高效液相色谱法同时测定蔬菜中多种磺酰脲类除草剂的残留量

建立高效液相色谱法同时测定蔬菜中8种磺酰脲类除草剂残留量的检测方法。样品经乙腈提取、凝胶渗透色谱净化、C18固相萃取柱净化后,采用高效液相色谱分离,二极管阵列检测器检测,外标法定量。本法简便、快速、定量准确、精密度高,适用于进出口蔬菜中多种磺酰脲类除草剂残留量的同时检测。     

Heavy metal contamination of water, soil and produce within riverine communities of the Río Pilcomayo basin, Bolivia

The Río Pilcomayo heads on the Cerro Rico de Potosí precious metal-polymetallic tin deposits of Southern Bolivia. Mining of the Potosí deposits began in 1545 and has led to the severe contamination of the Pilcomayo's water and sediments for at least 200 km downstream of the mines. This investigation addresses the potential human health affects of metal and As contamination on four communities located along the upper Río Pilcomayo by examining the potential significance of human exposure pathways associated with soils, crops and water (including river, irrigation and drinking water supplies). The most significantly contaminated agricultural soils occur upstream at Mondragón where Cd, Pb and Zn concentrations exceed recommended guideline values for agricultural use. Further downstream the degree of contamination decreases, and metal concentrations are below Dutch, German and Canadian guideline values. Metal and As concentrations in agricultural products from the four communities were generally below existing guidelines for heavy metal content in commercially-sold vegetables. Thus, the consumption of contaminated produce does not appear to represent a significant exposure pathway. A possible exception is Pb in carrots, lettuce and beetroots from Sotomayor and Tuero Chico; 37% and 55% of the samples, respectively, exceeded recommended guidelines. Most communities obtain drinking water from sources other than the Río Pilcomayo. In general, dissolved concentrations of metals and As in drinking water from the four studied communities are below the WHO guideline values with the exception of Sb, which was high at Tasapampa. The inadvertent ingestion of contaminated water from irrigation canals and the Río Pilcomayo represents a potential exposure pathway, but its significance is thought to be minimal. Given the degree of soil contamination in the area, perhaps the most significant exposure pathway is the ingestion of contaminated soil particles, particularly particles attached to, and consumed with vegetables. The risks associated with this pathway can be reduced by thoroughly washing or peeling the vegetables prior to consumption. Other exposure pathways that are currently under investigation include the consumption of contaminated meat from livestock and poultry, which drink polluted waters and the ingestion of contaminated wind-blown dust.     

Consumers' trust in vegetable supply chain members and their behavioural responses: A study based in Queensland,Australia

In the current era, food chains are becoming increasingly complex and consumer concerns about food safety are growing. As a result, consumers tend to rely heavily on chain actors to ensure the quality of the products they consume. Given this background, this study was conducted with a view to understanding the level of consumers' trust in vegetable supply chain members and how trust influences the consumers' behavioural responses. This paper is based on data obtained from 854 respondents in south-west Brisbane, Queensland, Australia. The results revealed that the level of trust placed in chain members varied across the chain. Respondents considered that domestic producers are more trustworthy in terms of producing safer vegetables and the lowest trust level was associated with imported vegetables. Gender, household size, years of stay in Australia, trust perceptions, and country of origin concerns had a significant influence on the respondents’ intentions to pay a premium price for domestically produced vegetables. The study revealed that consumers respond to food safety concerns and this creates an opportunity for the vegetable industry to respond to these concerns.     

蔬菜中腐霉利、克百威、对硫磷的检测能力验证样品研制及应用

目的 制备更贴近实际样品且均匀性和稳定性良好的能力验证样品,并通过能力验证项目分析全国实验室检测蔬菜中腐霉利、克百威、对硫磷的能力。方法 能力验证样品采用市售蔬菜汁添加目标物标准溶液的方式制备,并进行均匀性检验和稳定性检验;采用稳健统计得到指定值和能力评定标准差,利用z值对各参加实验室提交的结果进行评价。结果 所制备的样品经均匀性和稳定性检验样品符合能力验证要求;将所研制的样品应用于能力验证,全国共有94家实验室参加,其中参加腐霉利项目的实验室满意率为84.5%;参加克百威项目的实验室满意率为83.3%;参加对硫磷项目的实验室满意率为89.6%。结论 采用本研究中的制备方式制得的样品具有良好的均匀性和稳定性,能够满足能力验证样品的要求;能力验证统计结果表明,参加实验室的蔬菜中腐霉利、克百威、对硫磷的检测能力总体较好。通过本次能力验证活动对该领域实验室的检测水平有了一定了解,达到预期的效果。     

气相色谱内标法测定蔬菜中的乐果

目前,测定蔬菜中乐果农残主要使用外标法,仪器的重现性差,相对偏差达到10％左右,造成定量分析误差较大.产生重现性差的原因是PFD检测器测定乐果时信号的响应值有不断地增大的趋势,本文采用三唑磷为内标物,对仪器条件和处理方法进行了优化,较好地改善了测定方法的重现性,并且简化了处理方法,使样品前处理具有较好的可操作性和稳定性,方法的加标回收率达到92.2～105.0％.     

