Effects Of Different Thawing Methods On The Quality Of Largemouth Bass(Micropterus Salmoides)

Aquatic products are rich in a variety of nutrients,and their taste is delicious,which is greatly loved by consumers.Due to seasonal or geographical factors,the quality of the aquatic products are usually maintained by freezing to extend the shelf life.In this paper,the largemouth bass was used as the research object,and it was thawed by different thawing methods.The changes of quality in fillets of thawing process and after steamed were studied.In order to provide basic theoretical basis and technical support for promoting the development of aquatic product thawing.The main conclusions are as follows:In this paper,the largemouth bass were thawed by different thawing methods,then the changes of physicochemical properties and microstructure were explored.Thawing loss,cooking loss,pH,color and texture results were used to analyze the physicochemical properties of the samples;TVB-N,TBA were used to evaluate the oxidation of proteins and lipids;and the migration and distribution of water during the thawing process was measured by the LF-NMR;microscopic and SEM were used to observe the microstructure of fillets.The results showed that the degree of protein and lipid oxidation of the sample increased after thawing treatment,the gap between the tissue fibers more wide,and the fiber portion was broken.The changes of physicochemical properties in thawed fillets by the MVT and FMT are small,and the fibers of their are arranged neatly and smoothly.Therefore,the two thawing methods can better maintain the original physicochemical properties and microstructure of the fish.Myofibrillar proteins were extracted from fish samples thawed under different thawing methods to study the effects of thawing on the conformation and oxidation of myofibrillar proteins.DSC and dynamic rheological analysis the stability of sample.Raman,Intrinsic fluorescence and UV second derivative spectroscopy were used to explore the myofibrillar protein conformation.Surface hydrophobicity,Zeta potential and effective particle size measurements to assess the degree of protein aggregation.The total sulfhydryl,protein carbonyl content,Ca²⁺-ATPase activity and SDS-PAGE were used to evaluate the degree of protein oxidation.The results showed that the MVT and FMT samples had better viscoelasticity and protein stability;the protein conformation was more stable,and the protein aggregation and oxidation degree were lower.In summary,the two thawing methods of MVT and FMT are more helpful to maintaining the conformation of the protein and reducing the degree of oxidation.The effects of different thawing methods on the quality and flavor of steamed largemouth bass were studied.Sensory evaluation,measurements of basic nutrients（moisture,protein,fat and ash）,color and texture indicators to evaluate sample quality;TBA result to assess the degree of lipid oxidation in samples;moisture migration and distribution were analyzed by LF-NMR.The changes in flavor were qualitatively assessed using an electronic nose,electronic tongue,and GC-MS.The results showed that the sensory evaluation scores of the steamed samples after thawing treatment were decreased,the color was different,the hardness and chewiness were increased,the percentage of the immobilized water was decreased,the free water was increased,and the degree of lipids oxidation were increased.The thawing process had a great influence on umami,saltiness and astringency.69kinds of substances detected in the volatile components,mainly aldehydes,alcohols,ketones and ketones.