| Common vetch(CV,Vicia sativa L.),which is a leguminous crop,is widely used as green fertilizer in agriculture,and its seeds can be used as plant protein source for human needs.However,there are few studies and applications of common vetch protein.Therefore,in this study,seeds of four different common vetch varieties(CV2,CV58,CV59,CV60)were chosen.To explore the potential of common vetch protein in the food industry,the physicochemical and functional properties of their isolates(CVPI)and major protein fractions(CVAP,CVGP and CVGTP)were studied.The common vetch protein isolate from the CV60 variety(CVPI60)had advantages in physicochemical and functional properties,was selected as the next research protein to prepare the calcium chelate peptide.The CVPI60 peptide-calcium complex was prepared by enzymolysis technology.The structure was characterized by liquid spectrometry-electronic spray ion/mass spectrometry(LC-ESI/MS),ultraviolet-visible spectroscopy(UV-vis),fourier transforminfrared(FTIR)and nuclear magnetic resonance(NMR),which were used to predict the mechanism of calcium chelate peptide.The main results of this study were as follows:(1)It was found that CVPI content accounted for 27.70%?32.14% of the total dry weight of common vetch seed.The SDS-PAGE profile showed that CVPI CVAP and CVGP were mainly composed by 7S and 11 S,while CVGTP was mainly composed by11 S.Their thermal denaturation temperature was higher,which showed their better thermal stability.CVGTP had higher surface hydrophobicity,which was related to its higher content of disulfide bond and free sulfhydryl group.The results of circular dichroic analysis showed that the ?-helix was the main secondary structure of common vetch protein.Therefore,the conformations of CVPI and their protein fractions were highly ordered and stable.(2)In the study of the functional properties,it was found that the solubility of CVPI and their protein fractions varied with pH in a U-shaped curve,among which the solubility of CVGP59 and CVGTP was low.CVAP60 had the highest value of water absorption capacity(6.17 g/g),while CVGTP had an advantage in oil absorption capacity.CVPI60 and its protein fractions had advantages in emulsifying and foaming properties,so they can be used as food additives in food industry,particularly in cake,ice cream and other similar food fields.(3)The maximum calcium-binding activity of the common vetch protein(CVPI60)hydrolysate peptide was obtained at the following coditions: CVPI60 was heated for 5h after the enzymolysis performed by alkaline protease,and then enzymatic hydtolysis peptide was separated by ultrafiltration membrane.The calcium-binding activity of P4 was significantly higher than that of the other parts(P < 0.05).Through further purification using reverse phase preparation liquid phase,the calcium binding activity of F2 component in P4 was significantly higher than that of other components(P < 0.05).Analysis of the primary structure of the peptide by mass spectrometry revealed six possible amino acid sequences,and it was further speculated that the calcium-binding activity was related to the amino acid composition of F2.The results showed that the amino nitrogen and oxygen atoms on the carboxyl group were involved in the complexation reaction analyzed by ultraviolet-visible spectroscopy(UV-vis),fourier transforminfrared(FTIR)and nuclear magnetic resonance(NMR).In conclusion,calcium-binding peptide quantity depended largely on the type of enzyme hydrolysis degree of amino acid composition and molecular weight distribution of different hydrolysate.To sum up,this study had provided new insights to performance for common vetch protein.Common vetch protein is a potential source of plant protein,which can be used as a kind of biological active ingredient in the production of the nutrition food,such as calcium-binding chelating agent. |
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