Study On The Effect Of Different Cooking Methods On The Characteristics Of Buckwheat Protein

The effect of different cooking methods on the characteristics of buckwheat protein was explored to find the cooking method that can maximize the preservation of buckwheat protein nutrition and function.In this study,Bashang common buckwheat was taken as the research object,and cooked in three ways : steaming,boiling and frying.Then,crude protein and four component proteins(albumin,globulin,glutenin and gliadin)of buckwheat before and after cooked were separated and extracted by alkali-extraction and acid-precipitation,and Osborne grading extraction method.The changes of protein content,amino acid composition,morphology characteristics,functional characteristics(emulsification,foaming,oil absorption and water holding)and in vitro digestibility of buckwheat before and after different cooked methods were studied by Coomassie brilliant blue method,ninhydrin post-column derivatization ion exchange chromatography and scanning electron microscopy.The main research results are as follows :(1)The optimization results of extraction process of buckwheat crude protein by alkali-extraction and acid-precipitation showed that the main and secondary order of the factors affecting the extraction rate of buckwheat protein was as follows: p H > solid-liquid ratio >ratioextraction time >extraction temperature.The optimal process combination was as follows:solid-liquid ratio of 1:15,p H value of 10,extraction temperature of 55℃,extraction time of 140 min.Under these conditions,the protein extraction rate was the highest,reaching 71.5%.(2)The results showed that the crude protein content of boiled buckwheat was significantly higher than that of the unprocessed,steamed and stir-fried.Compared with the protein content of each component before cooking,there was no significant difference except that the gliadin content decreased significantly.There was no significant difference after steaming.The content of albumin and globulin decreased significantly after stir-frying,but the other contents had no significant difference.(3)The results of studies on the function and in vitro digestion characteristics of buckwheat protein before and after different cooking methods showed that the solubility,water holding capacity,foaming ability and foaming stability of each component protein after boiling were significantly higher than those before boiling(P < 0.05).There was no significant difference in emulsifying stability(P > 0.05);Except gliadin,the oil absorption of other components was significantly increased.Except globulin,there was no significant difference in emulsification of other histones;In addition to globulin,the in vitro digestibility of other component proteins was significantly increased.The water holding capacity of each component protein increased significantly after steaming(P < 0.05).There was no significant difference in emulsifying ability,emulsifying stability and foaming ability(P > 0.05);Except for glutenin,the solubility of the other components was significantly increased.There was no significant difference except that the oil absorption of glutenin was significantly reduced.Except for the significant increase in foaming stability of albumin,there was no significant difference in other proteins.There was no significant difference except for the significant increase in the digestibility of glutenin.After stir-frying,the water holding capacity,oil absorption and emulsion stability of each component protein decreased significantly(P < 0.05).There was no significant difference in solubility,emulsification and foaming(P > 0.05);There was no significant difference except that the foaming stability of gliadin and globulin was significantly reduced.In vitro digestibility was significantly increased.(4)The results of apparent morphology analysis showed that the ripening process could change the surface structure such as the number of bulges and pores on the protein surface,and the hydrophobicity of the structure,thereby affecting the emulsifying properties and water holding capacity of the protein.(5)The amino acid composition analysis and nutritional value evaluation results of buckwheat before and after cooked processing showed that compared with uncooked buckwheat,the total amino acid content increased to varying degrees after steaming and stir-frying,and decreased slightly after boiling.The content of most essential amino acids increased after steaming and stir-frying,and the increase was greater after stir-frying.The results of AAS and CS showed that compared with uncooked buckwheat,the scores of amino acid AAS and CS decreased after boiling,and increased to varying degrees after steaming and stir-frying.The amino acid content of buckwheat after stir-frying was higher than that of egg protein amino acid content and WHO / FAO score standard except Met.