Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

    We have a manual that explains all the features 

Current refinement(s):

Records 1 - 20 / 20

  • help
  • print

    Print search results

  • export

    Export search results

  • alert
    We will mail you new results for this query: keywords==esters
Check title to add to marked list
Analysis of Palmitoyl Apo-astaxanthinals, Apo-astaxanthinones, and their Epoxides by UHPLC-PDA-ESI-MS
Weesepoel, Y.J.A. ; Gruppen, H. ; Bruijn, W.J.C. de; Vincken, J.P. - \ 2014
Journal of Agricultural and Food Chemistry 62 (2014)42. - ISSN 0021-8561 - p. 10254 - 10263.
beta-carotene degradation - mass-spectrometry - hypochlorous acid - haematococcus-pluvialis - products - myeloperoxidase - autoxidation - stability - oxidation - esters
Food products enriched with fatty acid-esterified xanthophylls may result in deviating dietary apo-carotenoids. Therefore, free astaxanthin and its mono- and dipalmitate esters were subjected to two degradation processes in a methanolic model system: light-accelerated autoxidation and hypochlorous acid/hypochlorite (HOCl/OCl–) bleaching. Reversed phase ultrahigh-performance liquid chromatography photodiode array with in-line electrospray ionization mass spectrometry (RP-UHPLC-PDA-ESI-MS) was used for assessment of degradation products. Apo-astaxanthinals and -astaxanthinones containing 3 (apo-9) to 10 (apo-8') conjugated double bonds were found upon autoxidation for all three types of astaxanthin (except free apo-8'-astaxanthinal). Fragmentation of [M + H]+ and [M + Na]+ parent masses of apo-astaxanthins from dipalmitate astaxanthin indicated palmitate esterification. Astaxanthin monopalmitate degradation resulted in a mixture of free and palmitate apo-astaxanthins. HOCl/OCl– rapidly converted the astaxanthins into a mixture of epoxy-apo-9- and epoxy-apo-13-astaxanthinones. The palmitate ester bond was hardly affected by autoxidation, whereas for HOCl/OCl– the ester bond of the apo-astaxanthin palmitoyl esters was degraded.
Using genetic transformation to produce enhanced levels of erucic acid and novel wax esters in Crambe abyssinica
Qi, W. - \ 2014
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Robert van Loo; Frans Krens. - Wageningen : Wageningen University - ISBN 9789462570368 - 117
genetische modificatie - moleculaire veredeling - moleculaire genetica - crambe abyssinica - olieleverende planten - industriële gewassen - biobased economy - erucazuur - esters - genetic engineering - molecular breeding - molecular genetics - crambe abyssinica - oil plants - industrial crops - biobased economy - erucic acid - esters
Crambe abyssinica (crambe) is een oliehoudend gewas dat grote potentie heeft als industrieel uitgangsmateriaal. In het onderzoek beschreven in dit proefschrift werd een solide transformatieprotocol ontwikkeld voor crambe. Om tegemoet te komen aan de eisen voor introductie in het milieu die de EU stelt aan GM gewassen en om de kans op acceptatie door het publiek te vergroten is het 'merker-vrije' genetische vector systeem dat door Wageningen UR Plant Breeding is ontwikkeld in crambe toegepast en uitgetest. Verschillende transformatie experimenten zijn uitgevoerd om het gehalte erucazuur in de zaadolie van crambe te verhogen. Ten slotte is GM crambe gebruikt als productieplatform voor hoogwaardige, industriële wasesters van het type jojoba wasesters.
Structure elucidation of female-specific volatiles released by the parasitoid wasp Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)
Tröger, A. ; Beek, T.A. van; Huigens, M.E. ; Silva, I.M.M.S. ; Posthumus, M.A. ; Francke, W. - \ 2014
Beilstein Journal of Organic Chemistry 10 (2014). - ISSN 1860-5397 - p. 767 - 773.
sex-pheromone - aggregation pheromone - beetle - stereochemistry - identification - hydrocarbons - esters - acid
Females of the parasitoid wasp Trichogramma turkestanica produce the putative polydeoxypropionates (2E,4E,6S,8S,10S)-4,6,8,10-tetramethyltrideca-2,4-diene and (2E,4E,6S,8S,10S)-4,6,8,10-tetramethyltrideca-2,4-dien-1-ol or their enantiomers as sex specific volatiles. The structures were assigned on the basis of GC–MS investigations using synthetic reference compounds.
