Characterization of trace metals in vegetables by graphite furnace atomic absorption spectrometry after closed vessel microwave digestion

A simple and expeditious method for the determination of trace metals (cadmium, chromium, copper, manganese and lead) is proposed. The metals are extracted from their matrix by using nitric acid and hydrogen peroxide in a closed-vessel microwave digestion system for their subsequent detection by graphite furnace atomic absorption spectrometry (GFAAS). The sample preparation procedure facilitates the overall analytical process and enables the construction of calibration curves from inorganic standards. The ensuing method provides good linearity and sensitivity for the five metals, with limits of detection and quantization spanning the ranges 0.05–2.20 and 0.15–7.34 μg/kg, respectively. This sensitivity level is quite appropriate for the intended application. Accuracy was assessed by using a certified reference material (NCS ZC85006 Tomato), for which the proposed method provided amounts of metals consistent with their certified values. The proposed method was applied to tomato, pepper and onion, which are widely consumed in Mediterranean countries.     

主成分分析法在气调包装果蔬质量评价中的应用

用主成分分析法构造了气调包装后果蔬质量的综合评价模型,并将该方法用于实例作效果检验.结果表明用主成分分析法评价气调包装后果蔬质量的方法可行,结果客观合理.     

液相色谱—原子荧光联用技术测定蔬菜中砷形态的不确定度

本文介绍蔬菜样品中砷形态测量的不确定度评定方法,该法根据最小二乘法原理计算校准曲线的标准不确定度,并充分分析和识别分析过程中的不确定度来源,较为全面地评定测量不确定度,为蔬菜中砷形态的测定方法提供理论依据。     

陕西省2004-2005年蔬菜、水果中农药残留污染状况调查

目的了解陕西地区蔬菜、水果中使用农药残留情况。方法2004年9月和2005年9月对全省6个市县各大农贸市场及超市销售的蔬菜、水果以及个别蔬菜、水果产地的蔬菜、水果随机抽样检查,采用气相色谱仪法及气相色谱-质谱仪法对18种蔬菜、水果中的有机磷、氨基甲酸酯、菊酯、三氯杀螨醇4类22种农药残留量进行测定。结果2年共抽检蔬菜、水果样品455份。2004年采集174份,其中有机磷类农药总检出率18.39%,超标率18.39%。氨基甲酸酯类农药检出率为12.64%,超标率2.87%。菊酯类农药的总检出率为31.03%,均未超标。三氯杀螨醇农药检出率为4.02%,均未超标。2005年采集281份,其中有机磷农药总检出率34.16%,超标率27.40%。氨基甲酸酯类农药检出率5.34%,均未超标。菊酯类农药检出率为52.67%,超标率1.07%。三氯杀螨醇农药检出率为37.01%,超标率6.41%。结论陕西地区蔬菜、水果中滥施农药特别是有机磷和三氯杀螨醇等高毒、剧毒农药的情况较为严重,应加强监督管理。     

The relationship between lipid oxidation and antioxidant content in postharvest vegetables

Abstract

Lipid oxidation is the quality limiting attribute in many vegetables that generates off‐flavors. Lipoxygenases, which catalyze the oxygenation of polyunsaturated fatty acids are key enzymes in this pathway and their presence is believed to be the chief reason for the need for blanching (i.e., inactivation of enzymes) enabling frozen storage. Off‐flavor production in legumes, such as garden peas, is a particular problem, due to high levels of this enzyme found in these seeds.

The lipid oxidation pathway is triggered in response to tissue wounding which occurs during mechanical harvesting of peas in the field. Bruised peas that are not blanched develop strong off‐flavors within a few hours.

A number of studies has shown that antioxidants are consumed during lipid oxidation. Vitamin C (ascorbate) is an antioxidant and also an important micronutrient in peas. It is possible that the level of vitamin C is affected by the progress of lipid oxidation in postharvest peas.     

Characterization of the cultivable microbial community in a spinach-processing plant using MALDI-TOF MS

A better and regular control of the production chain of fresh fruits and vegetables is necessary, because a contamination of the product by human- and phyto-pathogenic microorganisms may result in high losses during storage and poses a threat to human health. Therefore, detailed knowledge about the occurrence and the diversity of microorganisms within single processing steps is required to allow target-oriented produce safety control. Recently, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was successfully used to identify bacterial colonies. Bacteria can be identified with high accuracy by comparing them with generated spectra of a reference database.     

Distribution pattern of eight heavy metals in the outer and inner tissues of ten commonly used vegetables

This study reports the distribution of eight heavy metals (Cd, Co, Cr, Cu, Hg, Mn, Ni, and Pb) in the outer and inner tissues of ten different vegetables from the Qassim region of Saudi Arabia. The oven-dried (65°C, 48 h) vegetable samples were subjected to microwave acid digestion before heavy metals analysis using inductively coupled plasma optical emission spectrometry. The results showed that Co, Cd, and Pb were absent in the outer tissues of all the vegetables, whereas these elements were detected in the inner tissues of some vegetables in the ranges of 0.01–0.23 mg/kg wet weight, 0.03–0.42 mg/kg, and 0.02–3.44 mg/kg, respectively. The traces of Hg (1.83–3.59 μg/kg) were noticed in the outer tissues of all the samples; however, it was not detected in the inner tissues of vegetables. The variable distribution of heavy metals in different vegetables is influenced by several factors, including exposure route, physicochemical properties of heavy metals, species of crops, cultivation strategy, soil type, and growing conditions. In conclusion, although the representative samples of vegetables used in this study contained safe levels of Cd, Co, Ni, and Pb, higher than recommended upper limits of Cr, Cu, and Mn were observed in some vegetables. These findings suggested that regular monitoring of heavy metals in vegetables is important to safeguard consumers.     

蔬菜中镉的氢化物-原子荧光光谱法测定

本文采用氢化物—原子荧光光谱法测定蔬菜中镉,具有操作简单、快速、基体干扰少、灵敏度高等优点。方法检出限为O.17μg/L,线性范围为(0～60.0)μg/L。     

谷物与蔬菜复合食品的研究开发现状及展望

对以谷物和蔬菜为主要原料的复合食品现状进行综述,初步阐述了这类复合食品的营养价值、应用前景及发展思路。