Effects Of Constant Power Microwave On The Binding Ability Of Myofibrillar Protein From Beef To Flavor Compounds

Beef is one of the important pillars in the food industry,and beef is rich in protein content,myofibrillar protein is a main protein existing in skeletal muscle of beef,it has a significant impact on the processing texture and flavor characteristics of beef.In recent years,microwaving is a popular thermal process due to its fast heating and minimal destruction of food nutrients compounds.Microwave heating can change the structure properties of beef myofibrillar protein,and thus influence the binding ability of myofibrillar protein to many different flavor compounds,which affects the physical and chemical properties of food and the perception of flavor compounds.Therefore,this paper used myofibrillar protein from beef as raw material,exploring the influence of microwave on the structure changes of myofibrillar protein,and presenting the binding ability changes of myofibrillar protein to 2-pentanone,2-heptanone,2-octanone,2-nonanone,hexanal,heptanal,furfural,3-methylthiopropanal flavor compounds under microwave conditions,meanwhile,we also investigated the main driving force for the interaction between myofibrillar protein and flavor compounds at the gas-liquid interface under different microwave conditions,which provides further information and guidance for achieving desired flavour properties of microwave processed protein-rich foods.The main results showed as the following:(1)At the early stage of the experiment,we explored the effects of traditional microwave and water bath heating on the structure properties of myofibrillar protein from beef,it was found that the thermal effect of microwave played a major role in the structural degeneration of myofibrillar protein,but the non-thermal effect of microwave also had some influence on the structure changes of myofibrillar protein.In order to ensure the reproducibility of the experimental data,this experiment constructed a constant power microwave system,and uniformity of the microwave field in sample area was also confirmed by simulation experiment.(2)UV absorption intensity of myofibrillar protein was increased after microwave treatment,and the endogenous fluorescence exhibited a red shift phenomenon,indicating that the surface hydrophobicity of myofibrillar protein increased significantly with the progressed microwave power or time.The relative content of?-helix decreased significantly,and the relative content of?-sheet,?-turn,the randomly coiled structure content increased significantly(p<0.05),demonstrating that the structure of myofibrillar protein transferred towards to disordered states gradually under microwave conditions.Moreover,the content of reactive sulfhydryl groups increased due to the exposure of internal sulfhydryl groups under microwave conditions,and the total sulfhydryl content of myofibrillar protein was slightly increased after microwave treatment.(3)Binding ability of myofibrillar protein to typical aldehyde and ketone flavor compounds was increased under microwave conditions.The binding ability order of myofibrillarproteintofourketoneflavorcompoundswas2-nonanone>2-octanone>2-heptanone>2-pentanone,and the binding ability order of myofibrillarproteintofouraldehyde flavorcompoundswas furfural>heptanal>hexanal>3-methylthiopropanal.Relationships between free flavor compounds percentage and the structure of myofibrillar protein(total sulfhydryl groups,reactive sulfhydryl groups,hydrophobicity)under different microwave conditions can be fitted according to the MLR model,discovering that the correlation between the measured and predicted values of the free percentage for 2-pentanone,2-heptanone,2-octanone,2-nonanone,hexanal,heptanal,furfural and 3-methylthiopropanal flavor compounds were R~2=0.9656,0.8970,0.8646,0.9202,0.7251,0.9444,0.9191,0.8578 respectively.Indicating that there existed in the binding sites for flavor compounds in the structure of total sulfhydryl groups,reactive sulfhydryl groups and surface hydrophobicity for myofibrillar protein.And microwave can influence the binding and release of ketone and aldehyde flavor compounds by changing the exposure conditions of binding sites.(4)The absolute value of Zeta potential increased significantly with the progressed microwave power or time conditions,mutual exclusion between homogenous charges setting the myofibrillar protein solution in a more stable state.The particle size of myofibrillar protein had a more uniform particle distribution with the increased microwave power and time conditions.The surface tension value and contact angle exhibited a decreasing and increasing treads due to the electromagnetic and thermal properties of microwave respectively,the main driving force for the binding of myofibrillar protein to aldehyde and ketone flavor compounds at the gas-liquid interface was spontaneously reduced interfacial energy under microwave conditions.