Study On Processing Technology And Quality Changes During Storage Of Crisp Grass Carp

Crisp grass carp?Ctenopharyngodon idellus C.et V,CGC?is a newly developed freshwater aquaculture fish in China,It gives people special taste with the tight and crisp,while high economic value.This paper studied the processing and preservation technology of CGC fillets,and determined the optimal processing technology by the physicochemical indexes and quality changes of CGC during storage.The main research contents and results are as follows:?1?To optimize the processing conditions of CGC fillets,the best conditions were determined by a single factor experiment and an orthogonal experiment with fresh CGC fillets.The best processing conditions were found as follows:10%?m/v?salt solution,the curing time of 15min,and the solid-liquid ratio of 1:4.Headspace solid-phase microextraction?HS-SPME?and gas chromatography-mass spectrometry?GC-MS?was used to analyze the changes of key volatile flavor substances in the processing.The higher contents of flavor substances of 1-octene-3-alcohol,nonanal,content were 17.72%and 2.45%,respectively.Most importantly,the ROAV value of nonanal was higher than the average of each factor under the condtion of 10%salt concentration,curing time of 15min and solid-liquid ratio of 1:4 conditions.As result,1-octene-3-alcohol,nonanal contributed to the flavor of CGC fillets.?2?In order to investigate the effects of water extract from Perilla?Perillafrutescens?L.?Britt?leaf on quality of fillets during chilling storage,CGC fillets were marinated in the water extract from Perilla leaf and analyzed the changes of texture,2-thiobarbituric acid?TBA?value,total volatile base nitrogen?TVB-N?,total aerobic counts,sensory score and so on.Results indicated that the inhibitory effects of water extract from Perilla leaf on the TBA value,TVB-N value,the total aerobic count of CGC were significant during chilling storage?p<0.05?.Most importantly,the TBA value of raw fish was low at 12 d.The TVB-N value of cooked fish was lower than the secondary freshness of national standard during chilling storage.In addition,the count of initial total bacteria of raw fish reached to 6.17 lg?CFU/g?at 12 d,which exceeding the end of the shelf life of aquatic products.During the chilling storage,the water extract from Perilla leaf delayed the decline of sensory quality of CGC fillets,the weight loss rate increased continuously and the texture analysis shows that the hardness and chewiness decreased.Conclusion:the water extract from Perilla leaf exhibits a protective effect against lipid oxidation and spoiled microbial growth in prepared CGC fillets during storage,and delay the spoilage of refrigerated fillets.?3?To improve the quality of CGC fillets during chilling storage,the fillets were treated by the water extraction of Perilla.And then SPME and GC-MS were used to analyze the changes in volatile components of CGC fillets during chilling storage.The total of 70 volatile components were identified.The results showed that relative contents of aldehydes and alcohols were higher than that of other volatile components.For the aldehydes,playing a major role on the flavor of CGC fillets,it increased at the beginning and then decreased during chilling storage.The relative contents of aldehyde and?E,E?2,4-decadienal were the highest on the 8th day,which were 15.84%and 6.07%,respectively,and then decreased continuously.For1-octene-3-alcohol,the relative content of it increased by 10.01%on the 16th day,resulting in fishy odors aggravation.Moreover,the relative content of linalool got lower and lower during chilling storage,the overall effect on the flavor of fish also gradually reduced.Additionally,the relative content of ester decreased by 85.19%on16 d and the degree of influence on the flavor of fillets decreased gradually.After 8days of chilling storage,the relative content of 2,3-octanedione was 8.77%,increasing by 4.56%.At the same time,the relative content of?-ionone decreased significantly with extension of chilling storage.On the 16th day,it decreased by 95.87%.However,?-ionone,which has special aroma and low threshold,is contributed to the flavor of CGC fillets.Besides,other kinds of volatile components were considered lower effect on flavor due to their high odor thresholds or low contents.In conclusion,the water extract of Perilla has an enhanced effect on the flavor of prepared CGC.?4?The study was to investigate the effect of packaging methods and packaging materials on the quality of prepared CGC fillets,which were marinated in the water extract from Perilla leaf during the storage at 4?.The results showed that the total bacteria count grew fastest in prepared CGC packaged with air-condition,whereas the lowest counts of total bacteria were found in the sample with modified atmosphere packaging?MAP?during chilled storage at 4?.When storage at 15th day,the average of total bacteria count of the fillets with MAP reached to 5.61 lg?CFU/g?,which didn't exceeded the end of the shelf life of aquatic products,while the total bacteria count of the fillets with other two packaging methods were exceeded the end of the shelf life of aquatic products.In the end of the storage,the drip loss rate,TVB-N value and TBA value of the prepared CGC fillets packaged with MAP were lower than that with vacuum packaging?VP?and air-conditioned packaging?AP?.For these samples packaged with MAP and PVC,the drip loss rate reached 5.07%at 15th day.At the same time,the TVB-N value reached 13.91 mg/100mg that was less than the secondary freshness of national standard.The preservation life of prepared CGC were more than 15 days with MAP during chilled storage at 4?.In addition,TBA values of the fillets with MAP were lower than that with VP and AP to 16.40%and 46.46%,respectively.During the whole storage,the texture characteristics of samples with MAP decreased slowly than that with VP and AP.Moreover,the hardness of prepared CGC fillets with MAP in the end of storage was higher to 26.41%and 27.08%than that of the other groups,respectively.For sensory evaluation,the sensory scores of fillets were not very significant difference between MAP and VP.For packaging materials,the differences of the quality among them were very significant.The differences of hardness,drip loss rate,TBA value and sensory score between different packaging materials were significant during chilled storage at 4?.More important,packaging materials is one of the most important factors affecting the quality of prepared CGC fillets,the prepared CGC packaged with the high barrier properties of NY/EVOH/PET composites had the best freshness.In summary,this paper provides the reference for the application of MAP and the high barrier properties material in the preservation of prepared CGC fillets.MAP and the high barrier properties material were more conducive to keeping the quality of prepared CGC fillets during chilled storage at 4?.?5?To improve the frozen quality of CGC fillets,fillets were treated with water extract from perilla and were frozen by immersion chilling and freezing?ICF?.The quality of prepared CGC were examined using texture,water holding capacity,total volatile base-nitrogen?TVB-N?,thiobarbituric acid?TBA?,salt-soluble protein content,Ca²⁺ATPase activity and sensory evaluation during frozen storage.The results showed that the TVB-N value and TBA value of the raw fish fillets during the frozen storage period were lower than those of the control group,and the difference was significant?p<0.05?with the prolonged storage time;the texture characteristics and salt solubility The protein content,Ca²⁺-ATPase activity and water holding capacity decreased with the prolonged storage time,and the protein gradually degenerated and its quality decreased,but the decline of raw was less than that of the control group.The TVB-N value,salt-soluble protein content,water-holding capacity and Ca²⁺ATPase activity of the cooked fish were lower than those of the other raw fish and the control group.The water holding capacity at the early stage of frozen storage was 6.30%,which was about 8.50%of the other two groups.Ca²⁺ATPase activity remained stable until the first 6 months of storage and began to decline,a decrease of 33.95%.Texture analysis showed that CGC fillet hardness and chewiness both showed a downward trend.The sensory evaluation further showed that the sensory quality of the three groups of samples was continuously declining.The texture,taste and turbidity scores of the three groups from the highest to the lowest were cooked fish,raw,and the control group.