Study On The Process Of Microwave Heat Penetration Of Large Yellow Croaker、Quality Analysis And Shelf Life Prediction

Large Yellow Croaker is one of four traditional seafood and coastal maileconomic fish in our country.It is rich in protein,trace elements and vitamin andhas a good tonic effect on the human body,especially in weak constitution andthe elderly. At present,the deep processing products of the large yellow croakeris rare and single,resulting in low added value.By microwave heat penetrationon the large yellow croaker,the processing time can be shorted and nutrientscan be avoided destruction by the traditional processing methods. So the largeyellow croaker was chosen as the experimental material,and the microwave heatpenetration was systematically studied in the paper.The technoloy of microwaveheat penetration has been determined by experments. The experimental contentsand results are showed as following:（1） Research on the technology of water conservation: Because of its owncharacteristic of microwave heat penetration,the temperatures between insideand outside of the heated large yellow croaker were different,resulting in fishwater evaporation easilly, tasting too hard,so it needed to protect water.Through the single factor experiment study single and composite phosphate tothe effect of water holding capacity of large yellow croaker.It was showed thatthe liquid water consist of0.012%sodium tripolyphosphate,0.024%disodiumhydrogen phosphate,0.024%Sodium pyrophosphosphate could effiectivelyimprove the water holding capacity of the large yellow croaker.On the basis ofthe single experiments,the water conservation techology was obtainedthrough uniform design were the ratio of the large yellow croaker to thesolution was1:3,the temperature was24℃,the timewas90min, the waterholding capacity of the large yellow croaker was92%.（2） Research on the technology of microwave heat penetration:Uneventhickness and irregular shape of the large yellow croaker and uneven microwaveelectromagnetic field caused process of heat easily uneven,the phenomenon offocal or raw.Therefore,the first phase of this experiment was through low powerand long time microwave heat penetrateion preheating the large yellowcroaker,the second stage was through high power and short time microwaveheat penetrateion rapid aging it to solve the above problems.Through the single factor experiment study microwave preheating power, microwave maturationpower, rate of preheating time and heat penetration time, transmission beltspeed and feed rate to the influence of temperature distribution and quality ofthe large yellow croaker after microwave heat penetrateion,which came tomicrowave preheating power, microwave maturation power, rate of preheatingtime and heat penetration time, transmission belt speed and feed rate hadsignificant influence. On the basis of the single experiment, duplicateorthogonal gyration combination design was adopted to obtain data forregression model. The relationship between the large yellow croaker maturationdegree Y₁,the maximum temperature difference Y₂, protein contentY3and fatcontent Y4and microwave preheating power X₁, microwave maturation powerX₂, rate of preheating time and heat penetration time X₃, transmission beltspeed X₄, and feed rate X5was studied.The optimal operation conditions:microwave preheating power1.197kw, microwave maturation power10.08kw,rate of preheating time and heat penetration time0.8789, transmission beltspeed0.73m/min and feed rate2190g/min, maturation degree was10, themaximum temperature difference was5.42℃,protein content was21.7347%and fat content was6.745%.In order to facilitate the production process, theoptimal operation conditions: microwave preheating power was1.05kw,microwave maturation power was10.45kw, rate of preheating time and heatpenetration time was8:9, transmission belt speed was0.7m/min and feed ratewas2100g/min.（3） Research on the quality of the microwave heat penetrateion largeyellow croaker: Through the analysis and comparison the quality of largeyellow croaker after microwave heat penetrateion treatment and traditionalcooking, it draw a conclution that the microwave heat penetrateion sample has21.73%protein,soluble protein accounted for72.4%of total protein, fatcontent was6.75%,peroxide value was7.91,selenium Retention rate was87.5%,the cooking sample has21.24%protein,soluble protein accounted for57.3%oftotal protein, fat content was5.13%,peroxide value was8.24,selenium retentionrate was72.5%.The experiment showed that microwave heat penetrateion sample had more protein、fat and soluble protein a lower level fat oxidation,selenium retention rate was also higher.（4） Research on shelf life of the microwave heat penetrateion large yellowcroaker:Respectively in three storage temperature（-15℃,-20℃,-25℃）,studythe charge of the large yellow croaker bacteria,TVB-N value and acid valuewith the storage time extended.The dynamic model of the total number ofbacteria,TVB-N value and acid value was established respectively,which was topredicted the quality changes and shelf life of the microwave heat penetrateionlarge yellow croaker during storage. And the shelf life of the microwave heatpenetrateion large yellow croaker the total number of bacteria,TVB-N value andacid value among three kinds of temperatures were predicted based on dynamicmodel,the results as follows: the total number of bacteria was262days（-15℃）,285days （-20℃）,310days（-25℃）, TVB-N value was275days（-15℃）,298days （-20℃）,370days（-25℃）, acid value was254days（-15℃）,303days （-20℃）,365days（-25℃）.Through three index,we can draw the shelf life of themicrowave heat penetrateion large yellow croaker in-15℃,-20℃,-25℃were254days,285days,310days respectively.