Inhibitory effect of moisture loss on braised pork quality by rapid cooling assisted with static magnetic field

This study aims to address the problem of moisture loss during vacuum cooling (VC) by employing the static magnetic field (SMF). The effect of six treatments on the cooling process and quality of braised pork was investigated, including natural cooling (NC), air blast cooling (ABC), refrigerating cooling (RC), SMF-assisted 4 °C cooling (RC + SMF), VC, and SMF-assisted VC (VC + SMF). The findings indicated that the VC and VC + SMF cooling rates substantially exceeded those of the other groups. The VC treatment led to a significant increase in mass loss (7.32%) and a decrease in moisture content (34.56%) of braised pork compared to NC (4.02%; 39.22%), but the VC + SMF showed lower mass loss (5.78%) and higher moisture content (35.78%) than VC. This was due to the change in water distribution in pork treated with SMF assistance, which decreased the water migration rate and enabled the conversion of immobilized water into bound water, as indicated by the results of low-field nuclear magnetic resonance. The scanning electron microscopy images revealed that the muscle fiber structure of pork cooled with SMF assistance was the most intact, with a neat and dense fiber arrangement, which facilitated a higher water-holding capacity. Furthermore, the SMF-assisted treatment substantially inhibited the lightness (L*, 41.32) decline of the braised pork cooled by VC (39.77), while improving its taste and texture. The overall acceptability of sensory scores in the VC (7.13) and VC + SMF (7.63) groups considerably exceeded those of the NC (5.50) and ABC (5.88) groups. The improvement of SMF on the rapid cooling process of VC was more prominent than the slow cooling of RC. Therefore, combining the magnetic field with novel pre-cooling technology offers a highly promising strategy for the industrial cooling of precooked meat products.