Peroxidase and Lipoxygenase Influence on Stability of Polyunsaturated Fatty Acids in Sweet Corn (Zea mays L.) during Frozen Storage

The effect of blanching treatments and packaging materials on lipoxygenase (LOX) and peroxidase (POD) activity and fatty acid stability of two cultivars of sweet corn (Jubilee and GH-2684) were evaluated during 9 mo storage at ?20°C. Complete inactivation of LOX and POD was obtained with 9 and 15 min of steam blanching, respectively. Relative fatty acid content revealed no change in fatty acid composition during storage. Control of degradation of polyunsaturated fatty acids (PUFA) did not depend on oxygen permeability of different packaging materials. Blanching had little effect on PUFA degradation after 9 mo storage.     

蛀食害虫对小麦淀粉酶及过氧化物酶活性的影响

探讨玉米象(Sitophilus zeamais)、米象(Sitophilus oryzae)和谷蠹(Rhyzopertha dominica)三种蛀食性害虫不同感染程度对小麦淀粉酶及过氧化物酶活性的影响及变化规律,为小麦科学储藏量化指标提供依据。选用河南产储藏2年的商用小麦,按不同虫种分组,设定不同的虫口密度和感染时间,检测小麦样品降落数值和过氧化物酶(POD)活性,并与虫口密度和感染时间作相关性分析。结果表明,随着虫口密度增加和感染时间延长,样品的降落数值呈波动上升趋势,POD活性呈下降趋势;三种害虫侵害后的样品降落数值与感染时间均存在极显著正相关,POD活性与感染时间均存在极显著负相关,降落数值与POD之间呈极显著负相关,而二者与虫口密度的相关性均不显著。     

阿魏酸存在下酪蛋白的酶促交联与一些性质变化

在pH值为9.5,阿魏酸存在和37℃的条件下,利用辣根过氧化物酶(EC1.11.1.7)和过氧化氢对酪蛋白进行氧化交联,并用十二烷基磺酸钠-聚丙烯酰胺凝胶电泳和紫外吸收分析确认交联作用。在蛋白质质量分数为0.04%时,交联酪蛋白的乳化活性指数、乳化稳定性分别比酪蛋白提高25.2%和7.0%。利用葡萄糖酸–δ–内酯制备酪蛋白和交联酪蛋白的酸化凝胶,扫描电子显微镜观察可以看出交联酪蛋白凝胶的微观结构中空穴减少,形成了更为致密的结构。     

Influence of water activity and molecular mobility on peroxidase activity in salt and sorbitol-maltodextrin systems

Solvent composition, system mobility and viscosity play a central role in the regulation of enzymatic activity.The aim of this study was to investigate the individual and combined effect of water activity (a_w), bulk viscosity and glass transition temperature () on the activity of horseradish peroxidase (HRP) in buffered solutions. For this purpose, the water activity of the solutions was modulated using both a ionic (sodium chloride) and a non-ionic (sorbitol) ligand and viscosity changed upon the addition of maltodextrin.In viscous solutions characterized by different compositions, the effectiveness of a solute in the inhibition of the HRP activity was dependent both on the chemical properties of the solution, as described by a_w, and on the mobility of the system, as described by the inverse of viscosity and T − . Viscosity was the most important factor in the inhibition of HRP activity in solutions characterized by the same value, but when was changed, due to changes in the solutes composition, the latter became a key factor in the regulation of the enzyme activity.In salt-maltodextrin systems the water activity reduction limited HRP activity with higher efficiency at low viscosities whilst in sorbitol-maltodextrin systems, characterised by different values, the a_w lowering by sorbitol addition resulted in the increase of HRP activity depending on its effect on .     

过氧化物酶在蔗汁澄清工艺中除酚脱色的研究

本文研究了pH值、温度、H2O2用量及辣根过氧化物酶(HRP)用量等因素对辣根过氧化物酶催化H2O2氧化多元酚类的影响,并分别用HRP处理亚硫酸法糖厂的混合汁、清汁、糖浆,考察其对糖汁的除酚脱色效果。试验结果表明,HRP催化H2O2氧化处理糖汁具有明显的除酚脱色作用。     

“东魁”杨梅在减压贮藏过程中品质及相关酶活性的变化

目的:研究减压贮藏保鲜杨梅的新技术.方法:以常规冷藏为对照,研究减压冷藏对"东魁"杨梅采后生理和品质的影响.结果:减压贮藏可显著抑制杨梅可滴定酸、维生素C含量的下降以及相对电导率的增加,保持果实较好的贮藏品质;减压贮藏可显著抑制果实的腐烂,贮藏16 d后对照果实的腐烂指数达41%,而处理果实的腐烂指数<20%.减压处理可诱导提高过氧化物酶的活性,且在整个贮藏期间一直高于对照水平.推测减压抑制杨梅果实腐烂的作用与诱导抗病相关酶的活性升高密切相关.     

