Abstract

Meat rapidly decomposes and discolours due to oxidation and enzyme activity; therefore, it must be frozen when stored. This study investigates the effects of different freezing and thawing processes on pork quality. Pork meat was frozen by natural convection freezing (NCF, -38°C), individual quick-freezing (IQF, -45°C), or liquid nitrogen freezing (LNF, -100°C). Freezing was completed when the thermocouple temperature reached -12°C. The meat was then placed in a general showcase at -24°C for 24 h. Thawing was conducted by natural convection thawing (NCT, 25°C) or running water thawing (RWT, 10°C). The cooking loss and drip loss contents of the samples did not significantly differ, whereas the thawing loss contents were higher in the NCF sample than that in the other samples. Compared to fresh meat, the L^*, a^*, and b^* colour values decreased and the total colour difference (ΔE) was similar in the samples subjected to IQF/RWT. The pH values of all the samples except for the one subjected to NCF were significantly increased than that in fresh meat (p < 0.05). IQF/RWT Treatment resulted in the highest water-holding capacity and maintained homogenous tissue similar to fresh pork; however, the shear force value was lower than those in the other frozen/thawed samples. These results suggest that the IQF/RWT process was optimal for pork.

Key words: Freezing, thawing, pork, shear force, pH