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Eric Thibout - One of the best experts on this subject based on the ideXlab platform.
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consequences for a specialist insect and its parasitoid of the response of allium porrum to conspecific herbivore attack
Physiological Entomology, 2006Co-Authors: Sebastien Dugravot, Eric ThiboutAbstract:Recent studies on the Leek Allium porrum L. demonstrate that a sharp increase in the release of volatile and nonvolatile sulphur compounds occurs in response to attack by the specialist phytophage, the Leek moth Acrolepiopsis assectella (Zeller). The consequences of that response on the developmental capacity and behaviour of the Leek moth and on the host-searching behaviour of the parasitoid hymenoptera Diadromus pulchellus Wesmael have been studied. No immediate adverse effect on larval development is seen, but the duration of male development is significantly longer. In addition, an almost 20% decrease is observed in the number of oocytes produced by adult females that developed on attack-damaged Leek plants. Leek moths do not avoid damaged plants system- atically. On attacked plants, larvae tend to consume more and females to lay more eggs, although the latter tendency disappears after intensive attack. Concerning host-searching by D. pulchellus, the data indicate that females make use of the induced Leek response. Parasitoids are attracted more strongly to attacked plants than to undamaged plants and mechanically damaged plants. The results of this study in a tritrophic system involving a biannual plant suggest a complex defence system combining direct and indirect mechanisms. Sulphur compounds may act by reducing second-generation pests, thereby preventing the specialist insect population from exploding at the expense of the Leek.
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increased sulfur precursors and volatiles production by the Leek allium porrum in response to specialist insect attack
Journal of Chemical Ecology, 2005Co-Authors: Sebastien Dugravot, Nicole Mandon, Nathalie Mondy, Eric ThiboutAbstract:To defend themselves against herbivory, plants use a variety of direct and indirect strategies involving induced increases in secondary substances. Species of the Allium genus (Alliaceae), such as the Leek Allium porrum (L.), produce nonprotein sulfur amino acids derived from cysteine, i.e., alk(en)yl-cysteine sulfoxides that are precursors of volatile thiosulfinates and disulfides. These defend most species including the specialist Leek moth, Acrolepiopsis assectella. We determined by measuring the increase in the sulfur precursor propyl-cysteine sulfoxide (PCSO) if production of this precursor is induced in response to moth attack and mechanical wounding. The concentration of PCSO was determined by HPLC in 2- or 6-mo-old Leeks after attacks of various intensity either by the specialist Leek moth or by a generalist moth, Agrotis ipsilon. Injury-induced release of sulfur volatiles was measured by GC/MS after the attacks. Results showed an increase in the production of sulfur compounds in both the precursor and volatile form, occurring only in association with intensive attacks by Leek moths. The increase in sulfur precursors also led to an increase in the release of sulfur volatiles. This induced response may provide an effective defense strategy against the plant’s main natural enemy, both directly and indirectly by attracting entomophagous insects.
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origin and identification of bacteria which produce kairomones in the frass of acrolepiopsis assectella lep hyponomeutoidea
Cellular and Molecular Life Sciences, 1995Co-Authors: Eric Thibout, J F Guillot, S Ferary, P Limouzin, J AugerAbstract:The volatiles used by the parasitoidDiadromus pulchellus to find its host, the Leek moth, are produced by the bacteria developing in the frass of the host larvae. The origin and the nature of these bacteria were investigated. Samples were taken from healthy Leeks and from infested Leeks in the field, as well as from the frass of larvae reared in the laboratory either on the host plant or on an artificial diet. The various species of bacteria identified were cultured in the presence of precursors of Leek sulphur volatiles and their volatile emissions were analysed.Klebsiella oxytoca and variousBacillus, common decomposers of plant matter, were the principal species producing active volatiles which were alkyl disulphides.
Anastasios S. Siomos - One of the best experts on this subject based on the ideXlab platform.
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Effect of degree of cutting of Leek on physicochemical characteristics of Greek traditional sausages.
