Staff Publications

Staff Publications

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    '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.

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    Milk fat triacyglycerols : their variabiblity, relations with fatty acids, DGAT1, B polymorphs and melting fractions
    Tzompa Sosa, D.A. - \ 2016
    Wageningen University. Promotor(en): Toon van Hooijdonk, co-promotor(en): Hein van Valenberg; G.A. van Aken. - Wageningen : Wageningen University - ISBN 9789462577503 - 122
    milk fat - triacylglycerols - fatty acids - composition - polymorphism - dairy cows - cows - crystallization - fat crystallization - melting - calorimetry - maldi-tof - thin layer chromatography - melkvet - triacylglycerolen - vetzuren - samenstelling - polymorfisme - melkkoeien - koeien - kristallisatie - vetkristallisatie - smelten - calorimetrie - maldi-tof - dunnelaagchromatografie

    Milk fat (MF) triacylglycerol composition varies within a population of dairy cows. The variability of MF triacylglycerols and their structure was partially explained by the fatty acid (FA) composition of the MF, and by DGAT1 K232A polymorphism. The FA C16:0 and C18:1cis-9 play a major role in understanding the changes seen in triacylglycerol profile and structure because they are the most abundant FAs in MF and are negatively correlated. MFs with low ratio C16:0/C18:1cis-9 were decreased in triacylglycerols with 34 and 36 carbons and were increased in triacylglycerols with 52 and 54 carbons. These changes in MF composition greatly affected the crystallization behavior of MF by changing the types of polymorphs formed during its crystallization. MF with low ratio C16:0/C18:1cis-9 formed stable and metastable polymorphs (β and β’, respectively), whereas MF with high ratio C16:0/C18:1cis-9 formed exclusively metastable polymorphs (β’) when the fat was crystallized at 20°C. The changes in MF composition also affected the melting behavior of MF by changing the melting point of the MF fractions.

    Mapping and fine-mapping of genetic factors affecting bovine milk composition
    Duchemin, S.I. - \ 2016
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Henk Bovenhuis; Marleen Visker; Willem F. Fikse. - Wageningen : Wageningen University - ISBN 9789462577305 - 190
    dairy cows - dairy cattle - milk composition - milk fat - genetic factors - quantitative trait loci - genomics - genetic mapping - animal genetics - melkkoeien - melkvee - melksamenstelling - melkvet - genetische factoren - loci voor kwantitatief kenmerk - genomica - genetische kartering - diergenetica

    Duchemin, S.I. (2016). Mapping and fine-mapping of genetic factors affecting bovine milk composition. Joint PhD thesis, between Swedish University of Agricultural Sciences, Sweden and Wageningen University, the Netherlands

    Bovine milk is an important source of nutrients in Western diets. Unraveling the genetic background of bovine milk composition by finding genes associated with milk-fat composition and non-coagulation of milk were the main goals of this thesis. In Chapter 1, a brief description of phenotypes and genotypes used throughout the thesis is given. In Chapter 2, I calculated the genetic parameters for winter and summer milk-fat composition from ~2,000 Holstein-Friesian cows, and concluded that most of the fatty acids (FA) can be treated as genetically the same trait. The main differences between milk-fat composition between winter and summer milk samples are most likely due to differences in diets. In Chapter 3, I performed genome-wide association studies (GWAS) with imputed 777,000 single nucleotide polymorphism (SNP) genotypes. I targeted a quantitative trait locus (QTL) region on Bos taurus autosome (BTA) 17 previously identified with 50,000 SNP genotypes, and identified a region covering 5 mega-base pairs on BTA17 that explained a large proportion of the genetic variation in de novo synthesized milk FA. In Chapter 4, the availability of whole-genome sequences of keys ancestors of our population of cows allowed to fine-mapped BTA17 with imputed sequences. The resolution of the 5 mega base-pairs region substantially improved, which allowed the identification of the LA ribonucleoprotein domain family, member 1B (LARP1B) gene as the most likely candidate gene associated with de novo synthesized milk FA on BTA17. The LARP1B gene has not been associated with milk-fat composition before. In Chapter 5, I explored the genetic background of non-coagulation of bovine milk. I performed a GWAS with 777,000 SNP genotypes in 382 Swedish Red cows, and identified a region covering 7 mega base-pairs on BTA18 strongly associated with non-coagulation of milk. This region was further characterized by means of fine-mapping with imputed sequences. In addition, haplotypes were built, genetically differentiated by means of a phylogenetic tree, and tested in phenotype-genotype association studies. As a result, I identified the vacuolar protein sorting 35 homolog, mRNA (VPS35) gene, as candidate. The VPS35 gene has not been associated to milk composition before. In Chapter 6, the general discussion is presented. I start discussing the challenges with respect to high-density genotypes for gene discovery, and I continue discussing future possibilities to expand gene discovery studies, with which I propose some alternatives to identify causal variants underlying complex traits in cattle.

