Effects Of Spontaneous Release CO₂ Treatments On Quality Of Broccoli Under The Simulated Logistics Conditions

Broccoli is rich in nutrition. In recent years the cultivated area, production and consumption of broccoli is increasing in China. However, the planting regions of broccoli in China are relatively concentrated and the seasonal and regional planting is obvious. The contradiction between the annual regional and seasonal production of broccoli and consumer demand lead to the development and application of broccoli logistics technology becoming particularly important. The edible part of broccoli is tender and the harvested products still remain strong metabolic activity at room temperature. Therefore, it is easy to deteriorate due to color fading, wilt and nutrient degradation which seriously influnce the value of the goods. At present, it is extensive used in logistics of broccoli that the broccoli is putting in bubble chamber accompany with some ice. The method of this can lower the temperature, delay the ripening and senencence, and maintain the appearance and nutritional value of broccoli in some extent. However, there are some problems of this method such as the high transport costs, the anaerobic respiration of broccoli because of immersed in melt ice and the increasing risk of microbial infection. CO₂ treatment can inhibit the ripening and senencence of the products. Nevertheless, the traditional controlled atmosphere storage is suitable for using in fixed site, it is difficult to use in transportation process. In this experiment, CO₂ spontaneous release agent developed in our laboratory was used, the release rule of it was analysed. Taking the optimum concentration of CO₂ and the respiration of the broccoli into account, the mathematical model between the initial respiration rate of broccoli and the optimum dosage of CO₂ spontaneous release agent under the conditions of low temperature and normal temperature were established. Furthermore, the effets of CO₂ spontaneous release agent treatment on broccoli under simulated transportation process according to seasonal temperature changes and for different varieties were tested. The result of this will provide technical support for development in gistics of broccoli. The main results are as follows:1. Using artificial filling method to adjust the concentration of CO₂ to 0（CK）,3,6,9 and 12%, and considering the changes in sensory quality, respriration, ethylene production rate, the contents of SSC, chlorophyll, Vc, total phenolics and flavonoids in broccoli, and the air composition around the products, the optimum level of CO₂ determined is range from 6% to 9% under the condition of low temperature and normal temperature.2. The release regularity of CO₂ spontaneous release was studied under different temperature conditions. The results show that there is a conversion coefficient between the actual CO₂ concentration and the prospective concentration. Moreover, the coefficient increases with the decrease of temperature. The average conversion coefficient was about 0.75 at low temperature ranging from 5℃ to 15℃, and the conversion coefficient is about 0.65 in the room temperature range of 15-25℃.3. Considering the influences of the initial respiration of broccoli on the concentration of CO₂ in the environment, and the favorable range of CO₂ concentration determined, the mathematical model between the appropriate amount of CO₂ spontaneous release agent （y in unit of g） and the initial respiration rate （x in unit of mgCO₂kg·h） were established under the conditions of low temperature and normal temperature respectively, which are:y= 0.0009x2-0.0631x+8.329, R2=0.9983 å'Œ y=0.001x2-0.0655x+7.9135, R2=0.9987.4. Choose the appropriate weight of the spontaneous CO₂ release agent to treat the broccoli by simulating the transporation process in different season such as long-distance from south to north in winter, long-distance from north to south in summer, and short-distance in spring and autumn, the effects of the treatment were analysed. Results show that it is effective to applying spontaneous CO₂ release agent for keeping the quality of broccoli during the transportation process at different seasons except for winter. In winter, the products is easy to suffer from freezing damage.5. The effect of treatment with spontaneous CO₂ release agent was better than that with ice or without any treatment for the four widely cultivated varieties of broccoli.