Extraction And Properties Of Tree Peony Seed Protein

In this paper,the extraction technology of tree peony seed protein was optimized,and the optimal extraction process parameters were obtained.The four proteins of protein isolate,albumin,globulin,and glutelin of tree peony seeds were extracted by alkali-extraction and acid-precipitation and Osborne method respectively.On this basis,the surface hydrophobicity,microstructure,surface morphology,molecular weight distribution and other structural properties of the four proteins were compared by ANS fluorescence probe method,scanning electron microscopy,and polyacrylamide gel electrophoresis.Similarities and differences in protein structure.Finally,the functional properties of the four proteins,including solubility,foaming and foam stability,emulsifying and emulsifying stability,water absorption,and oil retention,were determined,and the effects of their structure on their functional properties and the differences of functional properties of four protein were explored.This subject could provide theoretical basis and technical guidance for the future research and application of tree peony seed protein.The optimization experiment of the extraction technology of tree peony seed isolated protein showed that the optimum extraction process parameters were the ratio of material to liquid 1:45(w/v),extraction temperature 45?,extraction pH 11,extraction time 65 min.Under this condition,the extraction rate of the tree peony seed protein was 87.36%.The tree peony seed protein was extracted by alkali-extraction and acid-precipitation and the albumin,globulin,and glutelin were fractionated using the Osborne method.Determined by Kjeldahl method,the crude protein content in defatted tree peony seed powder was 25.32%;protein content of tree peony seed protein isolate,albumin,globulin,and glutelin protein was 74.18%,78.65%,60.36%,and 58.30%,respectively.The surface hydrophobicity,molecular groups and secondary structures,microstructure and molecular weight distribution of the four proteins were studied and found that the results of the four surface protein hydrophobicity indexes measured by ANS fluorescence probe method were glutelin(798.55)>isolated protein(679.08)>albumin(617.43)>Globulin(612.83).Fourier transform infrared spectroscopy showed that the four tree peony seed proteins contained more ?-structures,and globulin contained more a-helix structure.Glutelin and isolated protein contained more ?-structure and irregular coil structure.By scanning electron microscopy observation,the surface of the globulin has a more granular structure and is more compact;the surface of the albumin has a multi-lamellar structure and is more viscous;the surface of the gluten and the isolated protein are porous and relatively loose.The results of polyacrylamide gel electrophoresis showed that the molecular weight distribution range of albumin and globulin was the highest.Broad,followed by protein isolates,the glutelin protein has the smallest molecular weight distribution.In this experiment,the solubility,foamability,foam stability,emulsifying and emulsifying stability,water absorption,and oil retention of the four proteins at different pH values were measured.The effect of protein structure on the functional properties was analyzed.And compared the differences in the functional properties of the four.The main experimental results are listed as follows:In terms of solubility,the solubility of the four proteins showed a trend of decreasing first and then increasing with changes in the pH value of the system.The minimum solubility was obtained at pH 5,which were 6.19%of isolated protein,9.43%of albumin,12.27%of globulin and 5.18%of glutelin,respectively;glutelin in a strong alkaline environment showed better solubility than the other three.In respect of water absorption and oil retention,glutelin had stronger water absorption(6.40 g/g)and oil retention(4.20 g/g)than the other three,and globulin had poor water absorption and oil retention,which may be related to its lower surface hydrophobicity.In terms of foam properties,foaming and foam stability show an opposite trend with changes in the pH of the system:the foamability of the four proteins first rises and then falls with increasing pH,and they all have the most foaming at pH 5.The difference was 15.74%of isolated protein,18.03%of albumin,16.37%of globulin,and 14.40%of glutelin.The foaming property of the protein in the alkaline environment was significantly enhanced.In particular,glutelin was foamable at pH 11.Up to 67.47%;while the foam stability of the four proteins is best at pH 5,reaching 93.33%of isolated protein,45.45%of albumin,100.00%of globulin,and 36.67%of glutelin,respectively,wherein the foam stability of globulin Best of all,this may be related to its microstructure.In terms of emulsifying properties,the emulsifiability and emulsifying stability of the four proteins decreased first and then increased with increasing pH value.The emulsification properties were worst at pH 5.At this time,the emulsifying properties of the four were 5.66%of isolated protein,7.38%of albumin,8.44%of globulin,and 7.87%of glutelin.The emulsifying stability was 25.33%of isolated protein,31.67%of albumin,34.32%of globulin and glutelin of 30.73%.The emulsification properties of proteins in the alkaline environment were significantly enhanced,especially glutelin,and the emulsification properties of globulin were poor,which may be due to differences in the microstructure of the two.