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1.
Chitsuda Chaisakdanugull & Chockchai Theerakulkait 《International Journal of Food Science & Technology》2009,44(4):840-846
Polyphenol oxidase (PPO) from pulp of banana [Musa (AAA Group) 'Gros Michel'] was extracted and precipitated with 80% saturated ammonium sulphate followed by conventional column chromatography on Sephacryl S-200 HR and fast protein liquid chromatography on Mono Q column. The lyophilised PPO obtained from Sephacryl S-200 HR column was used for characterisation and inhibition studies. The partially purified PPO obtained from the Mono Q column exhibited at least three isoenzymes. The banana PPO had optimum pH for activity at 7 and it was stable around the same pH. Only 48% of initial enzyme activity was lost after heating at 70 °C for 30 min. The enzyme was completely inhibited by 2 m m sodium metabisulphite, 2 m m l -cysteine, 4 m m ascorbic acid, and 100 m m 4-hexylresorcinol. The K m and V max of banana PPO for dopamine were 2.08 m m and 0.124 m m min−1 respectively. 相似文献
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通过设计单一护色剂、不同浓度L-半胱氨酸、不同热处理时间及多因子护色处理四个实验研究其对冻藏香蕉片多酚氧化酶(PPO)活性的影响,结果表明,5种护色剂均能有效地抑制冻藏香蕉片PPO活性,但L-半胱氨酸对其抑制效果更佳;随着护色液中Cys浓度的增加,残余PPO活力呈下降趋势,表现为CK>0.05%Cys>0.1%Cys>0.2%Cys;热处理能有效地抑制冻藏香蕉片PPO活性,PPO活性随着热处理时间的增加而降低,但热处理却大大降低了冻藏香蕉片的品质;0.1%L-半胱氨酸、0.05%异抗坏血酸、0.1%蔗糖和0.1%氯化钙构成的护色剂组合能有效地抑制PPO活性,并起到良好的保质增脆效果。 相似文献
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Sukhontha Sukhonthara Chockchai Theerakulkait 《International Journal of Food Science & Technology》2012,47(3):482-487
Rice bran was extracted with water and its effects on potato and banana polyphenol oxidase (PPO) were investigated. Rice bran extract (RBE), conc. 0.3 g mL?1, exhibited PPO inhibition in potato and banana PPO with % inhibition of 69.31% and 47.63%, respectively (P ≤ 0.05). RBE showed a concentration‐dependent inhibition on potato and banana PPO. RBE (conc. 0.3 g mL?1) inhibited potato PPO higher than ascorbic acid, citric acid, NaCl and EDTA (final conc. 20 mg L?1); and it also inhibited banana PPO higher than citric acid, NaCl and EDTA (final conc. 20 mg L?1), respectively. The combination of RBE with citric acid or ascorbic acid appeared to be additive inhibitory effect on banana and potato PPO. Kinetic study of the inhibition on potato and banana PPO by RBE showed that RBE was a mixed‐type inhibitor; however, RBE appeared to be able to act directly on enzyme structure rather than substrate structure. 相似文献
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香蕉皮多酚氧化酶和过氧化物酶特性的研究 总被引:13,自引:0,他引:13
分别以邻苯二酚、愈创木酚为底物,采用分光光度计测定氧化产物的方法对香蕉皮多酚氧化酶(PPO)和过氧化物酶(POD)的性质进行研究。结果表明,PPO最适温度为30℃、最适pH5.5、Km=22.42mmol/L、Vmax=0.027OD420/min,75℃水浴处理5min基本完全失活,100℃水浴处理20s可钝化PPO活性,并且香蕉皮PPO有同工酶;香蕉皮过氧化物酶(POD)的最适pH6.0、最适温度30℃,其在80℃下处理5min后基本失活,在沸水浴25s后酶被钝化。 相似文献
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M. P. Cano Bego?a de Ancos M. Gloria Lobo Mariana Santos 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1997,204(1):60-65
Browning in banana (Musa cavendishii, cv. Enana) processed products is a result of phenol oxidation catalysed by polyphenol oxidase (PPO) and peroxidase (POD)
or of other non-enzymatic reactions (Maillard and Strecker mechanisms). Microwave and steam blanching significantly reduced
PPO and POD activities and phenol levels in banana flesh, steam blanching being the most effective method for enzyme inactivation.
