Fruit development and postharvest physiology of Pakchong 1 papaya

Pattern of fruit growth in "Pakchong 1" papaya in terms of increase in dimensions, weight and volume was simple sigmoid. Mesocarp color turned light yellowish orange and seed color became light grey at the mature green stage or 120 days after anthesis. A trace of yellow (5 % of the surface area) occured on skin at the blossom end of the 130-day-old fruit. Skin and mesocarp of older fruits became deeper yellow as seeds turned darker. The beta-carotene content in the flesh of 10 to 120-day-old fruits was low and ranged from 42.2 to 204.9 international units (I.U.). It was much higher in older fruits. Soluble solids (SS) and total sugars content of mature green fruit were 2.5 and 2.6 times those of the 10-day-old fruit. Vitamin C content in the flesh and concentration of ethylene (C2H4) in the fruit cavity decreased during early stages of fruit development, but increased at the mature green stage. In fruits older than 120 days, flesh was softer and titratable acidity (TA) remained low. At 25+-1 deg C, fruits harvested at the mature green stage and when 5 and 15 % of surface area turned yellow, exhibited the climacteric peaks of 23.33, 24.85 and 25.13 ml CO2/kg/h in 4.5, 4 and 2 days, respectively. The peaks of ethylene production at 1.01, 1.07 and 1.46 micro l/kg/h were attained 0.5, 0.5 and 1 day earlier. When skin color turned fully yellow, fruits harvested at the mature green stage lost the highest weight of 4.7 %. When ripe, fruits of the 15 % yellow stage had flesh firmness of 57.4 newtons, SS of 13.1 % and TA of 0.14 % which were significantly higher than those of the remaining two stages. Highly significant contents of vitamin C (179.0 mg/100 ml juice) and total sugars (142.5 mg/ml juice) were also found in fruit of the former stage. Beta-carotene content in flesh was 3,350.7 I.U. when fruits of 3 stages of harvest maturity reached the edible ripe stage.