氣調技術應用在蔬菜採後保鮮之研究

Abstract

本試驗是以青花菜為模式作物，經由試驗建立其氣變包裝所需之基本條件，並依此結果進行初步之氣變包裝貯藏試驗，藉此過程吸取研發之經驗，進而評估其應用於本地之易敗壞性蔬果產品保鮮之可行性。青花菜之採後生理與老化受到溫度的影響很大。在20℃中之呼吸速率及乙烯生成速率甚高且會快速轉黃；將溫度降至5℃以下時即能顯著減緩此一變化。降低氧氣濃度及提高二氧化碳濃度亦對青花菜之老化生理有抑制效果，在20℃中降低氧氣濃度至1％以下即可發揮抑制呼吸作用、乙烯生成速率及抑制黃化的效果。提高二氧化碳濃度至6％以上，也有抑制呼吸作用及花蕾黃化的效果。依濃度增加測定法測定LDPE、HDPE、PP及OPP四種薄膜在1-20℃中對氧氣及對二氧化碳的透氣性，OPP的透氣性最小，PP次之，LDPE與HDPE相近但以後者略高一些。各種薄膜對二氧化碳的透氣性比對氧氣的透氣性約高3-4倍。且薄膜的透氣性隨溫度之增加而增加，但是並非直線關係。青花菜以LDPE袋在20℃中做氣變包裝貯藏試驗，並比較空氣密封包裝、充入1%O2十6%CO2混合氣體密封包裝及充入氮氣密封包裝三種方式之效果。以空氣密封包裝者袋內大氣需6天才達到平衡且氧氣過低而二氧化碳過高，此時小花蕾已經變黃；以l%O2十6%CO2混合氣體密封包裝者及以氮氣密封包裝者袋內大氣在三天之內達到平衡且濃度適宜，小花蕾保持在綠色達7天以上。由本試驗結果顯示青花菜在20℃中可用l%O2十6%CO2之主動氣變方式做氣變包裝以延長其壽命，因此氣變包裝技術在易敗壞蔬菜採後保鮮上之應用應值得進一步研究。 In this study, broccoli was used as the model crop to evaluate whether controlled atmosphere technology, in the form of modified atmosphere packaging (MAP), could be used in the postharvest handling of perishable vegetables in this country. The optimum gas composition for MAP of broccoli was first investigated. Broccoli has very high respiration and ethylene production rate at 20℃ and turned yellow rapidly at this temperature. Lowering temperature to below 5℃ will slow down this process. Reducing oxygen concentration to near 1% and elevating carbon dioxide concentration to above 6% were also effective in inhibiting the senesence process in broccoli. The permeability of LDPE, HDPE, PP and OPP to oxygen and carbon dioxide at temperatures between 1-20℃ were measured using Concentration Increase Method. The permeabilities for carbon dioxide are about 3-4 time of that for oxygen in all four film tested and all the permeabilities increase with temperature with a non-linear relationship. OPP is the least permeable film, followed by PP. Both DEPE and HDPE have higher permeability, with HDPE slightly higher. A modified atmosphere packaging experiment was then conducted unsing LDPE bags under 20℃. The effectiveness of passive MA and active MA methods were compared. The gas composition in bags that were sealed directly with air reached equlibrium after 6 days with oxygen concentration below 0.5% and carbon dioxide concentration above 10%, and all the floret had already turned yellow. The gas composition in bags that were either flushed with 1%O2 + 6%CO2 or flushed with nitrogen before sealing reached equilibrium within less than three days with oxygen near 1% and carbon dioxide near 5%. And all the floret maintained green for at least 7 days. The result of this study indicated that the freshness of broccoli at 20℃ could be extended by using active MA method, and the application of MAP in postharvest handling of other perishable vegetables should be encouraged.