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Acta Alimentaria
Authors:
B. Šimundić
,
G. Krešić
,
A. Živkovićb
, and
B. Medugorac

Pesticides are used with the aim to control insects, diseases, fungi and other pests.  Along with the benefits, there are potential effects from trace amounts of residues remaining on fruits and vegetables. The objective of this study was to check for compliance with the maximum residue levels in fruits and vegetables from Kvarner region of Croatia. 14 Fourteen sorts of  vegetables and 6 sorts of fruits (n = 263), randomly selected from market,  were analysed for organochlorine, organophosphorus and fungicide residues. Multi residue analysis using GC/NPD, GC/ECD  and spectrophotometric methods were performedapplied. The results of this study indicated that though all the commodities were contaminated with pesticides, the levels were low and residues above MRL were found only in 1.52% of  samples. All other levels were below the criteria for maximum residue limits established by Croatia and the EU.

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Summary

An improved analytical method for determining the fungicide dimethomorph in vegetables is described. The method involved single extraction with dichloromethane followed by gas chromatography-tandem mass spectrometry (GC-MS/MS) determination. The average recovery rates from vegetable samples spiked with dimethomorph at 10 and 100 μg kg−1 (n = 5) ranged between 81 and 96% and with associated relative standard deviations ≤9%. The limits of detection (LOD) and limits of quantification (LOQ) were below 10 μg kg−1 for the three studied matrices, i.e., tomato, cucumber, and onion. Successful application of the method to the analysis of samples with incurred dimethomorph residues has been demonstrated.

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Acta Alimentaria
Authors:
K. Skowron
,
K. Grudlewska
,
D. Lewandowski
,
P. Gajewski
,
A. Reśliński
, and
E. Gospodarek-Komkowska

L. monocytogenes poses a serious threat to public health, since most cases of listeriosis are connected with eating contaminated food. L. monocytogenes is often detected both in fresh and frozen vegetables.

The aim of this study was to evaluate the antibiotic susceptibility and ability to form biofilm of L. monocytogenes strains isolated from frozen vegetable mixtures in Poland.

Ninetynine genetically different strains were found among 100 isolates of L. monocytogenes. Among the 99 strains, 80 (80.8%) were susceptible to all tested antibiotics. Nineteen (19.2%) strains were resistant to one or more antibiotics. From this group of L. monocytogenes strains, most strains were resistant to erythromycin (16; 16,1%), penicillin (15; 15.1%), meropenem (12; 12.1%), cotrimoxazole (12; 12.1%), and ampicillin (3; 3.1%). According to the obtained results, differences in intensity of biofilm, both between those isolated in successive years and in the particular year, were observed. Performed analysis showed statistically insignificant faint negative correlation (r=–0.088) between the number of antibiotics to which strains were resistant and the intensity of biofilm formation by them.

Food contamination with L. monocytogenes poses a threat to consumers, therefore it is necessary to monitor their antibiotic susceptibility, ability to form biofilm, and genetic similarity, in order to evaluate the strains persistence time in plant.

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This work describes the comparison of five sample extraction methods for the determination of pesticide residues in grapes and vegetables by using gas chromatography—time-of-flight mass spectrometry (GC—TOF-MS). These methods were based on original methods QuEChERS, mini-Luke, ethyl acetate, and DIN EN 15637, and some of these were slightly modified to increase the number of identified and quantified pesticides, to improve their quantification limits, and to be fast and less expensive in terms of material cost. The acceptable performance parameters combined with the properties of easy and quick handling and cost-effectiveness have made mini-Luke modified extraction method as the most favorable in the pesticide residues analysis from grapes and tomatoes by GC—TOF-MS. The efficiency of the chosen extraction method was also verified for lettuce; for this matrix, a cleanup step with graphitized black carbon (GBC) was added. Analysis of extracts was carried out by GC—TOF-MS within 29.2 min run time. The GC method was validated for grapes and tomatoes in terms of linearity, accuracy, limit of detection (LOD), and limit of quantification (LOQ). Good linearity with correlation coefficients (r 2) higher than 0.98 was obtained. For most analytes from both matrices, recoveries were in the range of 71–120% and LOQ values in the range of 0.01–0.05 mg kg−1. The GC—TOF-MS and modified mini-Luke extraction methods were successfully tested on real vegetable and fruit samples belonging to the same commodities group as those from validated methods according to European Guide DG SANCO 12571/2013 (tomatoes, pepper, cucumber, potatoes, carrots, eggplants, onion, lettuce and grapes) and in proficiency EU tests.

