Abstract:To explore the quality changes of pre-made chicken chops under different liquid nitrogen flash-freezing temperatures, liquid nitrogen spray (-80, -100, -120 ℃) was used to freeze chicken chops, whereas fresh storage at 4 ℃ and slow freezing at 18 ℃ were used as controls. The evaluation indicators included freezing speed, sensory score, water holding capacity, pH, color, texture and oxidation index. The results showed that treating chicken chops with liquid nitrogen flash-freezing considerably shortened the freezing time. The sensory score of chicken chops treated with liquid nitrogen flash-freezing at -100 ℃ (70.83 points) was the closest to that of chicken chops refrigerated at 4 ℃ (84.00 points), whereas treatment with liquid nitrogen flash-freezing at -120 ℃ caused cracks on the surface of the chops. The water holding capacity of pre-made chicken chops can be effectively maintained by liquid nitrogen flash-freezing. The centrifugal loss rate of chicken chops treated with liquid nitrogen flash-freezing at -100 ℃ was 20.95%, whereas that of chicken chops treated with slow freezing at -18 ℃ was as high as 32.84%. A significant difference was detected in pH among the different groups (P<0.05), but not in color (P>0.05). The texture indices of the liquid nitrogen flash-freezing groups were generally superior to those of the -18 ℃ slow-freezing group. Compared with slow freezing at -18 ℃, the malondialdehyde content of chicken chops treated with liquid nitrogen flash-freezing at -80 and -100 ℃ decreased by 22.54% and 15.02%, respectively, whereas their glutathione peroxidase activity increased by 66.13% and 132.58%, respectively. In conclusion, compared with the slow freezing at -18 ℃, chicken chops treated with liquid nitrogen flash-freezing retained superior eating quality. It is recommended that the processing temperature be maintained between -80 and -100 ℃.
