Studies on the growth and development of physico-chemical characteristics and post-harvest physiology of three cultivars of papaya fruits (carica papaya L.)

• Main Author: 蔡雅惠
• Other Authors: Lih-Shang Ke
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/09704244128540882753

碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作研究所 === 91 === A series of studies were conducted to elucidate the physico-chemical changes during fruit growth and development, and postharvest physiology and storage of three cultivars of papaya fruits (Carica papaya L.), named ‘Tainung No.2’, ‘Sunrise’, and ‘SR-mu’ (a newly selected line and has yet to be named), and their responses to 1-methylcyclopropene (1-MCP) and heat treatments. Results showed that the growth curves of fresh weight, volume, length, and width of fruits were in a typical single sigmoid pattern. The fresh thickness, seed weight, dry matter, vitamin C, total soluble solids (TSS) and sugar/acid ratio increased progressively with the days after pollination. However, the firmness, moisture content of fruit, and hue angle of peel and flesh decreased with the fruit growth and development. Papaya fruits, including ‘Tainung No.2’, ‘Sunrise’ and‘ SR-mu’ cultivars, are typical climacteric fruits. During the growth and development, fruits at different stages (ages) all exhibited climacteric respiratory and ethylene production peak at 20 oC after harvest. The only difference will be the time of the peaks appeared and the production rate. For example, the 130-day old fruits, the peak of respiration of ‘Tainung No.2’ fruits appeared on the fifth day at the rate of 42.13 mg CO2/kg-hr and the peak of ethylene production was found on the sixth day with a production rate of 3.87 µl/kg-hr. The peak of respiration of Sunrise fruits appeared on the fourth day at the rate of 40.96mg CO2/kg-hr and the peak of ethylene production was found on the seventh day with a production rate of 4.82 µl/kg-hr. The peak of respiration of ‘SR-mu’ fruits appeared on the sixth day at a rate of 42.35 mg CO2/kg-hr and the peak of ethylene production was also found on the seventh day with a production rate of 3.61µl/kg-hr. The peak of climacteric ethylene production usually appeared one to two days later than the peak of climacteric respiration. In these three cultivars, the concentrations of CO2 and ethylene in fruit cavities were not detectable before 105 days after pollination. Only until 120 days after pollination, CO2 and ethylene were clearly detected in the Sunrise fruits at a concentration of 5.92 % and 0.06 ppm, respectively, and in ‘Tainung No.2’ fruits were 3.98 % and 0.02 ppm, respectively. Although CO2 was also detected in ‘SR-mu’ at a concentration of 1.32 % in 120 days after pollination, but ethylene was detectable at a concentration of 0.09 ppm in 130 days after pollination. CO2 and ethylene concentrations reached their peaks in the fruit cavity of the three cultivars in 130-135 days after pollination. Afterwards, the more mature the fruits became, the lower the concentrations of CO2 and ethylene detected in fruit cavities. At the different maturities of papaya fruits (‘Tainung No.2’), the respiration rate of fruits increased with the increase of the storage temperature, and the time for climacteric rise of respiration and ethylene production were shortened. In addition, the higher the maturity of the fruits, the time for the climacteric respiration and ethylene production peak were earlier, and the rate at peak were higher with the more mature fruits. When the fruits of ‘Tainung No.2’ and ‘Sunrise’ were stored at 5-25oC, the weight loss in naked, unpackaged fruits was most serious; reaching 11-15 % in nine days storage. The weight loss was the least (about 2-4 %) in the fruits packed with sealed PE bag or sealed in PE bags containing ethylene absorbents. The weight loss significantly increased with the increase of the storage temperature. Therefore, lowering the storage temperature would reduce the weight loss. Different packaging methods affected storage life of fruits. Using 5-10o C as example, the fruits of ‘Tainung No.2’ packed in sealed PE bags or sealed PE bags containing ethylene absorbents significantly extended the storage life to 25-26 days compared to unpacked fruits with 21 days of storage life, whereas the ‘Sunrise’ fruits were 22-24 days and 19-21 days, respectively. The fruit qualities in TSS and titratable acidity (TA) were not affected by different packaging methods. Fruits packed in sealed PE bags or sealed in PE bags containing ethylene absorbents retained the vitamin C content and delayed fruit peel yellowing and softening. However, papaya fruits storing at 5oC for 14 days exhibited surface pitting and water soaked symptoms of chilling injury; therefore, papaya fruits were not suitable for storing at 5oC. It is suggested that the papaya fruits should be stored at 10oC during storage and transportation. The respiration and ethylene production rate of ‘Tainung No.2’ fruits subjected to 1-MCP treatment were lower than those of the fruits not subjected to the treatment. The higher the concentration of 1-MCP treatment at 0.1-5.0 ppm, the inhibition of the respiration and ethylene production was more pronounced. Also, the time for the peaks of climacteric respiration and ethylene production was delayed. In addition, the 1-MCP treatment also inhibited the enzyme activities of pectinesterase (PE) and polygalacturonase (PG). The higher the concentration of 1-MCP treatment at 1.0-5.0 ppm, the inhibition of the enzyme activities of PE and PG were pronounced. Even at seven days after 1-MCP treatment, the 1-MCP treated fruit retreated with ethephon (1,000 ppm), the activities of PE and PG were not recovery. The prestorage heat treatment of papaya fruit (‘Tainung No.2’) at 56-60 oC and 8-16 sec. decreased the respiration and ethylene production rate. The days required to reach the climacteric peak of respiration and ethylene also delayed. The flesh firmness of fruits with prestorage heat treatment were significantly higher than those of non-heated fruits. The higher treated temperatures (56-60 oC) and longer duration (8-16 sec.), the higher flesh firmness of fruits. Therefore, the prestorage heat treatment was significantly inhibited the softening of papaya fruits. Prestorage heat treatment did not significantly affect the fruit qualities in terms of TSS, TA, pH, and vitamin C, and the color of the fruit (peel and flesh) in terms of brightness, color saturation and hue angle.