Study On Drying Technology And Quality Of Semi-dried Takifugu Obscurus Fillets

The raised Takifugu obscurus owing to its excellent taste,unique flavor,and high nutritional content in addition to its non-toxicity,and can provide broader market prospects and better economic value.Taking Takifugu obscurus as raw material,the paper studied the effect of different drying methods on the quality of semi-dried Takifugu obscurus,analyzed the effect of cold-hot air combined drying on the physicochemical properties of semi-dried Takifugu obscurus fillets,and studied the effect of cold-hot air combined drying on the flavor of semi-dried Takifugu obscurus fillets.1.This study investigated the effects of sun drying(SD),hot air drying(HAD),cold air drying(CAD),vacuum drying(VD),and vacuum freeze drying(VFD)on the meat quality of semi-dried Takifugu obscurus fillets.The quality changes in the fish fillets were analyzed by comparing color,texture,shrinkage,water states,volatile flavor compounds,and a sensory assessment.The L* value of SD showed a downward trend,whereas that of the other drying methods showed an upward trend.SD and HAD had better texture properties than the other drying methods.The five drying methods promoted the conversion of immobilized water into free water,although the transverse relaxation time significantly decreased,especially in HAD.These drying methods altered the original flavor of the pufferfish though CAD retained the best fresh flavor and HAD produced more volatile compounds than the other methods.The five drying methods could be effectively distinguished using electronic nose(E-nose)and headspace-gas chromatography-ion mobility spectrometry(HS-GC-IMS).Overall,HAD improved the sensory score of the odor and chewability.Furthermore,HAD was determined as the appropriate thermal drying methods for the T.obscurus fillets to improve the products’ quality and flavor.Among the non-thermal methods,the CAD showed better color and tissue morphology.2.In order to investigate the effect of cold-hot air combined drying on the physicochemical properties of semi-dried Takifugu obscurus fillets.The effect of CAD,HAD and cold-hot air combined drying(C-HACD)on the p H,water states,lipid oxidation,protein degradation and microstructure of semi-dried Takifugu obscurus fillets were investigated in terms of texture analyzer,low-field nuclear magnetic resonance(LF-NMR),thiobarbituric acid(TBA),frozen section,sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE)and differential scanning calorimetry(DSC).The results indicated that the binding of moisture to the samples was enhanced in three drying methods,and the immobilized water content of C-HACD was between HAD and CAD.The p H of semi-dried fillets was improved by C-HACD.HAD had the highest hardness and chewiness,but fiber breakage and significant degradation were observed.Compared with HAD and CAD,C-HACD improved the springiness and chewiness of the fillets,among which CAD-90 had higher springiness and chewiness among the four combined drying methods,and the muscle fibers were arranged compactly and clearly outline,showing higher muscle toughness.All three drying methods had a certain degree of lipid oxidation on semi-dried pufferfish fillets,and C-HACD reduced the drying time and lipid oxidation degree through combined drying.In terms of protein degradation,CAD better maintained the protein components of fish,while HAD and C-HACD promoted the production of actin,and C-HACD had a higher protein denaturation temperature.Considering the effect of C-HACD on the physicochemical properties of semi-dried pufferfish fillet,C-HACD combined the advantages of CAD and HAD and shortened the drying time compared with CAD,and the lipid oxidation was reduced,protein stability was enhanced,and the tissue structure was more dense after C-HACD.3.In order to investigate the effect of cold-hot air combined drying on the flavor of semi-dried Takifugu obscurus fillets.The flavor of Takifugu obscurus fillets were identified by free amino acid and ATP-related compounds,combined with sensory assessment,equivalent umami concentration(EUC)and taste activity value(TAV)were determined and analyzed.In addition,the flavor substances of semi-dried Takifugu obscurus fillets were identified by E-nose,electronic tongue(E-tongue)and HS-GC-IMS.The results showed that a total of 17 free amino acids were detected in the semi-dried pufferfish fillets,and their contents all tended to increase,and CAD-90 was better in maintaining the flavor of pufferfish fillets.Compared with other substances of ATP-related compounds,the proportion of IMP of semi-dried pufferfish fillets treated with different drying methods was the largest,especially the IMP value of pufferfish fillets treated with C-HACD increased significantly.The results of EUC and TAV showed that the semi-dried pufferfish fillets treated with C-HACD was better than that of the other two drying methods.E-nose and E-tongue systems can effectively distinguish the flavor compounds in semi-dried pufferfish fillets treated by different drying methods.HS-GC-IMS identified 29 volatile organic compounds,including their monomers and dimers.Among them,the compounds in the C-HACD samples increased with the time of CAD,indicating that the changes in the content of volatile compounds were affected by both the treatment temperature and the length of treatment,while aldehydes were predominant among these substances,indicating that aldehydes were the main products of the physicochemical reactions occurring in the pufferfish fillets.The flavor characteristics of semi-dried pufferfish fillets treated with different drying methods were investigated by principal component analysis of E-nose,E-tongue and HS-GC-IMS,and the results showed that there was some correlation among the three results.Hence,C-HACD could bring better flavor substances to the semi-dried puffer fish fillets,and CAD-90 was more favorable for the formation of flavor and actual processing of semi-dried pufferfish fillets.These results can provide some theoretical basis for flavor information and practical application of aquatic products.