冷藏对蔬菜中亚硝酸盐及硝酸盐含量的影响

目的 探索冰箱冷藏(4℃)条件下蔬菜中硝酸盐和亚硝酸盐含量随时间的变化,对冷藏食品的安全性进行评价.方法 分别采用重氮偶合分光光度法和麝香草酚分光光度法对生菜、菠菜、油麦菜及苦苣4种常用蔬菜在冷藏条件下其亚硝酸盐及硝酸盐的含量变化进行测定.结果 1～4d内,生菜、苦苣中的亚硝酸盐含量随着时间的延长逐渐增加;菠菜、油麦菜中亚硝酸盐含量分别在第2天和第3天达到最大,之后逐渐降低,而菠菜中亚硝酸盐含量在第4天又出现上升趋势.4种蔬菜中亚硝酸盐含量4d中最大值仅为0.419 4 mg/kg(生菜),均＜4 mg/kg的限量值.苦苣和油麦菜中硝酸盐含量在1～4d内逐渐上升.菠菜中硝酸盐含量第2天达到418.48 mg/kg,之后又降低至20.83 mg/kg.生菜中硝酸盐含量在第3天达到最大值317.26 mg/kg,之后逐渐下降,但均在安全范围内(432 mg/kg).结论 在4℃下冷藏4d后,4种常见蔬菜均可安全食用.可见,冷藏能有效减缓亚硝酸盐和硝酸盐含量的升高.     

Enzymatic Firming of Processed Red Pepper by Means of Exogenous Pectinesterase

Abstract

The objective of this investigation was to demonstrate that the firmness of a commercial vegetable product, diced and frozen red pepper (Capsicum annum var. Sendt), could be improved by the use of exogenous pectinesterase in an industrially relevant process. The diced pepper pieces 10?×?10?×?7?mm³ were infused under vacuum with a commercially available pectinesterase. The range of optimal process conditions was: 15–20°C, 45?min infusion time, a 10–25?mM CaCl₂ infusion brine, a w/w ratio of pepper fruit to infusion brine of 1.5:1, and an enzyme dosage of 30–60 pectinesterase units (PEU) per kg pepper fruit. The firmness as measured by back extrusion was improved by a factor of two to three. The effect of firming was robust and conserved after freezing and heating in a simulated household cooking process. The firming process seems easily adaptable to industrial conditions and may be applicable to other vegetable and fruit products.     

Recent Application of Modified Atmosphere Packaging (MAP) in Fresh and Fresh-Cut Foods

Modified atmosphere packaging (MAP) has been applied in the food industry for about 90 years to extend shelf life and maintain quality of fresh and fresh-cut foods. Recently, MAP has experienced a rapid development in both scientific and industrial communities, which was one of the most appropriate and practical technologies for packaging fresh and fresh-cut produce. This paper reviews some recent developments of newly emerged MAP systems such as high-oxygen MAP, controlled MAP, and intelligent MAP and provides an overview of MAP applications for fresh and fresh-cut fruits, vegetables, mushrooms, meat, and aquatic products.     

Determination of Pyrethroid Insecticides in Crude and Canned Vegetable Samples by Supercritical Fluid Chromatography

A supercritical fluid chromatography method for the determination of seven pyrethroid insecticides (allethrin, resmethrin, phenothrin, permethrin, tetramethrin, cypermethrin, deltamethrin) and one of their common metabolites, phenoxybenzyl alcohol, in whole and peeled potatoes and mixed vegetables was developed. The efficiencies of the two extraction techniques, supercritical fluid extraction and microwave-assisted extraction, for the extraction of pyrethroids from vegetable samples were also compared. The retention times of various pyrethroids ranged from 8.4 to 22.9 min, while all of the peaks were well-resolved and distinctly identified. The limits of detection of pyrethroid insecticides ranged between 0.31 and 0.54 ppm, whereas the limits of detection of phenoxybenzyl alcohol was 0.62 ppm. The recoveries of pyrethroid insecticides from whole potatoes, peeled potatoes, and mixed vegetables ranged as 93.83–99.8%, 92.3–105.8%, and 93.67–102.7%, respectively, with the use of supercritical fluid extraction. The corresponding recovery ranges while using microwave-assisted extraction were 94.2–102%, 96.6–101.2%, and 96–103.2%. These findings suggested that supercritical fluid chromatography was a sensitive and rapid technique for the analysis of pyrethroids in complex matrices, such as vegetables, fruits, and other agricultural products.     

新型果蔬切丁机的设计

国内现有切丁机存在着结构复杂、生产效率低、切出10mm以上果蔬大丁形状不规整的问题,无法满足国内果蔬加工业的发展需求。提出采用离心切削法进行果蔬切片、圆盘刀切丝、横切刀切丁的三维切丁技术的新型果蔬切丁机方案。通过对果蔬的切丁成型分析,得到切10mm以上果蔬大丁形状不规整的原因。仿真分析得到切丁机推进器和横切刀之间的速比以及两者之间的中心位置布置的合理组合。对切丁机主要结构部件进行了设计,研制果蔬切丁机样机。性能试验表明:切出的(15×15×15)mm和(20×20×20)mm马铃薯立方块形状规整,其相对百分数均小于15%,达到了设计要求。