The Structure Of Soybean Proteinn Glycoated Products Under Thermal Treatment Conditions

The complex reactions between food components occur during the thermal processing.Both the structure and the nature of the reaction product will greatly affect the food quality.Soybean protein isolate is a kind of important food ingredient.And during its processing,glycosylation reaction will inevitably occur,which is based on the Maillard reaction.This paper mainly study the influence of common food heat treatment conditions on 11S and 7S glycinin structure,which is of great significance on the research of soy protein nutrition safety during its processing.In this study,we investigated the effects of common food thermal treatment on the structure of 11S glycinin and 7S ?-conglycinin soybean protein respectively with glucose and lactose.The principle of thermal conditions is common in the food processing,simulated conditions respectively are:cooking(100?,30 min-120 min),high pressure sterilization(121 ?,15 min)and baking(180 ?,7 min).Structural characterization:determination of grafting after glycation reaction,quantitative analysis of Amadori compounds,determination of tryptophan fluorescence of proteins,quantitative analysis of free amino and free arginine side chains,quantitative analysis of protein secondary structure,Quantitative analysis of carboxymethyl lysine and carboxyethyl lysine and mass spectrometry analysis of protein glycoation sites and modification types.The study found that,in the cooking(100?,30 min-120 min)under the conditions of glycation reaction,the degree of saccharification of 11S glycinin and 7S ?-conglycinin was directly proportional to the time,the tryptophan fluorescence of the protein,the free amino and free arginine side chain content were decreased with time.The secondary structure of the a-helix and ?-sheet decreased content and random coil content increased,the content of carboxymethyl lysine and carboxyethyl lysine was also proportional to time;The thermal treatment conditions include autoclaved(121?,15 min)and baked(180?,7 min),the above changes in the representation of indicators was more significant.The mass spectrometry analysis of modified types and sites showed that the glycation reaction occurred mainly in lysine and arginine residues.The modification types included glucose(+162.05 Da),CML(+58 Da)and CEL(+72 Da)modification,and higher the reaction temperature was,the more the modification type and site would be.