Evaluation of Zataria multiflora Boiss. essential oil activity against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes by propidium monoazide quantitative PCR in vegetables

Essential oils (EOs) have long been applied as flavoring agents in foods, and due to their content in antimicrobial compounds, they have potential as natural agents for food preservation. Recently, real-time PCR in combination with PMA has successfully been applied to discriminate between live Escherichia coli O157:H7 and dead bacteria killed by cumin, clove, oregano and cinnamon EOs. In this study, initial experiments were performed in order to elucidate the minimum bactericidal concentration of Zataria multiflora EOs on E. coli O157:H7, Salmonella enterica and Listeria monocytogenes. Thereafter PMA-qPCR was applied in order to selectively quantify life cells within a bacterial population treated with Z. multiflora EO. Inactivation was obtained at EO concentrations of 0.02, 0.035, 0.045 for L. monocytogenes, E. coli O157:H7 and S. enterica, respectively. L. monocytogenes were totally killed in 30 min while it took 1 h 30 min for the gram negative pathogens. As a conclusion Z. multiflora EO has potential as natural food additive or biopreservative since it was able to irreversibly inactivate the three pathogens tested, at lower concentrations than other EOs and short exposition times. In addition, the PMA-qPCR approach proved efficient to selectively detect live pathogenic bacteria in vegetables following inactivation with Z. multiflora EO.     

Consumption of raw vegetables and fruits: a risk factor for Campylobacter infections

The purpose of this study was to determine the prevalence of Campylobacter in fresh vegetables and fruits at retail level in the Netherlands, and to estimate its implications on the importance of vegetables and fruits as risk factor for campylobacteriosis.Thirteen of the 5640 vegetable and fruit samples were Campylobacter positive, resulting in a prevalence of 0.23% (95% confidence interval (Cl): 0.12-0.39%). The prevalence of packaged products (0.36%, 95% Cl: 0.17-0.66) was significantly higher than of unpackaged products (0.07; 95% Cl: 0.01-0.27). No statistical differences were found between seasons.Combining the mean prevalence found in this study with data on the consumption of vegetables and fruits, an exposure of 0.0048 campylobacters ingested per person per day in the Netherlands by transmission via vegetables and fruits, was calculated. This exposure, as input in a Beta-Poisson dose-response model, resulted in an estimated number of 5.3 × 10⁵ cases of infection with Campylobacter per year for the whole Dutch population. This constitutes the consumption of raw vegetables and fruits, especially when packaged, to be a risk factor for Campylobacter infections.     

栅栏技术在鲜切菜生产中的应用

介绍了栅栏技术的基本原理,分析了鲜切莱易出现的质量问题及控制鲜切菜质量的栅栏因子,概述了栅栏技术在鲜切菜生产中的应用。     

螺旋杀青机的热力学分析及结构参数的确定

通过对螺旋杀青机的热力学过程的分析，得出杀青机满足果蔬杀青效果所应具有的机械参数，即杀青机长度L，杀青机的外箱体的下圆弧半径R2，滚筒的外径R1，内径r等，为设计杀青机CAD的专用软件奠定了理论基础。     

Carotenoids and chlorophylls in processed xanthophyll-rich food

Processing of food modifies nutrient contents and food matrices. The present analyses provide information about the effects of heat steam sterilization (HSS), high pressure processing (HPP) and common household cooking on the stability of carotenoids and chlorophylls in spinach, parsley, dill and kale. For HSS, samples were heated in an autoclave for 5, 10, 15 and 20 min at 121 °C. Additionally, one sample was treated via HPP at 200, 400 and 600 MPa for 5, 10 and 40 min at room temperature. Carotenoid and chlorophyll contents were determined by reversed-phase HPLC. Lutein was the most abundant carotenoid in all samples. Furthermore, violaxanthin, zeaxanthin, β-carotene, chlorophylls a and b were quantified. Thermal treatment via HSS led to a significant decline of contents of lutein, chlorophylls a and b. HPP did not reduce the amounts of xanthophylls and chlorophylls. Conclusively, HPP seems to be a good alternative to HSS for the preservation of xanthophyll-rich food.     

混合辐照饲料喂养大鼠的骨髓多色性红细胞微核细胞率观察

本文用两组辐照饲料对Wistar大鼠进行了110天和150天喂养,观察其骨髓多色性红细胞(PCE)的微核效应。一组为混合辐照饲料组,辐照饲料占80％;另一组为辐照蔬菜组,辐照蔬菜占总饲料的3％,辐照剂量为2KGy,是实际需要的辐照剂量2倍以上。同时设有普通饲料的阴性对照组,和用环磷酰胺处理或给以全身整体照射的阳性对照组。微核测定采用Giemsa染色法、Harris苏本精复染法和荧光染色法,两批实验均表明,在本实验条件下,不论是喂养混合辐照饲料还是辐照蔬菜,都未见到大鼠骨髓PCE微核细胞率有所增高。     

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。