椰麸组分蛋白的氨基酸组成、结构与乳化性分析

为提高椰子加工副产物的利用,本研究从椰麸中依次提取4种组分蛋白,包括清蛋白、球蛋白、谷蛋白-1和谷蛋白-2.分析这4种组分蛋白的氨基酸组成,并利用SDS-PAGE技术分析其亚基组成和分子量.同时分析其表面疏水性,并研究不同离子强度对椰麸各组分蛋白的乳化性和乳化稳定性的影响.结果表明,椰麸蛋白质中清单白、球蛋白、谷蛋白-...

Analysis of Amino Acid Composition,Structure and Emulsion Properties of Coconut Cake Protein Fractions

To improve the utilization of coconut processing byproduct, four protein fractions including albumin, globulin, gluten-1 and gluten-2 were separately extracted from coconut cake. The amino acid composition of the protein fractions was analyzed. The subunit composition and molecular weight of the fractions were analyzed by SDS-PAGE. The hydrophobicity of coconut cake albumin, globulin, gluten-1 and gluten-2 were determined. The effects of different ionic strength on emulsifying capacity and emulsion stability of the protein fractions were studied, too. The content of coconut cake albumin, globulin, glutelin-1 and glutelin-2 was (8.84±1.16), (54.35±3.69), (20.49±1.11) and (6.14±1.42) g/100 g, respectively. The protein fractions are all rich in arginine and glutamic acid. In addition, the essential amino acid content of the protein fractions was relatively high than that recommended by FAO/WHO. The essential amino acid composition was reasonable. The albumin showed the highest biological value (58.63) among the four coconut cake protein fractions. This indicates that albumin has the highest nutritional value. Results of the SDS-PAGE analysis showed that there was significant difference in subunit composition among coconut cake albumin, globulin and gluten-1. The molecular weight was ranged from 17.7 to 53.3 kDa. Acid subunit composition of glutlelin-1 was 46.1%, in contrast the content of basic subunits in glutelin-2 was 27.5%, which was one of the main reasons why glutelin-1 and glutelin-2 has different solution. Glutelin-2 was composed of ten subunits with a molecular weight range of 18.8-119.2 kDa, which is the widest range among coconut cake protein fractions. The hydrophobicity of globulin and glutelin-2 was higher than that of albumin and glutelin-1 (P<0.05). In addition, at the same ionic strength, the globulin showed the highest emulsifying capacity (127.3 m²/g) and emulsion stability (98.13%) among the fractions, following which was the glutelin-2 and albumin, whereas glutelin-1 exhibited the lowest emulsifying capacity (11.79 m²/g). There was no significant difference on emulsion stability among coconut cake globulin, glutelin-2 and albumin. But the emulsion stability of globulin, glutelin-2 and albumin was higher than that of soybean protein isolate (P<0.05). When ionic strength was from 0 to 0.4 mol/L, the emulsifying capacity and emulsion stability of globulin were improved as ionic strength increased. In contrast, the emulsifying capacity of albumin and glugelin-2 was reduced as ionic strength increased. This study would provide a theory basis for the further application of coconut cake protein.