Carotenoid composition of berries and leaves from six Romanian sea buckthorn (Hippophae rhamnoides L.) varieties
Pop, R.M. ; Weesepoel, Y.J.A. ; Socaciu, C. ; Pintea, A. ; Vincken, J.P. ; Gruppen, H. - \ 2014
Food Chemistry 147 (2014). - ISSN 0308-8146 - p. 1 - 9.
mass-spectrometry - esters - identification - quantification - fruits - acid - zeaxanthin - lutein - seeds
Berries and leaves from six varieties of Carpathians’ sea buckthorn (Hippophae rhamnoides L., ssp. Carpatica) were analysed for their carotenoid composition (free and esterified) using a combination of HPLC-PAD, GC–MS and UHPLC–PAD–ESI-MS techniques. GC–MS techniques revealed the fatty acid profile specific for each berry variety, while targeted UHPLC–MS analysis identified the fatty acids involved in carotenoids esterification: palmitic (C16:0), myristic (C14:0) and stearic (C18:0). Total carotenoid content varied between 53 and 97 mg/100 g dry weight in berries, and between 3.5 and 4.2 mg/100 g DW in leaves. The carotenoid di-esters represented the main fraction among berry varieties having zeaxanthin di-palmitate as major compound, while leaves contained only free carotenoids like lutein, ß-carotene, violaxanthin and neoxanthin. Principal component analysis identified the suitable carotenoid biomarkers characteristic for the Carpathians’ sea buckthorn from Romania with contribution to their taxonomic classification and authenticity recognition.
The effect of diesters and lauric acid on rheological properties of air/water interfaces stabilized by oligofructose lauric acid monoesters
Kempen, S.E.H.J. van; Schols, H.A. ; Linden, E. van der; Sagis, L.M.C. - \ 2013
Journal of Agricultural and Food Chemistry 61 (2013)32. - ISSN 0021-8561 - p. 7829 - 7837.
enzymatic-synthesis - esters - esterification - oligosaccharides - viscoelasticity - lipase - shear
In this study, the rheological properties of interfaces stabilized by oligofructose fatty acid esters were elucidated. First, the properties of interfaces stabilized by monoesters (ME), diesters (DE), lauric acid (LA), oligofructose (OF), and mixtures of ME with DE, LA, or OF were studied. Second, the properties of interfaces stabilized by the crude product (CP) containing ME, DE, LA, and OF were studied. The dependency of the dilatational modulus on frequency and deformation amplitude indicated the possible formation of a soft glass phase for ME, and a viscous interface for DE. When ME and DE were mixed at a ratio of 0.8/0.2, the experimental results suggest that the interfacial structure consists of islands of a glass phase formed by ME, dispersed in a 2D viscous phase of DE. CP stabilized interfaces, where the ratio ME/DE was higher, lead to a different rheological response. The ratio ME/DE plays an important role in the surface properties of the CP. This may have significant consequences for applications in macroscopic systems such as foams.
Refined hazard characterization of 3-MCPD using benchmark dose modeling
Rietjens, I.M.C.M. ; Scholz, G. ; Berg, I. van den; Schilter, B. ; Slob, W. - \ 2012
European Journal of Lipid Science and Technology 114 (2012)10. - ISSN 1438-7697 - p. 1140 - 1147.
3-monochloropropane-1,2-diol 3-mcpd - edible oils - in-vivo - esters - mutagenicity - 3-chloropropane-1,2-diol - exposure - acid - food
3-Monochloropropane-1,2-diol (3-MCPD)-esters represent a newly identified class of food-borne process contaminants of possible health concern. Due to hydrolysis 3-MCPD esters constitute a potentially significant source of free 3-MCPD exposure and their preliminary risk assessment was based on toxicological data on free 3-MCPD. 3-MCPD is a non-genotoxic carcinogen and a (provisional maximum) tolerable daily intake ((PM)TDI) of 2 mu g/kg bodyweight per day was established by the Scientific Committee on Food and the Joint FAO/WHO Expert Committee on Food Additives. Both committees derived the TDI from a lowest observed adverse effect level, not a no observed adverse effect level, for renal tubular hyperplasia, using an uncertainty factor of 500. When using the Benchmark Dose (BMD) approach and a BMDL10 value as point of departure, part of this uncertainty factor of 500 would no longer be needed. The present study presents a BMD analysis of the currently available chronic data on 3-MCPD mediated induction of tubular hyperplasia in rats as the most sensitive endpoint. The results indicate a (model-averaged) BMDL10 value of 0.72 mg/kg bw/day. The TDI that would be derived based on this BMDL10 value will depend on the uncertainty factor chosen. Using the default uncertainty factor of 100 for inter- and intraspecies extrapolation would result in a TDI of 7 mu g/kg bw/day.