Meat Science, 2007Co-Authors: F. Papastamatiou, Dimitrios Gerasopoulos, Anastasios S. Siomos, J.g. BloukasAbstract:Fresh-cut Leek is one of the principal ingredients of Greek traditional sausages. In this study the effect of the degree of cutting of Leek on the physicochemical traits of Greek traditional sausages was investigated. Leek was cut to three different degrees (coarse, medium and fine), before being mixed with meat, salt and seasonings; the mixture was placed in natural casings and stored for six days at 15-18°C. Sausages lost about 25% of their initial weight by the end of storage. While pH decreased in all treatments, it was significantly more so (to pH 4.1) in sausages with fine-cut Leek, from as early as the second day of storage. During storage all sausages showed a decrease in lightness and a change in colour from yellow to red. The internal atmosphere of the sausages with fine-cut Leek showed peak CO(2) concentrations of 30% while those with coarse and medium-cut Leek showed peak CO(2) concentrations of 20% by day one of storage and equibrated to 5%. Ethylene in the internal atmosphere of sausages with fine and medium-cut Leek peaked by day one at 5.5μll(-1) but to only 2μll(-1) for those with coarse-cut Leek. Sausage nitrate content and antioxidant capacity did not show major differences between treatments. Fine-cut Leek contributed to sausage stability and quality more rapidly than medium or coarse-cut Leek.
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effect of Leek and onion on processing and quality characteristics of greek traditional sausages
Meat Science, 2004Co-Authors: G.a. Fista, J.g. Bloukas, Anastasios S. SiomosAbstract:The objective of this study was to investigate the effect of Leek and onion on processing and quality characteristics of sausages and select the most appropriate, to determine the optimum level of selected vegetable and to improve its effectiveness on quality characteristics of sausages, in comparison to the addition of nitrites (100 ppm), by using a starter culture of Staphylococcus carnosus and ascorbate. The nitrate content of Leek ranged from 213 to 255 ppm and that of onion was 79 ppm. Sausages produced with Leek had higher (p<0.05) nitrite content (1.3-2.1 ppm) and a (∗)(+) values and higher scores for sensory attributes than sausages with onion. Sausages made with the total Leek plant had the highest score for overall acceptability. The higher the Leek level the higher the nitrate and nitrite content of sausages and the lower the redness, a (∗)(+). Sausages with 240 g of Leek/kg had the highest (p<0.05) overall acceptability. Sausages with higher Leek level had an intensive wrinkling on the surface and also an intensive and undesirable green colour. Sausages produced with 240 g of Leek/kg had the same low level of nitrate and nitrite content, higher weight losses and lower pH values after the 3rd day of storage, compared to sausages produced with the addition of sodium nitrite. The addition of starter culture and ascorbic acid improved the redness (a (∗)) of sausages and reduced the 2-thiobarbituric acid value. Sausages with Leek, starter culture and ascorbic acid had the highest score for odour and taste and overall acceptability.
Hanne Lakkenborg Kristensen - One of the best experts on this subject based on the ideXlab platform.
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Stepwise incorporation of white clover (Trifolium repens L.) as fertiliser increases nitrogen fixation and improves nitrogen retention when intercropped with Leek (Allium porrum L.)
Plant and Soil, 2017Co-Authors: Yue Xie, Karen Koefoed Petersen, Jorn Nygaard Sorensen, Hanne Lakkenborg KristensenAbstract:Background and aimsWe investigated whether the incorporation of intercropped white clover as a split-dose fertiliser improves N retention of the plant-soil system in Leek production.MethodsWhite clover and Leek were grown in pots where clover was stepwise incorporated into soil as fertiliser. Half of the clover was incorporated before Leek transplantation (LT), the other half was incorporated 26 (S1) or 41 (S2) days after LT, compared with full incorporation of all clover (F) before LT. 15N injection and leaching studies were performed to investigate interspecific competition and the effects of precipitation on soil N availability.ResultsStepwise incorporations increased or had no effect on Leek growth, despite competition for N between white clover and Leek. Compared to F, Leek grown with stepwise incorporations had similar and lower N accumulation before the second incorporation, but N was higher at the end of the experiment. N2 fixation by white clover increased the total N input into soil and matched N availability with Leek N demand and growth rate. Loss of inorganic N by leaching was lowest in S2 and highest in F.ConclusionsStepwise incorporations of white clover improved N retention in the plant-soil system and could be used to increase Leek yield.
