Synthesis and sensorial properties of mercaptoaldehydes   总被引：1，自引：0，他引：1  

Vermeulen C  Collin S 《Journal of agricultural and food chemistry》2002,50(20):5654-5659

Mercaptoalcohols and mercaptoketones have been described in the past decade as relevant character-impact compounds in various food products. On the other hand, very little is known of mercaptoaldehydes. Only 3-mercapto-2-methylpentanal and 3-mercaptohexanal have been found in onions and beef liver, respectively. The aim of this work was to synthesize 13 mercaptoaldehydes not commercially available by combinatorial chemistry. Chromatographic analyses of the mixture allowed the determination of their retention indices and mass spectroscopy fragments for further identification in foods. Gas chromatography-olfactometry demonstrated how some of them are characterized by unusual odor and very low perception threshold.  相似文献   

Establishment of feline intestinal epithelial cell cultures for the propagation and study of feline enteric coronaviruses     

Lowiese MB Desmarets  Sebastiaan Theuns  Dominique AJ Olyslaegers  Annelike Dedeurwaerder  Ben L Vermeulen  Inge DM Roukaerts  Hans J Nauwynck 《Veterinary research》2013,44(1):71

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Soil,crop and emission responses to seasonal-controlled traffic in organic vegetable farming on loam soil     

G.D. Vermeulen  J. Mosquera 《Soil & Tillage Research》2009,102(1):126-134

Some organic arable and vegetable farms in the Netherlands use cm-precise guidance of machinery to restrict wheel traffic to fixed traffic lanes and to achieve non-trafficked cropping zones with optimized soil structure in between the lanes. Contrary to controlled traffic farming (CTF) the traffic lanes are not yet used for harvesting and primary tillage. Therefore, the system is called a seasonal-controlled traffic farming (SCTF) system. A field experiment was conducted on an organic vegetable farm to reveal soil, crop and emission responses of SCTF with traffic lanes at 3.15-m centres compared with conventional random traffic farming (RTF) using low ground pressures in spring from 2002 till 2005. The traffic systems were investigated in the crops green pea (Pisum sativum L.), spinach (Spinacea oleracea L.), onions (Allium cepa L.) and carrots (Daucus carota L.). Compared with RTF, the topsoil structure in the SCTF system improved for the crops sown on the flat but not for carrot grown on ridges. Crop yields increased significantly in green pea, spinach and planted onion sets but not in carrot and direct-sown onion. The available N-min at the end of the cropping period was not different between systems and, therefore, leaching losses in winter are expected to be the same. SCTF resulted in a significant reduction of N₂O emissions (by 20–50% compared to RTF). For CH₄, application of the SCTF system resulted in increased CH₄ uptake (by a factor 5–20) compared to the RTF system in three of the four measured fields. At the fourth field, lower (but not significant) CH₄ emissions (by a factor 4) were measured in the SCTF system compared to RTF. Effects of SCTF on timeliness and on the economic feasibility are discussed.  相似文献   

Influence of peptide supply and cosubstrates on phenylalanine metabolism of Lactobacillus sanfranciscensis DSM20451(T) and Lactobacillus plantarum TMW1.468     

Vermeulen N  Ganzle MG  Vogel RF 《Journal of agricultural and food chemistry》2006,54(11):3832-3839

Bread spoilage is mainly due to the growth of filamentous fungi, and metabolites produced during sourdough fermentation by lactobacilli can inhibit fungal growth. One of these metabolites is phenyllactic acid (PLA), which is a catabolite from phenylalanine. In this work, the influence of peptide supply and cosubstrates was determined on PLA formation from phenylalanine by Lactobacillus plantarum TMW1.468 and Lactobacillus sanfranciscensis DSM20451(T). Transport of single amino acids is not efficient in lactobacilli, and only 1% of the offered phenylalanine was converted to PLA. PLA yields were increased 2-4-fold when peptides instead of single amino acids were used as a substrate. The accumulation of phenylalanine after peptide addition indicated that, after transport, transamination was the second limiting factor. In L. plantarum TMW1.468, PLA yields were increased from 5 to >30% upon the addition of alpha-ketoglutarate. In L. sanfranciscensis DSM20451, a combination of both citric acid and alpha-ketoglutarate increased PLA formation. The combined effect of citric acid and alpha-ketoglutarate can be attributed to changes in the NAD/NADH ratio.  相似文献   

Investigations into the cause of the phloem necrosis disease of Coffea liberica in Surinam,South America     

