Study On The Difference Mechanism Of Functional Characteristics Of Three Varieties Of Walnut Protein

As one of the nutritional components of walnut,walnut protein has extremely high nutritional value.With the increase of walnut yield,deep processing has become the source of walnut industry upgrading,but there is a lack of research on walnut nutrients and processing-related functional characteristics.Based on the differences in functional characteristics between the budded varieties of Lvling-Xiangling(Shangsong No.6× Akesu No.9)and the walnut protein of Wen 185 and Yangbidapao,this paper discusses the root causes of the differences,and provides a theoretical basis for the rational processing and utilization of walnut protein and the breeding of special walnut varieties in the future.It mainly includes the following four aspects.1)Comparative analysis of the solubility,emulsifying property,emulsifying stability,foaming property,foaming stability,water and oil absorption and other processing-related characteristics of three varieties of walnut protein.It was found that the solubility,emulsifying property,emulsifying stability,foaming property,foaming stability and water and oil absorption of Yangbidapao walnut protein were significantly better than those of Wenl85 walnut protein and Lvling walnut protein(p<0.05),and the solubility,emulsifying property,emulsifying stability,foaming stability and water and oil absorption of Wen 185 walnut protein were significantly better than those of Lvling walnut protein(p<0.05)Yangbidapao and Wen185 are more suitable for walnut protein products with high water content,while Lvling is more suitable for walnut protein products with low water content.2)Comparison of amino acid composition of three varieties of walnut protein.Glutamate and arginine are the highest amino acids in the total protein of different varieties of walnuts,among which the glutamic acid content of the total protein of Lvling is the highest,which is 145.40mg/g,while that of Yangbidapao is 131.23mg/g and that of Wen 185 is 142.18 mg/g.The contents of hydrophilic amino acids and acidic amino acids in walnut protein are high,and there are significant differences in essential amino acids,acidic amino acids,basic amino acids,hydrophilic and hydrophobic amino acids among different varieties of walnut protein.The amino acid scores of three walnut proteins,Yangbidapao,Wen185 and Lvling,were 0.65,0.62 and 0.51,respectively,which were higher than those of general cereals.3)Comparison of molecular weight distribution and structure of three varieties of walnut protein.The bands of three walnut protein subunits are mainly concentrated in two regions with molecular weight of about 23kDa and 35kDa.The content of walnut protein in Yangbidapao and Wen 185 is higher than that in Lvling at low molecular weight,while the content of walnut protein in Lvling is higher at high molecular weight of 130kDa,so Yangbidapao walnut protein is more favorable for dispersion.The analysis of protein surface microstructure shows that the surface morphology of Yangbidapao vesicle presents a flat and smooth fine fragment structure,which is beneficial to the infiltration of liquid.The surface morphology of Wen 185 is a mixture of flat structure and uneven spherical structure,while the surface of Lvling walnut protein is convex,irregular and rough,which is not conducive to liquid dissolution.Further secondary structure analysis of three varieties of walnut protein showed that the contents of β-sheet from high to low were Yangbidapao(41.82%),Wen185(37.54%)and Lvling(34.48%),while the α-helix was just the opposite,Lvling(32.44%),Wen185(27.89%)and Yangbidapao(21.92%).From the secondary structure of the protein,we can see that the overall structure of Yangbidapao walnut protein is looser,which makes it more soluble,thus making its surface activity stronger,followed by Wen 185,and the worst is Lvling walnut protein.Similarly,the results of surface hydrophobicity showed that the surface hydrophobicity of Yangbidapao walnut protein was significantly higher than that of Wen185 and Lvling walnut protein at different pH values(P<0.05),which increased the strength of its protein interfacial film and made its emulsifying performance better.4)Determination of key proteins affecting functional characteristics.By analyzing the dynamic protein expression profiles of protein group of Yangbidapao,Wen185 and Lvling walnut proteins.The results showed that 1706 proteins were identified in Yangbidapao,Wen185 and Lvling,among which 1032 proteins were differentially expressed.701 proteins were up-regulated in Yangbidapao and Lvling group,82 proteins were up-regulated in Yangbidapao and Wen 185 group,and 613 proteins were up-regulated in Wen185 and Lvling group.185 proteins were up-regulated in Yangbidapao and Lvling group,50 proteins were up-regulated in Yangbidapao and Wen 185 group,and 168 proteins were up-regulated in Wen185 and Lvling group.Finally,five up-regulated proteins,A01,A02,A03,A04 and A05,were identified.The three down-regulated proteins A06,A07 and A08 are the key proteins that determine the different internal structure of walnut protein,that is,the different functional characteristics.Proteins A01,A04,and A06 are present in gluten,proteins A03 and A08 are present in albumin,proteins A05 and A07 are present in globulin,and proteins A02 are present in gliadin.The three-dimensional structure of eight proteins was studied.It was found that the contents of β-sheet and a-helix of five up-regulated differential proteins A01,A02,A03,A04 and A05 were extremely high,while the contents of β-sheet and α-helix of three down-regulated differential proteins A06,A07 and A08 were extremely low,which further confirmed that these proteins were the main proteins affecting the functional characteristics of walnut proteins.Finally,the scenic spots,contents and soluble residues on the protein surface were analyzed.The results showed that the proportion of the surface net charge content and soluble residues content of the five up-regulated differential proteins were much larger than those of the three down-regulated differential proteins,so the solubility of Yangbidapao and Wen185 walnut proteins was significantly better than that of Lvling.