Arabinose content of arabinoxylans contributes to flexibility of acetylated arabinoxylan films
Stepan, A.M. ; Hoïje, A. ; Schols, H.A. ; Waard, P. de; Gatenholm, P. - \ 2012
Journal of Applied Polymer Science 125 (2012)3. - ISSN 0021-8995 - p. 2348 - 2355.
wheat-straw hemicelluloses - n,n-dimethylformamide/lithium chloride - xylan derivatives - esterification - system - glucuronoxylan - esters - wood
Arabinoxylans (AX) from rye were partly debranched by chemical hydrolysis methods, and AXs differing in arabinosyl substitution were acetylated using chemical methods. The resulting materials are film forming, and these films underwent molecular structural analysis and were tested for their material properties. The composition and structure of the modified polymers were determined using high performance anion exchange chromatography and two dimensional nuclear magnetic resonance; it was shown that all free hydroxyl groups (of both xylose and arabinose) were acetylated. Further characterizations were done by dynamic mechanical analysis and thermo-gravimetric analysis to evaluate the thermal behavior of the material. The observed glass transition temperatures (Tg) increased with a decrease in arabinosyl substitutions. The thermal degradation temperatures were all close to 380°C. The mechanical properties were characterized with tensile tests of the films. Tensile tests showed that the strain at break, which reflects the flexibility of the material, was significantly higher at higher arabinosyl substitution levels. The elastic Young's modulus was not significantly affected, although a tendency was seen toward a less stiff material at higher arabinosyl substitution. The ultimate strength of the materials was remarkably high in all cases, around 60 MPa, with little difference between them. Considering these properties, a great potential is foreseen in the application of acetylated arabinoxylans as packaging films and as matrix for composites
Biocatalytic acylation of sugar alcohols by 3-(4-hydroxyphenyl)propionic acid
Croitoru, R. ; Fitigau, F. ; Broek, L.A.M. van den; Frissen, A.E. ; Boeriu, C.G. - \ 2012
Process Biochemistry 47 (2012)12. - ISSN 1359-5113 - p. 1894 - 1902.
lipase-catalyzed esterification - candida-antarctica lipase - phenolic-acids - enzymatic preparation - organic media - esters - glycosides - condensation - copolyesters - solvents
Enzymatic synthesis of aromatic esters of four different sugar alcohols (xylitol, arabitol, mannitol, and sorbitol) with 3-(4-hydroxyphenyl)propionic acid was performed in organic solvent medium, using immobilized Candida antarctica lipase (Novozyme 435), and molecular sieves for control of the water content. The influence of reaction parameters on the conversion has been investigated, including reaction time, temperature, alcohol/acid molar ratio, and enzyme amount. The highest conversions (94% for xylitol, 98% for arabitol, 80% for mannitol, and 93% for sorbitol) were obtained in pure tert-butanol at 60 °C and 72 h reaction time, 0.3 alcohol/acid molar ratio, and 0.5 g/mol enzyme/substrate ratio. The isolated new sugar alcohols esters were identified by different spectral analyses. MALDI-TOF MS analysis showed the formation of monoesters, diesters, and small quantities of triesters for all investigated sugar alcohols. The catalytic efficiency of the enzyme was higher for the pentitol substrates, decreasing in the following order: arabitol > xylitol > sorbitol > mannitol. These new compounds could have interesting applications in food, pharmaceutical and cosmetic formulations
Endogenous steroid profiling by gas chromatography-tandem mass spectrometry and multivariate statistics for the detection of natural hormone abuse in cattle
Blokland, M.H. ; Tricht, E.F. van; Rossum, H.J. van; Sterk, S.S. ; Nielen, M.W.F. - \ 2012
Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 29 (2012)7. - ISSN 1944-0049 - p. 1030 - 1045.
