Postharvest Handling and Storage Technology of Jicama (Pachyrhizus erosus (L.) Urban) Tuberous Root

本試驗之目的為研究豆薯塊根採後處理技術及最適貯藏溫度。尋求最適合豆薯塊根的貯存溫度，並探討塊根寒害發生症狀與生理變化。豆薯主要寒害的症狀為腐爛及褐化，而寒害會使豆薯喪失商品價值。本試驗結果顯示豆薯塊根在9℃及以下溫度貯藏即有可能發生寒害。豆薯塊根若貯藏低溫再移溫（25℃）時，其呼吸率及乙烯釋放率皆有上升現象，與寒害的嚴重程度成正相關，隨著貯藏時間延長而有加劇的情形。 豆薯塊根貯於6℃及以下溫度2週或於9℃3週時塊根腐爛；塊根貯藏於9℃或低於9℃溫度下1週褐化嚴重。豆薯塊根貯於12℃或以上溫度1-4週，則無明顯寒害出現，塊根顏色明度高彩度低，呼吸率及乙烯釋放率亦低。若再降低溫度至10℃，豆薯在2週內無寒害症狀，故9℃2週應為豆薯塊根的寒害臨界溫度。而豆薯於9℃貯藏2週後，不需回溫，塊根褐化情形馬上顯現，並且隨回溫時增長，塊根褐化顏色加深；豆薯於1℃貯藏1週後，再經回溫48小時以上，塊根褐化才會顯現。豆薯塊根低溫貯藏後，再移至15℃、20℃、25℃、30℃及35℃下回溫，結果顯示於20℃以上溫度回溫，所引發塊根寒害症狀最為明顯。 豆薯塊根利用溫度管理、聚乙烯包裝處理及溫湯處理等技術，以期減輕豆薯塊根寒害症狀。結果顯示豆薯塊根經聚乙烯袋包裝處理，對於降低低溫貯藏造成塊根的褐化效果有限，但可以減低塊根腐爛程度。豆薯塊根利用溫度馴化處理亦沒有改善其低溫傷害情形。而間歇加溫處理豆薯塊根，可以減輕塊根寒害症狀。豆薯塊根於貯藏前利用50℃溫湯處理10分鐘，可以有效減輕塊根寒害症狀的發展。The objectives of this experiment were to investigate the postharvest handling technique, to find suitable temperature for storage, and to map the symptom of chilling injury as well as physiological changes of the jicama tuberous root under low-temperature condition. Jicama is a tropical crop, and thus is prone to low-temperature injury. Decay and browning being the principal visual symptom, cause the loss of commercial values. Results indicated that the jicama tuberous root stored at a temperature lower than 9℃ would show sign of chilling injury. When the chilled jicama root was moved to a higher temperature, its respiration and ethylene production rates would increase in proportion to the severity of the damage brought about by the cold. The jicama tuberous root stored at 6℃ or below for 2 weeks, or stored at 9℃ for 3 weeks resulted in chill-induced decay and at 9℃ or below for a week led to severe browning. No obviously chilling injury was observed when it was stored at 12℃ or above for 1-4 weeks. However, a decrease in chroma and increase in lightness (L) values of root color were noticeable; the respiration and ethylene production rates remained relatively low. The critical storage temperature has found to be 9℃ for 2 weeks. After storing at 9℃ for 2 weeks, browning appeared on the tuberous roots before returning to the room temperature, and browning was deepened over time after storage. Furthermore, after storing at 1℃ for 1 week, browning was observed only after 48 hours under the room-temperature condition. Storing at 1℃ for 1 week then moved to 15℃, 20℃, 25℃, 30℃ and 35℃, the symptom of chilling injury was most significant while the root was placed above 20℃. Utilizing techniques of temperature regulation, PE packaging and hot-water treatment, it appeared that wrapping with PE bag at low temperature had limited effect on browning but reduced the severity of decaying. Temperature conditioning seemed to be ineffective either. Intermittent warmming regulation ameliorated the symptom of the chilling injury. Hot-water treatment at 50℃ before storing reduced the development of the chilling- injury symptom on the jicama tuberous root.目錄 中文摘要..................................................i Summary..................................................ii 目錄....................................................iii 表目錄....................................................v 圖目錄..................................................vii 壹、前言..................................................1 貳、前人研究..............................................2 一、根莖類採收及貯藏之問題................................2 二、根莖作物之寒害........................................4 三、寒害發生之機制........................................5 四、減輕寒害之方法 .......................................10 參、材料與方法...........................................13 一、豆薯之貯藏溫度與寒害.................................13 二、包裝對豆薯塊根寒害之影響.............................16 三、溫度管理對豆薯塊根寒害之影響.........................17 四、溫湯處理對豆薯塊根寒害之影響.........................19 五、溫湯處理及低溫貯藏對豆薯多酚氧化酵素、過氧化酵素、苯丙 胺酸裂