椪柑、桶柑與柳橙長期貯藏之濕度與失重率之關係

Effect of Humidity in Long­term Storage on Losses of Weight by ‘Ponkan’ Mandarin (Citrus reticulata Blanco), Tankan (C. tankan Hayata), and ‘Liucheng’ Orange (C. sinensis Osbeck)

本研究將椪柑、桶柑與柳橙放在15℃恒溫庫中，80%、85%、90%及95%相對濕度（RH）之壓克力缸內，貯藏1­3個月後，測定果實失重率及失水徵狀。調控相對濕度之方法為混合一定比例之飽和濕空氣與乾燥過的乾空氣後，連續流通壓克力缸中。結果顯示果實失重率與相對濕度成接近直線之關係，而果實失重率與蒸氣壓差（VPD）之直線迴歸相關顯著。但是迴歸直線皆不經過原點。VPD由0.5 mbar加倍增至1.0mbar，由1.0 mbar加倍增至2.0 mbar，或由1.5 mbar加倍增至3.0mbar時，果實失重速率增加比率依次為58.2±3.7%、73.8±3.2%或80.6±2.4%；依次遞增而非一定之常數。在15℃95% RH缸中貯藏椪柑2個月、桶柑3個月及柳橙3個月依次失重3.11%、4.19%、1.83%，且無縐皮或軟化現象。在15℃90% RH貯藏椪柑2個月、桶柑2個月及柳橙3個月，依序失重7.54%、7.22%及5.99%，部分果實有輕度縐皮或軟化。在15℃90%RH貯藏椪柑及柳橙各一個月之失重率為3.30%及2.03%，皆無縐皮或軟化；而在15℃85%RH貯藏椪柑及柳橙各一個月之失重率為4.75%與3.52%，小部分果實有輕度縐皮或軟化。因此推薦3種柑桔之貯藏濕度貯藏一個月者用90%或85­90%RH而貯藏達2個月或更長時間者用95%或90­95% RH。 Ponkan' mandarin (Citrus reticulata Blanco), tankan (C. tankan Hayata), and ‘Liucheng’ orange (C. sinensis Osbeck) were stored in 80%, 85%, 90%, and 95% relative humidity (RH) boxes in a 15℃ room. Relative humidities were controlled by continuously flowing through individual boxes with mixtures of proportionated water­vapor saturated air and desiccated air. Weight losses and rind shrivelling and softening symptoms of fruits were evaluated after 1 to 3 months of storage periods. Linear regressions with significant correlation coefficients were obtained between the rate of weight loss and the vapor pressure deficit (VPD) in 6 experiments. However, none of the 6 regression lines passes through the origin. Therefore, a constant rate of weight­loss increase by every 100% increase in VPD does not exist. Instead, the higher the VPD, the higher weight­loss rate increase by doubling the VPD. Based on percent weight losses and the occurrence of shrivelling and softening data, desirable relative humidities for the 3 citrus fruits shall be 90% or 85 to 90% for one month of storage, and 95% or 90 to 95% for two months or longer periods of storage.