幾丁聚醣膜之透氣性與對香蕉果實後熟之影響

Gas Permeability of Chitosan Coating and Its Effect on Ripening of Banana Fruit

謝欣彣(Hsin-Wen Hsieh)

指導教授 ： 王自存

共同指導教授 ： 許明仁

國立臺灣大學/生物資源暨農學院/園藝學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.02413

摘要

本試驗的目的為研究幾丁聚醣(chitosan)成膜特性、透氣性與對香蕉後熟行為影響，並評估幾丁聚醣是否可作為具氣變(Modified Atmosphere)效果的可食膜。
幾丁聚醣成膜特性受展著劑、溶劑、pH值的影響。添加0.01%之Tween80即可改進溶液的散布性而形成平整的被膜。幾丁聚醣膜的濃度會影響厚度和透氣性。以1%醋酸所製成的1%幾丁聚醣膜所測得的氧氣透氣性與二氧化碳透氣性分別為3.64×10-5 cc-mil/day．m2．atm和4.96×10-5 cc-mil/day．m2．atm，可知氧氣透氣性較低而二氧化碳透氣性較高，幾丁聚醣濃度越高則透氣性越低。
綠熟香蕉用3%幾丁聚醣處理可以延緩果實之自然後熟達6天，但3%幾丁聚醣處理會造成果皮轉色不完全。香蕉在乙烯催熟處理之前以幾丁聚醣被膜，除3%之外，其餘均可正常後熟；但隨幾丁聚醣濃度增加，會使香蕉之乙烯及二氧化碳生成速率降低。香蕉在乙烯催熟處理之後以幾丁聚醣被膜，結果與催熟處理前被膜者相同；經3%幾丁聚糖被膜者在出現芝麻斑點時，其內部之二氧化碳較未處理者高約2%，而氧氣濃度約低2%。
綠熟香蕉與後熟的黃香蕉被覆幾丁聚醣對於內部氣體之氣變效果不同。呼吸速率低的綠香蕉處理幾丁聚醣時僅可稍微減少內部氧氣，3%幾丁聚醣處理組的內部氧氣可比對照組降低約2%，二氧化碳與乙烯無差異。後熟的黃香蕉呼吸作用旺盛，任一濃度幾丁聚醣被膜處理後內部乙烯會累積，內部氧氣與二氧化碳則在6小時內達到平衡濃度，有被覆幾丁聚醣比對照組其內部氧氣濃度較低而內部二氧化碳濃度較高。由透氣性試驗與香蕉後熟試驗可得知幾丁聚醣膜確實具有氣變的效果，且此氣變的效果會隨幾丁聚醣膜的濃度與果實本身之後熟程度而變。

關鍵字

幾丁聚醣 ； 被膜 ； 透氣性 ； 後熟 ； 氣變

並列摘要

The object of this study was to investigate the potential of chitosan as an edible coating material with modified atmosphere effect for fresh fruit. The characteristics for the formation of chitosan film were studied and the gas permeability of chitosan film was measured. Then the effects of chitosan coating on the ripening behavior of banana were studied.
The formation of chitosan film was affected by several factors, including addition of emulsifier, type of solvent and the pH value. Adding 0.01% Tween 80 to the solvent enabled the chitosan solution to spread out evenly on a flat surface and facilitate the formation of a flat layer. The thickness and gas permeability of the film was affected by the concentration of the chitosan solution. Chitosan film had higher permeability for oxygen than for carbon dioxide. The measured gas permeability of the film made from1% chitosan dissolved in 1% acetic acid was 64x10-5 cc-mil/day•m2•atm and 4.96x10-5 cc-mil/day•m2•atm for oxygen and carbon dioxide respectively. The gas permeability of the chitosan film will decrease as the chitosan concentration further increased.
Coating green banana fruit with 3% chitosan could delay the natural ripening for 6 days, but the same coating caused incomplete coloration of the skin. Banana fruit that were coated with chitosan before ethylene treatment all showed normal ripening behavior except the 3% treatment. However, with the increase in chitosan concentration, lower ethylene and respiration rate was observed. Banana fruit that were coated with chitosan after ethylene treatment had similar results as the previous treatment. At the brown-fleck stage, the internal carbon dioxide concentration of the 3% chitosan treated fruit was approximately 2% higher than the control, and the internal oxygen concentration was approximately 2% lower than the control.
Different results were observed with respect to the internal atmosphere composition of chitosan-coated green and yellow-ripe banana fruit. In the green banana, which had low respiration rate, only 3% chitosan coating caused a slightly reduce in the internal oxygen concentration, and the internal carbon dioxide and ethylene concentration were not affected. In the yellow-ripe banana fruit, which had a high respiration rate, the internal ethylene concentration accumulated in all chitosan-coated fruit, and the internal oxygen and carbon dioxide concentration reached steady-state within 6 hours. At steady state, the internal carbon dioxide was higher than the control and the oxygen concentration was lower than the control. The above results showed that chitosan coating did cause modified atmosphere(MA) effect in treated fruit, and the MA effect will vary depending on the concentration of chitosan used as well as the ripening stage of the fruit.

並列關鍵字

chitosan ； coating,gas permeability ； ripening,modified atmosphere

參考文獻

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Amarante, C., N. H. Banks, and S. Ganesh. 2001c. Relationship between character of skin cover of coated pears and permeance to water vapour and gases. Postharvest Biol. Technol. 21:291-301.

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