台灣柑桔實用催色技術之研發

Studies on Practical Degreening Methods Suitable for Taiwan Citrus Fruits

本研究之目的在研發實用於台灣柑橘的催色技術。試驗之柑橘包括‘Eureka’檸檬、椪柑及柳橙。以拼裝式冷藏庫加開一扇通風換氣門作為催色室，用間歇換氣方式控制室內CO2濃度及適量加入乙烯催色柑橘，簡易又實用。催色室內維持在25℃及相對濕度95％左右。檸檬用10或20ppm乙烯催色4～5日就完成轉色；用100ppm乙烯會嚴重傷害果蒂，不適用。椪柑用10或20ppm乙烯催色需3～4日依採收時果實轉色程度而定；亦可用100ppm乙烯催色，只需2～3日。柳橙用20ppm乙烯催色3～4日已足。椪柑與柳橙用乙烯催色不僅加速轉色，而且會增高轉色後的Huntera*值或a*/b*值，加深橙紅色澤。催色前浸泡25ppm之2,4-D可有效改善催色引起之褐蒂或落蒂；用50ppm2,4-D效果更佳。用較高濃度乙烯催色時會需要更高濃度的2,4-D才能保護果蒂延遲老化。

This study was aimed at finding practical degreening methods which would be suitable for‘Eureka’lemons,‘Ponkan’mandarins, and‘Liucheng’oranges produced under present agricultural and marketing conditions in Taiwan. Conclusions were drawn on the basis of repeated experiments on fruit maturity at harvest, ethylene concentrations, duration of gassing, 2,4-D pretreatment etc. using a small polyurethane board constructed cold storage room with an additional ventilation door. The room was maintained at 25℃and 95％RH with small fluctuations. Ethylene was added in batches. The room was ventilated periodically just frequent enough to keep CO2 concentrations below 5％. It seems that similar facilities and methods, except bigger sized degreening rooms when necessary, would be suitable for commercial use. Lemons could be degreened promptly by exposure to 10 or 20 ppm ethylene for 4 to 5 days. Exposure to 100 ppm ethylene caused severe button damages.‘Ponkan’mandarins could be degreened by 10 or 20 ppm ethylene gassing for 3 to 4 days or by 100 ppm ethylene for 2 to 3 days. Half-colored‘Ponkan’mandarins needed 1 to 2 days shorter gassing time than the fruits harvested greener, just at the color-break stage.‘Liucheng’oranges degreened rapidly in and after 3 to 4 days of ethylene gassing. Ethylene degreening inevitably hastened fruit button senescence. Pretreatment by dipping in 25 ppm 2,4-D solution was an effective remedy for the problem. Higher concentrations of 2,4-D seemed necessary when higher concentrations of ethylene were used or when the degreened fruits were kept for extended time periods before disposition.