Effect Of Different Drying Methods On Quality,flavor And In Vitro Digestive Characteristics Of Golden Pompano(Trachinotus Blochii) Fillets

Golden pompano(Trachinotus blochii)is a dominant fish in the South China which favored by consumers.However,the fish is prone to spoilage due to the active cathepsin.Dried aquatic products have the advantages of lightweight,easy transportation and long storage period.Therefore,the fish were dehydrated by using vacuum freeze-drying(VFD),vacuum microwave drying(VMD),hot air drying(HAD),and microwave drying(MD)until the water content between 10% and 12%.The quality,flavor and simulated digestion characteristics of golden pompano fillets in different drying methods were studied.The main results are as follows:1.Effect of the different drying methods on the physical quality of golden pompano fillets.The microstructure of VFD fillets was loose and porous,with bright color,good rehydration ratio(45.61%),recovery ratio(106.48%)and good thermal stability.Compared with HAD and MD fillets,the VMD fillets had lower shrinkage,better hardness and chewiness.During the drying process,the transverse relaxation time of the immobilized water was significantly decreased.MRI showed that VFD and VMD were uniform drying methods.The results showed that four drying methods had different effects on the physical quality of golden pompano fillets.2.Effect of the different drying methods on lipid and protein oxidation of golden pompano fillets.The results showed that the thiobarbituric acid(TBARS)values were in descending order of HAD group(0.300 mg MDA/kg),MD group(0.167 mg MDA/kg),and VMD group(0.015 mg MDA/kg),VFD group(0.014 mg MDA/kg).VFD fillets had a high content of protein(62.72 g/100g)and total sulphur bonds,low content of disulphide bonds,light degree of protein oxidation.In the thermal drying method,MD fillets had the lowest content of the total sulphur and hydrogen bonds,its myosin and actin were completely denatured.In addition,the MD fillets contained higher random coil and ?-sheet structure,and lower ?-helixes structure.The results showed that the deep lipid and protein oxidation occurred in the thermal drying process.3.Effect of the different drying methods on flavor compounds of golden pompano fillets.In four dried samples,VFD fillets had the highest content of inosinic acid(IMP)(49.83?mol/g),while HAD fillets had the highest content of hypoxanthine nucleoside(Hx R)(12.71?mol/g)and hypoxanthine(Hx)(5.60 ?mol/g).The electronic nose and electronic tongue could effectively differentiate volatile compounds of four samples.A total of 86 volatile flavor components were identified in the dried fillets;the main flavor components,mainly hydrocarbons(39),aldehydes(15),esters(10)and alcohols(9).VFD,HAD,MD,VMD fillets had been detected 63,54,48,and 37 compounds,respectively.HAD,MD and VMD promoted a gradual reduction in ketones and the generation of esters,while the fillets that were processed by VFD contained more hydrocarbon(29.68%)and alcohol(2.64%)compounds.The cluster analysis results showed that HAD and VMD fillets had similar flavors,VFD and MD fillets differed from other samples due to the content of 1-octen-3-ol(mushroom flavor)and piperazines(barbecue flavor),respectively.The results showed that four drying methods had different effects on the flavor of golden pompano fillets.4.Effect of the different drying methods on in vitro simulated digestion characteristics of golden pompano fillets.Among the four dried fillets,the pepsin(49.14%)and pepsin + trypsin digestibility(55.33%)in HAD fillets were the highest.After the simulated digestion of intestinal fluid,the particle size of the HAD digested products was the smallest.In MD fillets,the pepsin(22.15%)and pepsin + trypsin(44.84%)digestibility were the lowest.In the process of simulated digestion,the particle size of the digestive products of MD fillets was the largest,resulting in the largest viscosity at each stage of digestion.Electronic nose results showed that the digestive process of fillets produced ammonia,sulfide and other odor substances.Among them,the odor of VFD fillets digestion products was the most difficult to accept.The results showed that the in vitro simulated digestion characteristics of the four dried fillets were significantly different.