Ultrasound-assisted Extraction And Separation Of Pea Protein And Preliminary Study On Its Application In Electrospinning

China is one of major countries in pea planting.However,the pea output declined year by year due to its low economic benefits.The high-value development and utilization of peas is an urgent task.Pea protein has attracted much attention due to its hypoallergenicity,high nutritional value,and low cost.It has a good prospect in high-value development.Therefore,pea protein was selected as the research subject in this study.For this purpose,an ultrasound-assisted alkali extraction method was established for pea protein extraction after the optimization of process parameters.Meanwhile,the effects of ultrasound on the structure,functional properties and biological activities of pea protein were investigated.Based on these researches,preliminary studies on fractionation and electrospinning of pea protein were further explored.These results provided new idea and method for the development of high value-added pea protein products.The main conclusions of this study are as follows:?1?Single-factor optimization was conducted for alkali extraction and ultrasound-assisted extraction of pea protein.Compared to the alkali extraction method,the ultrasound-assisted extraction method could reduce the amount of solvent by 55.00%,shorten the extraction time by 50.00%,and increase the extraction rate by 12.51%.After lyophilization,the compositions of pea protein extracted by ultrasound assisted extraction method?UAEPPI?were different from pea protein extracted by alkali method?AEPPI?,where the protein content was increased by 6.97%,the water was reduced by 50.70%and ash content was decreased by 51.43%compared to those in AEPPI.However,there was no change in major amino acid composition of pea protein with/without ultrasound.By using the combined method of Box-Behnken design and response surface analysis,the optimal condition for ultrasound-assisted extraction was achieved as follows:solid-liquid ratio of 1:11.45?w/v?,pH 9.55,ultrasonic time of13.45 min,and amplitude of 33.68%.The predicted extraction rate was 83.62%and was proved by the actual experimental value of 82.56%.After that,an efficient method of pea protein extraction was established.?2?Ultrasound treatment resulted in the enhancement of surface hydrophobicity and intrinsic fluorescence intensity in pea protein.UAEPPI also possessed the increased content of?-sheet and random roil and the decreased particle size of protein.However,disulfide bond and protein subunit in pea protein were not destroyed after the ultrasound treatment.Compared with AEPPI,the solubility,oil holding capacity,water holding capacity,foaming capacity and stability of UAEPPI were increased by 57.89%,39.42%,28.45%,17.02%and 13.18%,respectively.The ultrasound treatment also improved the adsorption capacity of oil droplets and gelatinization characteristic in pea protein.UAEPPI exhibited better bioactivities than AEPPI.The DPPH free radical scavenging capacity of UAEPPI was 7.91%higher than that of AEPPI at the same protein concentration of 8 mg/mL,where the hydroxyl radical scavenging capacity of UAEPPI was twice as high as that of AEPPI.This research laid the theoretical foundation for the higher-value application of pea protein.?3?The results of Osborne extraction and separation showed that the major constituent of pea protein was albumin?61.94%?,followed by globulin?17.46%?.In addition,the high-content albumin was the major antioxidant component in pea protein.The P₂ fraction in the albumin was separated by ion exchange chromatography,which played the dominant role in the antioxidant activity of the albumin.The antioxidant fraction F₂ in P₂ was further achieved by gel filtration,which accounted for 67.81%of P₂.The distribution of molecular weight in F₂ was mainly at the range of 14⁷0 kDa.The DPPH free radical scavenging capacity of F₂ reached 35.27%at the concentration of 0.2 mg/mL.The globulin in pea protein possessed strong hydrophobic and ionic interactions,complex network structure and low charge density.And thus,the globulin was more difficult to be electrospinned than pea protein and the albumins.However,the uniform nano-fibers were achieved by electrospinning with pea protein and the albumins,where the increased proportion of pullulan facilitated the formation of spinning fibers in larger diameter.These results provided new idea for the high-value utilization of pea protein.