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intercropping Leek allium porrum l with dyer s woad isatis tinctoria l increases rooted zone and agro ecosystem retention of nitrogen
European Journal of Agronomy, 2017Co-Authors: Yue Xie, Hanne Lakkenborg KristensenAbstract:Nitrate leaching can be high in organic vegetable production. Late-harvested crops like Leek limit the use of autumn catch crops. The aim of this study was to investigate the growing of a combination of a deep-rooted catch crop and a shallow-rooted vegetable to reduce the risk of nitrate leaching. We compared a Leek sole crop (S) with two intercropped systems of Leek and early-sown dyer’s woad (five weeks after Leek planting) (IE) or late-sown dyer’s woad (eight weeks after Leek planting) (IL) in two seasons: 2012 and 2013. To reveal root and resource competition, Leek with dyer’s woad rows left empty (Semp), and early and late-sown dyer’s woad with Leek rows left empty (DEemp, DLemp) were included. Yield, dry above-ground biomass, aboveground N accumulation and soil inorganic N (Ninorg) were measured as well as root growth by use of minirhizotrons to 2.3 m soil depth. Results showed that the marketable yield of Leek in IE and IL systems was comparable with the yield in the S system when calculated per length of Leek row. The Relative Competition Index (RCI) revealed that interspecific competition facilitated the growth of Leek but hampered that of dyer’s woad. The rooted zone increased from 0.5 m in the S system to more than 2 m depth in those of the intercropped systems. Dyer’s woad ceased growing above ground but kept growing below ground after crop harvest and extended roots under the Leek root system in 2012. Intercropping increased the root intensity of late-sown dyer’s woad after Leek harvest in the 0.75–1.75 m soil layer compared to dyer’s woad growing alone (DLemp), while the root depth was not affected. The intercropped system with early-sown dyer’s woad reduced soil Ninorg by 52 kg ha−1 relative to the sole-cropped system, and dyer’s woad accumulated 48 kg N ha−1 in aboveground biomass at harvest in 2013. Late-sown dyer’s woad had fewer roots, left higher soil Ninorg and had lower aboveground N accumulation than early-sown dyer’s woad until the following spring. Therefore, early-sown dyer’s woad is applicable in an organic intercropped system with high yields of Leek to decrease the risk of nitrate leaching.
Sebastien Dugravot - One of the best experts on this subject based on the ideXlab platform.
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consequences for a specialist insect and its parasitoid of the response of allium porrum to conspecific herbivore attack
Physiological Entomology, 2006Co-Authors: Sebastien Dugravot, Eric ThiboutAbstract:Recent studies on the Leek Allium porrum L. demonstrate that a sharp increase in the release of volatile and nonvolatile sulphur compounds occurs in response to attack by the specialist phytophage, the Leek moth Acrolepiopsis assectella (Zeller). The consequences of that response on the developmental capacity and behaviour of the Leek moth and on the host-searching behaviour of the parasitoid hymenoptera Diadromus pulchellus Wesmael have been studied. No immediate adverse effect on larval development is seen, but the duration of male development is significantly longer. In addition, an almost 20% decrease is observed in the number of oocytes produced by adult females that developed on attack-damaged Leek plants. Leek moths do not avoid damaged plants system- atically. On attacked plants, larvae tend to consume more and females to lay more eggs, although the latter tendency disappears after intensive attack. Concerning host-searching by D. pulchellus, the data indicate that females make use of the induced Leek response. Parasitoids are attracted more strongly to attacked plants than to undamaged plants and mechanically damaged plants. The results of this study in a tritrophic system involving a biannual plant suggest a complex defence system combining direct and indirect mechanisms. Sulphur compounds may act by reducing second-generation pests, thereby preventing the specialist insect population from exploding at the expense of the Leek.