    Smediger kaas door juiste voer
    Hettinga, K.A. ; Dijkstra, J. - \ 2014
    De zelfkazer 66 (2014)6. - ISSN 0166-4549 - p. 10 - 11.
    kazen - smaak - eiwitgehalte - vetgehalte - voersamenstelling - onverzadigde vetten - vetzuren - melk - melkvet - cheeses - taste - protein content - fat content - feed formulation - unsaturated fats - fatty acids - milk - milk fat
    Veel kaasmakers willen smedige (zachte, smeuïge) kaas maken, want de gemiddelde consument vindt die kaas het lekkerst. Kasper Hettinga en Jan Dijkstra van Wageningen Universiteit vertellen hoe de smedigheid van kaas kan worden beïnvloed door de samenstelling van het veevoer.
    Genetic variation of milk fatty acid composition between and within dairy cattle breeds
    Maurice - Van Eijndhoven, M.H.T. - \ 2014
    Wageningen University. Promotor(en): Johan van Arendonk; Roel Veerkamp, co-promotor(en): Mario Calus. - Wageningen : Wageningen University - ISBN 9789462571488 - 184
    dierveredeling - melkkoeien - vetzuren - melk - genetische variatie - rundveerassen - heritability - melkvet - genetische bronnen van diersoorten - melkveehouderij - animal breeding - dairy cows - fatty acids - milk - genetic variation - cattle breeds - heritability - milk fat - animal genetic resources - dairy farming

    Abstract

    Maurice – Van Eijndhoven, M.H.T. (2014). Genetic variation of milk fatty acid composition between and within dairy cattle breeds. PhD thesis, Wageningen University, the Netherlands

    Fat is one of the main components in bovine milk and comprises a large number of individual fatty acids (FA). The composition of FA in milk varies considerably due to differences in the genetics and nutrition of cows and an increasing interest in the possibilities for modifying FA composition can be noticed nowadays. In this thesis two fields of interest were combined, namely: production of milk with specific milk fat composition and conservation of native cattle breeds. Therewith, the overall objective of this thesis was to investigate the variability of detailed milk FA composition between and within different dairy cattle breeds, including the mainstream Holstein Friesian (HF) and Jersey, and the native dual purpose breeds Meuse-Rhine-Yssel (MRY), Groningen White Headed (GWH) and Dutch Friesian (DF) in the Netherlands. For this study the accuracy of mid-infrared (MIR) spectrometry was evaluated for predicting FA composition in different breeds. Differences of milk FA composition within and between breeds were investigated using MIR and Gas Chromatography (GC) information. Finally, similarities in genomic variation associated with detailed milk fat composition between the mainstream HF breed and native dual purpose breeds were studied. Results show that MIR is an accurate method for predicting FA composition among different breeds and countries. Evaluating the FA composition in different breeds, differences were found in milk FA composition among herds using different cattle breeds in the Netherlands, based on detailed milk FA measurements using GC. Evaluating the FA composition in milk between and within breeds using a large dataset that included MIR spectra of milk from cows from a range of farms using one or more breeds, in general, only minor breed differences in FA composition were found and HF showed more genetic variation in FA composition compared to MRY. Furthermore, differences were detected between the native breeds MRY, DF and GWH in genomic variations of regions that are associated with FA composition in HF, while most variation in these main regions was clearly observed in HF. Overall, it was concluded that no large differences existed in milk FA composition among the native Dutch dual purpose breeds and the mainstream HF breed. It is suggested, however, that selecting specific FA composition differences in farms using different breeds in the Netherlands can attribute to modifying the FA composition in bovine milk production.

