Determination of α‐hydroxy acids and their enantiomers in fruit juices by ligand exchange CE with a dual central metal ion system

The content of α‐hydroxy acids and their enantiomers can be used to distinguish authentic and adulterated fruit juices. Here, we investigated the use of ligand exchange CE with two kinds of central metal ion in a BGE for the simultaneous determination of enantiomers of dl ‐malic, dl ‐tartaric and dl ‐isocitric acids, and citric acid. Ligand exchange CE with 100 mM d ‐quinic acid as a chiral selector ligand and 10 mM Cu(II) ion as a central metal ion could enantioseparate dl ‐tartaric acid but not dl ‐malic acid or dl ‐isocitric acid. Addition of 1.8 mM Sc(III) ion to the BGE with 10 mM Cu(II) ion to create a dual central metal ion system permitted the simultaneous determination of these α‐hydroxy acid enantiomers and citric acid. The proposed ligand exchange CE was thus well suited for detecting adulteration of fruit juices.     

Fruit tree model for uptake of organic compounds from soil

Apples and other fruits are frequently cultivated in gardens and are part of our daily diet. Uptake of pollutants into apples may therefore contribute to the human daily intake of toxic substances. In current risk assessment of polluted soils, regressions or models are in use, which were not intended to be used for tree fruits. A simple model for uptake of neutral organic contaminants into fruits is developed. It considers xylem and phloem transport to fruits through the stem. The mass balance is solved for the steady-state, and an example calculation is given. The Fruit Tree Model is compared to the empirical equation of Travis and Arms (T&A), and to results from fruits, collected in contaminated areas. For polar compounds, both T&A and the Fruit Tree Model predict bioconcentration factors fruit to soil (BCF, wet weight based) of >1. No empirical data are available to support this prediction. For very lipophilic compounds (log K OW >5), T&A overestimates the uptake. The conclusion from the Fruit Tree Model is that the transfer of lipophilic compounds into fruits is not relevant. This was also found by an empirical study with PCDD/F. According to the Fruit Tree Model, polar chemicals are transferred efficiently into fruits, but empirical data to verify these predictions are lacking.     

水果糖度可见-近红外光谱手持式检测装置开发与试验

基于可见-近红外光谱分析技术开发了手持式水果糖度检测装置,并用于水果糖度的现场实时分析。硬件系统主要包括微型光谱仪、卤素灯、OLED显示屏、单片机及驱动电路等。采用Keil 5开发工具,用C语言开发单片机程序。配合上位机以LabView编写的光谱采集程序,实现光谱信息的采集。以苹果和大桃作为检测对象,对装置的检测精度和模型在2台装置（主机、从机）间的传递效果进行了探讨。在实验室和果园环境下,分别获取了苹果、大桃样本在600～950 nm范围的可见-近红外光谱。对实验室条件下采集的主机校正集光谱进行分析,经过平滑、最大值归一化、二阶导数等预处理后,利用偏最小二乘算法分别建立了苹果、大桃的糖度检测模型。模型导入主机装置后,对预测集样本进行检验。对苹果、大桃的预测集相关系数和预测均方根误差分别为0.925,0.587%和0.821,0.613%。采用分段直接校正和基于典型相关分析算法的模型传递方法将模型由主机传递到从机。对比后发现,基于典型相关分析算法取得了更好的模型传递结果。从机对苹果、大桃糖度的预测集相关系数和预测均方根误差分别为0.883,0.641%和0.805,0.626%。将实验室条件下建立的模型用于树上采集到的水果光谱数据分析,得到预测集相关系数和预测均方根误差分别为0.866,0.741%和0.816,0.627%。整体检测结果表明,该装置可以满足对苹果、大桃糖度的有效检测,借助模型传递算法,实现了模型在不同装置间的共享和有效传递,且实验室环境下采集的数据建立的模型可以用于树上水果糖度的有效检测,该装置具有较大的经济价值和应用前景。     

Assessment of the Antioxidant Capacity of Standard Compounds and Fruit Juices by a Newly Developed Electrochemical Method: Comparative Study with Results from Other Analytical Methods

The antioxidant capacity (AOC) of some standard compounds and commercial beverages was determined using an electroanalytical method which measures the OH radical scavenging ability (OH‐RSC). It is based on the degradation of a thin polyphenol film electrodeposited on glassy carbon following the attack by OH radicals produced by hydrogen peroxide photolysis. The degradation is prevented in presence of increasing concentrations of antioxidants. The same samples were also analyzed by DPPH, ABTS, and ORAC assays. The OH‐RSC method provided AOC values highly correlated with those resulting from the application of ORAC assay for both juices (R=0.90) and standard antioxidants (R=0.96).     

