臺灣博碩士論文加值系統

本研究的目的是希望能了解荔枝果實乾燥時，與其果皮褐化有關的酵素活性之變化，並且發展一個替代二氧化硫燻蒸的荔枝保鮮處理方法。
荔枝在採後於常溫下12小時內，果實便快速失水並且發生果皮褐化，此時水分主要是從果皮喪失。在‘玉荷苞’、‘黑葉’和‘糯米糍’荔枝的果皮褐化期間，果皮的過氧化酵素活性均比多酚氧化酵素活性高，並且隨著貯藏時間其活性呈增加的趨勢，在低濕環境下時變化更大，但是多酚氧化酵素活性在不同品種間則無一致的變化，因此，過氧化酵素活性對荔枝果皮褐化的影響似乎比多酚氧化酵素活性更明顯。
本試驗將1% 甲殼素溶液、1N鹽酸溶液及溫湯處理結合成加溫之甲殼素處理，期望能提高荔枝的保鮮效果。雖然溫湯、鹽酸及甲殼素等不同處理組合對‘黑葉’荔枝果皮a值的影響在回溫後均無顯著差異，但是以40℃之甲殼素溶液（溶於鹽酸）浸泡5分鐘比單獨浸泡1N鹽酸6分鐘，其處理前與回溫後的a值差值下降地更少，並且其果皮的離子滲漏率明顯高於對照組，顯示加溫之甲殼素溶液（溶於鹽酸）處理後，果皮細胞的原生質膜通透性增加，而使酸更容易到達果皮細胞的液胞內，進一步地降低液胞內的pH值，因此可穩定果皮內的花青素分子並且呈現出紅色。此外，加溫之甲殼素處理可明顯降低果皮的多酚氧化酵素和過氧化酵素活性，因而減少果皮的酵素性褐化反應之發生，所以在回溫後可維持荔枝果皮的紅色。
雖然加溫之甲殼素處理可維持荔枝果皮的紅色，但是在處理後可能會有裂果的問題發生，而在回溫後則可能會有腐敗及果實凹陷的情形。於冷藏後以打孔的0.04mm聚乙烯封口袋包裝處理過的荔枝果實，則在回溫後均無果實凹陷的情形發生，可明顯改善此現象。然而，在果實腐敗的控制與裂果現象的原因及防止方面仍待進一步地研究與改善。

The objectives of this experiment were to investigate the changes in enzyme activities with regard to litchi (Litchi chinensis Sonn.) pericarp browning, and to develop an alternative method to SO2 fumigation for color retention of litchi fruits.
After harvest, the water loss of litchi fruits was very rapid and the pericarp began to brown at 25℃ within 12 hours. Water loss of fruits mainly occurred through pericarp. During pericarp browning of ‘Yuh Her Bau’, ‘Hei Yeh’, and ‘Nuoh Mii Tzy’ litchi fruits, peroxidase activity of the peel was higher than the polyphenol oxidase activity. Variations in the peroxidase activity were also higher at low relative humidity, and showed a tendency to increase during storage. However, variations of polyphenol oxidase activity were not coincidental among three cultivars. It seemed that changes in the peroxidase activity were more significant than the polyphenol oxidase activity in respect of litchi pericarp browning.
Experiments were also conducted to prevent pericarp browning of litchi fruits with the treatments of 1% chitosan solution, 1N hydrochloric acid (HCl) solution, and the combination of chitosan and 1 N of hydrochloric acid solution. The temperature of the solution was raised to 40℃ in the experiments. Results showed that the ‘a’ values of peel decreased in fruits dipping in 1% chitosan and 1N HCl solution at 40℃ for 5 minutes; significantly less than samples immersed in 1N HCl solution for 6 minutes. The ions leakage of the peel of fruits dipping in 1% chitosan and 1N HCl solution at 40℃ for 5 minutes was higher than that of the control. This seemed to indicate that permeability of plasma membrane of the fruit was increased after the heated 1% chitosan treatment, and made it easier for the acid to permeate into vacuole. Thus pH of the vacuole decreased, the anthocyanin molecules stabilized, the red color of the peel retained. Moreover, the hot 1% chitosan treatment obviously depressed polyphenol oxidase and peroxidase activities of the fruits, and thus reduced enzymatic browning of the peel. Therefore, the fruits could retain the red color of the peel after fruits were returned to the room temperature.
Although hot 1% chitosan treatment maintained the color of the peel, there were probabilities of dehiscence, decay and sinking of peel of fruits after they were returned to room temperature. Cold storage of the fruits in the perforated polyethylene bags (0.04mm) significantly improved the sinking of peels. Further investigations are needed to improve and control of fruit decay and dehiscence.

壹、前言
貳、前人研究
一、荔枝果皮褐化之研究
(一)、荔枝採後果皮快速失水的原因
(二)、多酚氧化酵素與荔枝果皮褐化之關係
(三)、過氧化酵素與荔枝果皮褐化之關係
(四)、花青素及總酚類化合物與荔枝果皮褐化之關係
二、荔枝採後的保鮮處理
(一)、二氧化硫燻蒸與浸酸處理
(二)、熱處理及浸酸處理
(三)、甲殼素處理
參、材料與方法
一、荔枝採後果皮褐化之研究
(一)、果實生長與發育之調查
(二)、貯藏期間果皮褐化之研究
(三)、果實採後的預冷處理對果皮褐化之影響
二、荔枝採後的保鮮處理之研究
(一)、二氧化硫燻蒸及浸酸處理
(二)、溫湯處理
(三)、溫湯及不同酸液處理
(四)、甲殼素處理
(五)、浸酸、溫湯及甲殼素處理效果之比較
肆、結果
一、荔枝採後果皮褐化之研究
(一)、果實生長與發育之調查
(二)、貯藏期間果皮褐化之研究
(三)、果實採後的預冷處理對果皮褐化之影響
二、荔枝採後的保鮮處理之研究
(一)、二氧化硫燻蒸及浸酸處理
(二)、溫湯處理
(三)、溫湯及不同酸液處理
(四)、甲殼素處理
(五)、浸酸、溫湯及甲殼素處理效果之比較
伍、討論
一、荔枝採後果皮褐化之研究
(一)、果實生長與發育之調查
(二)、貯藏期間果皮褐化之研究
二、荔枝採後的保鮮處理之研究
(一)、二氧化硫燻蒸及浸酸處理
(二)、溫湯及浸酸酸液處理
(三)、甲殼素處理
(四)、裂果、腐敗及果實凹陷之問題
中文摘要
SUMMARY
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