A heat stress application technique for retaining the freshness of fruit during storage.

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In this study, a heat stress application technique for retaining the freshness of fruit during storage was developed using intelligent control techniques and then its capability for practical use was examined.Dynamic changes in the water loss, respiration and firmness of tomato during storage, as affected by temperature in the range of 5-45℃, were investigated. Although the water loss and respiration of the fruit increased with the temperature, they decreased over 35-℃. The water loss and respiration of the fruit after the heat stress application of 40℃ kept lowering for about 1 week when the temperature was returned to the first level (15℃).A simple and non-destructive measurement technique for fruit firmness was developed using the concept of chaos. The acoustic response was obtained by hitting the fruit with a small hummer. The attractor of the acoustic response was first described ; then, its slope was calculated. There was a close relationship between the slope of attractor and fr … More uit firmness. This showed that use of the attractor allowed quantitative evaluation of fruit firmness in the time-domain.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, which is the combination of the l-step set points for temperature that minimized the rate of water loss, 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℃}.The optimal temperature operation obtained here was applied to Satsuma mandarin and Iyokan fruit. As the result, more significant reductions of water loss and respiration were observed comparing to the case of tomato.These results suggest that the optimal heat stress application to the fruit is effective for retaining the freshness of the fruit during storage and there is sufficiently the practicability. Less