【作者】 郑连姬；

【导师】 钟耕； 张盛林；

【作者基本信息】 西南农业大学 ， 农产品加工及贮藏工程， 2004， 硕士

【摘要】 魔芋是天南星科魔芋属多年生草本植物，主要分布在亚洲和非洲的热带及亚热带的一些国家和地区。亚洲国家栽培较为普遍．全世界约有170种，我国有21种，其中至少13种为我国特有。魔芋初加工过程中由于去皮和切片导致组织细胞破裂，使细胞内的化学成分在酶的作用下发生作用，迅速产生褐变，引起外观色泽的变化，降低魔芋干片的商品价值，进一步影响魔芋精加工产品的外观和商品价值。为了抑制魔芋脱水烘烤中引起的褐变，魔芋初加工过程中普遍采用熏硫的方法，这种方法烘烤出来的魔芋角或魔芋片虽然颜色白，但是不好控制魔芋角或片中残留SO₂的含量，超过国标和行标1～2倍，严重影响我国的魔芋粉在国际市场上的竞争能力，并且不利与人体健康和引起环境污染。本文以万源花芋和白魔芋为研究材料，比较两个品种魔芋在室温贮藏过程中的多酚氧化酶活性的变化情况以及总酚含量的变化情况，两个品种的多酚氧化酶种类的不同，分析比较两个品种的酶促褐变的底物，探讨魔芋多酚氧化酶的部分特性，并选择几种安全无毒的单因子抑制剂和几种组合抑制剂来处理脱水烘烤前的魔芋，控制褐变的发生，并确定抑制剂的最佳浓度，烘烤出无硫无公害的安全的魔芋角或魔芋片。研究结果如下： 1．选用分光光度法测定多酚氧化酶活性和褐变强度，FoLin法测定总酚类物质含量的结果，魔芋采收后室温贮藏过程中同一时期内，白魔芋的多酚氧化酶活性低于万源花芋的多酚氧化酶活性，白魔芋球茎中的总酚类物质的含量高于万源花芋的总酚类物质的含量，白魔芋的褐变强度弱于万源花芋的褐变强度。 2．选用褐变产物的紫外波长扫描来比较确定白魔芋和万源花芋引起褐变的酶的底物的结果，两个品种的褐变产物扫描波峰和多巴胺标准物的褐变产物波峰都出现在300nm附近。说明两种魔芋品种的褐变底物同样可能是多巴胺。 3．选用浓缩胶浓度为4.5％，分离胶浓度7.5％的聚丙烯酰胺凝胶电泳来分离白魔芋和万源花芋球茎的酶，利用特殊的底物染色方法显现酶带的结果表明。白魔芋和万源花芋的酶条带出现在同一水平线上。说明两种魔芋品种引起褐变的酶是同一种酶。 4．温度、pH值、几个不同浓度梯度的抑制剂对魔芋多酚氧化酶活性影响的研究结果表明，白魔芋多酚氧化酶活力的最适温度为35℃左右，万源花芋多酚氧化酶活力的最适温度为30℃左右，100℃以上的温度保温30min后多酚氧化酶的相对活力，白魔芋降低95％，万源花芋降低99.5％；魔芋多酚氧化酶最适pH值为5或5.5左右，pH值2.2以下和8以上时会完全丧失其活力；植酸浓度6‰以上，L-半胱氨酸浓度各达到0.04‰以上和0.07‰以上，柠檬酸浓度各达到9‰以上和10‰以上，抗坏血酸浓度各达到0.1‰以上和0.12‰以上时白魔芋和万源花芋基本丧失PPO活力。 5．选用四种单因子抑制剂和几种组合抑制剂处理后，在60℃烘烤的结果为，L-半胱氨酸浓度0.01％、柠檬酸浓度3％和植酸浓度0.5％的单因子抑制剂浸泡5分钟后，白魔芋的烘烤效果都能达到所需白度，0.5％以上浓度的L-半胱氨酸抑制剂浸泡5分钟后，万源花芋烘烤效果能达到所需白度；0.35％浓度的L-半胱氨酸和1％浓度的柠檬酸两组分组合抑制剂浸泡5分钟西南农业大学2004届硕士学位论文中文摘要后，万源花芋烘烤效果能达到所需白度;0.15%浓度的L一半肤氨酸、1%浓度的柠檬酸和2%浓度植酸，0.15%浓度的L一半肤氨酸、3%浓度的柠檬酸和0.03%浓度的抗坏血酸，0.15%浓度 的L一半肤氨酸、0.05%浓度的抗坏血酸和l%浓度的植酸三种三组分组合抑制剂浸泡5分钟后，万源花芋烘烤效果都能达到所需白度;0.15%浓度的L一半肤氨酸、l%浓度的柠檬酸、l%浓度的植酸和0.01%浓度的抗坏血酸四组分组合抑制剂浸泡5分钟后，万源花芋烘烤效果能达到所需白度。 6.上述处理对魔芋产品的葡甘露聚糖的含量和粘度值基本不会带来不利的影响。 7.对所处理的抑制剂成本进行计算的结果:白魔芋采用0.01%浓度的L一半胧氨酸单因子.抑制剂处理l吨魔芋时只增加23.86元的成本;万源花芋采用0，15%L一半胧氨酸+3%柠檬酸+0 .03%抗坏血酸浓度的组合抑制剂处理1吨万源花芋时，增加402.3元的成本。其他抑制剂的成本都比上述的成本高。 本研究方法规范可靠，所得结论可完全有效地应用于魔芋脱水烘烤生产中。更多还原