carbon-isotope analysis - urine - testosterone - population - esters - misuse - calves
For years it has been suspected that natural hormones are illegally used as growth promoters in cattle in the European Union. Unfortunately there is a lack of methods and criteria that can be used to detect the abuse of natural hormones and distinguish treated from non-treated animals. Pattern recognition of steroid profiles is a promising approach for tracing/detecting the abuse of natural hormones administered to cattle. Traditionally steroids are analysed in urine as free steroid after deconjugation of the glucuronide (and sulphate) conjugates. The disadvantage of this deconjugation is that valuable information about the steroid profile in the sample is lost. In this study we develop a method to analyse steroids at very low concentration levels (ng l-1) for the free steroid, glucuronide and sulphate conjugates in urine samples. This method was used to determine concentrations of natural (pro)hormones in a large population (n¿=¿620) of samples from male and female bovine animals and from bovine animals treated with testosterone-cypionate, estradiol-benzoate, dihydroepiandrosterone and pregnenolone. The data acquired were used to build a statistical model applying the multivariate technique ‘Soft Independent Modeling of Class Analogy’ (SIMCA). It is demonstrated that by using this model the results of the urine analysis can indicate which animal may have had illegal treatment with natural (pro)hormones.
The effect of conjugated linoneic acid, a natural trans fat from milk and meat, on human blood pressure: results from a randomized crossover feeding study
Engberink, M.F. ; Geleijnse, J.M. ; Wanders, A.J. ; Brouwer, I.A. - \ 2012
Journal of Human Hypertension 26 (2012). - ISSN 0950-9240 - p. 127 - 132.
body-composition - vaccenic acid - hypertension - rats - esters - lipids - men
Cis-9, trans-11 conjugated linoleic acid (CLA) is a natural trans fatty acid that is largely restricted to ruminant fats and consumed in foods and supplements. Its role in blood pressure (BP) regulation is still unclear. We examined the effect of cis-9, trans-11 CLA on BP compared with oleic acid. A total of 61 healthy volunteers were sequentially fed each of 3 diets for 3 weeks, in random order, for a total of 9 weeks. The diets were identical except for 7% of energy (18.9¿g in a diet of 10¿MJ¿day–1) that was provided either by oleic acid, by industrial trans fatty acids or by cis-9, trans-11 CLA. We measured BP on two separate days at the end of each intervention period. At baseline, mean BP was 113.8±14.4¿mm¿Hg systolic and 66.3±9.6¿mm¿Hg diastolic. The effect of the CLA diet compared with the oleic acid diet was 0.11¿mm¿Hg (95% confidence interval: -1.27, 1.49) systolic and -0.45¿mm¿Hg (-1.63, 0.73) diastolic. After the industrial trans fatty acid diet, the effect was 1.13¿mm¿Hg (-0.25, 2.51) systolic and -0.44¿mm¿Hg (-1.62, 0.73) diastolic compared with the oleic acid diet. Our study suggests that short-term high intakes of cis-9,trans-11 CLA do not affect BP in healthy volunteers
Optimized enzymatic synthesis of C-terminal peptide amides using subtilisin A from Bacillus licheniformis
Boeriu, C.G. ; Frissen, A.E. ; Boer, E. ; Kekem, C. van; Zoelen, D.J. van; Eggen, I.F. - \ 2010
Journal of Molecular Catalysis. B, Enzymatic 66 (2010)1-2. - ISSN 1381-1177 - p. 33 - 42.
amidation - ammonolysis - ammonia - amidase - esters - acids
A mild and efficient method for the conversion of C-terminal esters of side-chain protected peptides into an amide function via enzyme-catalysed ammonolysis in organic media with low water content is described. Subtilisin A, the alkaline serine protease from Bacillus licheniformis, was used as biocatalyst and ammonium carbamate as source of ammonia. Response surface methodology (RSM) and central composite design were employed to estimate the effects of reaction parameters such as molar ratio of ammonia source to peptide methyl ester (2:1–10:1), composition of the solvent system (ButOH/DMF, % v/v, 70:30–95:5) and water concentration (0.2–0.8%) at different temperatures (30–50 °C) for the preparation of Z-Ala-Phe-NH2 starting from Z-Ala-Phe-OMe. Optimum reaction conditions for maximum amide yield and minimum secondary hydrolysis were determined from cross-section analysis: temperature 30 °C, solvent composition ButOH/DMF 82.5:17.5 (v/v) containing 0.2% water (v/v) and molar ratio of ammonia source to peptide methyl ester of 10:1. The maximum yield of Z-Ala-Phe-NH2 was 87% after 21 h for a quantitative substrate conversion. The method proved to be generally applicable for the synthesis of C-terminal amides of dipeptides with different terminal amino acids and sequence.
