番石榴果實的後熟生理及細胞壁水解酶在後熟期間的變化

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論文名稱: 番石榴果實的後熟生理及細胞壁水解酶在後熟期間的變化
研究生姓名: 洪紫馨
指導教授姓名: 王自存
出版年: 1996
學校名稱: 國立臺灣大學
系所名稱: 園藝學研究所
關鍵字: 番石榴;後熟;細胞壁水解;Guava;Ripening;Cell wall hydrolase
摘要: 本論文研究''白拔''品種番石榴(Psidium guajava L. cv. ''Bai Ba'')於不同溫度中之後熟生理以及果肉中細胞壁水解■活性之抽取與變化。 ''白拔''為具有呼吸更年性之番石榴品種,綠熟之''白拔''果實於20C中之 呼吸速率及乙烯生成速率均呈上升趨勢,分別於貯藏之第7天及第8天達到 高峰。果實在20C中貯藏出現明顯而劇烈之後熟變化。果實之硬度在1天後 急劇下降,到第2天即完全變軟;果皮顏色在4天內由綠轉為黃色,至第6天完 全轉白;果皮中之總葉綠素含量在2天內下降60%。果實之香氣自第2天開始 產生,果肉之可溶性固型物及可滴定酸度僅緩慢下降。在15C中之果實其呼 吸速率及乙烯生成速率均較低,果肉之軟化,葉綠素之分解及香氣之生成則 延後2-3天。在10C中果實之後熟變化受到更明顯的抑制,香氣的生成則完 全被抑制。 將''白拔''果肉加入PEG溶液中均質,再經離心可得到果肉沈澱物,此沉 澱物中之聚半乳糖醛酸■及果膠甲酯■可以用食鹽溶液將其萃取出。聚半 乳糖醛酸■活性之測定受到酵素粗萃取液及反應液中所含之還原糖之干擾 。果肉沈澱物在用鹽溶液萃取之前,先用去離子水清洗三次,可將酵素萃取 液中之還原糖除去99%,將反應液中聚半乳糖醛酸鈉溶液由2%減為0.5%可除 去約80%之還原糖。經清洗過之果肉沈澱物以0.5M的食鹽溶液可萃取得到 最高之聚半乳糖醛酸■活性,在反應液中加入SDS比在沸水中加熱10分鐘對 酵素活性不活化之效果較佳。在30C中,聚半乳糖醛酸■反應的最適pH為 4.0,對聚半乳糖醛酸鈉的Km值為0.096%。未經清洗之果肉沈澱物以2.0M的 食鹽溶液萃取可得到最高之果膠甲酯■活性。在25±2C中,果膠甲酯■的 最適pH出現兩個高峰,分別是pH7.0及9.0。 在20,15及10C中,''白拔''果實的聚半乳糖醛酸■的活性分別在貯藏後 的第1,2,3天出現大幅上升,在一天內增加一倍左右,之後趨於平緩。在各 溫度中果膠甲酯■的活性在貯藏後的第0天至第2天時都呈現降低的趨勢, 之後在20C中之果實其果膠甲酯■的活性開始增加,在15C及10C中之果實之 果膠甲酯■的活性則無變化。由以上結果顯示''白拔''果肉中之聚半乳糖醛 酸■在後熟時的變化似乎與果實硬度的變化有較密切的關係。This research was to study the physiological changes of guava (Psidium guajava L. cv. ''Bai Ba'') during storage at different temperatures, and to study the extraction and activity changes of two cell wall hydrolases during ripening. ''Bai Ba'' guava displayed the characteristics of a climacteric fruit. During storage at 20C,ethylene production and respiration reached peak on the 6th day and 7th day respectively.The fruit soften completely in 2 days.It''s peel color changed from green to yellow in 4 days,and turned to white on the 6th day.Total chloro- phyll content of peel decreased 60% during the first 2 days of storage.The fruit started to release aroma on the 2nd day. Storage at low temperature as 15C will delay these changes. Aroma production was completely inhibited in fruit stored at 10C. A pellet was obtained by centrifuging the homogenate of pulp and PEG solu. The PG activity determination was interfered by the high reducing sugar content in both the enzyme extract and the reaction mixture.By washing the pellet with deionize water three times,99% of reducing sugar content in crude enzyme extract can be removed. By decreasing the NaPG solu. in reaction mixture from 2% to 0.5%,80% of reducing sugar will be reduced. The pH of PG at 30C was 4.0, and Km for NaPG was 0.096%. Most of PE activity could be extracted with 2.0M NaCl from pellet without washing by deionize water. At 25C, two pH opt. of PE was obtained at 7.0 & 9.0. At 20,15 and 10C,the activity of ''Bai Ba'' PG increased remarkably on the 1st,2nd and 3rd day respectively. The activity of PE decreased during the first 2 days, then started to increase in fruits stored at 20C. These results seems to indicate that there might be some correlation between the changes of PG activity with the change of fruit firmness in ''Bai Ba'' during ripening.
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