【Abstract】 Amorphophallus Konjac is a herb of the Araceae Amorphophallus, which distributed mainly in some countries in the tropic and semitropical zone of the Asia and parts of the Africa, And it is very abundant in ous country. But a commonly encountered problem in the initial process of the Konjak when peeling off or sliceing up, is the brown stain. So this thesis performed a systemic research about the brown stain on it. Briefly, we took the Amorphophallus mairei (A.mairei) in wanyuan, and the A.white as the study material first, then we compared the changes of the polyphenol oxidases’ activity and the total polyphenol in this two kinds of konjacs. Centred with the brown stain and the polyphenol’s oxidadation, this paper has also carried out some other eperiments relevant them. The main contents and the results are as follows:1. We took the spectrophotometre to measure the activity of the polyphenol oxidase and the extent of the brown stain, and the method of Folin to measure the content of the polyphenol, and the results shown that the extent of the decreasing of the white konjac’s is lower than the A.mairei, when preservatived in normal temperature after the postharvest. And the quantity of the total polyphenol in white konjak’s corm is higher than the A.mairei’s. The extent of the white konjac’s brown stain is less than that of A.mairei’s.2. When using the ultraviolet scan on the two konjac’s brown stain of their substances, the wave peaks of them were at the same place with the dopamine. So the substances of their brown stain maybe a substance of the dopamines.3. Using the gel electrophoresis of the condense concentration 4.5% and the separate concentration 7.5% of the polyacrylamide, to apart the two kinds of konjacs. Then according the same zone when coloration the gel electrophoresis, we got the conclusion that it’s a same kind of enzymes leading to the brown stain in the two konjaks.4. When we researched the influences of the temperature, the pH values,and the inhibitor of different concentrations on the activity of the polyphenol oxidase, the experents showed that the proper temperarure of the white konjak’s polyphenol oxidase is about 35℃, whereas the other’s 30 ℃ or so. When incubation 30min above 100℃, the activity of the white konjac is decreased by 95%, whereas the A.mairei decreased by 99.5%. The optimum pH values of the PPO (polyphenol oxidate) is 5~5.5, and below 2.2 or above 8 the activity is loss totally. And the activity of the PPO will loss in the gross when the concentration of the phytic acid is 6‰ above, and the concentration of the L-cysteine is above the 0.04‰~0.07‰, and the concentration of the citric acid is above 9‰ ~10‰, and the concentration of the ascorbic acid is above 0.1‰~0.12‰.5. After adopting four single factor inhibitors and combined inhibitor in treating with the them, we roasted them at 60℃. Then the results showed that the white konjac can reach the acceptable white of color when the L-cysteine’s concentration is 0.01%, and the citric acid is 3%, and the plant acid is 0.5%, make the white konjac diping in them 5min. whereas the A.mairei need theL-cysteine’s concentration reaching at 0.5% and diping in 5min .The concentration of the L-cysteine at abve 0.35%, and the citric acid 1%, then with the inhibitor together dip in 5min, the A.mairei ’s color can be acceptable. And the concentration of L-cysteine 0.15%, the citric acid 1%, the phytic acid 2%, etc. Four groups can make the A.mairei reach the acceptable chroma.6. We found that all the management above are reasonable also when taking the polyglucomannose into grant.更多还原