H. Vermeulen 《European journal of plant pathology / European Foundation for Plant Pathology》1968,74(6):202-218

The presence of the flagellatePhytomonas leptovasorum, Stahel in the phloem vessels ofCoffea liberica Bull. ex Hiern., suffering from phloem necrosis, was once more demonstrated. The association of the organism with the multiple division of sieve tubes in affected trees was confirmed. The different nature of a wilting disease caused by the fungusCeratocystis fimbriata Ellis et Halst. has again been established.No viruses, bacteria and nematodes could be detected as pathogenes of phloem necrosis.Although phloem necrosis is found almost exclusively in mature trees, it was possible to infect young ones by root grafting thesymptoms were, however, less acute here than in older trees. Other species ofCoffea can be affected, either by natural infection or by artificial inoculation, but there too, the symptoms—internal as well as external—are less severe than in, mature trees ofC. liberica. The way of natural infection is still unknown. Hemipteran insects are suspected to transmit the disease, since such insects are known to be vectors ofPhytomonas (=Leptomonas) davidi Lafont inEuphorbia spp. Attempts to grow the organism in pure culture have failed and hence its pathogenicity could not be established. However, the absence of any evidence towards fungi, viruses, nematodes or bacteria supports the hypothesis thatPhytomonas leptovasorum Stahel is the causal agent of the phloem necrosis disease ofCoffea liberica in Surinam.Samenvatting Het voorkomen van de flagellaatPhytomonas leptovasorum Stahel in het floëem van bomen vanCoffea liberica, die de typische verschijnselen van de zeefvatenziekte vertonen, is opnieuw aangetoond (Tabel 1). De flagellaat komt alleen voor in bomen met een abnormale deling (=multipele deling) van de zeefvaten (Fig. 1–6). Deze anatomische afwijking is kenmerkend voor de floëemnecrose en treedt niet op bij de verwelkingsziekte, veroorzaakt door de schimmelCeratocystis fimbriata (=Ophiostoma coffeae). Het onderzoek naar een mogelijke rol van virussen, nematoden en bacteriën heeft geen positieve resultaten opgeleverd.De ziekte komt in de natuur alleen voor in volwassen bomen (Fig. 7), maar het is opnieuw mogelijk gebleken om door middel van wortelenten deziekte op jonge bomen over te brengen (Tabel 2 and 3). De ziekteverschijnselen zijn dan echter minder extreem en het ziekteverloop niet fataal. Ook andereCoffea-soorten kunnen zowel natuurlijk als kunstmatig door de floëemnecrose worden aangetast. De verschijnselen zijn minder opvallend en de aangetaste bomen schijnen zich na, verloop van tijd te herstellen.Het is nog onbekend op welke wijze de ziekte in de natuur wordt overgebracht. Het vermoeden bestaat dat een insekt van de Hemiptera-groep de overbrenger is, aangezien deze insektenPhytomonas (=Leptomonas) davidi inEuphorbia spp. kunnen overbrengen. Pogingen om de flagellaten in reincultuur te kweken zijn mislukt. Het uiteindelijke bewijs datP. leptovasorum het pathogeen is kan daarom nog niet worden geleverd.This paper is dedicated to Prof. Dr. G. Stahel, whose meticulous observations proved to be correct after 30 years.  相似文献   

Purification of Cowdria ruminantium by immunoadsorbent affinity chromatography     

A W Neitz  N M Vermeulen 《The Onderstepoort journal of veterinary research》1987,54(3):247-253

Immunoselective methods with special reference to immunoadsorbent affinity chromatography as a means for the isolation of Cowdria ruminantium are reviewed. Attention is given to the source of the organism, immunization, purification of antibodies, coupling of antibodies to insoluble matrixes and desorption procedures.  相似文献   

The development of an ELISA-assay for semi-quantitative detection of dihydrogriesenin, a sesquiterpene lactone from Geigeria     

J A Verschoor  L Bornman  N M Vermeulen 《The Onderstepoort journal of veterinary research》1987,54(1):1-4

Certain species of Geigeria contain sesquiterpene lactones which cause vomiting disease in sheep. Dihydrogriesenin (DHG), a sesquiterpene lactone from G. asperta, contains an alpha-methylene function which can spontaneously react with thiol groups on proteins to form a covalent adduct. A specific antiserum against a DHG-protein adduct can be used to determine the fate of DHG in poisoned animals. The preparation of such an antiserum is reported in this paper. DHG was reacted with cysteine and subsequently coupled to serum albumin using the carbodiimide reaction. When rabbits were immunized with one such conjugate (DHG-bovine serum albumin), it was found that the carrier determinants were immunodominant. A DHG-specific anti-serum of sufficient (ELISA) titre could, however, be obtained by alternating serum albumin carriers for DHG in booster immunizations. The ELISA antigen-antibody reaction could be inhibited by prior reaction of the antisera with cysteinyl-DHG in solution.  相似文献   

