包裝方式對茭白筍貯藏品質之影響

Abstract

茭白筍(Zizania latifolia Turcz.)是屬於新鮮的幼嫩組織，採收下來之後會因為旺盛的呼吸作用而造成品質的衰敗，除了溫度是影響其品質變化的重要的因素之外，包裝方式是另一影響品質的因子。本試驗研究不同的包裝形式對茭白筍貯藏品質的影響。結果顯示真空包裝可維持茭白筍的外觀完好程度如新鮮的狀態下一樣；密封及捆綁處理則隨著儲藏期增加，筍身會有皺縮，並且組織內部會發生空洞化及破裂的情況；未包裝的對照組，在第三天外葉即出現萎凋，第七天筍身也逐漸萎縮並且有雜菌感染並失去食用價值。品質的部分，真空包裝處理對外葉的黃化程度、基部切口褐化、硬度、失水程度以及總可溶性醣的減少，皆是所有處理中變化最少的，其次是密封及捆綁，最後是未包裝的處理。 由於真空包裝處理對於茭白筍的保鮮有較佳的效果，因此進一步使用不同厚度的包裝袋來比較真空包裝之效果，結果顯示幾乎所有的品質項目皆沒有差異，唯獨在乙醇的濃度變化上，0.05 mm的包膜產生的量比0.08 mm 少，無氧呼吸的情況輕微一點。真空抽氣的程度不同，對袋內的氣體含量變化趨勢也有不同的影響，氧氣及二氧化碳均會快速的下降與上升，以抽氣時間12秒處理最為明顯；因抽氣12秒，負壓達755 mmHg，會讓茭白筍很快的進行無氧呼吸，造成代謝物濃度的上升較其他抽氣時間快速。 由本試驗結果得知茭白筍的最適當真空包裝方式是以厚度0.05 mm LDPE袋，以真空壓力- 680 mmHg抽氣6秒包裝。真空包裝的茭白儲藏在5℃冷藏庫，各項品質之保存最完好，在無氧呼吸的異味感出現前，可維持4-5周的貯藏壽命。

Water bamboo (Zizania latifolia Turcz.) possesses fresh and tender tissue and its quality deteriorates rapidly after harvest due to high respiration. In addition to temperature, packaging method was considered as another important factor that will affect the deterioration rate. In this study, the effect of packaging on the quality of water bamboo during storage at 5℃ was investigated. The results showed that water bamboo packed in vacuum packages maintained its appearance as good as freshly harvested. On the other hand, water bamboo packed in sealed package and tied package showed shrunk appearance as the storage time increased, and there were hollowness and cracking within the tissue. For the unpacked treatment, its sheath leaf wilted after 3 days and its body shrank after 7 days with the appearance of bacteria contamination, and became totally unsalable. With respect to the effect of packing methods on quality changes during storage, the vacuum package showed least change in all the quality factors observed, including yellowing of sheath leaf, browning of cut end, hardness, water loss and total soluble sugar contents. It is followed by sealed and tied package, and the unpacked showed the worst changes. Since the vacuum package showed the better result in maintaining the quality of water bamboo during cold storage, the conditions of vacuum package were further studies. When water bamboo was vacuum-sealed in LDPE bags of different thickness, most of the quality factors were not affected during cold storage. The only difference was the ethanol concentration inside the tissue, with 0,05 mm bags having lower ethanol than the 0.08 mm bags, indicating less anaerobic respiration. The degree of vacuum, which was controlled by the length of vacuum pumping, also affected the gas contents within the bag. The longer pumping time, the greater changes in oxygen reduction and carbon dioxide increase inside the bag. Twelve second pumping, which resulted minus 755 mmHg vacuum, was considered too long; because it results a rapid anaerobic condition and the accumulation of more anaerobic metabolites. The results of this study indicated that the optimum vacuum package condition for water bamboo were: using 0.05 mm LDPE bags and vacuum packed with 6 second pumping to minus 680 mmHg vacuum, and stored at 5℃. The water bamboo will have a storage life of 4 weeks in good quality before the appearance of anaerobic off flavor.