QuEChERS前处理结合气相色谱电子捕获检测器检测果蔬中30种农药残留

目的 应用QuEchERS前处理法处理样品,建立了气相色谱-电子捕获检测器检测多种水果蔬菜中30种常见农药残留的分析方法。方法 用乙腈作为溶剂,分别采用无缓冲盐体系、醋酸缓冲盐体系和柠檬酸盐缓冲体系提取对蔬果中30种农药进行提取,用PSA进行净化后上机处理。结果 采用不加缓冲盐体系提取,经PSA净化的方法适用于本文所选30种农药的检测,将该方法用于黄瓜、西红柿、生菜、苔菜、包菜、胡萝卜、梨、草梅,苹果等蔬果中30种农残的检测,结果表明30种农药残留的回收率在75%-122%之间,相对标准偏差在1%-12%之间;结论 该方法准确、简单、快速、灵敏度高,可以满足日常农残快速筛选的检测要求。     

Determination of nitrates by a novel ion chromatographic method: occurrence in leafy vegetables (organic and conventional) and exposure assessment for Italian consumers

A novel ion chromatographic method to detect nitrates in vegetables was developed, and the nitrate contents in green salad (a mixture of endive and prickly lettuce), lettuce, chicory, rocket and spinach were determined from Italian markets in 1996 -2002. These leaf vegetables were included because they are currently supposed to provide most of the nitrate intake in the typical Italian diet. The highest content of nitrate was detected in chicory (6250 mg kg -1 ) and rocket (6120 mg kg -1 ), which are consumed in large quantities in some regions of Italy. Green salad and lettuce contained less nitrate (highest values = 4200 and 3300 mg kg -1 , respectively), but because they are consumed more generally, they provided 60% of the total intake of nitrates. Only a few samples were above the legal limits, with seasonal variation. A significantly higher nitrate content was found in organically grown green salad and rocket than in those conventionally produced. These data indicate that the average intake of nitrates from leafy vegetables is below the acceptable daily intake, i.e. 3.7 mg nitrate ion kg -1 body weight day -1 , but the total intake should be monitored to protect groups at risk, such as children and vegetarians.     

Optimization for Preservation of Selenium in Sweet Pepper Under Low-Vacuum Dehydration

Response Surface Methodology (RSM) was used for optimizing the drying technology of sweet pepper under low-vacuum. It was found that pH value has greater influence on the organic Se index, while drying temperature has greater effect on the chlorophyll index. The optimized parameters of drying temperature, pH value and blanching time were obtained, respectively.     

Second order derivative spectrophotometric method for determination of vitamin C content in fruits,vegetables and fruit juices

A second-order derivative UV spectrophotometric method for determination of vitamin C [ascorbic acid (AA)] content in a variety of natural samples is described. The method is based on the measurement of a peak–baseline amplitude in the second derivative of the AA spectrum at 267.5 nm. The following corresponding regression equation was obtained within the concentration range 2×10^-5 to 1×10^-4 M AA (3.5–17.6 g/cm³ AA) in 1.0 M HCl solution: ²D_267.5=2.420×10⁴ c+0.025; the correlation coefficient was 0.9993 and the detection limit 4.2×10^-6 M. The results obtained by analysing 21 different species of fruits, vegetables and juices indicated a possibility for a more extensive application of the proposed method. This method is rapid, simple and requires no pretreatment of the analysed material, which makes it suitable for routine analyses. The reliability of the method was confirmed by comparative determinations with the generally accepted 2,6-dichloroindophenol method.     

Concentrations of organophosphorus pesticides in fresh vegetables and related human health risk assessment in Changchun,Northeast China

This study was designed to investigate organophosphorus pesticides (OPs) concentrations in fresh vegetables and estimate potential health risks to inhabitants. A total of 214 samples of seven types of vegetables were collected from Changchun, the capital of Jilin province, one of the most important vegetable production areas. The eleven OPs were analyzed by gas chromatography coupled with flame photometric detector (GC-FPD). Results showed that 23.4% of samples contained OPs above maximum residue limit (MRL), 68.7% of samples below MRL and only 7.9% of samples were found free of OPs. Detection rates of OPs decreased in the following order: diazinon (82.2%) > phorate (45.8%) > dimethoate (29.4%) > parathion-methyl (27.6%) > omethoate (23.8%) > dichlorvos (22.9%) > fenitrothion (21%) > fenthion (18.7%) > parathion (18.2%) > methamidophos (17.3%) > malathion (12.1%). The OPs levels were higher for leafy than for non-leafy vegetables. The percentages of OPs above MRL: welsh onion (82.5%) > radish (37.5%) > pepper (17.2%) > Chinese cabbage (14.3%) > cucumber (3.2%) > eggplant (2.9%) > tomato (0%). 49.5% samples contained two or more OPs. The average target hazard quotients (ave THQ) were all less than one and the average Hazard Index (ave HI) for adults and children were 0.448 and 0.343, respectively. It is concluded that inhabitants who are exposed to average OPs levels may not be endangered by health risk.     