Aphrodisiac pheromones from the wings of the Small Cabbage White and Large Cabbage White butterflies, Pieris rapae and Pieris brassicae
Yildizhan, S. ; Loon, J.J.A. van; Sramkova, A. ; Ayasse, M. ; Arsene, C. ; Broeke, C.J.M. ten; Schulz, S. - \ 2009
ChemBioChem 10 (2009)10. - ISSN 1439-4227 - p. 1666 - 1677.
male sex-pheromone - enantioselective total-synthesis - 2 macrolide pheromones - colias-eurytheme - male scent - cuticular lipids - idea leuconoe - lepidoptera - esters - identification
The small and large cabbage butterflies, Pieris rapae and P. brassicae, are found worldwide and are of considerable economic importance. The composition of the male scent-producing organs present on the wings was investigated. More than 120 components were identified, but only a small portion proved to be male specific. Major components were the known beetle pheromone ferrulactone (1) in P. rapae and its previously unknown larger analogue, brassicalactone (2), in P. brassicae. The latter carries an additional isoprene unit and is closely related to 1. Other components present in larger amounts on male relative to female wings were hexahydrofarnesylacetone (18) and phytol (23). Brassicalactone (2) was fully characterized by synthesis of its various diastereomers by using ring-closing metathesis. A similar approach to ferrulactone (1) failed, presumably because of its smaller ring size. Instead, this compound was synthesized by using a modified literature procedure. The biological activity of the compounds in the extract was tested by coupled gas chromatographic-electroantennographic (GC-EAD) analysis, which showed that both macrolides and the other major components of the wings can be detected by the antennae of the conspecific female butterflies. Other detectable compounds included several alkanes, which are typical constituents of the butterfly cuticula, derivatives of phytol (23) and long-chain secondary alcohols. Finally, bioassays with males showed that the mixture of 1 (P. rapae) or 2 (P. brassicae) together with 18 and 23 applied to freshly eclosed males increased mating success compared to untreated males. Therefore, the two macrolides 1 and 2 are aphrodisiac pheromone components of male small and large cabbage white butterflies, respectively
Application of proteases in the C-terminal modification of peptides
Gini, F. ; Eggen, I.F. ; Zoelen, D.J. van; Boeriu, C.G. - \ 2009
Chimica Oggi = Chemistry today 27 (2009)2. - ISSN 1973-8250 - p. 24 - 26.
alkaline protease - organic-solvents - resolution - esters
The high selectivity and the mild reaction conditions of enzymatic processes prompted their application in the synthesis of peptides, where selectivity is a feature of pivotal importance. Here we report the use of the serine protease subtilisin for the selective deprotection of C-terminal tert-butyl esters, achieved in good to quantitative yield for most of the natural amino acids. The same enzyme was active in the C-terminal amidation affording excellent yields with several peptides in the presence of a variety of amino sources. Subtilisin, finally, can also catalyse the transesterification of C-terminal primary esters. All the reactions are highly selective and neither side chains modifications nor N-terminus reactions have been observed. The endopeptidase activity, an important drawback in the use of proteases, was minimized upon extensive optimization of the reaction conditions.
Covalent interactions between amino acid side chains and oxidation products of caffeoylquinic acid (chlorogenic acid)
Prigent, S.V.E. ; Voragen, A.G.J. ; Li, F. ; Visser, A.J.W.G. ; Koningsveld, G.A. van; Gruppen, H. - \ 2008
Journal of the Science of Food and Agriculture 88 (2008)10. - ISSN 0022-5142 - p. 1748 - 1754.
