Comparison of Immobilisation Procedures for Development of an Electrochemical PPO-Based Biosensor for on Line Monitoring of a Depuration Process

SUMMARY

The development of amperometric biosensors based on polyphenol oxidase (PPO) as a novel tool for the determination of phenolic compounds is described.

Biosensors have been obtained using different PPO-rich matrices: tissue slices from mushroom and potato, acetonic powder from mushroom; lyophilised enzyme from mushroom (tyrosinase-SIGMA). A large variety of immobilisation procedures have been used with pure enzyme and acetonic powder. Behaviour of all biosensors obtained has been investigated in terms of sensitivity. linearity range, response time and half life time. Preliminary experiments have been carried out, using a Flow Injection Analysis, with standard solutions of catechol and phenol in the range 1-10 mM, then biosensors have been also tested on a real sample (green water from crushers) with a direct method and a standard addition, one obtaining good reproducibility.     

应用主动作物冠层传感器对马铃薯氮素营养诊断

氮肥的充足供应是马铃薯高产的重要条件,然而氮肥的过量投入会导致资源浪费、环境污染,因此,氮素精准管理势在必行,而实时的氮素营养诊断是实现马铃薯合理氮素养分管理的前提。本研究通过在内蒙古武川县和林西县进行的田间试验,采用主动作物冠层传感器GreenSeeker对马铃薯各生育时期进行实时监测,建立了传感器读数NDVI值与地上部植株氮浓度以及整株吸氮量的关系。研究表明,由于受到土壤背景的影响,苗期NDVI值与马铃薯氮营养指标相关性较差。苗期以后,马铃薯在封垄前NDVI值与植株吸氮量呈显著的指数关系(R2=0.665),封垄后NDVI值与地上部植株氮浓度呈显著的线性关系(R2=0.699),且不受地域以及生育时期的影响。结果表明,主动作物冠层传感器GreenSeeker能够用于马铃薯氮素营养诊断,该结果为进一步建立应用主动作物冠层传感器的氮肥管理提供了理论依据。     

半透射高光谱结合流形学习算法同时识别马铃薯内外部缺陷多项指标

针对马铃薯内外部缺陷多项指标难以同时识别的问题,提出了一种半透射高光谱成像技术采用流形学习降维算法与最小二乘支持向量机(LSSVM)相结合的方法,该方法可同时识别马铃薯内外部缺陷的多项指标。试验以315个马铃薯样本为研究对象,分别采集合格、外部缺陷(发芽和绿皮)和内部缺陷(空心)马铃薯样本的半透射高光谱图像,同时为了符合生产实际,将外部缺陷马铃薯的缺陷部位以正对、侧对和背对采集探头的随机放置方式进行高光谱图像采集。提取马铃薯样本高光谱图像的平均光谱(390~1 040 nm)进行光谱预处理,然后分别采用有监督局部线性嵌入(SLLE)、局部线性嵌入(LLE)和等距映射(Isomap)三种流形学习算法对预处理光谱进行降维,并分别建立基于纠错输出编码的最小二乘支持向量机(ECOC-LSSVM)多分类模型。通过分析和比较建模结果,确定SLLE为最优降维算法,SLLE-LSSVM为最优马铃薯内外部缺陷识别模型,该方法对测试集合格、发芽、绿皮和空心马铃薯样本的识别率分别达到96.83%,86.96%,86.96%和95%,混合识别率达到93.02%。试验结果表明：基于半透射高光谱成像技术结合SLLE-LSSVM的定性分析方法能够同时识别马铃薯内外部缺陷的多项指标,为马铃薯内外部缺陷的快速在线无损检测提供了技术参考。     

蒽酮比色法测定马铃薯淀粉深加工工艺废液总糖含量的研究

研究了葡萄糖、果糖、蔗糖、马铃薯淀粉标准液、马铃薯粉渣和马铃薯淀粉深加工工艺废液,确定了蒽酮比色法测定马铃薯淀粉深加工废液总糖含量的最佳实验条件。在马铃薯淀粉深加工废液中加入盐酸,在105℃消煮120min,用活性碳脱色,过滤,滤液加入蒽酮,沸水浴中加热12min,显色体系在620nm处的吸光度达到最佳值,糖的浓度在1—100μg/mL范围内符合比耳定律,线性相关系数为0.9997。用所拟方法对凉山洲盐源世富农业科技公司马铃薯淀粉深加工工艺废液总糖进行测定,相对误差在5%以内,加标回收率在96.42%—103.16%之间,结果满意。     