Prevalence and trends of bacterial contamination in fresh fruits and vegetables sold at retail in Canada

In recent years, fresh fruits and vegetables have been linked to numerous foodborne illness outbreaks in different regions of the world, including in Canada. In light of rising concerns over the microbial safety of these commodities, the Canadian Food Inspection Agency conducted retail surveys to obtain information on the occurrence of bacterial pathogens in a wide range of produce available in the Canadian marketplace (local vs. imported, organic vs. conventional). Samples (n = 31,329) were collected across Canada over four years (2009–2013) and consisted of leafy vegetables (n = 12,073), leafy herbs (n = 6032), green onions (n = 3381), cantaloupes (n = 3230), tomatoes (n = 4837) and berries (n = 1776). These samples were analysed in ISO 17025-accredited laboratories for various bacterial pathogens (Salmonella, Escherichia coli O157, Shigella, Campylobacter and Listeria monocytogenes), as well as for generic E. coli, an indicator of fecal contamination. The Wilson confidence interval was used to determine the prevalence of the different micro-organisms in the commodities investigated. Control charts and seasonal indices, statistical tools adapted here to explore the large amount of data collected for each commodity, were used to identify potential adverse events or trends in bacterial contamination. The prevalence of bacterial contamination observed during this study in the six commodities examined was generally very low, with prevalence intervals ranging from [0, 0.08%] in tomatoes to [0.79, 1.30%] in leafy herbs. Most of the samples that were reported as “positive for bacterial contamination” had elevated (>100 CFU or MPN/g) levels of generic E. coli, but did not have detectable levels of the bacterial pathogens investigated. Of the samples that did have detectable levels of bacterial pathogens, the only bacteria that were both detected and isolated were Salmonella and L. monocytogenes. Despite the overall low prevalence of contamination seen in most produce, a notable seasonal trend was observed in the leafy vegetable group, where higher bacterial contamination rates were confirmed in the summer in organic as opposed to conventional products. These findings provide valuable baseline information that can support food safety decisions, and confirm that the vast majority of fresh fruits and vegetables available on the Canadian market are safe in terms of bacteriological hazards.     

Determination of atrazine and carbaryl pesticide residues in vegetable samples using a multianalyte dipstick immunoassay format

A dipstick assay for the simultaneous determination of atrazine and carbaryl in vegetable samples was developed. The analytical method involved a fast extraction procedure followed by a multi-strip membrane test. The assay took 10 min, with a detection limit (naked eye) of 10 and 200 µg l^-1 for atrazine and carbaryl, respectively. The cross-reactivities to related compounds tested were negligible except for propazine. Quantification of the pesticides was carried out by measuring the dot colour with a spectrophotometer. IC₅₀ values (inhibition constant at 50% of the maximum binding) of 2.04 μg l^-1 for atrazine and 92.8 μg l^-1 for carbaryl were achieved by this approach. Vegetable samples were extracted with MeOH. The proposed methodology was used to analyse atrazine and carbaryl and check for compliance with European Union maximum residue levels for vegetables. Recoveries (75-105%) were in agreement with those obtained by GC/MS or HPLC. Standard curves using 25% methanol/75% TBS were used for food sample assays using a multi-analyte dipstick. IC₅₀ values were 9.2 μg l^-1 for atrazine and 179.2 μg l^-1 for cabaryl.     

北京市蔬菜、水果中有机磷农药残留现状调查

为了解北京市蔬菜、水果中有机磷农药残留情况，2002年在北京市抽检样品354件进行13种有机磷监测，其中蔬菜28l件，水果73件。检测结果显示7．6％的检品不符合国家标准。叶菜类(14，占9．3％)和根茎类(8，占17．4％)蔬菜的不合格率明显高于瓜菜、果菜类(2，占2．4％)蔬菜和水果(3，占4．1％)。13种有机磷检测出12种，其中禁用农药占53％。本市种植的蔬菜、水果与外埠进京产品的有机磷农药残留情况无显差别，超市、集贸市场、批发市场销售的产品的不合格率亦无显差别。     

微酸性电解水去除蔬菜农药残留效果的研究

目的探讨微酸性电解水(slightly acidic electrolyzed water,SAEW)对蔬菜农药残留的去除效果。方法 利用酶抑制法,建立了蔬菜表面农药残留的定量分析方法 ,酶活抑制率与农药浓度近似呈对数关系,对辛硫磷的检出限为0.49 mg/kg。结果与普通自来水浸泡处理效果比较,SAEW浸泡的去除效果有显着提高(P0.05),处理30 min后,农药去除率高达92%。随着SAEW用量的增加、浸泡时间的增长、以及温度的升高,农药残留率不断降低、农残去除率不断地增加。结论 SAEW由于其特殊的理化性质能有效地降解蔬菜的农药残留,它可能对蔬菜上面有机磷农药起到有效的降解作用,更多问题还有待研究。     

Effects of a family-based sensory education on vegetable and fruit variety in children

Several experimental studies implemented in schools have shown that sensory education reduces children’s neophobia and increases their sensory discrimination abilities. However, it is not known whether sensory education has an effect on children’s consumption, particularly on the variety of fruits and vegetables consumed, and whether it is effective when implemented in families.The effect on fruit and vegetable intake of a five months family-based sensory programme was examined in children aged 7–11 (with 32 children in the intervention group and 19 in the control group). The children's parents completed four 24-hour recalls at the beginning and after the intervention to assess their children’s fruit and vegetable intake. Variety indexes were calculated on the basis of the number of different fruits or vegetables consumed during the four 24-hour recalls.The results showed that the vegetable variety decreased in the control group, while it remained stable in the intervention group. No effects of the programme were observed for the fruit variety.The sensory education programme implemented in families prevented the variety of vegetables from decreasing over time. The results of this preliminary study and its long-term effects need to be confirmed by further investigations, with a different methodology than the 24-hour recall.