芒果核提取物的抑菌活性组分分析

对芒果核乙醇提取物采用AB-8大孔树脂和SephadexLH-20柱进行初步纯化得到不同级分。抑菌实验表明,芒果核多酚在一定的浓度下对供试的大肠杆菌、枯草芽孢杆菌、苏云金芽孢杆菌和金黄葡萄球菌都有较强的抑菌活性,随着浓度的升高,抑菌效果也明显升高,但是对供试的两种真菌均无明显抑菌活性;不同级分芒果核多酚的抑菌活性不同,芒果核多酚经SephadexLH-20柱分离所得的组分III是芒果核多酚的主要抑菌活性组分,结合HPLC-ESI-MS的分析,表明芒果核多酚的抑菌活性组分主要为含有不同取代度的没食子酰基葡萄糖类物质。     

苦杏仁多酚氧化酶的分离纯化及部分特性分析

以苦杏仁为原料,采用(NH4)2SO4分级沉淀法对苦杏仁多酚氧化酶进行初步分离后经Sephadex G-75凝胶柱层析进一步纯化,冷冻干燥后即得苦杏仁多酚氧化酶纯品;通过凝胶电泳和热分析试验测定多酚氧化酶的相对分子质量和变性温度。结果表明:经分离纯化后苦杏仁多酚氧化酶的纯化倍数为49.03倍,该酶可能存在同工酶且相对分子质量分别约为21.9 k D和23.2 k D;苦杏仁多酚氧化酶变性温度为60.03℃。为苦杏仁加工过程中的酶促褐变控制提供部分理论参数。     

板栗仁中多酚氧化酶活性的研究

采用分光光度法对板栗仁中多酚氧化酶的活性进行了研究.结果表明,酶液加入量与吸光度值成正比关系,多酚氧化酶的最适反应温度为30～40 ℃,最适反应pH值为5.4,板栗仁表层多酚氧化酶的活性显著高于心部的活性.同时,对酶的热稳定性以及抑制剂亚硫酸钠、抗坏血酸对酶活力的影响进行了探讨.     

Pectic polysaccharides during ripening of mango (Mangifera indica L)

The content of pectin decreased from 2.0 to 0.7% fresh weight (FW) and there was a concomitant increase in free galacturonic acid from 36 to 168 mg% FW during ripening of mango. Ion exchange chromatography on DEAE/cellulose resolved the pectic fraction into seven distinct peaks, with all of them showing a drastic decrease in pectin content and molecular weight as fruit ripening progressed, which indicated significant depolymerisation in vivo. Fraction I appeared to be an arabinogalactan‐type polymer, while fractions II and III were heterogalacturonans containing more than 60% galacturonic acid. Hydrolases implicated in pectin depolymerisation were polygalacturonase (PG), pectin methyl esterase (PME), galactanase, arabinanase and β ‐galactosidase. They all showed a climacteric peak in activity during ripening, except for PME which showed a continuous decrease in activity after an initial increase. These results are discussed in the light of fruit softening during ripening. Copyright © 2003 Society of Chemical Industry     

Pectic polysaccharides of mango (Mangifera indica L): structural studies

Pectic polymers of raw and ripe mango fruits revealed several distinct fractions upon diethylaminoethyl‐cellulose chromatography. Fraction I, the arabinogalactan, had a relative ratio of 3:1 for galactose and arabinose, while the two rhamnogalacturonans (fractions II and III) were composed of galacturonic acid, arabinose, galactose and rhamnose in the relative ratios of 69:15:14:2 and 62:10:23:4, respectively. Specific rotation, FTIR, GC‐MS and NMR data revealed fraction I to be a 1→5‐α‐L arabinofuranan linked to the main chain of 1→4‐β‐D ‐galactopyranan through 1→3 linkages. The carboxyl‐reduced fraction II had 1→4‐α‐D galactopyranuronic acid residues in the main chain, which were further involved in branching through rhamnose. The striking drop in their abundance and M_r at the end of ripening, denoting depolymerization in situ, is discussed in the context of textural softening. Copyright © 2004 Society of Chemical Industry     

Physical,Chemical and Functional Properties of Nigerian Mango (Mangifera indica) Kernel and its Processed Flour