高浓度二氧化碳气调包装通过调节酚代谢抑制鲜切莲藕的酶促褐变

鲜切莲藕褐变的主要原因是酶促褐变,高浓度CO_2气调包装(Modified-atmosphere packaging,MAP)可以有效延缓鲜切果蔬褐变,而苯丙氨酸解氨酶(L-phenylalanine ammonia-lyase,PAL)、多酚氧化酶(Polyphenol oxidase,PPO)和过氧化物酶(Peroxidase,POD)的编码基因是引起果蔬褐变的主要基因。然而,高浓度CO_2 MAP对鲜切莲藕片PAL、PPO、POD酶及其编码基因表达的影响却鲜有报道。本文分析了100%CO_2MAP对鲜切莲藕贮藏过程中褐变度、总酚含量、PAL、PPO和POD酶活性及其编码基因表达的影响。结果表明:100%CO_2 MAP对延缓鲜切莲藕褐变有较好效果,且100%CO_2 MAP贮藏期间鲜切莲藕PAL、PPO和POD酶活性随褐变程度的增加而同步变化。此外,Nn PAL1,Nn PPOA和Nn POD2/3的表达变化与PAL,PPO和POD酶活性的变化及褐变相一致,说明高浓度CO_2 MAP可能通过下调Nn PAL1,Nn PPOA和Nn POD2/3的表达来延缓鲜切莲藕褐变。     

不同茶树品种悬浮发酵对茶黄素形成的影响

以同一嫩度的英红9号、福鼎大白、金观音、槠叶齐4 个差异性较大品种的鲜叶为原料进行悬浮发酵实验,开展茶树品种、酶源类型（多酚氧化酶（polyphenol oxidase,PPO）、过氧化物酶（peroxidase,POD）活性等）、儿茶素组分（含量、配比等）对茶黄素形成影响的研究,结果表明：PPO活性/POD活性比值以福鼎大白最高,英红9号和金观音次之;简单儿茶素总量（total simple catechin,TSC）和酯型儿茶素总量（total ester-type catechin,TETC）均以英红9号最高,福鼎大白和金观音次之,槠叶齐最低;各儿茶素组分除没食子儿茶素没食子酸酯和儿茶素没食子酸酯外均呈前期迅速下降、后期平稳的趋势,儿茶素剧烈消耗期在发酵前30?min;茶黄素组分形成量均呈先升后降的趋势,峰值点在发酵15?min和30?min,不同品种不同茶黄素组分峰值时间和高度不同;整体上,以最高儿茶素底物含量和第2高PPO活性/POD活性比值的英红9号品种茶黄素的形成量显著最多,最高PPO活性的福鼎大白和金观音品种可最快形成茶黄素,但较高活性的POD和较低含量的儿茶素,导致茶黄素的形成量较低,而具有最低PPO活性/POD活性比值和最低含量的儿茶素底物的槠叶齐品种形成茶黄素的能力最差。即PPO活性/POD活性比值越大,儿茶素底物含量越大,TETC/TSC比值越大,形成茶黄素的能力越强。     

电化学聚合N,N-二甲基苯胺固定过氧化物酶生物传感器

选用苯胺及其几个衍生物作聚合单体,用电化学聚合方法在玻碳电极上固定辣根过氧化物酶制备了测定Ｈ２ Ｏ２ 的传感器,经比较筛选出最灵敏的聚合单体Ｎ,Ｎ－ 二甲基苯胺进行了详细的研究。传感器的最佳操作电位为－ ０．０５Ｖ,在此电位下,常见的电活性物质在传感器上响应很小,因此干扰较小。传感器具有较高的灵敏度,对Ｈ２ Ｏ２ 的线性响应范围为１×１０－ ８ ～１×１０－ ５ ｍｏｌ／Ｌ,检测限达５×１０－ ９ ｍｏｌ／Ｌ。