caffeic acid - polyphenol oxidase - plant phenols - proteins - model - inhibitor - compound - quinone - esters
BACKGROUND: Physicochemical properties and digestibility of proteins can be modified by covalent interactions with oxidized phenolic compounds, i.e., quinones. In order to control these interactions in food products, the covalent interactions between quinones from caffeoylquinic acid (CQA) and amino acid side chains were studied with mass spectrometry using N-terminally protected amino acids. RESULTS: The addition of two molecules of CQA, presumably in the form of a pre-formed dimer, was observed for lysine, tyrosine, histidine and tryptophan. A monomer of CQA seemed to be able to react with histidine and tryptophan, whereas no interaction with a CQA monomer was observed for lysine and tyrosine. Serine and threonine showed no covalent interactions with CQA. Cross-linking between CQA and the side chains of two molecules of lysine is likely to occur also in proteins. The results show that protein cross-linking may also be expected to occur via two tyrosine residues in the absence of other phenolic substrates. The side chains of lysine and tyrosine are more reactive than that of histidine and tryptophan. CONCLUSIONS: These results show that covalent protein modification by oxidized phenolics occurs preferentially via an initial dimerization and encompasses not only lysine and cysteine residues.
The formation of fat-derived flavour compounds during the ripening of Gouda-type cheese
Alewijn, M. - \ 2006
Wageningen University. Promotor(en): J.T.M. Wouters, co-promotor(en): E.L. Sliwinski. - Wageningen : - ISBN 9085043816 - 136
goudse kaas - geurstoffen en smaakstoffen - vetten - vetzuren - lactonen - esters - ketonen - kaasrijping - gouda cheese - flavour compounds - fats - fatty acids - lactones - esters - ketones - cheese ripening
Cheese flavour is an important quality attribute, and is mainly formed during cheese ripening. Besides compounds that are formed from protein and carbohydrates, milk fat-derived compounds are essential for cheese flavour. Before, but mainly during ripening, free fatty acids, lactones, ketones, esters, alcohols and aldehydes can be formed from milk fat, compounds that all contribute their own special character to the final cheese flavour. The formation mechanisms that lead to these compounds are not completely understood, and therefore cheese flavour formation is not under full control.
Liquid chromatography-electrospray ionisation-mass spectrometry based method for the determination of estradiol benzoate in hair of cattle
Hooyerink, H. ; Lommen, A. ; Mulder, P.P.J. ; Rhijn, J.A. van; Nielen, M.W.F. - \ 2005
Analytica Chimica Acta 529 (2005)1-2. - ISSN 0003-2670 - p. 167 - 172.
gas-chromatography - anabolic-steroids - doping control - esters - testosterone - ethinylestradiol - nandrolone - residue - plasma
A liquid chromatography (LC)-based method with mass spectrometric (MS/MS) detection was developed for the determination of estradiol benzoate residues in hair of cattle. First hair samples were pulverized with a ball mill followed by treatment with the reducing agent Tris(2-carboxyethyl)phosphine hydrochloride (TCEP). After liquid/liquid extraction samples were further purified by solid-phase extraction. Finally samples were analyzed with LC¿MS/MS using deuterated estradiol benzoate as internal standard. The method was validated following the latest EU guidelines for screening methods using blank hair samples spiked at 5 ng g¿1. The detection capability (CCß) was less than 5 ng g¿1 and the decision limit (CC¿) was 1.6 ng g¿1. The recovery was 27% at the 5 ng g¿1 level and the accuracy was 95%. Confirmation, with two MS/MS transitions, was possible at a concentration of 5 ng g¿1 or higher. Incurred samples obtained from different animal experiments were analyzed and the presence of estradiol benzoate was confirmed. Finally hair samples from different slaughterhouses were analyzed.
Effect of whey protein on the In Vivo Release of Aldehydes.
Weel, K.G.C. ; Boelrijk, A.E.M. ; Burger, J.J. ; Claassen, N.E. ; Gruppen, H. ; Voragen, A.G.J. - \ 2003
Journal of Agricultural and Food Chemistry (2003). - ISSN 0021-8561 - p. 4746 - 4752.
bovine beta-lactoglobulin - 20 aroma compounds - flavor compounds - mass-spectrometry - binding - perception - saliva - chromatography - ionone - esters
Retention of aldehydes by whey proteins in solutions buffered at a range of pH values was studied under static and dynamic headspace conditions and in vivo in exhaled air. Static headspace measurements showed a clear increase in retention in the presence of whey proteins for aldehydes with longer carbon chains and for buff er solutions with higher pH values. For in vivo aldehyde release measurements, these effects were much less pronounced. The presence of saliva or the binding of aldehydes to the surface of the oral cavity was not responsible for this effect. This difference can be explained by the highly dynamic conditions of in vivo aroma release of liquid products, due to the relatively large flow of air during exhalation. After swallowing, a thin film of aldehyde solution remains in the pharynx; subsequent exhalation will release both the free aldehydes present in this film and those reversibly bound to the whey protein.
