Study On The Storage Quality Control And Shelf Life Prediction Of Sauced Duck

Sauce duck is one kind of traditional food.Due to the high nutritional quality and good taste,it is popular with consumers in China.However,because of the high fat content,it is easy to cause lipid oxidation,thus the deterioration of flavor and the unstability of storage quality.Moreover,so far the shelf life for commercially available sauce duck is not established rigorously.Therefore,the sauce duck is used as the research object in this thesis,the quality changes of sauce duck under different packaging systems,the preparation of chitosan-coated tea pholyphenols nanoparticles and the influence of chitosan-coated tea pholyphenols nanoparticles coating on the storage characteristics of sauce duck were studied.Additionly,quality changes and predictive modeling of shelf life for sauce duck stored at different temperatures were analyzed.The main results are as follows:?1?Quality changes of sauce duck stored at 25°C under vacuum packaging,modified atmosphere packaging?60%CO₂,40%N₂?and customary packaging during storage were studied.The results showed that with the increase of storage time,the total viable counts?TVCs?,total coliform count?COLIs?,thiobarbituric acid?TBA?value,peroxide value?POV?,acid value?AV?,the relative content of metmyoglobin?met-Mb%?of all samples were significantly increased?P<0.05?,but a*value and sensory value were significantly decreased?P<0.05?.Among them,samples of vacuum packaging had higher a*value and lower met-Mb%,lipid oxidation indicators?POV,AV,TBA?and microbial indicators?TVCs and COLIs?than other packagings?P<0.05?.The free fatty acid content and volatile flavor compounds of alkanes substances content of vacuum packaging group were also lowest among all samples.Results showed that vacuum packaging had a better effect on inhibiting lipid oxidation,and could maintain the flavor attributes of sauce duck.?2?Chitosan-coated tea pholyphenols nanoparticles solution was prepared by ion crosslinking method and the structure was characterized.Tea polyphenols were dissolved into chitosan solution,then the sodium tripolyphosphate?2.5g/L STPP?was injected for crossling under the continuous stirring.After the reaction,samples were ultrasoniced to obtain chitosan-coated tea pholyphenols nanoparticles solution.The loading rate of tea pholyphenols in nanoparticles soulution was 86.76±0.01%.DPPH free radical scavenging capacity reached 85.11±0.01%.The size of nanoscale chitosan and chitosan-coated tea pholyphenols nanoparticles was 163nm and 227nm respectively,which were in agreement with the results observed by transmission electron microscopy.Combined thermal analysis?TGA-DSC?analysis showed that after 650?temperature decomposition,the solid state residues of nano chitosan and chitosan-coated tea pholyphenols nanoparticles were more than 38%,indicating that the properties of nanoparticles were stable,and could be used for subsequent storage experiments.?3?Under 25°C,aseptic condition,the changes of chitosan-coated tea pholyphenols nanoparticles coating sacue duck storage of the TVCs,COLIs,Moulds,TBA value,AV,POV,met-Mb%,free fatty acid and volatile flavor substances was studied.The results showed that during the storage period,the microbial indexs and lipid oxidation indexes of chitosan-coated tea pholyphenols nanoparticles were lower than those of other experimental groups,and there was a significant difference?P<0.05?.Meanwhile,in the entire storage period chitosan-coated tea pholyphenols nanoparticles coating sauce duck had higher content of aldehydes volatile flavor compounds,and alcohols volatile flavor compounds.With the extension of storage time,the low threshold volatile flavor compounds decreased slower than other treatments.Therefore,chitosan-coated tea pholyphenols nanoparticles treatment group can effectively inhibit lipid oxidation and microbial breeding of sauce duck,and can preserve the flavor and color of sauce duck in the storage period better,and can also prolong its shelf life.?4?The storage quality of vacuum packaging sauce duck under different storage temperature?4°C,25°C,37°C?was analysed,and shelf life prediction model was also been built.During storage,the TVCs,COLIs,moulds,acid values,peroxide value and TBA value of sauce duck under different temperature were increased,but sensory scores decreased.Pearson correlation analysis between quality indexes of sauce duck indicated that moulds and TBA had a high correlation with sensory attributes,and their variation tendency fit to zero-order dynamic model.Arrhenius equation was used to predict the shelf life model of sauce duck.The activation energy?Ea?and rate constant?K₀?of moulds value and TBA value were 16034.13 kJ/mol,25809.98kJ/mol and 165097.25,1072.32.We use the measured value of shelf life,which sauce duck stored at the temperature of 4,25 and 37°C,to verify the predictive modeling of shelf life,and the results turn out the theoretical shelf life is agreed with the actual shelf life.Therefore,we can predict the shelf life of sauce duck using indexes of mould and TBA.