Study On The Improvement Of Freezing/Thawing Quality Of Fresh Meat Based On Superchilling Solution Assisted Electric/Magnetic Field

China is a major country in meat production and consumption,ranking first in the world in 2022.In the actual production and life process,the most widely used method of meat storage is frozen storage.However,due to the formation and melting of ice crystals,it can lead to the destruction of meat tissue structure,and meat can have a certain degree of juice loss,leading to serious economic losses.Therefore,it is important to study new freezing and thawing techniques for reducing meat quality losses and increasing economic benefits.Superchilling technology can extend the storage period of meat and reduce the loss of meat quality on the basis of refrigeration（4℃）.If liquid immersion freezing is assisted on the basis of superchilling technology,it could further reduce the degree of meat structural damage.Physical fields such as electrostatic fields and magnetic fields have also made varying degrees of progress in assisting meat freezing and thawing research,and there is literature supporting the positive effects of electrostatic fields and magnetic fields on improving the quality of frozen meat.Based on the superchilling technology,this study improved the quality of pork by optimizing the formulation of the superchilling solution and using the-3℃superchilling solution immersion freezing technology.Subsequently,based on the superchilling assisted immersion freezing technology,the improvement of pork quality and characteristics by different intensities of electrostatic field or magnetic field assisted freezing and thawing was explored.Finally,the optimized superchilling solution and electromagnetic field parameters were applied to different types of fresh meat（pork,beef,mutton and silver fish）to explore the degree of improvement in the quality of different types of fresh meat.The specific research content and conclusions are as follows:（1）Studied the optimization of superchilling solution formulation and the effect of superchilling solution assisted immersion freezing on pork quality.The temperature of superchilling（-3°C）was determined by the freezing point of pork（-1.5°C）,and three cryoprotectant（trehalose,sorbitol and edible glycerol）were subsequently selected as the base ingredients of the superchilling.Through single-factor experiments,the freezing point changes of single cryoprotectant solutions with different mass fractions and their effects on pork color were explored,and the mass fraction range of three cryoprotectant with mass fractions of 4%～8%was selected as the response surface experiment.Then,through the response surface design experiment,the formula of the superchilling solution with the actual freezing point of-3.07°C was selected under the consideration of the freezing point and the color of pork:6.1%sorbitol,8.0%edible glycerol and 7.8%trehalose.Finally,studied the effect of-3℃superchilling solution assisted immersion freezing technology on improving the quality of pork after storage at-3℃for 48 h.The experimental results showed that the-3℃superchilling could effectively improve the quality of pork,and its effect was better than that of the 4℃group.The superchilling solution assisted immersion freezeing could further reduce the loss of pork quality,and close pork’s quality to the-80℃treatment group.（2）The effect of assisted electrostatic or magnetic field freezing on the quality of pork was studied based on-3℃superchilling immersion freezing.The treatment group includes fresh group,non-physical field immersion group,non-immersion group,as well as different intensity electric field（1 kV,2 kV,3 kV and 4 kV）and magnetic field（1 m T,2 m T,3 m T and 4 m T）assisted superchilling solution group.The experimental results showed that both electrostatic field and magnetic field assisted freezing treatment could effectively improve the characteristics of pork myofibrillar proteins and inhibit the degree of lipid oxidation.Electrostatic field or magnetic field assisted freezing treatment could effectively reduce the turbidity,surface hydrophobicity and TBARS value of myofibrillar proteins,and increase the sulfhydryl content,dityrosine content and maximum fluorescence intensity of pork myofibrillar protein.In the results,it could be seen that the improvement effect of the 3 kV and 3 m T groups were the most significant groups among all the groups.However,the effect of the electric/magnetic field does not linearly increase with the increase of its strength,and the worst effect were found in the 1 kV and 2 m T groups.In the electric/magnetic field treatment groups,the index of 3 kV group was the best,superior to the 3 m T group.Therefore,it was selected as an auxiliary freezing process parameter to explore the optimal parameters for thawing technology based on this.（3）The effects of electrostatic field or magnetic field assisted thawing on the quality of pork were studied based on the technology of superchilling solution assisted 3 kV electrostatic field freezing.During the thawing process,electrostatic field or magnetic fields of different intensities were used to thaw the pork.After electrostatic field or magnetic field assisted thawed treatment,the turbidity,surface hydrophobicity,total sulfhydryl content,foaming property and foam stability,dityrosine content,secondary structure,fluorescence intensity and LF-NMR water distribution of pork were improved to varying degrees,and were better than those without physical field assisted thawed treatment.And the best results among all the electrostatic field or magnetic field treatment groups were also the 5 kV group or the 5m T group.This indicateed that the electrostatic or magnetic field could effectively improve the quality of pork,and the quality of 5 kV group was better than that of the 5 m T group.Therefore,5 kV was selected as the optimal parameter for thawing.（4）The effects of different thawing and freezing techniques on the quality of fresh meat and the pilot test content:the effects of different freezing methods on the color and sensory evaluation of fresh meat were studied.In different thawing methods,electrostatic field assisted thawing had better effects on the quality of other physical fields（microwave,ultrasound,and infrared）,room temperature thawing,and still water thawing.The results showed that electrostatic field thawing technology could effectively reduce the thawing loss of meat and inhibit its lipid and protein oxidation.Subsequently,in the impact of different freezing methods on the quality of fresh meat,the optimized physical field assisted superchilling solution and thawing technology was applied to pork,beef,mutton,and silver fish,and the different effects of this technology and other freezing methods on the quality of fresh meat were explored.The results showed that the-3℃electrostatic field assisted superchilling solution freezing treatment could effectively improve the quality of fresh meat,and was superior to the-20℃immersion group,the-20℃ultrasonic immersion group,and the-80℃group,but lower than the liquid nitrogen（LN₂）freezing group.Finally,in the pilot experiment,the color of pork,beef,and mutton in the-3℃superchilling solution treatment group was the worst among the treatment groups,but the color of silver fish was better than that in the treatment group except for the LN₂group;In sensory evaluation,the six sensory indicators of pork,beef,and mutton in the-3℃group were superior except for color,while the six sensory indicators of the-3℃group of silver fish were the closest to the LN₂group,superior to the-80℃group,and the-20℃combined with the-20℃ultrasonic treatment group.