The dimensions and kernel pH of several Nigerian mangoes were measured and correlated. Thereafter, a local mango kernel (the Ikanekpo variety) was studied with respect to its physical and proximate compositions, indices of the crude fat and the fatty acid composition, amino acid profile, and the bitter principle. The proximate composition and some functional properties of the processed kernel flour were also discussed. Results showed that the linear correlation coefficient between the dimensions of an unshelled seed was higher (+0·95) than that of the fresh kernel (+0·65). The kernel had a pH between 4·8 and 5·0. However, for lengths or breadths lower than 10 cm, correlation with pH was negative. The volatile matter, crude fat and tannin contents were distinguishing features of the composition. The level of unsaturated fatty acids was about double that of the saturated fatty acids. The level of linoleic acid was about three times higher than literature values for other known varieties. Compared with standard proteins, each of six essential amino acids >70% was available. Valine was the limiting amino acid. The level of tannin (45 g kg^-1) was high and 48% was extracted by a combined soaking and thermal treatment employed during flour production. Consequently, the calculated LD₅₀ per 70 kg body weight were 0·78 kg raw kernel and 1·5 kg processed flour, respectively. The latter has potential application in the preparation of steamed solid meals for adults in a traditional Nigerian household and could also be suitable for infant formulations considering its particle size distribution. © 1997 SCI.     

芒果多酚提取条件的研究

研究了从芒果核中提取芒果多酚的工艺条件,通过实验确定了从芒果核中提取芒果多酚的最佳工艺条件为提取温度为60℃、提取时间为1h、乙醇浓度为60%、料液比为1∶10。     

Rheological and high gelling properties of mango (Mangifera indica) and ambarella (Spondias cytherea) peel pectins

Ambarella and mango peels are good sources of pectins (15–20%), with high degree of methylation (60–78%) and high molar masses. Ambarella and mango ( Améliorée and Mango varieties) peel pectins were extracted using HCl or oxalic acid/ammonium oxalate (OAAO). Purified pectins were analysed for their flow behaviour and phase diagrams were established at pH 3 as sucrose vs. pectin concentration. The gelation kinetics and mechanical spectra of these pectin gels were studied and compared to those of commercial citrus (lime) pectins. At a concentration of 1% (w/v), all pectic solutions had a shear thinning behaviour but at 0.6% (w/v), only OAAO-extracted pectins exhibited such behaviour. Phase diagrams showed that at pH 3, gelation of OAAO mango extracted pectins was possible at low polymer concentration (0.2%; w/w) for a sucrose concentration of 60% (w/w). OAAO-extracted pectins exhibited a higher gelling ability than HCl-extracted ones. Sucrose (45–50%) and pectin (0.2–0.6%) concentration had a deep impact on the gel strength. Our results enable to conclude that the OAAO extraction from mango and ambarella peels allowed the recovery of pectins that exhibit high gelling properties.     

百合中多酚氧化酶的部分性质

通过丙酮酚法从百合中提取出多酚氧化酶(PPO)的粗酶液。以儿茶酚为底物时它有两个最适pH,分别为4.0、7.0,在pH5.0-6.5之间酶活力可以在4℃保持至少10h。PPO的最适温度为40℃,从40℃开始酶出现热失活,热失活速度符合一级反应动力学。PPO除对L-酪氨酸没有活力外,对儿茶酚、儿茶素、没食子酸均有活力,其中对儿茶素具有最好的底物特异性。亚硫酸钠对PPO的抑制作用最强,高浓度的抗坏血酸、半胱氨酸、硫脲也有很好的抑制作用,氯化钠、氯化钙、柠檬酸的抑制作用较差。     

Changes in individual carotenoids on processing and storage of mango (Mangifera indica) slices and purée

Susceptibility of different carotenoids to degradation during thermal processing and storage of two mango cultivars was investigated. The carotenoid composition was practically maintained on processing mango (cultivar Tommy Atkins) slices. The only significant change was the increase in luteoxanthin, compatible with the conversion of 5,6- to 5,8-epoxide. More evident transformations occurred on processing mango (cultivar Golden) purée. The major pigment β-carotene decreased 13%, resulting in a corresponding reduction of the vitamin A value. Auroxanthin, not found in the fresh fruit, appeared while violaxanthin and luteoxanthin decreased. During storage of mango slices in lacquered (epoxy) or plain tin-plate cans, no appreciable loss of β-carotene was observed during 10 months. Between the tenth and fourteenth month, about 50% reduction of β-carotene occurred. The degradation continued, resulting in a total loss of 84% after 24 months. A tendency of violaxanthin to decrease, and auroxanthin to increase, during storage was also noted. β-carotene showed a greater susceptibility to degrade in bottled mango purée (18% loss after 10 months) than in the canned product. As in the case of mango slices, however, both bottled and canned purée suffered 50% loss of β-carotene after the tenth month, and a total loss of 83% after 24 months. Violaxanthin and luteoxanthin tended to decrease while auroxanthin maintained a comparatively high level throughout storage. The vitamin A values reflected the degradation trend of β-carotene, a pattern that appears to agree with a free radical mechanism.     