    Fate of fatty acids during ensiling: relationship with milk fat composition of dairy cows
    Khan, N.A. - \ 2011
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): John Cone; V. Fievez. - [S.l.] : S.n. - ISBN 9789085859581 - 158
    melkkoeien - melkvet - melksamenstelling - vetzuren - kuilvoerbereiding - graskuilvoer - maïskuilvoer - stabiliteit - voer - ruwvoer (forage) - rundveevoeding - diervoeding - dairy cows - milk fat - milk composition - fatty acids - silage making - grass silage - maize silage - stability - feeds - forage - cattle feeding - animal nutrition

    Transition of dairy cows from grazing to silage based rations significantly increases the saturated: unsaturated fatty acids (FA) ratio and decreases the content of beneficial C18:1 cis-9, C18:1 trans-11, C18:2 cis-9,trans-11 and C18:3n-3 in milk fat. This is partly related to a lower polyunsaturated FA (PUFA) supply from ensiled forages. The aim of this thesis was to investigate the scope of increasing the content PUFA in grass and maize silages, and to establish relationships between silage quality on the one hand and the FA content and composition, post-ensiling stability of PUFA, and milk FA composition of dairy cows on the other hand. The first focus of this thesis was to quantify the variation in FA content and composition in grass (n = 101) and maize (n = 96) silages, randomly sampled from commercial dairy farms in the Netherlands, and use multivariate analysis to identify the causes of this variation. The FA content and composition of grass and maize silages were highly variable, and this variation was primarily caused by differences in plant maturity at harvest. Silages made from younger grass and maize have higher contents of C18:3n-3.Most of the variation in FA content in the ensiled forages was caused by differences in plant maturity at harvest. Changes in FA content and composition were investigated in stover (leaves and stem) and ears (cob, shank and husks) in a set of maize genotypes, grown on sandy and clay soils and harvested at 14, 42, 56, 70, and 84 days after flowering (DAF). The contents of C18:3n-3 and total FAs in the stover dry matter (DM) declined at a slow rate up to 56 DAF and then decreased rapidly during 56–84 DAF. On the other hand the content of C18:2n-6 and total FAs in the ears DM increased up to 56 DAF and thereafter remained more or less constant. The maximum amount of PUFA in silage maize can be harvested around 56 DAF. Identifying pre and post-ensiling processes that optimize the stability of PUFA was the next goal. The stability of FA were investigated in untreated and mechanically bruised perennial ryegrass (Lolium perenne L.), wilted under field conditions for 0, 12, 24, 36, and 48 h, or wilted under controlled climate conditions at three temperatures (15, 25 or 35 °C) and two light (dark or light) regimes to DM contents of 425, 525 or 625 g/kg. The oxidation of FAs during wilting of grass was mainly caused by the duration of the wilting, wilting temperature only provoked small differences, whereas mechanical bruising of grass and light intensity did not affect the changes in FA contents. The highly esterified lipids of forages are extensively hydrolysed in the silo. Therefore, the post-ensiling stability of FAs was investigated in grass and maize silages, with a wide range in qualities, exposed to air for 0, 12, and 24 h. Exposure of grass and maize silages to air results in a quantitatively small, but consistent decline in the contents of major unsaturated FAs with a concomitant increase in the proportion of C16:0. The final study evaluated the effects of feeding maize silages, ensiled at different maturities, in combination with a high or low degradable carbohydrate concentrate on nutrient intake, milk production, and composition of milk and milk fatinearly lactating dairy cows. Maize maturity at harvest at a DM content of 300-420 g/kg fresh weight, did not affect the production performance of dairy cows, but resulted in decreased contents of C18:3n-3 and total n-3 and a decreased n-6:n-3 ratio in the milk fat of dairy cows.

