Effects Of Steaming And Frying On Muscle Quality And In Vitro Digestive Characteristics Of Sea Bass

Sea bass（Lateolabrax japonicas）is one of the important species in mariculture.It is loved by consumers because of its tender and delicious meat,rich nutrition and essential amino acids.At present,Sea bass is mainly sold in fresh,the processing method is relatively single and the added value of the product is low.With the improvement of people’s living standard and the acceleration of the pace of life,prepared dishes gradually rise.The temperature and time of cooking have important effects on the final quality,flavor and nutritional value of the food.This study takes the back muscles of sea bass as the research object,and the effects of steaming and frying on muscle processing characteristics,flavor quality and in vitro digestion characteristics of sea bass were investigated.This study aims to provide some theoretical references for the development of sea bass food dishes.The main research results are as follows:1.During the process of steaming and frying,the weight loss rate of sea bass meat increased significantly（p<0.05）,and a large amount of water was lost.Among them,The weight loss rate of the steamed sample was about 29%,while that of the fried sample was about 43%,which was significantly higher than that of the steamed sample.According to the results of nuclear magnetic imaging of water,it can be seen more intuitively that with the extension of heating time,free water and non-flowing water in fish gradually diffused and lost from the middle to the edge,while the change of bound water was not obvious.L*and b*values of the cooked samples were significantly higher than those of the fresh samples（p<0.05）,while a*value were significantly lower than those of the fresh samples（p<0.05）.With the extension of the heating time,the L*value of fried samples decreased,the a*value increased,making the overall color gradually deepened.While the color change of the steamed sample was not significant,and its L*value is always higher than that of the fried sample.The hardness,elasticity and chewiness of sea bass increased significantly after steaming and frying（p<0.05）.Microscopic observations showed that muscle fibers and tissue structures were damaged during heating.Among them,the muscle tissue structure of the steamed sample was kept in good condition.2.The fish samples with different steaming and frying time could be effectively distinguished by the electronic tongue and electronic nose,indicating that the cooking temperature and time had great influences on the flavor of sea bass muscle.The total amount of free amino acids in fresh sea bass was 175.14 mg/100 g,while the content of 5’-GMP,5’-IMP and 5’-AMP in fresh sea bass meat was 32.03μg/m L,361.25μg/m L and98.46μg/m L,respectively.The content of free amino acids and nucleotides increased significantly after steaming and frying（p<0.05）.Then the volatile compounds in the sea bass meat were qualitatively and quantitatively analyzed by gas chromatography-ion mobility spectroscopy（GC-IMS）.Results showed that a total of 43 and 45 volatile compounds were identified in steamed and fried fish.It mainly includes aldehydes,alcohols and ketones.The content of flavor substances such as3-methyl-butanol,dimethyl disulfide and propionic acid was high in fresh fish,while the content decreased after cooking.It shows that heat treatment can improve the flavor of fish.With the extension of cooking time,the content of nonaldehyde,octanal,heptanal,hexanal,pentaldehyde and other aldehydes increased in the steaming samples.Furfural and 2,5-dimethylpyrazine were detected in fried samples.3.The digestibility of meat protein in vitro and the degree of proteolysis after simulated digestion in vitro were significantly improved by both steaming and frying（p<0.05）,and the particle size of protein was significantly reduced.The results of atomic force microscopy（AFM）and laser confocal microscopy（LSCM）showed that with the extension of digestion time,the protein aggregates were decomposed into fine particles and dispersed in the digestive solution,which was consistent with the change of particle size.The TBARS value of samples increased significantly after in vitro digestion（p<0.05）,indicating that in vitro digestion could accelerate lipid oxidation.The oxidation degree of fried samples was significantly higher than that of steamed samples（p<0.05）.With the extension of digestion time,the chelating ability of Fe²⁺was improved.At the end of digestion,the Fe²⁺chelating ability of the digestive juice of the steamed sample was significantly higher than that of the fried and fresh samples（p<0.05）,indicating that the digestive juice of the steamed sample had a strong oxidation resistance.