EFFECTS OF HUMIDITY ON PHYSIOLOGICAL-ACTI VITY AND TEXTURE OF TOMATO AND CUCUMBER FRUITS

Physiological responses and texture changes were investigated on tomat o and cucumber fruits held in high (95%), medium (80%) and low (60%) r elative humidity at 20 degrees 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 i n terms of the Hunter L, a* and b* values. Loss in flesh firmness, wh ich was rapid in the fruit held in low RH, was positively correlated t o increased water-soluble pectin (WSP), decreased hydrochloric acid-so luble pectin (HP) and decreased hemicellulose in the tomatoes, and to decreased sodium hexametaphosphate-soluble pectin (HMP) in the cucumbe rs. These results suggested that water deficit stress in low RH was un favorable in the view of keeping quality of the tomatoes and the cucum bers, because of accelerating their physiological activities and degra ding enzyme activities of cell wall polysaccharides.