Effects of humidity on physiological activity and texture of tomato and cucumber fruits

Physiological responses and texture changes were investigated on tomato and cucumber fruits held in high (95%), medium (80%) and low (60%) relative humidity at 20°C. High respiration rates and elevated ethylene productions were observed in both the tomato and the cucumber fruits at low RH. Low RH hastened the peel coloring of the tomatoes in terms of the Hunter L*, a* and b* values. Loss in flesh firmness, which was rapid in the fruit held in low RH, was positively correlated to increased water-soluble pectin (WSP), decreased hydrochloric acid-soluble pectin (HP) and decreased hemicellulose in the tomatoes, and to decreased sodium hexametaphosphate-soluble pectin (HMP) in the cucumbers. These results suggested that water deficit stress in low RH was unfavorable in the view of keeping quality of the tomatoes and the cucumbers, because of accelerating their physiological activities and degrading enzyme activities of cell wall polysaccharides.