小麦主产区小麦粉多酚氧化酶特性分析

将收集我国10个小麦主产区省(区)200多份小麦样品磨成粉,对这些小麦粉多酚氧化酶活性进行测定,评估各主产区小麦粉多酚氧化酶活性含量分布情况。实验结果表明,在10个主产区省(区)中,以陕西省小麦粉多酚氧化酶活性最高,宁夏小麦粉多酚氧化酶活性最低;小麦粉多酚氧化酶活性在7~11min-1g-1范围内分布较集中,占样品总数70.3%。另外,小麦粉多酚氧化酶活性越小,鲜湿面片L*值变化越小。     

多酚氧化酶的提取及分离纯化研究进展

多酚氧化酶(PPO)是自然界中分布极广的一种金属蛋白酶,能催化邻-苯二酚氧化成邻-苯二醌,也是许多果蔬等农产品酶促褐变的主要原因。本文综述了国内外多酚氧化酶的提取及分离纯化技术的研究进展,包括传统提取方法(如缓冲液匀浆法、丙酮提取法、丙酮粉提取法等)和新型提取方法(超声波辅助提取法和超高压提取法等),传统经典分离纯化方法(如溶剂法、沉淀法)和新型分离纯化方法(如凝胶色谱分离法和离子交换色谱分离法等),旨在为多酚氧化酶的研究和应用,特别是为抑制农产品酶促褐变提供参考。     

Fluidized bed and tray drying of thinly sliced mango (Mangifera indica) pretreated with ascorbic and citric acid

The purpose of this work was to determine the influence of air temperature, sample diameter and antioxidants on water activity, moisture content and colour difference of thinly sliced mango in a fluidized bed and tray dryer. Mango samples were treated with antioxidants solutions (ascorbic and citric acid) before the drying process. Fluidized bed and tray drying of control and treated samples were carried out at two temperatures: 50 and 60 °C. A fractional factorial design 2^4?1 was used in both drying methods. The Newton semi‐theoretical model was found to represent thin‐layer drying kinetics of mango. For both drying types, moisture content of thinly sliced mango was well characterised (R² ≥ 0.975) by the model. The temperature increment increases the drying constant and decreases the equilibrium moisture content and water activity of the dehydrated samples. Colour closest to the original colour of fresh mango was obtained when 2 cm diameter mango pretreated with citric acid (1%) was dehydrated by fluidized bed at 60 °C. In addition, it was observed that the drying time at equilibrium by using fluidized bed was lower (60 min) than the tray dryer (120 min).     

蓝莓中多酚氧化酶的酶学特性

为分析蓝莓中多酚氧化酶的酶学特性,本文对影响蓝莓多酚氧化酶（PPO）的酶活力的主要因素:p H、温度、金属离子、抑制剂及热稳定性进行了研究。结果表明:蓝莓中PPO最适p H为6.5,最适温度为30℃,Ca²⁺和Mn²⁺对蓝莓PPO有抑制作用,Cu²⁺、Mg²⁺、Zn²⁺、Fe³⁺对蓝莓PPO有激活作用。柠檬酸、抗坏血酸、L-半胱氨酸及亚硫酸氢钠能抑制PPO酶活,但柠檬酸抑制效果较差。热稳定性实验结果表明:蓝莓果PPO耐热性较差,高温短时可显著抑制PPO酶活性。      

Characterization of polyphenol oxidase and peroxidase from peach mesocarp (Prunus persica L. cv. Babygold)

The two enzymes involved in enzymatic browning reactions—polyphenol oxidase (PPO) and peroxidase (POD)—were extracted from peach fruit mesocarp. PPO was mainly located in the membrane fraction and was in its latent state. However, POD activity was found in the soluble fraction. The kinetic characterization of PPO and POD was carried out with a natural substrate (chlorogenic acid) and with a non‐physiological substrate. Under native isoelectric focusing (IEF), several PPO isoenzymes were present in the pH range 5.4–5.8. A partially denaturing sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS‐PAGE) showed the presence of two active bands with apparent molecular masses of 49 and 50 kDa. A totally denaturing SDS‐PAGE indicated the presence of a single polypeptide with a molecular mass of 60 kDa, as revealed by western blot. POD was also analyzed by IEF, showing the presence of two strongly basic isoenzymes, which were resolved by cationic native PAGE into two different bands. Copyright © 2007 Society of Chemical Industry     

