| In recent years,with the progress of society,people’s living standards continued to improve,especially in the diet,a variety of high nutrition food that has been never pay much attention,which come to be known.Auricularia auricula has both edible and officinal functions,and has attracted the attention of researchers.At present,the research on Auricularia auricular is mainly focused on the extraction of polysaccharides and pigment substances,as well as the development of the relevant health products and the clinical drugs.For the composition of the protein in Auricularia auricular and the functional properties were poorly understood.In order to understand and clarify the applications of protein components in Auricularia auricula and its adhibitions in food industry,Auricularia auricular was used in this study,take advantages of water,salt solution,athanol solution and alkaline liquor to extract the protein in Auricularia auricular.The contents of albumin,globulin,prolamin and alkali-soluble protein in Auricularia auricular were extracted through Osborne extraction,the physicochemical properties and functional properties were determined.The effects of different factors on the extraction ratio were investigated and studied.The Response Surface was used to optimize the technological parameters in order to achieve the best extraction ratio.Finally,the extraction ratios of albumin,globulin,prolamin and alkali-soluble protein of Auricularia auricular were 13.02%,4.14%,1.64%,17.51%respectively,the purity of four crude proteins was 54.78%,49.56%,37.93%and 45.06%.Physicochemical properties of four proteins in Auricularia auricular were analyzed.The isoelectric point of albumin,globulin,prolamin and alkali-soluble protein was 3.8,2.2,3.0 and 3.4.There were no random coils in secondary structure of four proteins.The proportion of secondary structure was that:albumin contained a-helix 4.7%,β-folding 65.1%,β-corner 5.7%,random coil 24.5%,globulin contained a-helix 9.5%,β-folding 83.0%,P-corner 4.4%,random coil 3.1%,prolamin contained a-helix 5.7%,β-folding 68.8%,P-corner 2.5%,random coil 23.0%,alkali-soluble protein contained a-helix 25.6%,β-folding 51.8%,β-corner 16.9%,random coil 5.7%.The molecular weight of albumin was 44.68KDa,39.82KDa,33.50KDa,26.61KDa,22.39KDa,the molecular weight of globulin was 31.63KDa,25.12KDa,22.39KDa,the molecular weight of paolamin was 44.68KDa,23.72KDa,21.14KDa,15.85KDa,and alkali-soluble protein was 28.19KDa,23.72KDa.The contents of free sulfhydryl groups of four Auricularia auricular proteins were 6.78±0.85μmol/g,3.47±0.54μmol/g,3.91±0.42μmol/g,6.04±0.76μmol/g respectively.The surface hydrophobicity of four Auricularia auricular proteins were 721.3±20.2,975.4±19.8,147.0±30.1,1148.9±20.0.The total amino acid contents of four proteins was 801.8 mg/g,756.4 mg/g,613.7 mg/g,761.5 mg/g,the contents of essential amino acid were 371.7 mg/g,339.1 mg/g,264.1 mg/g,323 mg/g.Functional properties of four proteins in Auricularia auricular were analyzed,and contrasted with soybean protein isolate(SPI).Finally came to a conclusion:if the protein with the higher surface hydrophobicity,the lower of its solubility,the Auricularia auricular albumin and globulin had best water absorption,prolamin had best oil absorption.Albumin foaming ability was better than SPI,while the other three proteins only at pH 5 the foaming ability better than SPI.Under acidic conditions,the foaming stability of the four proteins was better than SPI,with the increase of pH,the foaming stability of all five proteins declined,the stability of albumin,globulin and alkali-soluble protein had little difference with SPI in numerical,while the stability of prolamin was always lower than SPI.Under acidic and normal conditions,the emulsifying ability of albumin was better than SPI,while the emulsion stability was poor,when pH got 5,the emulsifying ability of SPI lower than both globulin and promalin,the emulsion stability of globulin was always lower than SPI,promalin was better than SPI only at the conditions of pH 5,7,9.In normal and alkaline conditions,the emulsifying ability of alkali-soluble protein better than SPI,the stability still poorest. |
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