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The texture changes during the initial phase of blanching of potatoes, carrots and green peas at different blanching times (0–240 s) and temperatures (85 °C, 95 °C, 100 °C) were investigated. The breaking force (N) was determined by compression or Back extrusion tests with an Instron texture tester. Electronmicroscopic studies (SEM) were made to support the interpretation of the results.For each vegetable several sections of changes of the breaking force (lnF) were identified. For potatoes a three phase change of the breaking force by all temperatures (85 °C, 95 °C, 100 °C) was observed. In the first of the 3 different observed stages of potato blanching the breaking forces increased with time (0–40 s). In the second and third stage of the blanching process of potato a linear relationship was found between the logarithm of the breaking force and the blanching time. The second phase observed was faster (40–160 s) than the consecutive slower third phase (160–240 s).For green peas the change of the breaking force (lnF) can be described by two consecutive first rate reactions. A faster decreasing period between 0–25 s was followed by a slower decreasing one between 70–140 s. Between the first and second stage of the blanching process there was an initial lag period (25–70 s), which will not be described here. In the period after 140 s, there was not any change, this period is constant.For carrots the fastest change can be observed at 100 °C compared to the results at 85 and 95 °C. A three-phase curve was observed as well. An initial lag period (0–90 s) was followed by a faster (90–190 s) and a slower (190–240 s) decreasing one. In the second and third stage of the blanching process of carrots a linear relationship was found. For the changes of the breaking force (lnF) a kinetical approach was applied, reaction rate constants and apparent activation energies were calculated. The kinetical approach helps to compare and forecast changes at different process conditions.

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Vegetables are the major source of dietary nitrate, with wide variations in nitrate content. The presence of nitrate in vegetables is often associated with harmful effects on human health, i.e. with toxic effects of methaemoglobinaemia and the possibility of causing an endogenous formation of carcinogenic N-nitroso compounds. However, it is also associated with beneficial health effects, since nitrate represent an important alternative pathway to bioactive NO and its important physiological roles in vascular and immune function. In this review the concentrations of nitrate in different vegetables from different countries are given. Furthermore, the reasons for the different contents of nitrate in vegetables, the daily intakes and comparisons to the acceptable daily intake (ADI) values, legislation, metabolism and toxicology of nitrate are described as well as harmful and beneficial effects of nitrate on human health.

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Thrips (Thysanoptera) and their predators were investigated from 2005–2007 on a wide range of vegetables grown mostly in the winter period in Çukurova region of Turkey. A total of 2989 adult thrips and 406 thrips larvae were extracted from the vegetables. The adults belonged to 14 thrips species of which Melanthrips spp. were the most dominant species. The dominance of the commonly found pests Thrips tabaci and Frankliniella occidentalis differed greatly. F. occidentalis was the predominant thrips infesting broad bean, lettuce and parsley, while T. tabaci was more abundant on leek, onion and pea. The most thrips were collected from flowers or heads of vegetables in early spring. Numbers of predatory insects dwelling on the sampled vegetables were lower in comparison to total numbers of thrips obtained in the years 2006 and 2007. Of the predators, the hemipteran generalists Orius laevigatus and O. niger were the most prevalent and high numbers of them were recorded often on flowers of broad bean in winter. Further investigations should be planned to understand clearly the predatory habit of Melanthrips .

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The present paper evaluates the results of field experiments conducted during two consecutive growth seasons (2008–2009) to assess the environmental impact of cement dust pollution on foliar physiology (pigments), growth performance and yield of three commonly cultivated vegetable crops, tomato (Lycopersicon esculentum), radish (Raphanus sativus) and knol-khol (Brassica oleracea var. gongyloides) in Kashmir Himalayan valley, India. Two experimental sites (S1, S2) were selected in the vicinity of the cement factory at Khrew, Pulwama (Kashmir) at a distance of 0.5 km (S1) and 2 km (S2) and compared with a dust free control site (S3) located at about 6 km from the factory in a crosswind direction. The data revealed that cement dust had an adverse effect on morphological and biochemical characteristics of the crops. Differential level of crop sensitivity to cement dust was markedly evident. Knol-khol (Brassica oleracea var. gongyloides) reflected a higher degree of tolerance to particulate emissions as compared to tomato (Lycopersicon esculentum) and radish (Raphanus sativus). Photosynthetic pigment analysis showed adverse impact on chlorophyll-a, while chlorophyll-b marginally decreased in the leaves of tomato plants at S1; the effect being non-significant for the other test crops. Carotenoids also exhibited a remarkable reduction due to cement dust impact. The yield of tomato recorded severe losses (12.28–23.95%) as compared to radish (7.46–21.4%), while the effect was non-significant in knol-khol. Other growth and yield related attributes also followed a similar trend; tomato and radish showing remarkable effects in response to cement dust and knol-khol showed the least effect. The soil characteristics indicated significant reduction in available P. Except available N, other variables (pH, conductivity, available K, exchangeable Ca and Mg) recorded higher values in the polluted soils as compared to control. The need for installation of appropriate devices in cement manufacturing factories to combat the emission of dust in ambient environment together with environmental monitoring of agro-ecosystems is stressed.

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Progress in Agricultural Engineering Sciences
Authors:
Mai Sao Dam
,
Vuong Duc Nguyen
,
Tamás Zsom
,
Lien Le Phuong Nguyen
, and
Géza Hitka

Introduction Fruits and vegetables are essential foods for daily healthy diet. The postharvest ripening results in changing the quality of products including nutrition and appearance ( Liu, 2014 ). Thus, maintaining quality of fruits and vegetables

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characteristics for the quality assessment of tomatoes. Fruit, Nut, and Vegetable Production Engineering , 487–492. Dewulf, W., P. Jancsók, B. Nicolai, G. De Roeck, D. Briassoulis (1999): Determining the Firmness of a

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