Biochemical studies of cocoa bean polyphenol oxidase

Polyphenol oxidase (EC 1.14.18.1) was isolated and partially purified from cocoa beans. The properties of the enzyme were studied. The Michaelis constant K_m for catechol was 1 × 10^?2 M . The pH optimum of polyphenol oxidase activity assayed with catechol as substrate occurred at pH 6.8 and was characterised by a relatively high thermal stability, 50% of its activity was lost after heating for 40, 25 and 5 min at 60, 69 and 80°C respectively. The optimum temperature for the enzyme activity with catechol as substrate was around 45°C. The enzyme was reactive towards 3-(3,4-dihydroxy phenyl)-DL -alanine, 3-hydroxytyramine hydrochloride and 4-methyl catechol but showed no activity towards tyrosine, p-cresol, and 4-hydroxy-phenol. A rapid deactivation of the enzyme was observed when catechol of concentration > 40 mM was used as substrate. The enzyme activity was inhibited by ascorbic acid, L -cysteine, sodium bisulphite and thiourea.     

Fatty acid composition and characteristics of the kernel fat of different mango (Mangifera indica) varieties

The kernels of 13 different mango varieties were examined. The kernels contained, depending on variety, from 6.8 to 12.6% fat, 5.2 to 6.3% protein (Nx6.25) and 1.4 to 2.0% ash on a moisture-free basis. The fat was yellow-coloured and melted at 32.5-35.8°C. Stearic and oleic acids constitute about 85% of the total fatty acids. The ratio of stearic: oleic acids varied according to variety from 0.56 to 0.97. The remaining fatty acids are, in decreasing order, palmitic, linoleic, arachidic and lino-lenic acids. Oleic and linoleic acids represented about 88 and 10%, respectively, of the fatty acids incorporated at the sn-2-position of the triglycerides.     

Some properties of polyphenol oxidase from lily

A study of crude polyphenol oxidase (PPO) from lily bulbs was carried out to provide information useful for guiding food processing operations. Optimum pH for the enzyme activity in the presence of catechol, were 4.0 and 7.0 at room temperature(approximately 20 °C) and the enzyme was stable in the pH range from 5.0 to 6.5 at 4 °C for 10 h. Its optimum temperature was 40 °C and the heat inactivation of the enzyme followed first‐order kinetics. Lily PPO possessed a diphenolase activity toward catechol, catechin and gallic acid; catechin was the best substrate for the enzyme considering the V_max/K_m ratio. The most effective enzyme inhibitor was sodium sulphite, although ascorbic acid, l ‐cysteine and thiourea were also effective inhibitors at high concentration. But NaCl and citric acid were poor inhibitors of the enzyme. Data generated by this study might help to better prevent lily bulbs browning.     

Optimisation of fermentation conditions for mango (Mangifera indica L.) wine production by employing response surface methodology

Response surface methodology (RSM) was employed for the simultaneous analysis of fermentation conditions of temperature, pH and inoculum size on chemical characteristics such as ethanol, glycerol and volatile acidity, produced during mango wine production by Saccharomyces cerevisiae ( var. bayanus ). The experiments were carried out according to the central composite design to establish the optimum conditions for improving the quality of mango wine. The predicted values for optimisation process conditions were in good agreement with experimental data. The results showed that a satisfactory production of ethanol from the mango juice could be achieved reaching up to 10% (v/v), glycerol concentration is increased to 6.94 g L⁻¹ and volatile acidity is minimised to 0.29 g L⁻¹ at optimised fermentation conditions of temperature 22.5 °C, pH 3.8 and inoculum size 11.9%. Verification of the model indicated no difference between predicted and observed values. Sensory evaluation studies shown overall acceptance of mango wine with good quality.     

一种小麦多酚氧化酶活性测定方法的改进研究

参照美国谷物化学家协会标准方法(AACC 22-85),以L-DOPA为底物,测定了22份小麦样品其籽粒的PPO活性,发现测定结果的重复性较差.在籽粒PPO活性测定原理的基础之上,优化了测定参数,改进、完善了一种评价小麦全粉PPO活性的新方法,其操作简便、快速,实验结果的重复性好、稳定性高,与籽粒PPO活性的测定结果极显著相关.