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increased sulfur precursors and volatiles production by the Leek allium porrum in response to specialist insect attack
Journal of Chemical Ecology, 2005Co-Authors: Sebastien Dugravot, Nicole Mandon, Nathalie Mondy, Eric ThiboutAbstract:To defend themselves against herbivory, plants use a variety of direct and indirect strategies involving induced increases in secondary substances. Species of the Allium genus (Alliaceae), such as the Leek Allium porrum (L.), produce nonprotein sulfur amino acids derived from cysteine, i.e., alk(en)yl-cysteine sulfoxides that are precursors of volatile thiosulfinates and disulfides. These defend most species including the specialist Leek moth, Acrolepiopsis assectella. We determined by measuring the increase in the sulfur precursor propyl-cysteine sulfoxide (PCSO) if production of this precursor is induced in response to moth attack and mechanical wounding. The concentration of PCSO was determined by HPLC in 2- or 6-mo-old Leeks after attacks of various intensity either by the specialist Leek moth or by a generalist moth, Agrotis ipsilon. Injury-induced release of sulfur volatiles was measured by GC/MS after the attacks. Results showed an increase in the production of sulfur compounds in both the precursor and volatile form, occurring only in association with intensive attacks by Leek moths. The increase in sulfur precursors also led to an increase in the release of sulfur volatiles. This induced response may provide an effective defense strategy against the plant’s main natural enemy, both directly and indirectly by attracting entomophagous insects.
Nathalie Bernaert - One of the best experts on this subject based on the ideXlab platform.
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antioxidant changes during domestic food processing of the white shaft and green leaves of Leek allium ampeloprasum var porrum
Journal of the Science of Food and Agriculture, 2014Co-Authors: Nathalie Bernaert, Marc De Loose, Erik Van Bockstaele, Bart Van DroogenbroeckAbstract:BACKGROUND Evaluating the effect of domestic cooking on the health benefits of vegetables has great practical importance. However, only a limited number of reports provide information on the effect of these treatments on the antioxidant capacity, polyphenol and S-alk(en)yl-l-cysteine sulfoxide (ACSO, e.g. isoalliin and methiin) content of the white shaft and green leaves of Leek (Allium ampeloprasum var. porrum). RESULTS In the present study, the antioxidant capacity of Leek was highly influenced by cooking (blanching, boiling and steaming). Boiling had a negative effect on total phenolic content in the white shaft and green leaves. An obvious increase could be observed in the antioxidant capacity of the steamed green leaves, while steaming did not influence the polyphenolic content. Remarkably, blanching resulted in a slight increase in the ACSO content. Subjecting Leek samples to a longer thermal treatment appeared to have a negative influence on the ACSO content in Leek. Steaming was also responsible for a decrease in ACSOs. Methiin was less susceptible to heat treatment than isoalliin. CONCLUSION In general, steaming appeared to be responsible for better retention of the bioactive compounds present in Leek compared with boiling. © 2013 Society of Chemical Industry
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antioxidant changes during postharvest processing and storage of Leek allium ampeloprasum var porrum
Postharvest Biology and Technology, 2013Co-Authors: Nathalie Bernaert, Herve De Clercq, Marc De Loose, Erik Van Bockstaele, Bart Van DroogenbroeckAbstract:The evaluation of the impact of postharvest processing and storage on the health benefits of vegetables is of great practical importance. Reports on their effect on the antioxidant capacity, polyphenol and S-alk(en)yl-l-cysteine sulfoxide (ACSO) content, i.e. isoalliin and methiin of the white shaft of Leek (Allium ampeloprasum var. porrum), however, are limited. This study determined the levels of the antioxidant properties of Leek from postharvest processing at the farm until refrigerated storage of 13 days at the consumer. Two cases were investigated, (1) Leek sold as an entire plant and (2) Leek with a large part of the green leaves removed, where the shafts are sold in a plastic package. The antioxidant capacity and the total content of phenolic compounds in the white shaft of the entire and packaged Leek was stable during 13 days of refrigerated storage. A significant increase in the concentration of isoalliin was observed. Comparing the entire and processed/packaged Leek, significant differences could be observed in antioxidant properties. The ACSO content in the white shaft of packaged Leek was significant lower than the content in the white part of the entire Leek. Therefore, the minimal processing step of cutting the green leaves and roots had an influence on the levels of antioxidant properties.