Differential feeding of worker larvae affects caste characters in the Cape honeybee, Apis mellifera capensis
Allsopp, M.H. ; Boot, W.J. ; Calis, J.N.M. - \ 2003
Behavioral Ecology and Sociobiology 54 (2003). - ISSN 0340-5443 - p. 555 - 561.
ovary development - scutellata colonies - bees - queen - brood - pheromone - behavior - esters - food
Sections of brood from colonies of the Cape honeybee ( Apis mellifera capensis), the African honeybee ( A. m. scutellata), and hybrid bees of the two races were exchanged between colonies to study the effect of different brood-origin/nurse-bee combinations on development of caste characters. When Cape larvae were raised by African workers the amount of food provided almost doubled in comparison with Cape larvae reared by their own workers. In contrast, African larvae raised by Cape workers were provided with only half the amount they received from their own workers. After the bees emerged, we found a large degree of plasticity in characters related to caste differentiation, which corresponded closely to the amount of food provided. Super-fed Cape bees had enlarged spermathecae, were heavier than normal workers and developed more rapidly, and had reduced pollen combs, all typical for a more queen-like condition. Ovariole numbers did not appear to be enhanced by additional feeding. Cape bees that behave as social parasites in African bee colonies were most queen-like in the characters studied, albeit within the range that was found for Cape bees from normal colonies, suggesting within-colony selection for characters that enhance reproduction.
Improvement of the systemic prime/oral boost strategy for systemic and local responses.
Lauterslager, T.G.M. ; Stok, W. ; Hilgers, L.A.T. - \ 2003
Vaccine 21 (2003)13-14. - ISSN 0264-410X - p. 1391 - 1399.
mucosal immune-responses - squalane-in-water - oral immunization - vaccine adjuvant - tolerance - mice - infection - efficacy - animals - esters
This paper describes oral boost immunisations of primed animals as an alternative oral vaccination strategy. Mice were primed orally (PO), intranasally (IN), subcutaneously (SC), or intraperitoneally (IP) with ovalbumin (OVA) with or without adjuvant. Boost immunisations were given orally with or without cholera toxin (CT) as adjuvant. Prime immunisations induced variable IgA and IgG1 titres in serum depending on the route. A subsequent oral boost increased these titres. Use of an adjuvant in the priming significantly increased serum IgA and, to a lesser extend, IgG1. Oral boost immunisation induced significantly higher serum IgA titres in animals primed via the SC, IP and the IN route compared to the PO route. This was independent of the use of CT. Three oral boosts with OVA plus 5 ¿g CT given in 5 days to primed mice revealed higher IgA titres compared to single oral boosts and anti-OVA IgA titres in faeces were also detected. Finally, we put together our findings and propose a systemic priming/oral boost strategy in which mice were primed via the SC route with 100 ¿g OVA plus 50 ¿g Butyl16-p(AA), and subsequently orally boosted with three doses of 300 ¿g OVA plus 5 ¿g CT each. We concluded that oral immunisation is more effective in IN, SC, or IP primed mice than in PO primed mice, and that the IgA antibody response in serum and faeces can be improved by increasing the immunisation frequency and the use of appropriate adjuvants in primary and boost immunisation. The here-formulated strategy improves the probability of success of oral vaccination. The results are discussed in the light of the development of edible vaccines.
Onderzoek naar de stabiliteit van methylesters bij de bepaling van de vetzuursamenstelling van monsters botervet
Kamp, H.J. van de; Wolters, Th.C. ; Muuse, B.G. - \ 1981
Wageningen : RIKILT (Verslag / RIKILT 81.08) - 3
esters - carbonzuren - methanol - natriumbisulfiet - boter - vet - boterzuur - carboxylic acids - sodium bisulfite - butter - fat - butyric acid
Doel van dit onderzoek was: verbetering van de stabiliteit van de methylesters van botervet bereid volgens NEN 6302 sub 5. Voor één botervetmonster werd de invloed nagegaan van natrium-bisulfiet op de stabiliteit van de methylesters. Gedurende 3 dagen werd het verloop van de samenstelling gecontroleerd onder verschillende proefomstandigheden.
Check title to add to marked list

Show 20 50 100 records per page

 
Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.