Construction Of Oat Protein High Internal Phase Emulsion System Based On Dynamic High-Pressure Microfluidization And Loading Of DHA Algal Oil

Docosahexaenoic Acid(DHA)belongs to the ?-3 series of polyunsaturated fatty acids and has physiological functions such as promoting the development of brain cells and retinal cells in children and preventing cardiovascular diseases.Algae oil is rich in DHA and has the advantages of high safety performance,abundant resources and weak fishy smell.However,DHA algae oil has problems such as poor water solubility,easy oxidation and low bioavailability,which greatly limit the application of DHA algae oil in food industry.The plant protein-based Pickering high internal phase emulsion system has great potential to transport large amounts of DHA algae oil and improve its stability and bioavailability due to its high loading capacity,green safety and good biocompatibility.Oat protein has received much attention due to its soy protein-like structure and gel properties and relatively high content,but its solubility is low and it needs to be modified to improve solubility and further enhance emulsification and interfacial activity.In this study,oat protein isolates(OPIs)were treated using dynamic high-pressure microfluidization(DHPM)technology.The treated OPIs were used as stabilizers to prepare DHA algal oil high internal phase emulsions(HIPEs).The effects of DHPM treatment on the structure and functional properties of OPIs,and the effects of changes in the properties of OPIs after DHPM treatment on the stability of DHA algal oil HIPEs and their digestive properties were investigated.The main results of the study are as follows:(1)The effects of different pressures of DHPM on the physicochemical,structural and functional properties of OPIs.The results showed that the particle size of OPIs decreased significantly by 70.96% and the absolute Zeta potential increased by 33.51% when the pressure of DHPM was increased to 120 MPa.The main substructure of OPIs was not destroyed and the secondary structure of OPIs was changed after DHPM treatment.The significant increase of hydrophobicity and free sulfhydryl content on the surface of OPIs and the fluorescence burst indicated the structural unfolding and rearrangement of OPIs.In addition,the structural changes of OPIs affected their functional properties.The 120 MPa DHPM treatment significantly increased the solubility of OPIs by 156.11%,obtained better amphiphilicity,and significantly improved their water/oil holding,emulsification,foaming,and interfacial activity.(2)Effect of property changes of DHPM with different pressure treated OPIs on the performance of HIPEs with different oil phase volume ratios(?: 0.75,0.80,0.89).The results showed that with the increase of DHPM treatment pressure,the particle size of OPIs became smaller so that they could quickly adsorb to the oil-water interface to form a more dense interfacial layer,and the microstructure of HIPEs showed a regular polygonal network structure,which improved the solid-like viscoelasticity of HIPEs.The DHA algae oil HIPEs prepared with DHPM treatment pressure of 120 MPa as the carrier had the best comprehensive performance.When increasing the volume share of the oil phase(?)led to a larger number of HIPEs oil droplets,the emulsion viscosity increased,but it would reduce the stability of HIPEs and even lead to emulsion breakage.In addition,the effects of different preparation conditions(p H: 3.0,5.0,7.0,9.0 and 11.0;protein concentration c: 2%,3% and4%)on the performance of DHA algal oil HIPEs were investigated.The results showed that under acidic conditions,the OPIs had large particles,high viscoelasticity but poor stability of emulsion-like solids,and easy flocculation and aggregation of droplets.As the p H increased,the particle size of OPIs became smaller and could adsorb to the oil-water interface more quickly to form regular and dense polygonal microstructures,and the HIPEs were slightly less viscoelastic but more stable.Increasing c can increase the stability and solid-like viscoelasticity of HIPEs.This resulted in the optimal parameters for the preparation of DHA algal oil HIPEs from OPIs,with DHPM treatment pressure of 120 MPa,p H 7.0,c of 4%,and? of 0.80.(3)The effects of DHPM with different pressure-treated OPIs on the stability and digestive properties of DHA algal oil HIPEs system.The results showed that the modified OPIs effectively improved the storage stability,retention rate,thermal stability,freeze-thaw stability and oxidative stability of DHA algal oil HIPEs.The stability of DHA algal oil HIPEs during oral and gastric digestion was enhanced,and the FFA release after 2 hours of intestinal digestion reached 85.81% and finally increased the bioacceptability of DHA by 2.16 times.