Effects Of Freezing And Cooking Treatment On Quality Of Ctenopharyngodon Idellus C.et V

Crisp grass carp(Ctenopharyngodon idellus c.et V)is a new species of freshwater fishes developed by grass feed to a certain weight and then fed to broad bean for a long time.Crisp grass carp was deeply loved by consumers because of its very tight,high viscoelasticity,and delicious taste after cooking.At present,the frozen preservation is a commonly used method of preservation of Crisp grass carp.Because of the cold chain development imperfect,the Crisp grass carp changes in quality during the process of processing,transport and sale process,and improper heat processing will have a great influence on the quality of crisp grass carp.So taking Crisp grass carp raised in Poyang lake as the research object,analysis of the freezing process in repeated freeze-thaw cycles(0,1,3,5,7,10),thawing method(air thawing,thawing in water,lowtemperature thawing,microwave thawing and ultrasonic thawing),postmortem stagnation time before frozen(1 h,2 h,8 h,12 h,24 h)effect on the meat quality of crisp grass carp,and different heating methods(steaming,boiling,frying)effect on the nutritive value and flavor of crisp grass carp.Aims to reveal the influence mechanism of the freezing process and heating mode of crisp grass carp muscle characteristics.This study could provide a theoretical basis for the preservation of crisp grass carp and deep processing.The main research contents and results are as follows:(1)Effect of Freeze-thaw Cycles on Quality of crisp grass carpIn order to explore the effects of freeze-thaw cycles(0,1,3,5,7,and 10 cycles)on quality characteristics of Ctenopharyngodon idellus C.et V,the changes of basic eating quality,full textural properties,thiobarbituric acid-reactive substances(TBARS),total volatile base-nitrogen(TVB-N),protein carbonyl content,and total sulfhydryl content of treated samples were analyzed after repeatedly frozen-thawed in this paper.The resulted showed that with increasing the number of freeze-thaw cycles,thawing loss significantly increased(p < 0.05).Cooking loss and pressure filtration rate increased firstly and then decreased,but the pH value was just opposite;L* value(brightness),whiteness,TBARS,TVB-N and protein carbonyl content increased gradually,a*value,b*value,hardness,springiness decrease gradually with during freeze-thaw cycles.The microstructure of the samples had changed a lot,and the degree of tightness and fracture of myofibril increased as the number of freeze-thaw cycles increased.All the results demonstrated that freeze-thaw cycles decreased the quality of samples and this effect was positively related to the number of freeze-thaw cycles.(2)Effect of Different Thawing Methods on Quality Characteristics of crisp grass carpThe effect of five different thawing methods including natural air thawing,thawing in water,low-temperature thawing,microwave thawing,ultrasonic thawing on quality characteristics of Ctenopharyngodon idellus C.et V meat were studied.The changes of basic eating quality,textural properties,TBARS,protein carbonyl content,total sulfhydryl content were analyzed among five thawed samples.The result showed that different thawing methods exerted a certain impact on quality changes of Ctenopharyngodon idellus C.et V meat.After thawing of frozen meat in water,there were not significant differences in the pH value compared to the control group(p>0.05),thawing loss,cooking loss and pressure filtration rate were lower,the L,a *,b * values were most closely to the control group,and water-holding capacity and color were maintained at higher levels.After thawing of frozen meat in water,there were not significant differences in the total sulfhydryl content compared to the control group(p>0.05),the protein carbonyl content and TBARS value were lower than other group.Compared with other thawing methods,thawing in water was more suitable to maintain the quality of Ctenopharyngodon idellus C.et V meat.(3)Effects of postmortem stagnation time before frozen on Quality Characteristics of crisp grass carpThe effect of postmortem stagnant time before frozen(1 h,2 h,8 h,12 h,24 h)effect on the meat quality of crisp grass carp were studied.The changes of basic eating quality,textural properties,TBARS,protein carbonyl content,total sulfhydryl content were analyzed.The result showed that the cooking loss,thawing loss and protein oxidation at 12 h were significantly lower(P < 0.05)than other postmortem stagnation time before frozen.The color at 1h was better than other postmortem stagnation time.And the myofibril white carbonyl content is less than others too.But the difference of 8h and 24 h was not significant(P > 0.05);the degree of fat oxidation and pressure loss rate at 8h were significantly lower than(P < 0.05)other dead time after slaughter.(4)The effects of different cooking methods on nutritional quality of crisp grass carpThe effect of different ways of cooking(steaming,boiling,frying)nutritional quality of crisp grass carp were studied.The changes of moisture and ash of crisp grass carp fish,texture,crude fat,crude protein,fatty acids and amino acids were analyzed.The results show that three kinds of cooking methods have great influence on the quality of crisp grass carp.The cooking loss was minimum after boiling heating.The cooking loss,crude protein content,ash content and crude fat content were maximum,and moisture content was lowest.After heating,the degree of lipid oxidation carp were significantly increased,which the fried heating is lower than other heating methods.Different heating methods did not change the amino acid composition in the muscle of crisp grass carp.However,the total amount of amino acids were increased obviously,and the total amount of amino acids in the samples were largest after treated by frying.After different cooking methods,fatty acid composition in muscle of crisp grass carp were increase in different degrees.The content of MUFA were the highest after steaming,and its content is48.46%,followed by fried heating method at 46.48%.The content of PUFA were the highest after boiling,and its content is36.36%,followed by fried heating method at 22.83%.(5)The effects of different cooking methods on flavor of crisp grass carpDifferent ways of cooking have a big influence on flavoe on crisp grass carp.The electronic nose could distinguish the different heating methods crisp grass carp and control sample.This paper analyzed the volatile substances of crisp grass carp by SPME-GC-MS.The results showed that the amount of volatile components in the samples which the steaming and boiled cooking process were same with control sample,but the kinds of volatile substances changed.More volatile compounds of crisp grass carp were find in samples after frying treatment than control sample.The highest content of aldehydes,followed by alcohols and alkanes in the volatile compounds of all samples.The main flavor compounds of aldehydes were nonanal and caprylic aldehyde.The main flavor compounds of alcohol was 1-nonene-3-alcohol.