关键词: 供需结构, 供需结构, 预测, ARIMA-GRNN模型

Abstract: The purpose of the study is to screen cool-storage materials with an appropriate phase-transition temperature and good fresh-keeping effect for different vegetables. The phase-transition temperatures of four cool-storage materials including water, 4.8% sodium chloride (NaCl), 10% ammonium acetate (C2H7NO2) and 15% sodium formate (CHNaO2) were determined to clarify their thermodynamic properties during freezing and melting process. Meanwhile, fresh-keeping effect of the four cool-storage materials on cucumber, bell pepper, lettuce and broccoli were determined to select suitable cool-storage materials for different vegetables. The results showed that phase-transition temperature of water, 4.8% NaCl, 10% C2H7NO2 and 15% CHNaO2 were 0, -6, -12 and -16℃. Under the frozen temperature of -28℃, their phase transition time from liquid to solid was about 6, 12, 11 and 18 h, respectively. Under the room temperature (22℃) and sealed condition, their phase transition time from solid to liquid was about 15, 6.5, 6 and 7.5 h, respectively. 4.8% NaCl had a better fresh-keeping effect on cucumber and bell pepper. And 15% CHNaO2 had a better fresh-keeping effect on bell pepper, lettuce and broccoli. In practice, 4.8% NaCl could be applied to vegetables which were sensitive to temperature such as cucumber and bell pepper. And 15% CHNaO2 could be applied to half-hardy vegetables such as lettuce and broccoli.