用于水果品质检测的小型成像光谱仪

利用成像光谱可同时获得水果的成像信息和光谱信息,实现水果外部和内部品质的高精度、无损伤、无污染的大面积瞬态检测。为了获得水果的成像光谱,设计了一种以自主研发的凸面光栅作为核心元件的小型成像光谱仪,它具有成像质量好、体积小、重量轻等优点,光谱分辨率在578nm波长处达2.1nm,光谱谱线弯曲和色畸变均小于0.6%。对该小型成像光谱仪进行了检测和苹果成像光谱测量实验,结果表明:该成像光谱仪满足设计要求且可以快速的获得苹果的高精度成像光谱,从而进行水果的品质检测。     

Modeling of clarified tropical fruit juice deacidification by electrodialysis

Electrodialysis (ED) using two-stack configurations with homopolar or bipolar membranes was investigated for deacidification of tropical fruit juices (passion fruit, mulberry, naranjilla). The objective was to develop a mathematical treatment for ED to predict the behavior of a fruit juice at industrial scale from ED performances at laboratory scale. From parameters such as current efficiency, electric resistance of the anion exchange membrane, and coefficients of variation with temperature determined in a laboratory-scale stack, modeling was applied to a pilot-scale stack that has a total effective membrane area 70 times larger. If no fouling took place, and except for conductivity at pH higher than 3.8, the differences between the experimental and simulated values for pH, titrable acidity, voltage, and energy consumption were inferior to 7%, 16%, 20%, and 15%, respectively, for all the fruit juices and operating conditions. Moreover, the average electrical charge of citric acid species transferred was 2.16 for all fruit juices, indicating that the current transport was mainly due to the ionic species issued from the secondary dissociation of the citric acid.     

电感耦合等离子体串联质谱法测定野生皂荚中多种微量元素

采用电感耦合等离子体串联质谱(ICP-MS/MS)法测定野生皂荚中多种微量元素的含量。皂荚样品以HNO₃+H₂O₂+HCl为混合消解试剂经微波消解后直接测定。在MS/MS模式下向碰撞反应池中通过氧气或氨气,分别利用氧气质量转移、氧气原位质量和氨气质量转移消除多原子离子质谱干扰。通过分析国家标准参考物质绿茶(GBW10052)和芹菜(GBW10048)验证方法的准确性和精密度,所测定结果与参考值基本一致,RSD≤7.8%。采用所建立的方法分别分析了来自中国云南和重庆武陵山区野生皂荚中的12种微量元素(V,Cr,Co,Cu,Zn,Fe,Mn,Ni,As,Cd,Hg,Pb),12种微量元素的检出限为0.29～21.36 ng·L-1。结果显示,野生皂荚12种分析元素中Fe含量最高,其次为元素Zn,重金属元素As,Cd,Hg和Pb的含量远低于《中国药典》限量标准。该研究为野生皂荚中微量元素的安全评价和监管提供了科学方法和数据。     

蔬菜和水果的显微激光拉曼光谱研究

采用显微激光拉曼光谱技术,研究测定了未经任何处理和经过清洁处理的多种蔬菜和水果表面的拉曼光谱。结果表明不同样品的表面拉曼光谱具有明显的胡萝卜素特征峰,这一相似性为进一步研究农药残留的识别提供了方便;也有一些样品出现胡萝卜素以外的其他拉曼光谱峰,为以后详细分析蔬菜和水果中各种有效营养成分提供了理论依据。利用显微激光拉曼光谱研究蔬菜、水果表面的组成和农药的残留具有简便、快速和绿色分析的前景。     

Guianofruits C–I from fruit oil of andiroba (Carapa guianensis,Meliaceae)

Two novel chukrasone-type limonoids, named Guianofruits C and D (1 and 2), a guianolide derivative named Guianofruit E (3), and four novel phragmalin–type limonoids named Guianofruits F–I (4–7), were isolated from the fruit oil of Carapa guianensis AUBLET (Meliaceae), a traditional medicine in Brazil and Latin American countries. Their structures were mainly elucidated based on spectroscopic analyses using 1D and 2D NMR techniques. The effects of compounds 1–6 on the production of NO by LPS-activated mouse peritoneal macrophages were investigated. Two new chukrasone-type limonoids, Guianofruits C (1) and D (2), exhibited moderate inhibitory activities.     

近红外光谱分析技术在水果品质无损检测上的应用

近红外光谱分析技术具有快速、非破坏性、低成本及同时测定多种成分等特点,在很多领域得到广泛应用。本文简介了近红外光谱技术的检测原理,指出其检测优点和不足。综述了国内外将近红外光谱技术应用于水果品质无损检测方面的研究进展,并对利用近红外光谱技术进行水果品质无损检测的研究前景进行了展望。