Coffee berry disease in Kenya. II. The role of Glomerella cingulata in the Colletotrichum population,colonizing the bark of Coffea arabica     

H. Vermeulen 《European journal of plant pathology / European Foundation for Plant Pathology》1970,76(5):285-292

On the maturing bark of cut branches ofCoffea arabica previously sprayed with copper fungicides perithecia ofGlomerella cingulata were easily found after two to ten days of incubation. Without fungicides the number of perithecia was decidedly lower. On prunings left on the ground under the coffee trees for 6 to 24 weeks the perithecia could also be found, but the numbers declined rapidly with time. Perithecia ofG. cingulata could forcibly discharge ascospores under laboratory conditions. Monospore cultures obtained by catching ascospores on agar, invariably belonged to threeColletotrichum types. It was rarely possible to isolate aColletotrichum able to infect green coffee berries. Growthrate, colour of the mycelium, number of conidia producedin vitro and infectivity on green coffee berries, however, differed substantially fromC. coffeanum, the cause of coffee berry disease. In Kenya no evidence has been obtained that ascospores from perithecia on bark could infect wounded or unwounded green coffee berries. Neither has any infection been obtained with ascospores from perithecia grownin vitro. Possible explanations for the difference with previous findings are offered. Based on the data presented in this paper, it is concluded thatG. cingulata is not likely to play a role in the epidemiology of the coffee berry disease in Kenya.  相似文献   

Morphological Deformities in Chironomus Riparius Meigen Larvae after Exposure to Cadmium over Several Generations     

Janssens de Bisthoven  L.  Postma  J.  Vermeulen  A.  Goemans  G.  Ollevier  F. 《Water, air, and soil pollution》2001,129(1-4):167-179

In order to test the potential of chironomiddeformities for biomonitoring, induction of morphologicaldeformities in Chironomus riparius larvae was assessed afterchronic exposure (static with renewal) of eggs and subsequentinstars to sublethal nominal cadmium concentrations of 0, 3 (NOEC),9 (intermediate) and 27 (chronic _LC50) μg Cd l^-1 during 7to 10 generations. Deformities which could be associated with anindirect or direct cadmium effect were split medial mentum teeth(more frequent in 9 and 27 μg Cd l^-1) and premandibledeformities (especially in 3 μg Cd l^-1). The controlcontained more larvae with additional teeth in mentum and mandiblethan the metal-exposed conditions. In the 9 μg Cd l^-1 condition the frequencies of larvae with split medial mentumteeth increased in the last four generations, to reach 40%. Theunpredictability of fluctuations of deformity frequencies over thegenerations was associated with parental effects and experimentalmanipulation. The deformity percentages correlated positively withthe mortalities and could be related to the induction of toleranceto cadmium, as was concluded on the basis of life cycle analysis ina previous paper. This experiment demonstrated a concentration-response relationship between deformities and sublethal levels ofcadmium. However, the observed generation fluctuations caution for(1) the use of single-generation experiments for definingecotoxicological threshold values, and (2) experimentally inducedgenetical drift in multi-generation experiments.  相似文献   

Combinatorial synthesis and sensorial properties of polyfunctional thiols.   总被引：1，自引：0，他引：1  

C Vermeulen  J Pellaud  L Gijs  S Collin 《Journal of agricultural and food chemistry》2001,49(11):5445-5449

Over the past few years, polyfunctional thiols present as trace components have been found to play a major role in many food flavors, due to their exceptionally low odor thresholds. Unfortunately, their presence in minute concentration (in ng/kg to a few microg/kg) and their high reactivity make it very difficult to extract and identify them. Furthermore, most of them are not yet commercially available. The aim of this work was to characterize the chromatographic and sensorial properties of 10 synthetic mercaptoketones and mercaptoalcohols. Combinatorial chemistry proved to be a very useful way to synthesize them rapidly. Sulfur-selective sulfur chemiluminescence detection chromatograms coupled with mass spectroscopy enabled the target compounds to be identified. Flavor profiles and best estimate gas chromatography lowest amount detected by sniffing (BE-GC-LOADS) values were further determined by GC-olfactometry. As expected, new, exceptionally odorant molecules (BE-GC-LOADS < 0.1 ng) were revealed by this unusual approach.  相似文献