英文摘要 |
The shelf life of broccoli (Brassica oleracea var. italica) can be extended by pre-cooling immediately after harvest. And ice-precooling is commonly used for commercial operations in Taiwan. In this study, the precooling rates of 10 L crushed ice, 15 L crushed ice, and 1.5:1 crushed ice to water treatments were compared. After pre-cooling, the shelf life and quality changes under ordinary shelf temperatures of markets, 5°C, 8°C, and 25°C, were also investigated. The results indicated that the highest pre-cooling rate was shown in 15 L crushed ice treatment which took 65 minutes to reach the terminal temperature of 5°C. Five°C is the best shelf temperature for maintaining broccoli quality. Among the 3 precooling treatments, 1.5:1 crushed ice to water showed the best result, especially under a shelf temperature of 5°C with no visible yellowing to the end of the experiment. Under shelf temperature 8°C, the weight loss of 1.5:1 crushed ice to water treatment was also significantly less than that of 15L crushed ice treatment. There were no significant differences among the 3 precooling treatments under subsequent shelf temperature of 25°C according to both color parameters and respiration rate. Precooled by 1.5:1 crushed ice to water, among subsequent lower shelf temperatures, 5°C showed the most apparent advantage of maintaining quality. Among 3 precooling treatments, the lowest total decay rate of 1.7% was also obtained under shelf temperature of 5°C, especially from precooling by 1.5:1 crushed ice to water, which is lower than the corresponding values under 8°C and 25°C, by more than 60 and 80%, respectively. Our results reveal that the optimal post-harvest condition for broccoli is pre-cooling with 1.5:1 crushed ice to water for two days under 0°C followed by storage under 5°C. The shelf life can last to 36 days. |