Freezing/thawing processes produced a significant increase in phenol levels in all samples, due to cellular breakdown. After
microwave heating browning processes occurred while steam-treated samples did not exhibit a significant colour change. Extractable
PPO and POD activities in all banana samples increased as a consequence of freezing/thawing: steam-blanched slices exhibited
lower residual activities. High correlations occurred between phenols and browning (r=0.86) in control samples. Blanched samples (microwave or steam) only exhibited correlations between PPO (r=0.80) and POD (r=0.80) activities and browning.
Received: 22 February 1996 相似文献
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M. P. Cano Begoña de Ancos M. Gloria Lobo Mariana Santos 《European Food Research and Technology》1997,204(1):60-65
Browning in banana (Musa cavendishii, cv. Enana) processed products is a result of phenol oxidation catalysed by polyphenol oxidase (PPO) and peroxidase (POD)
or of other non-enzymatic reactions (Maillard and Strecker mechanisms). Microwave and steam blanching significantly reduced
PPO and POD activities and phenol levels in banana flesh, steam blanching being the most effective method for enzyme inactivation.
Freezing/thawing processes produced a significant increase in phenol levels in all samples, due to cellular breakdown. After
microwave heating browning processes occurred while steam-treated samples did not exhibit a significant colour change. Extractable
PPO and POD activities in all banana samples increased as a consequence of freezing/thawing: steam-blanched slices exhibited
lower residual activities. High correlations occurred between phenols and browning (r=0.86) in control samples. Blanched samples (microwave or steam) only exhibited correlations between PPO (r=0.80) and POD (r=0.80) activities and browning.
Received: 22 February 1996 相似文献
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ABSTRACT: We have investigated the mechanism of action of 4-hexylresorcinol (4-HR) and ascorbic acid (AA) on the polyphenol oxidase (PPO) catalyzed oxidation of phenolic substrates. Incubation of PPO with 4-HR diminishes strongly PPO activity. This effect can be erroneously interpreted, due to the high affinity of 4-HR for PPO, as irreversible inactivation of PPO. However, PPO activity can be recovered by dialysis after incubation with 4-HR. 4-hexylresorcinol is a canonical enzyme inhibitor that binds preferentially to the oxy form of PPO. It is a mixed-type inhibitor, because it influences both apparent V max (1.26 compared with 0.4 units in the absence and presence of 4-HR, respectively) and K m values (0.28 mM compared with 0.97 mM in the absence and in the presence of 4-HR, respectively) of PPO. AA can prevent browning by 2 different mechanisms: In the absence of PPO substrates it inactivates PPO irreversibly, probably through binding to its active site, preferentially in its oxy form. In the presence of PPO substrates, AA reduces PPO oxidized reaction products, which results in a lag phase when measuring PPO activity by monitoring dark product formation but not when monitoring O2 consumption. The simultaneous use of both 4-HR and AA on PPO results in additive prevention of browning. 相似文献
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J S Chen D J Charest M R Marshall C I Wei 《Journal of the science of food and agriculture》1997,75(1):12-18
The effects of different stirring time and two treatment methods (salt and organic solvent) on the recovery of shrimp polyphenol oxidase (PPO) were investigated. Stirring for 30 min yielded maximal PPO recovery. With respect to PPO specific activity, yield and purification fold enhancement, the use of butanol treatment followed by Phenyl Sepharose CL-4B chromatography was shown to be better than ammonium sulphate fractionation and then Phenyl Sepharose chromatography. White shrimp PPO was more susceptible than pink shrimp PPO to inactivation during purification. © 1997 SCI. 相似文献
