Effect Of Low Voltage Electrostatic Field-Assisted Frozen Storage/Thawing On Quality Of Pork

As the most common way of meat preservation,frozen storage plays an important role in meat production.However,frozen storage/thawing often leads to deterioration of water holding capacity,color,texture and other quality of meat,resulting in economic loss.In this study,pork longissimus thoracis et lumborum muscles were used as experimental materials.Firstly,by comparing and analyzing the changes in protein oxidation,lipid oxidation and other quality indexes of meat samples under LVEF and in the absence of LVEF,the effect of LVEF-assisted short-term frozen storage on pork quality was confirmed.Secondly,the myowater mobility and distribution of meat samples were dynamically monitored during frozen storage by using low-field nuclear magnetic resonance(LF-NMR)to clarify the role of ice crystal growth in the migration and“state change”of myowater.Combined with the analysis of protein physicochemical properties such as the protein structure and hydration capacity,the interaction of muscle protein and water in the process of LVEF-assisted frozen storage was further explored.Lastly,the thawing rate,color,water holding capacity,texture and microstructure of meat samples under different thawing treatments were analyzed to clarify the combined impacts of LVEF and high humidity assisted-thawing on quality of pork.The results should provide a theoretical basis for the development of novel technology in meat preservation.The specific results list as follows:Quality indices of the meat samples frozen at-18,-12 and-6? under LVEF or in the absence of LVEF(control group)were determined during short-term frozen storage(0,7,14,21 and 28 d).Throughout storage period of samples,LVEF samples showed significantly lower(P<0.05)total bacterial counts,TVB-N contents and TBARS values than that of control group.Besides,the meat samples subjected to LVEF groups exhibited higher water holding capacity and fresher color compared to control group.It is noteworthy that at 28 d,no significant differences(P>0.05)were observed among the total bacterial counts(4.50 lg(CFU/g)),TVB-N content(8.73 mg/100g)and TBARS value(0.1691 mg MDA·kg^-1)in LVEF samples at-12? and those of control group at-18?(4.48 lg(CFU/g),8.91mg/100g and 0.1754 mg MDA·kg^-1,respectively).Additionally,the purge loss,shear force and color between those two groups showed no significant difference(P>0.05).In general,LVEF could effectively alleviate the quality deterioration of pork during frozen storage.However,there were no significant differences observed(P>0.05)in the meat quality traits between LVEF group at-12? and control group at-18? throughout the short-term storage(28 d),and the similar trend was found between LVEF group at-6? and control group at-12?.The quality indices and the protein-water interaction in meat samples frozen at-18? and-38? under LVEF or in the absence of LVEF(control group)were explored.During storage(0,1,2,3,4 and 5m),compared with control group at-18?,the meat samples subjected to LVEF at-18? exhibited significantly higher L*and a*values,lower?E values and lower shear force(P<0.05).The thawing loss and cooking loss of the LVEF group at-18? meat samples were significantly reduced(P<0.05)with lower water mobility,relative proportion of free water and higher relative proportion of bound water and immobile water,which proved that LVEF could effectively maintain the water holding capacity of pork during-18? frozen storage.The protein surface hydrophobicity and relative ratio of?-turn and random coil of meat samples subjected to LVEF group at-18? were lower than that of control group at-18?,which showed that meat samples subjected to LVEF group at-18? had less severe protein denaturation.The meat samples under LVEF at-18? formed smaller and more uniform ice crystals in muscle,which resulted in less damage to the muscle microstructure.However,there were no significant differences observed(P>0.05)in the quality traits between LVEF and control group at-38? of storage.The quality traits of meat samples under refrigerator thawing(RT,4?,RH 50%),low voltage electrostatic field thawing(LT,4?,RH 50%),high humidity thawing(HT,4?,RH 98%)and low voltage electrostatic field combined with high humidity thawing(LHT,4?,RH 98%)were determined.Results showed that LHT effectively maintained the color stability of pork steaks by inhibiting the formation of metmyoglobin.Meanwhile,LHT significantly reduced thawing loss,centrifugal loss(P<0.05)and water mobility while effectively improving the muscle texture.Based on the thaw curve and PCA results,we can conclude that the LVEF could effectively shorten the thawing time and maintain the WHC of muscle,while the high humidity treatment seemed to play a more important role in maintaining the colour stability of thawed pork.