Effects of liquid nitrogen spray pretreatment at different low-temperatures on the storage quality of frozen pork

The cryo-protective effects of liquid nitrogen (LN) spray pretreatment at different low-temperatures (-60°C, -80°C and -100°C) on frozen pork (storage at -18°C) for 30 d, 60 d and 90 d were studied by evaluating water-holding capacity (WHC), color, water migration, protein traits, microstructure and ice-crystal morphology. The results declared that LN effectively maintained the quality properties of frozen pork, and -80°C was the best pretreatment temperature. The LN-80 treatment had higher WHC, L* -value, a* -value, solubility of myofibril protein, total sulfhydryl content, and lower b* -value and surface hydrophobicity compared to the other treatments ( P < 0.05). Besides, the fibres of pork treated by LN, especially LN-80, had significantly more compact microstructure, smaller ice-crystal area and equivalent diameter than control ( P < 0.05) after 90 d frozen storage. Consequently, LN spray (especially LN-80) is a potential, and efficient pre-treatment method for improving the quality of frozen pork.