柿果貯藏及脫澀技術之改進及脫澀機制之研究

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論文名稱: 柿果貯藏及脫澀技術之改進及脫澀機制之研究
研究生姓名: 阮雅蘭
指導教授姓名: 謝慶昌
出版年: 2004
學校名稱: 國立中興大學
系所名稱: 園藝學系
關鍵字: 柿子;脫澀技術;苯丙胺酸解氨酶;貯藏技術;脫澀機制;persimmon;deastringency technology;phenylalanine ammonia-lyase;Storage technology;Deastringency Mechanism
摘要: 柿子葉可溶性單寧濃度因品種而異,本調查中以‘牛心柿’最高,其次為‘花御所’,再者‘富有’、‘蜂屋’及‘平核無’,三者間差異不大;葉片中PAL活性和可溶性單寧濃度變化趨勢一致。柿葉經二氧化碳處理後可溶性單寧呈下降趨勢,和果實一樣有脫澀情形,似可作為研究脫澀之材料。柿果發育中生長曲線呈雙S型曲線,幼果期‘牛心柿’即有較高的可溶性單寧濃度,且成長中單果含量有累積現象,而‘富有’柿可溶性單寧含量及濃度皆低,且其PAL活性亦較‘牛心柿’低,由結果顯示,‘富有’柿合成單寧能低,加上果實成長之稀釋效應,至採收時已不具澀味。 ‘牛心柿’以各種脫澀方法處理時,其脫澀速度由快而慢依序為二化碳脫澀法、酒精脫澀法、石灰懸浮液脫澀法及益收脫澀法。100%氮氣處理時柿果果肉亦可和二氧化碳處理一樣累積酒精和乙醛,但脫澀效果不及二氧化碳處理者,而酒精處理時,以電泳分析酒精去氫酵素(ADH)之表現,在處理後60小時才見ADH條帶出現,但柿果於12小時後即開始脫澀,結果顯示,乙醛可能非促成脫澀之主要因子。在果肉圓片系統下,二氧化碳處理時,Cycloheximide及Tween-60不會抑制脫澀,Aminooxyacetic acid,Sodium cyanide及熱處理會抑制脫澀;另外,完整果實在脫澀時皆可見果實硬度下降,由此結果推測,柿果脫澀處理時,有一非附膜且需pyridoxal phasphate酵素被活化,而催化細胞壁水解產生滲透性脫水,促使脫澀。 ‘牛心柿’在6℃低溫貯藏時,果皮由黃綠色轉橙黃色,果肉較暗呈水浸狀,硬度下降及不易脫澀等寒害症狀。本試驗主要探討‘牛心柿’果實於低溫貯藏前,利用溫湯處理,對果實品質之影響。‘牛心柿’先以溫湯處理,再低溫貯藏(6℃) 30天後,各處理以酒精脫澀處理3天,有脫澀不完全的情形;貯藏60天後澀味指數經3天酒精脫澀處理,澀味指數可降至1,可能和果肉軟化有所關聯,且有寒害症狀產生;其中以48℃熱水處理30分鐘及50分鐘可維持較高的果肉硬度及品質。 本試驗將‘筆柿’以不同脫澀方法處理,以了解‘筆柿’脫澀所需之最適條件及觀察物理性狀和化學組成分之變化。‘筆柿’以10ppm乙烯催熟,在20-30℃下後熟,3日可完全脫澀,果實顏色由黃橙變紅呈現橙紅色;酒精脫澀處理,在30℃下,每公斤柿果需6ml之酒精量,於3日後可完全脫澀。果實以酒精及二氧化碳處理,脫澀之速度隨溫度增加而加速,25℃下需5日以上,30及35℃需4-5日,而在40℃下則只需2-3日即可完成脫澀,但以30及35℃脫澀後之品質較佳。 The concentrations of the soluble tannin in persimmon leaves differed markedly in different varieties. ‘Bull Heart’ and ‘Hanagoshiyo’ leaves had particularly high concentrations of soluble tannin while no significant differences were found among ‘Fuyu’, ‘Hachiya’ and ‘Hiratanenashi’. Similar trends were observed for PAL activity as in the case of soluble tannin. Like fruit deastringency, the concentration of soluble tannin in leaves decreased after carbon dioxide treatment. Thus the leaves could be used as material to investigate the mechanism of deastringency. The curve of fruit development in ‘Fuyu’ and ‘Bull Heart’ persimmon tended to be a double sigmoid. At the young fruit stage, the PAL activity and tannin content of ‘Bull Heart’ fruits were higher than those of ‘Fuyu’ fruits and had the tendency of accumulation during growth and development. Meanwhile, soluble tannin content of the ‘Fuyu’ fruit was low and the PAL activity was also lower than the ‘Bull Heart’. The results indicated that tannin synthesis ability of ‘Fuyu’ and the dilution effects of fruit growth were responsible for the low astringency of fruits at harvest. In vivo and whole fruit studies were conducted on the effectiveness of deastringency of persimmon “Bull Heart” fruit. Carbon dioxide treatment was found to have higher deastringency rate than alcohol, CaO suspension and ethrel. Further studies showed that fruits treated with 100% nitrogen, as in the case of carbon dioxide, accumulated acetaldehyde and ethanol in fruits but the rate of deastringency was low and the method was less effective. While removal astringency with alcohol, electrophoresis bands of alcohol dehydrogenase (ADH) appeared at 60 hours during deastringency period, but the deastringency reactions of the fruit were observed 12 hours after the treatment, which indicates that acetaldehyde is not a key factor in the process. Fruit discs were also used in the deastringency experiments of ‘Bull Heart’. Soaking discs in various solutions and then treating with carbon dioxide and revealed that deastringency was inhibited by aminooxyacetic acid, sodium cyanide and hot water treatments (70-100℃for 10 min) but not by cycloheximide and Tween-60. This indicates that deastringency of persimmon requires the activation of a non-peripheral and pyridoxal-phosphate dependent enzyme, which catalyzes cell wall hydrolysis and leads to the osmosis dehydration which is followed by triggering the polymerization of tannin to complete the process. Persimmon fruits ‘Bull Heart’ when stored at 6℃, the peel color turned from yellow-green to orange-yellow, and the color of pulp became dark and water soaked. Firmness decreased and astringency could not be eliminated. Those symptoms were confirmed to be chilling injuries. The objectives of this study were to evaluate the effects of warm-water treatment before cold storage (6℃) on the qualities of the fruits. ‘Bull Heart’ treated with warm water and stored in cold storage for 30 days, followed by 3-day alcohol treatment resulted in an incomplete deastringency; The astringent index was down to 1 after 60 days of cold storage and 3 days of alcohol treatment. This could relate to the softening of the fruits and chilling injury. Warm-water treatments (48℃-30min and 48℃-50min) reduced the damage of chilling injury and retained the firmness and quality of fruits. The effects of different deastringent treatments on physical character and chemical compositions changes of the ‘Bi-Su’ persimmon were evaluated in this experiment. The astringency of persimmon fruits was completely removed by 10 ppm ethylene together with after-ripening for 3 days at 20-30℃. The peel color turned from yellow-green to red after the completion of deastringency. Ethanol treatment at the dosage of 6ml/kg completely eliminated the astringency after 3 days at 30℃. The effects of temperature on ‘Bi-Su’ persimmon fruits treated with carbon dioxide and ethanol were examined during the process of deastringency at various temperature ranging from 20-40℃. The time required to reach astringent index 1 were 2-3, 4-5 and more than 5 days at 40℃, 30-35℃and 20-25℃, respectively. The deastringency temperatures required for the better fruits qualities were 30-35℃.
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