stabilizing effect of WPI-polyphenol composite particle under different conditions.The effects of preparation conditions such as particle concentration,oil volume fraction,p H value and salt ion concentration on the emulsion stabilizing effect of WPI-polyphenol composite particles were studied.It was found that under the conditions of 2%(w/v)particle concentration,60%(v/v)oil phase,original p H and 50-100 m M of salt ions,the emulsion formed was more uniform and stable.Among them,WPI-CA and WPI-GA covalent composite particles stabilized emulsions have better storage stability.(4)Storage stability of Acer truncatum seeds oil emulsion stabilized by WPI-polyphenol composite particles.WPI-polyphenol composite particles were used to stabilize Acer truncatum seed oil.The formed emulsion was stored at 25 ℃ and 55℃,respectively.It was found that the composite particles-stabilized emulsion effectively inhibited the oxidation of fats and oils and prolonged the storage time of the emulsion as indicated by the changes in peroxide value(PV)and malondialdehyde(MDA)content.GC-MS results show that the emulsion has a better protection effect on fatty acids,especially on the functional fatty acid-neuratic acid.(5)Acer truncatum seeds oil emulsion was used for loading resveratrol.The emulsion stability of resveratrol was studied by using the emulsion system formed earlier.The results showed that the resveratrol content in resveratrol-loaded emulsion group decreased more slowly than that in control group.After 15-day storage,the resveratrol was retained 44.46%and 39.35% at 25℃ and 55℃,respectively.