貯藏溫度與包裝技術應用在茭白筍採後保鮮之研究

Abstract

摘要 茭白(Zizania latifloia Turcz.)為禾本科菰屬植物，受菰黑穗菌寄生後形成可供食用之茭白筍，為台灣夏季及秋季重要蔬菜之ㄧ。目前茭白筍採收後處理相關報告並不多，因此藉由本試驗來暸解其採收後生理之變化及不同包裝技術對品質之影響。本試驗包括了: 1. 測量茭白筍儲藏於不同溫度下之呼吸、乙烯及品質之變化。2. 使用不同包裝方式並觀察帶殼程度對茭白筍儲藏品質之影響。3. 應用真空包裝技術在茭白筍採後保鮮之可行性，視其對組織內氣體成分及品質之影響。 茭白筍為幼嫩之生長組織，採收後生理變化極為旺盛，其生理作用與品質變化，受溫度之影響很大。茭白筍在20及15 ℃高溫下儲藏之呼吸率，相較於10 ℃、5 ℃、0 ℃高出了2~9倍之多；而第二週時，20及15 ℃下儲藏的茭白筍，已經出現了基部腐敗及微生物作用而呼吸作用為起始值的2倍。儲藏在5 ℃、0 ℃的呼吸率自第一週開始直至試驗結束，始終維持很低。茭白筍儲藏在20 ℃及15 ℃高溫下，其乙烯的生成量在第七天時即較其他較低溫儲藏下，多出2~3倍；第二週時，20 ℃的乙烯生成量甚至達到0 ℃的10倍。高溫儲藏下茭白筍之失重率第一週達到3%，第二週後，20 ℃下儲藏失重率更是達到了10%，同時高溫下維他命C及醣類均下降較快，基部切口快速褐化，出現長根的現象，並且失去商品價值，品評時出現異味。低溫5 ℃及0 ℃儲藏下，直至試驗結束，上述之生理變化及品質外觀下降均較緩和。 茭白筍以PE袋打孔及不打孔後袋口紮緊兩種包裝方式5℃下儲藏四周後，在官能品評上，外觀、咀嚼之纖維感及整體表現上不打孔包裝之茭白筍均有較佳之表現。然則就切口顏色、脆度、維他命C的變化差異不大。充入不同氣體之氣變包裝對茭白筍基部顏色褐化的程度，充氮包裝無論在L＊、a＊或b＊值相較於其他處理都可保持較穩定之表現。官能品評上，低氧充氣密封包裝處理在外觀、甜味、纖維、風味及整體接受的結果均高於利用空氣密封者。本試驗中在0% 、0.5% 或1% O2低氧充氣包裝處理，直至實驗結束後袋內氧氣濃度仍保持5%以上並未觀察到無氧呼吸的發生，無異味的產生。氣變包裝處理約在第十天之後，袋內氣體均達到一低氧(＜10%)及高二氧化碳(＞3.5%)之狀態。 茭白筍以PE袋打孔紮緊、不打孔紮緊及真空包裝三種不同之包裝方式在5 ℃下經過四週儲藏，結果顯示真空包裝下硬度及維生素C之表現最佳。且真空包裝者切口顏色之褐化程度較低，其他處理均出現明顯之褐化劣變。真空包裝處理之官能品評在外觀及風味上的表現較其他包裝方式處理者佳，雖其在真空包裝狀態下儲藏一個月，但是並未出現低氧儲藏常出現之的問題，並無異味之產生。若相較真空包裝及氣變包裝之茭白筍醣類含量，果糖含量變化幾乎一致，但真空包裝之葡萄糖的含量則是在整個儲藏期間均高過氣變包裝者。 以完全帶殼、帶兩片外殼及不帶殼之茭白筍經真空包裝，在硬度、切口顏色、維生素C中的表現三種處理間並無太大之差異。茭白筍以不同真空時間 (10、15、20秒)包裝後，在硬度表現上以15秒真空包裝相較於其他兩種處理之表現為佳，茭白筍真空10秒後密封包裝其儲藏期結束後，其醣類含量無論是在葡萄糖或果糖中，都較15或20秒之含量高。 就本試驗而言，氣變包裝儲藏試驗中，充氮密封包裝及混合低氧氣體密封者，可延長產品儲運壽命及減緩品質劣變。茭白筍以真空包裝處理，5 ℃下儲藏50天，沒有產生不良氣味，且外觀品質劣變速率較其他包裝方式和緩。

Summary This research is divided into three parts. First, to study the effects of temperature, oxygen and carbon dioxide concentration on the physiological and quality changes of Zizania latifloia Turcz. head after harvest. Then, to investigate the feasibility of application of modified atmospheric packaging (MAP) and vacuum packaging (VAP) to the postharvest handling of Zizania latifloia Turcz. Temperature has a very large influence on the respiration rate of Zizania latifloia Turcz . Lowering temperature to below 5 ℃ can effectively inhibit the respiration and ethylene production rate, delay softing of Zizania latifloia Turcz, and reduce production rate, less the color change of cutting surface, and reduce vitamin C and weight loss. It had a higher respiration rate and ethylene evolution in 20 ℃ then in 5 ℃ when measured 1 week after harvest. In 15, 20 ℃ was 2~3 times the ethylene evolution of the 0 ℃, 5 ℃ and 10 ℃. After 2 weeks, in 20 ℃ was 10 times the ethylene evolution of the 0 ℃.The respiration rate in 15, 20 ℃ was 168.2 and 53.55 CO2 mg/kg/hr that was 2~3 times respiration rate in 0 ℃, 5 ℃ and 10 ℃ at first week. The respiration rate in 15, 20 ℃ was 265.6 and 149.6 CO2 mg/kg/hr. Low temperature effective in reducing respiration, ethylene production and quality. Weight loss in 15 and 20 ℃ at 7 days were . The estimated storage life were as follows: at 20 ℃ , 2~5 days; 15 ℃ , 10~14 days; 10 ℃ , 25~28 days; 5 ℃ and 0 ℃,more 28 days. Low temperature effective in reducing respiration, ethylene production and quality losses at 5 ℃ with MAP of Zizania latifloia Turcz. Both active and passive MAP treatments under 5 ℃ were effective in reduce ethylene evolution , respiration rate as well as reduce production rate, less the color change of cutting surface, and reduce vitamin C and sugar content. It also provided good evaluation in panel text. The active MAP treatment of low oxygen (0~1%) under 5 ℃ was no off-order. The evaluation of panel text showed that the treated active MAP ones had better than passive ones. The deterioration rates of Zizania latifloia Turcz were significantly inhibited when they were stored in bags that were either flushed with pure nitrogen gas or nitrogen gas containing 0.5~2% O2 before sealing. Deterioration of Zizania latifloia Turcz at 5 ℃ was significantly retarded by using air and 1.5% O2 flush to modify the atmosphere within the package. Although active modification implies some additional cost, its main advantage is that it ensures the rapid establishment of the desired atmosphere. Both respiration and ethylene production rates were significantly inhibited under low O2 plus high CO2. The inhibitory effect the active MAP was better than passive one. The gas concentrations of Zizania latifloia Turcz in vacuum packaging were always under low O2 plus high CO2. There is no low-oxygen damage in vacuum packaging. The optimal storage temperatures should be between 0 and 5 ℃. The vacuum packaging treatment at 5 ℃ for 50 days was no off-order. For the best quality maintenance of Zizania latifloia Turcz in vacuum packaging (VAP), vacuum 10 seconds is recommended.