Abstract: In order to investigate the location where drip channels are formed in fresh pork and to complement the current knowledge about the mechanism of drip loss in meat, 20 pork Longissimus dorsi muscle samples were chosen to measure the relative contents of bound water (P2b), immobilized water (P21) and free water (P22) at 12 h and 24 h post-mortem by low-field nuclear magnetic resonance in this study, and the distance between the myofibrillar and the myocyte membrane (intracellular space) and the distance between the myocytes (extracellular space) at 45 min, 3, 9, 12 h, and 24 h post-mortem. The results showed that P21 and P22 at 24 h post-mortem were respectively significantly lower and higher in the high drip loss group than in the low drip loss group (P < 0.01). The intracellular space at 45 min and the extracellular space at 9 h post-mortem in the high drip loss group were significantly greater than those in the low drip loss group (P < 0.05). The intramuscular space at 45 min post-mortem was positively correlated with drip loss (P < 0.01), explaining 24.8% and 45.3% of the variation in P22 and drip loss at 24h post-mortem, respectively. P22 at 24 h post-mortem was positively correlated with drip loss (P < 0.01), explaining 39.5% of the variation in drip loss. The above results suggest that the contraction of pork myofibrils during rigor can cause the formation of intra- and extracellular drip channels. The intracellular space of myocytes at 45 min post-mortem could explain the variation in free water content and drip loss. Larger intracellular space at 45 min post-mortem results in higher free water content in muscle, higher drip loss and weaker water-holding capacity.

Key words: water-holding capacity; low-field nuclear magnetic resonance; intra- and extracellular spaces of myocytes; drip loss rate