Effect Of Superchilled Storage On The Shelf Life And Quality Of Pork

The storage temperature has significant effects on the quality of pork.The growth of microorganisms and the process of biochemical reactions during traditional chilled storage(4℃)make the meat spoil and deteriorate quickly in a short period of time.The formation and growth of ice crystals cause damage of muscle tissue during frozen storage,which is not conducive to water holding capacity and texture of pork.As consumers have higher requirements for raw meat quality,it is necessary to seek a storage method that can extend the shelf life of pork while ensuring the quality of pork.The superchilling technology uses low temperature treatment to freeze part of the water in the food,and the temperature of the product is 1 to 2℃ below its freezing point.Products are partially frozen during superchilled storage,which reducing damage to muscle tissue and reducing quality loss.The temperature of superchilled storage is low,and the surface of the product is frozen,which limits the growth of microorganisms and can effectively extend the shelf life of meat products.In this paper,the effects of different degrees of superchilled storage on pork quality is studied,and pork quality changes are compared with the traditional chilled,superchilled and frozen storage.It provides a theoretical basis for the optimization of superchilled storage conditions and the superchilling technology of processing and storage of meat.The main contents and results are as follows:1.Research on the influencing factors of freezing point of porkFour different pork cuts(Boston butt,Picnic shoulder,Loin and Ham)were selected,and their freezing points were measured and compared.The factors affecting the freezing point of pork were studied by measuring their compositions,thermodynamic parameters,and water distribution of pork.The results showed that there were significant differences in the freezing point of different pork cuts.The freezing point of Loin was significantly lower than the other pork cuts and the freezing point of Boston butt and Picnic shoulder was significantly higher.The correlation analysis results show that the freezing point of pork was extremely significantly negatively related to sarcoplasmic protein solubility,and significantly negatively related to the ash content.In vitro experiment,the freezing point had a significant quadratic polynomial correlation(R=-0.99,P<0.001)with sarcoplasmic protein solubility.According to the analysis of the results of water distribution,mobility and thermodynamic properties,pork sample with lower freezing point has higher sarcoplasmic solubility,while high sarcoplasmic protein solubility reduces water mobility,and unfreezable water content increases.This makes the formation of ice crystal more difficult,resulting in lower freezing points.2.Effects of different degrees of superchilling on shelf life and quality of pork during storageThe relation curve is set up by measuring the ice fractions and impedance value of pork at different degrees of superchilling,thereby exploring a rapid method for obtaining the ice fraction of pork.-1℃(0.00%ice fraction),-2℃(20.85%ice fraction),and-3℃(37.21%ice fraction)is selected as the storage conditions.The changes of microbial growth,biochemical indicators and quality in pork of different degrees of superchilling are investigated to obtain the optimal superchilled conditions.The results show that the ice fraction of pork has an exponential correlation with the impedance modulus:y=117.22 × e^ 0.0440 x(R2=0.9922).The difference between the ice crystal content measured by the impedance method and the thermodynamic method is small.The method of measuring the ice fraction of superchilled food by impedance method is fast and convenient,which is beneficial to the rapid detection of the ice fraction on the production line.The lower the temperature of the frozen storage,the longer the shelf life of the pork.The shelf life of-1℃,-2℃,and-3℃ are 15 days,25 days,and 35 days,respectively,and the growth rate of microorganisms,TVB-N content increase rate and pH value of pork stored at-3℃ are significantly lower.In addition,the pork stored at-3℃ had lower carbonyls contents and thiobarbituric acid-reactive substances,indicating that the high degree of superchilling can inhibit protein and lipid oxidation.Furthermore,pork stored at-3℃ is found to reduce drip loss,although it might inevitably result in enhanced cooking loss due to ice crystal formation,and retard the decrease in tenderness compared to the low degree of superchilling(-2℃).In brief,the high degree of superchilling can extend the shelf life of pork longer and maintain better meat quality.3.Effects of chilled,superchilled and frozen storage on shelf life and quality of porkThe changes of microbial growth,biochemical indicators and quality in pork during chilled,superchilled and frozen storage was investigated in order to further study the effect of superchilled storage on pork quality and compare the advantages and disadvantages of the three storage methods.The results show that the shelf life of chilled pork is about 6 days,and the shelf life of slightly frozen storage at-3℃ is about 36 days,which is 4.5 times that of chilled storage,and the shelf life of frozen pork is long.Chilled storage is beneficial to maintain tenderness of pork,but the pH value is significantly increases,water holding capacity and color are significantly reduced.Superchilled storage and frozen pork have lower pH and better color.The growth of ice crystals in frozen pork has a greater degree of damage to the tissue structure of muscle than superchilled storage.The tenderness of frozen pork increases significantly and the water retention decreases.The superchilled storage tissue structure of muscle remains relatively complete,and the drip loss is significantly reduced,which is conducive to water retention and is suitable for short-term storage of pork.