酸解淀粉物理化学性质的研究

玉米淀粉和马铃薯淀粉分别在35C条件下用浓度为2．4mol／L的HCI处理不同时间,采用X射线衍射分析、差热分析和扫描电镜等测试方法对酸解后的淀粉颗粒进行结构和性能分析。结果表明,淀粉的酸解过程可分为两个阶段：首先淀粉无定形区进行水解,颗粒结晶度、结晶热稳定性和酶解速率增加;随着酸解时间的延长,结晶结构受到破坏,热稳定性降低,达到酶解平衡的时间减少。酸解4d时,玉米淀粉和马铃薯淀粉颗粒的结晶均最完整,结晶转变温度最高,分别为87．0C和93．5C。     

新型发酵蔬菜制品乳酸菌发酵剂的筛选研究

从榨菜等一些自然腌制蔬菜制品中分离得到一些乳酸菌菌株,通过细胞形态及生理学特性观察研究,初步筛选出Lactobacillus 8株菌株,并进一步通过发酵产酸和细胞生长比较实验得到3株乳酸菌菌株Lact,2,Lact．6和Lact．8,通过菌株间不同配比和发酵榨菜验证实验,最后确定了榨菜发酵制品的最适发酵剂为Lact．2和Lact.8,最佳配比为1：1．     

Enorme Unterschiede in der qualitativen und quantitativen Zusammensetzung der Fettsäurefraktion von rohem und gekochtem Gemüse

Summary Potato tubers und vegetables, introduced into the body contain — in dependance if boiled or not — very different amounts of multiple unsaturated fatty acids. In boiled vegetables linoleic and linolenic acid remain unchanged. In contrast, if the vegetable is shred and then analysed, the content of multiple unsaturated fatty acids is lowered for a factor of 2–5. If vegetable is shred, lipoxygenases are liberated, resulting in oxidizing the multiple unsaturated acids. The lipoxygenases are destroyed if vegetable is cooked before shreding. An easy comparison of the effect of lipoxygenases on fatty acid can be made by gas chromatography. The effect is especially strong incruciferae e.g. in cabbage or cauliflower.

     

Determination of phenolic acids by capillary zone electrophoresis and HPLC

Selected phenolic acids are determined by capillary zone electrophoresis and HPLC, each using UV detection. The optimised CZE background electrolyte contained 50 mM acetic acid, 95 mM 6-aminocaproic acid, 0.1% polyacrylamide, 1% polyvinylpyrrolidone, and 10% methanol. Twelve phenolic acids (gallic, p-hydroxybenzoic, 3,4-dihydroxybenzoic, vanillic, syringic, o-coumaric, p-coumaric, caffeic, sinapic, ferulic, salicylic and chlorogenic) were separated within 10 minutes. Chromatographic separation of these phenolic acids was carried out on an Eclipse XBD C8 column using a mobile phase gradient (acetonitrile / methanol / water / 0.1% phosphoric acid); all were separated within 25 minutes. Electrophoretic and chromatographic determinations of ferulic and chlorogenic acids were compared on barley, malt, and potato samples. The methods’ characteristics were: linearity (1–20 mg ml and 0.2–4 mg ml⁻¹), accuracy (recovery 94 ± 5% and 96 ± 4%), intra-assay repeatability (4.1% and 3.5%), and detection limit (0.2 and 0.02 mg ml⁻¹).      

Determination of Maleic Hydrazide in Potato Samples Using Capillary Electrophoresis with Dual Detection (UV‐Electrochemical)

A new method for the separation of a mixture of different herbicides (propham, chlorpropham, asulam, metamitron, linuron, and maleic hydrazide) using MEKC is proposed. A base‐line separation for the mixture of herbicides is achieved in less than six minutes. The detection limits obtained for all the herbicides were lower than 1.0 μM using UV detection. This separation method was used for the determination of maleic hydrazide in potato samples. If a dual (UV‐electrochemical) detection system is employed, chlorpropham can be also detected. The results obtained showed that electrochemical detection was ten folds more sensitive than UV detection for maleic hydrazide. The detection limit of the proposed method for maleic hydrazide employing electrochemical detection was 1.3 μg g^?1, this value is lower than 50 μg g^?1, which is the maximum residue level permitted for this plant growth regulator in potato samples. The results obtained in the work clearly demonstrate the advantage of using electrochemical detection coupled to capillary electrophoresis, using this detection the concentration limits are not compromised by miniaturization and the components required are simple and inexpensive.