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Species diversity, community dynamics, and metabolite kinetics of spontaneous Leek fermentations
Food Microbiology, 2013Co-Authors: Dorrit Wouters, Nathalie Bernaert, Marc De Loose, W. Conjaerts, B. Van Droogenbroeck, L. De VuystAbstract:Leek (Allium ampeloprasum var. porrum) is one of Belgium's most important vegetables. All or part of the green Leek parts are often left on the fields because of their limited cooking applications compared to the white Leek parts. Therefore, the possibility to perform Leek fermentations in view of product valorization and diversification was investigated. This study deals with the community dynamics, species diversity, and metabolite kinetics of spontaneous Leek fermentations, thereby studying the influence of added NaCl concentration, harvesting season, and duration of the fermentation. The combination of a culture-dependent and culture-independent approach revealed the prevalence of lactic acid bacteria (LAB) from the third day of fermentation onwards, which was not influenced by the fermentation conditions applied. Enterobacteriaceae, Pseudomonadaceae, and yeasts disappeared after one week of fermentation. Leuconostoc mesenteroides, Lactobacillus sakei, and Lactobacillus plantarum, Lactobacillus brevis, and Lactobacillus parabrevis were the most frequently isolated LAB species. Both added NaCl concentrations were suitable to perform successful fermentations within three weeks. By that time, glucose and fructose, the main Leek carbohydrates, were metabolized into mainly lactic acid, acetic acid, ethanol, and mannitol. A sensory analysis revealed that the fermented white Leek parts were generally more appreciated than the fermented green Leek parts.
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Application' and validation of autochthonous lactic acid bacteria starter cultures for controlled Leek fermentations and their influence on the antioxidant properties of Leek.
International Journal of Food Microbiology, 2013Co-Authors: Dorrit Wouters, Nathalie Bernaert, Marc De Loose, B. Van Droogenbroeck, N. Anno, E. Van Bockstaele, L. De VuystAbstract:Abstract Leek ( Allium ampeloprasum var. porrum ) is one of Belgium's most important outdoor vegetables, mainly cultivated for its white shaft. Fermentation of Leek offers opportunities in view of biomass valorization and product diversification. This study deals with the implementation and validation of starter cultures to perform controlled Leek fermentations and to ensure a high quality of the end-products. Therefore, a thorough study of the fermentation microbiology and the influence of three starter culture strains ( Lactobacillus plantarum IMDO 788, Lactobacillus sakei IMDO 1358, and Leuconostoc mesenteroides IMDO 1347) on the metabolite kinetics of Leek fermentation and antioxidant properties of Leek was performed. Overall, the application of lactic acid bacteria starter cultures resulted in a fast prevalence of the species involved, coupled to an accelerated acidification. Of the three starter cultures tested, the mixed starter culture of L. plantarum IMDO 788 and L. mesenteroides IMDO 1347 was most promising, as its application resulted in fermented Leek of good microbiological quality and in a more extensive carbohydrate consumption, whereby diverse end-metabolites were produced. However, high residual fructose concentrations allowed yeast outgrowth, resulting in increased ethanol and glycerol concentrations, and indicated the lack of a prevailing strictly heterofermentative LAB species. The antioxidant capacity of fermented Leek samples, as measured with the oxygen radical absorbance capacity assay, increased when starter cultures were used, whereas with regard to 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity, only Leek fermented with L. sakei IMDO 1358 scored higher than spontaneously fermented Leek. The total phenolic content was not influenced by the use of starter cultures, while the S -alk(en)yl- l -cysteine sulfoxides content decreased strongly. A preliminary sensory analysis revealed that the spontaneously fermented Leek and the one obtained with the mixed starter culture were preferred by consumers, emphasizing again the importance of microbial successions in vegetable fermentations.
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Antioxidant capacity of different Leek types and the comparison with its related species
Acta Horticulturae, 2012Co-Authors: Nathalie Bernaert, Marc De Loose, B. Van DroogenbroeckAbstract:Extracts of the white part and green leaves of 3 Leek cultivars and 7 related species (Egyptian Leek, Chinese Leek, chives, onion (red and white), bunching onion and shallot) were investigated for their antioxidant properties, including free radical scavenging activities against peroxyl (ORAC) and 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH) and their Fe3+ reducing capacity (FRAP). The results from this study suggest that the green leaves generally have significantly stronger antioxidant properties than the white part, except for the ORAC and DPPH results of Allium fistulosum (bunching onion) and the DPPH results of Allium cepa (onion, 'Red Creole'). In general, extracts of red onion gave the highest antioxidant capacity. The antioxidant capacity of the white shaft of Leek was in most of the cases in the same range as the antioxidant capacity of the bulb of the related species, except for Allium cepa ('Red Creole') and Allium fistulosum. The green leaves of Leek contained a significantly lower antioxidant capacity as compared with the green leaves of the other related species.
