Applications of heat stress and low temperature for qualitative improvement of fruit during storage.

本研究采用智能控制技术，研究了热胁迫（40℃）和低温（-2℃）组合对苹果贮藏保鲜的影响，并探讨了其实用性，研究了在-2 ~40 ℃温度范围内，苹果贮藏过程中失水速率和呼吸速率的动态变化。虽然失水速率（或呼吸速率）随温度的降低而降低，但在相同的低温下，它们具有恒定值。采用人工神经网络对失水速率随温度的变化规律进行了研究，并采用遗传算法对最佳热胁迫处理进行了研究。在6步控制过程和15[≤]T[≤]40℃的范围内，最佳温度操作为{40，15，15，15，15和15℃}的时间序列。特别地，温度从最高水平到最低水平的突然下降提供了比在整个控制过程中将温度恒定地保持在最低水平更低的水分损失速率值。番茄不仅耐高温（40-50℃），而且耐低温（-2℃）。适宜的热胁迫处理显著降低了果实贮藏期间的冷害。最后，以爱媛县特产伊与柑为试材，研究了一种简单、低成本的热胁迫处理技术，并将其应用于伊与柑的贮藏过程中。

In this study, combinatorial uses of a heat stress (40℃) and a low temperature (-2℃) was investigated for maintaining the freshness of fruit during storage using intelligent control techniques and then its capability for practical use was examined.Dynamic changes in the rate of the water loss and the respiration rate of fruit during storage, as affected by temperature in the range of -2 to 40℃, were investigated. Although the rate of the water loss (or respiration rate) decreased with decreasing the temperature, they had constant values under the same low temperature. However, increasing the temperature to 40℃ from -2℃ for 12 hours and then dropping it to -2℃ provided the significant reduction of the rate of water loss.The dynamic change in the rate of water loss as affected by temperature was first identified using neural networks, and then the optimal heat stress application was investigated using genetic algorithms. Under the 6-step control process and the range of 15【less than or equal】T【less than or equal】40℃, the optimal temperature operation was the time series of {40, 15, 15, 15, 15 and 15℃}. In particular, the sudden drop in temperature from the highest level to the lowest level provided lower values of the rate of water loss than maintaining the temperature constantly at the lowest level throughout the control process.Optimal heat stressed fruits (e.g., tomato) not only have tolerance against high temperature (40-50℃), but they also had tolerance to low temperature (-2℃). Optimal heat stressed fruits significantly reduced the chilling injury of the fruit during storage. This means that a heat stress application technique is effective for lower temperature storages.Finally, a simple and low cost heat stress application technique was investigated and then applied to the storage process for Iyokan fruit which is the special product of Ehime prefecture.