Influence Of Different Pretreatment Methods On The Quality Of Frozen Pork

Freezing is one of the most common techniques for food preservation,and freezing can maintain the quality of meat and inhibit the growth and reproduction of microorganisms.However,during conventional freezing,the generation of ice crystals causes irreversible damage to the structure of meat,leading to loss of juice,flavor,lipid oxidation,protein denaturation,and microscopic structure damage.To improve the quality of frozen pork,this study investigated the effects of three freezing pretreatments: soaking in alginate oligosaccharide(AOS),low voltage alternating electric field(LVAEF)assistance,and liquid nitrogen(LN)spray-on the quality of pork stored at-18℃ for 90 d.The results of this study will provide a theoretical basis for the application of high quality and authentic fresh pork in freezing and transportation.The main research findings were as follows:(1)Influence of AOS concentration on the quality of pork during frozen storageThe effects of different concentrations of alginate oligosaccharides(AOS)pretreatment on the quality of frozen pork were investigated by evaluating its WHC,color,moisture distribution,protein characteristics,microscopic structure,and histological changes after thawing.The frozen pork samples were subjected to soaking pretreatment with AOS at concentrations of 1.0%,2.0%,3.0%,and 4.0%(w/v)before freezing at-18°C.The research findings revealed that AOS was capable of maintaining the quality attributes of frozen pork.Specifically,the 3.0% AOS treatment exhibited better preservation of WHC and protein characteristics during the freezing period.The a*-value,protein solubility,and total sulfhydryl content were significantly higher than those of the control group(P < 0.05),while surface hydrophobicity and fragmentation index were significantly lower(P < 0.05).Moreover,the myofibers of samples treated with 3.0% AOS and 4.0% AOS exhibited tighter microscopic structures,smaller ice crystal areas,and equivalent diameters compared to the control group after 90 d of freezing.Therefore,the addition of 3.0% AOS was found to effectively inhibit the deterioration of frozen pork quality.(2)Influence of LVAEF with different distance on the quality of pork during frozen storageBy measuring the WHC,color,moisture distribution,protein characteristics,microstructural changes,and histological variations of pork stored at-18°C,the present study investigated the impact of low voltage alternating electric field(LVAEF)assistance with different inter-electrode distances(15 cm,25 cm,35 cm)on the quality of frozen pork.The research findings indicated that employing LVAEF assistance during the freezing process helped maintain the quality characteristics of frozen pork.Among the different interelectrode distances,the LVAEF-25 exhibited the most favorable assistance effect.The LVAEF-25 treatment significantly increased the a*-value,protein solubility,and total sulfhydryl content compared to the control group(P < 0.05).Moreover,the surface hydrophobicity and fragmentation index were significantly lower than those of the control group(P < 0.05).Additionally,the LVAEF-25 treatment showed good preservation of the microstructure.Consequently,LVAEF assistance with an inter-electrode distance of 25 cm effectively suppressed the deterioration of frozen pork quality.(3)Influence of LN spray pretreatment at different temperatures on the quality of pork during frozen storageBy measuring the WHC,color,moisture distribution,protein characteristics,microscopic structure,and histological changes of frozen pork stored at-18°C,the effects of different liquid nitrogen(LN)spray pretreatment temperatures(-60°C,-80°C,-100°C)on the quality of frozen pork were investigated.The research findings indicated that LN spray pretreatment before freezing could maintain the quality characteristics of frozen pork,with-80°C being the optimal spray temperature.The a*-value,protein solubility,and total sulfhydryl content were significantly higher than the control group(P < 0.05),while surface hydrophobicity and fragmentation index were significantly lower than the control group(P < 0.05).At this temperature,the samples were rapidly frozen without experiencing expansion and fracture.The generated ice crystals were small and uniform,contributing to better preservation of the microscopic structure.Therefore,LN spray pretreatment at an environmental temperature of-80°C could effectively inhibit the deterioration of frozen pork quality.