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为解决生菜加工贮藏过程中出现的褐变问题,研究了结球生菜多酚氧化酶(polyphenol oxidase,PPO)动力学特性,分析了pH、温度及底物浓度等因素对PPO活性的影响,建立了结球生菜褐变的反应动力学方程。结果表明,结球生菜最适pH为8.0,最适温度为40℃。用Michaelis-Menten机理描述可得结球生菜PPO相应的动力学参数Km=0.0691mol/L,vmax=26.5957U/min。生菜叶片组织中的PPO活性较强,叶柄和茎部组织中的PPO活性差异不大,均低于叶片组织中的PPO活性,且结球生菜茎部切口处已经发生褐变的部分PPO活性为6.12U/min,远高于没有发生褐变的部分。 相似文献
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S S Arogba O L Ajiboye L A Ugboko S Y Essienette P O Afolabi 《Journal of the science of food and agriculture》1998,77(4):459-462
Polyphenol oxidase (PPO) activity of filtered extract of ground mango kernel suspension (400 g litre−1) was studied spectrophotometrically at 420 nm using catechol as substrate. The enzyme was most active at pH 6·0 and 25°C. Activity was reduced by 50% at pH values of 5·0 and 7·1, and also at temperatures of 14°C and 30°C. The calculated activation energy and the Michaelis constant (Km) were 21·4 kcal mol−1 °C−1 and 24·6 mM , respectively. The Vmax value was 2·14 units g−1 mango kernel. The time to heat inactivate PPO decreased rapidly to < 10 min with increasing temperature of ⩾ 70°C at 50% activity. © 1998 SCI. 相似文献
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板栗品种褐变度差异性及其多酚氧化酶活性的相关性研究 总被引:1,自引:0,他引:1
以37个板栗品种为试材,研究了板栗果实褐变差异性及其与多酚氧化酶(PPO)活性之间的关系,并根据褐变差异性对各品种进行聚类分析。结果表明:板栗不同品种间褐变差异显著(p<0.05),根据褐变差异性聚类分析,可将37个品种可以分为5个等级;不同品种间PPO活性差异显著(p<0.05);通过探讨不同品种间褐变度与PPO活性的关系,发现随着板栗品种间PPO活性的升高,褐变度也开始升高,当PPO活性达到90 U·min-1·g-1时,PPO活性对褐变影响开始降低;通过褐变聚类分析,将板栗PPO活性分为5类,在优选或改良品种时,可将品种的PPO活性在第一或第二类活性范围以下作为选择依据之一。 相似文献
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虾体多酚氧化酶特性及其抑制技术研究进展 总被引:3,自引:0,他引:3
多酚氧化酶是虾体中普遍存在的一种含铜金属蛋白,它是虾体发生黑变的主要原因,也是虾保鲜品质控制中亟待解决的技术关键。研究多酚氧化酶的酶学特性,抑制酶促褐变,对于提高虾的食用价值和商品价值至关重要。本文综合介绍了多酚氧化酶的虾体分布、活性特征、分离纯化、分析测定、黑变机理及其抑制方法。 相似文献
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Mustafa Ümit Ünal Aysun ener & Kemal en 《International Journal of Food Science & Technology》2007,42(9):1123-1127
Polyphenol oxidase (PPO) was extracted from Sultaniye grapes grown in Turkey, and its characteristics in terms of pH and temperature optima, thermal inactivation, kinetic parameters and potency of some PPO inhibitors were studied. Optimum pH and temperature for grape PPO were found to be 3.4 and 30 °C, using catechol as substrate. Km and Vmax values were found to be 44.5 ± 5.47 mm and 0.695 ± 0.0353 OD410 min?1, respectively. Four inhibitors were tested in this study and the most potent inhibitor was sodium metabisulphite, followed by ascorbic acid. From the thermal inactivation studies in the range of 65–80 °C, the half‐life values of the enzyme ranged between 2.6 and 49.5 min. Activation energy (Ea) and Z values were calculated to be 208.5 kJ mol?1 (r2 = 0.9544) and 10.95 °C (r2 = 0.9517), respectively. 相似文献
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Yueming Jiang Jiarui Fu Giora Zauberman Yoram Fuchs 《Journal of the science of food and agriculture》1999,79(7):950-954
Polyphenol oxidase (PPO, EC 1.10.3.2) was purified to homogeneity from litchi peel yielding a single protein with a molecular weight of about 75.6 kD by Sephadex G‐100 gel filtration, and a 108‐fold purification of PPO achieved. The enzyme was determined to be composed of two similar subunits. Glutathione, L ‐cysteine and citric acid suppressed PPO activity markedly, whereas ascorbic acid and n‐propyl gallate showed a little inhibition. Moreover, the effect was enhanced by the addition of citric acid. On the basis of the inhibition of PPO activity in vitro, the use of 10 mmol l −1 glutathione and 100 mmol−1 l citric acid was found to give good control of the browning of litchi fruit, and an 80–85% inhibition of PPO activity was observed. It is suggested that application of glutathione in combination with citric acid may slow down the browning of litchi fruit. © 1999 Society of Chemical Industry 相似文献