【作者】 李延清；

【导师】 郁志芳；

【作者基本信息】 南京农业大学 ， 农产品加工与贮藏工程， 2007， 硕士

【摘要】 溧阳白芹采后极易发生失水、失去脆嫩清香、褐变和腐烂等现象，丧失商品价值。本论文通过对溧阳白芹采后生理生化变化、褐变特性等研究，探索溧阳白芹贮藏的适宜条件和控制褐变的方法。研究结果如下：1．试验研究了不同贮藏温度对溧阳白芹品质及生理生化特性变化的影响。结果显示，0±1℃低温有利于溧阳白芹贮藏时间的延长。溧阳白芹在0℃贮藏9天失重率比20℃下少7％；0℃下溧阳白芹的呼吸明显低于20℃(差值最大可达40mgCO₂·kg^-1·hr¹)，纤维化速度慢（差异极显著，r=0.9728，p＜0.01），还原糖消耗少，组织褐变度低，且PPO、POD活力都显著的低。试验测定获得溧阳白芹组织中总酚含量为85.33μg／100gFW，且极大多数以结合酚存在（游离酚占总酚的11.6％）；0℃和20℃贮藏期间总酚都逐渐下降，游离酚变化不明显。溧阳白芹即使贮藏在0℃条件下，褐变速度也较快；溧阳白芹的PPO、POD活力都很强，但统计分析提示褐变与PPO关系密切，而与POD相关性不大。2．试验研究了采收期对溧阳白芹品质和生理特性差异的影响。试验结果表明，2005年12月9日采收的溧阳白芹贮藏期间的失重率显著低于其它采收期（p＜0.05）、褐变速度慢、纤维素含量低(1.9mg·g^-1FW)，超氧阴离子和MDA水平低，且贮藏期间增加少；呼吸强度低(32.9 mgCO2·kg^-1．h^-1)且贮藏期间稳定。3．试验鉴定了溧阳白芹酚的种类。TLC、紫外扫描和高效液相色谱方法结果显示溧阳白芹中的主要酚类物质为儿茶酚。4．试验研究了溧阳白芹PPO和POD的部分酶学特性。结果表明，溧阳白芹PPO最适pH值为6.0，溧阳白芹PPO的最适温度为25℃，溧阳白芹PPO对60℃以下的温度不敏感，而在80℃以上温度下处理7min，活性几乎完全丧失。溧阳白芹PPO与各底物的亲和力顺序为：绿原酸＞咖啡酸＞没食子酸＞儿茶酚＞焦性没食子酸＞愈创木酚＞表儿荼酚，且与绿原酸结合时出现最大活力。溧阳白芹POD在pH 3～10范围内均有活力，且pH5.0时活力最大，pH6.4时有一肩峰；溧阳白芹的POD最适温度为40℃，溧阳白芹POD热稳定性较差，80℃保温3min，酶已经完全失活，在90℃下不到50s即几乎失去其全部活力；同时，在低温条件下，白芹POD活力相对较高，因此，低温下的酶促反应不容忽视。溧阳白芹POD与不同底物的亲和力顺序为：焦性没食子酸＞绿原酸＞咖啡酸＞没食子酸＞羟酪氨＞表儿茶酚＞儿茶酚＞愈创木酚。5．试验研究了不同抑制剂对溧阳白芹PPO、POD活力的影响。结果显示，L-Cys对PPO、POD抑制效果最好，其次是草酸、NaHSO₃、CA和4-HR；AA对PPO的抑制效果很好，但对POD的抑制效果较差；CaCl₂和EDTA-2Na对PPO、POD的活力影响不大。更多还原

【Abstract】 Oenanthe stolonifera （Cv. Liyang） after harvest is very sensitive to weight loss, is easy to loss its tenderness and fresh flavor, and to be brown, and to decay, and then commodity characteristic. This thesis studied the quality, physiology and browning characteristics of Oenanthe stolonifera （Cv. Liyang） after harvest to search optimal storage condition and control browning method. The results were as following:1. The effect of storing temperature on the quality and physio-biochemical characteristics of Oenanthe stolonifera （Cv. Liyang） was investigated. The results showed that 0+1℃was effective enough to prolong the storage life of Oenanthe stolonifera （Cv. Liyang）. Compared to 20℃, 0+1℃slowed down weight loss by as high as 7%, reduced respiratory rate as much as 40mgCO₂·kg^-1·hr^-1, decreased the increase of fibre significantly and loss of reducing sugars, and inhibited tissue browning of Oenanthe stolonifera （Cv. Liyang）.The total phenol in Oenanthe stolonifera （Cv. Liyang） was 85.33μg/100gFW, and most them was in bound form （free phenol was only 11.6%）. The total phenol was decreased slowly, while free phenol changed little in Oenanthe stolonifera （Cv. Liyang） both stored at 0℃and 20℃.Oenanthe stolonifera （Cv. Liyang） was easy to be brown even at 0℃, and had very high activity of PPO and POD. Statistical analysis showed that the browning was related to the PPO and not related to POD.2. The effect of harvesting time on the quality and physiological—biochemical characteristics of Oenanthe stolonifera （Cv. Liyang） was investigated. The results showed that Oenanthe stolonifera （Cv. Liyang） harvested at Dec. 7, 2005 had a significantly slower weight loss （p＜0.05）, browned more slowly, and had less contents of fibre (only 1.9mg.g^-1FW) , O₂^- and MDA, and increased more slowly during storage. The respiratory rate of Oenanthe stolonifera （Cv. Liyang） harvested at Dec. 7, 2005 was 32.9 mgCO2.kg^-1.h^-1, smaller than that harvested at other dates, and stabler during storage.3. TLC, ultraviolet scanning and HPLC analyses showed that main phenols in Oenanthe stolonifera （Cv. Liyang） were catechol.4. The characteristics of PPO and POD in Oenanthe stolonifera （Cv. Liyang） was investigated. The result showed that the PPO from Oenanthe stolonifera （Cv. Liyang） shows its greatest activity at 25℃and pH 6.0, and loss its activity easily when temperature was up 80℃with treating 7 minutes, while the enzyme after being treated at 60℃will be insensitive. The combining capability of PPO to different phenol substrate was in the order:chlorogenic acid＞dihydroxycinnamic acid＞gallic acid＞catechol＞pyrogallic acid＞methyl catechol＞epicatechin. The PPO shows the highest activity when combined with chlorogenic acid.The POD of Oenanthe stolonifera （Cv. Liyang） had its greatest activity at pH 5.0 and the second highest at pH 6.4. The optimal temperatures of POD was 40℃. Oenanthe stolonifera （Cv. Liyang） POD had worse heat resistance, lost its activity quickly when temperature above 80℃for 3 minute. The enzyme after treated at 90℃for 50 second would be inactivated completely. The POD of Oenanthe stolonifera （Cv. Liyang） shows its high activity at Low Temperature so enzyme reaction on browning should be noticed. The combining capability of POD to different phenol substrate was in the order: pyrogallic acid＞chlorogenic acid＞dihydroxycinnamic acid＞gallic acid＞hydroxytyramine＞epicatechin＞catechol＞methyl catechol.5. The effect of various inhibitors on PPO and POD of Oenanthe stolonifera （Cv. Liyang） was studied. The results demonstrated that L-Cys had strongest inhibition on the activities of PPO and POD; all Oxalic acid, NaHSO₃, CA and 4—HR were good for inhibiting PPO and POD activity; AA was effective to PPO but not very effective to POD; both CaCl₂ and EDTA-2Na had little effect on PPO and POD.更多还原