Abstract: To explore the mechanism behind the effect of different freezing methods on the water-holding capacity of frozen pork, immersion-frozen and air-frozen pork were subjected to determination of freezing loss, thawing loss, cooking loss, pH, water distribution and protein degradation and their microstructure were observed. Chilled samples were considered as control. Results showed that the freezing loss of 3-day and 3-month immersion-frozen samples was significantly lower than that of their respective air-frozen counterparts (P < 0.05). The pH value of immersion-frozen samples did not significantly change with increasing freezing time (P > 0.05), and the immobilized water was transformed into bound and free water, with a significant increase being observed in the proportion of bound water (P < 0.05). On the other hand, the pH value of air-frozen samples decreased significantly (P < 0.05), and the immobilized water and bound water were all transformed into free water, with a significant increase being observed in the proportion of free water (P < 0.01). The intermuscular space decreased in immersion-frozen samples as compared to air-frozen samples. Overall, these results could explain why the water-holding capacity of immersion-frozen samples was superior to that of air-frozen samples, which will provide technical support for the optimization of pork freezing.

Key words: immersion chilling and freezing, air freezing, pork, water, mechanism