高溫妨礙‘台農二號'番木瓜果實之後熟軟化

High Temperature Impedes Fruit Ripening in 'Tainung No.2' Papaya

臺灣在網室栽培的‘台農二號’番木瓜，在高溫的夏天常見後熟不正常，出現「橡皮肉」的現象。本試驗比較果實採後放置30℃，35℃或40℃，0，3，6或9天後之狀況與品質，以及此種不同溫度處理後再以電石催熟3天之果實狀況與品質。各處理果實之細胞壁酵素活性亦于測定。結果顯示，35℃或40℃高溫處理阻礙果實後熟作用，導致果肉轉色不良及軟化困難，高溫並抑制β-半乳糖苷酶活性與β-葡萄糖苷酶活性及減緩果膠溶解速度。以40℃高溫處理6天後之果實，再經3天催熟處理，也無法正常軟化；果肉出現局部硬塊。高溫可能妨礙番木瓜果肉之果膠溶解，因而發生「橡皮肉」症狀。 Net-house grown 'Tainung No.2' papayas are prone to develop ”rubbery pulp”, disorder in the hot summer in Taiwan. The effect of postharvest exposure to high temperature on papaya ripening, softening and cell-wall enzyme activities was investigated in this study. Some fruits were evaluated after being kept at 30℃, 35℃ or 40℃ for 0, 3, 6, or 9 days. Others were evaluated after an artificial ripening with calcium carbide for 3 days at 30℃ following the high-temperature treatments. The results showed that high temperature inhibited pulp-color change and pulp softening of the fruits either with or without artificial ripening. High temperature also inhibited β-galactosidase and β-glucosidase activities and reduced the rate of pectin dissolution. The fruit exposed to 40℃ for 6 days followed by calcium carbide ripening treatment did not have normal softening but developed hard lumps in the pulp instead. High temperature seemed to have blocked normal papaya ripening and caused rubbery pulp due to impediment in pectin dissolution.