Vacuum pre-cooling can quickly cool down, fresh-keeping effect. Storage and transportation after harvesting flowers is a quite complicated technology. The application of vacuum pre-cooling machine preservation technology in storage and transportation after flower harvesting has begun. Effectively adjust the ambient temperature to extend its storage period and maintain the excellent quality of the flowers.
One of the most important measures for flower preservation is cooling. After the flower is harvested, due to the rapid increase of breathing, a large amount of heat is generated, which is called field heat. This field heat must be quickly removed, otherwise it is extremely unfavorable for the storage and transportation of flowers. Experiments have shown that if the flower is not harvested quickly, it can be placed at room temperature (20 ° C) for 1 day, which is equivalent to reducing the storage life of flowers for 5 to 7 days under suitable storage temperature (such as 0 ° C). . Therefore, the harvested flowers should be quickly cooled down, that is, pre-cooled. The harvested flowers can enter the storage or transport vehicle directly without pre-cooling. Not only do the storage tanks or transport vehicles provide a large amount of cold, but also because the storage and transport vehicles are not designed to cope with the large amount of field heat. Designed with flowers, the unpre-cooled flowers can enter the warehouse directly or the car can not fall for a long time. In addition, the temperature difference between the cargo temperature and the storage temperature is large, and it is easy to condense a large amount of water droplets on the top of the reservoir. These water droplets infiltrate the flowers and cause rot. The post-harvest pre-cooling treatment of the flowers requires only a small amount of cold after the flowers enter the storage or transport vehicle, and only requires a certain cold-proof and heat-proof measure, and the cooling efficiency is also high.
There are many preservative methods for flower pre-cooling, and one of the most effective ones is vacuum pre-cooling. Vacuum pre-cooler preservation is based on the characteristics of vacuum evaporation under vacuum conditions. The flowers are placed in a vacuum pre-cooling tank for vacuum treatment. Some of the water in the flowers is transpiration, and the latent heat is released from the water vapor. The flowers quickly cool down. Vacuum pre-cooling not only has a fast speed and a relatively uniform temperature drop, but also reduces the oxygen pressure of the flower tissue and lowers the concentration of ethylene released, which can effectively maintain the freshness of the flower and prolong the storage period.
The vacuum pre-cooling preservation of flowers mainly controls the humidity and temperature by controlling the vacuum degree of the pre-cooling process. The required degree of vacuum is related to the physiological characteristics of the flowers in the pre-cooling tank, the number of flowers, the humidity of the flowers themselves, and the performance of the vacuum equipment. Problems and countermeasures in flower vacuum pre-cooling preservation The flower vacuum pre-cooling preservation process will cause flower water loss phenomenon. When the temperature drops by 10 °C, the water loss is 1%. If the temperature drops from 30 °C to 5 °C, about 3% of water loss. . If the flower loses water seriously and the surface pores are open, it will lead to a decrease in freshness and affect the quality of the flowers. Therefore, it is necessary to strictly control the flower to have a suitable humidity. In the United States, a spray vacuum pre-cooling device has been applied to effectively prevent dehydration of the flower pre-cooling process and to quickly cool down. At present, the author mainly absorbs water or sprays water on flowers before vacuum pre-cooling. Water absorption means that the flower is placed in an aqueous container before pre-cooling, so that the flower is immersed for a period of time and then placed in a vacuum chamber together with the container for vacuum pre-cooling. This method is mainly suitable for the requirement of pre-cooling and lower final temperature. Flower (if required 1 ° C to 2 ° C). In addition, for flowers with more flower buds after harvesting, about 1% silver nitrate is added to the container water as a preservative. The water absorbing treatment affects the production efficiency because the container occupies a certain space of the vacuum chamber. Water spray treatment refers to the use of a humidifier to uniformly spray and humidify flowers before pre-cooling, so that the flowers have sufficient moisture before pre-cooling. Practice has proved that water spray treatment is simple and applicable.
Vacuum flower fresh pre-cooling has the characteristics of fast cooling time (generally only 20 to 30 minutes), high efficiency, uniform temperature drop, and no influence on packaging. It is especially suitable for pre-cooling and fresh-keeping of such surface area and volume ratio. The vacuum pre-cooling preservation of flowers has yet to be continuously explored and experimented. With the continuous improvement of the pre-cooling process, the performance of vacuum pre-cooling equipment is further improved, and the application of vacuum pre-cooling preservation in flower storage or transportation will become more and more popular.
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