    Melkvet met meerwaarde
    Stoop, W.M. ; Arendonk, J.A.M. van; Bovenhuis, H. ; Heck, J. - \ 2009
    Veeteelt 26 (2009)6. - ISSN 0168-7565 - p. 12 - 14.
    melkveehouderij - melkvee - dierveredeling - melkvet - samenstelling - dairy farming - dairy cattle - animal breeding - milk fat - composition
    Fokken op melkvet richt zich vooralsnog alleen op de hoeveelheid vet. Onderzoekers van Wageningen Universiteit tonen aan dat niet alleen de hoeveelheid melkvet, maar ook de melkvetsamenstelling met behulp van fokkerij verbeterd kan worden
    Zoeken naar genen voor melkvetsamenstelling : milk genomics-onderzoek vindt twee genen die een grote rol spelen in de genetische verschillen in melkvetsamenstelling
    Schennink, A. ; Visker, M.H.P.W. ; Arendonk, J.A.M. van - \ 2009
    Veeteelt 26 (2009)7. - ISSN 0168-7565 - p. 10 - 12.
    melkveehouderij - melkkoeien - melkvet - samenstelling - melksamenstelling - heritability - dierveredeling - merkers - dairy farming - dairy cows - milk fat - composition - milk composition - heritability - animal breeding - markers
    Verschillen in de samenstelling van het melkvet zijn voor een groot deel erfelijk bepaald. Twee genen spelen een grote rol in deze verschillen. Merkerinformatie kan in de toekomst gebruikt worden om te selecteren op een verbeterde samenstelling van het melkvet
    Genes involved in bovine milk-fat composition
    Schennink, A. - \ 2009
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Marleen Visker; Henk Bovenhuis. - [S.l.] : S.n. - ISBN 9789085853534 - 169
    koeien - melkvet - vetzuren - melksamenstelling - genen - genetische parameters - heritability - genetica - cows - milk fat - fatty acids - milk composition - genes - genetic parameters - heritability - genetics
    The aim of the research described in this thesis was to identify genes that underlie the genetic variation in bovine milk-fat composition. The fat composition of milk samples from approximately 2,000 Dutch Holstein Friesian cows in their first lactation was measured by gas chromatography.

    Quantitative genetic analysis showed substantial genetic variation in milk-fat composition: heritabilities were high for short and medium chain fatty acids and moderate for long chain fatty acids. We demonstrated that polymorphisms in the DGAT1 and SCD1 genes had clear influence on milk-fat composition and explained large part of the genetic variation in milk-fat composition. Sequencing of the coding regions of SCD1 in a number of animals representing 6 dairy cattle breeds, buffalo, goat and sheep identified new polymorphisms within and between species. In addition to these 2 major genes, polymorphisms in 5 other genes were shown to affect bovine milk-fat composition. To identify chromosomal regions linked to variation in milk-fat composition, without any prior knowledge on genes or functions, a genome-wide scan was performed. Quantitative trait loci (QTL) were detected for short and medium chain fatty acids on 4 chromosomes, and QTL were detected for long chain fatty acids on 3 chromosomes.

    Furthermore, effects of DGAT1 and SCD1 genotypes on conformation traits in the Dutch Holstein Friesian cattle population were analyzed and suggested an association between DGAT1 genotype and conformation traits related to body size.

    We conclude that selective breeding could make a significant contribution to change the fat composition of cow’s milk, and that selective breeding can capitalize on genotypic information.

    Genetic variation in bovine milk fat composition
    Stoop, W.M. - \ 2009
    Wageningen University. Promotor(en): Johan van Arendonk, co-promotor(en): Henk Bovenhuis. - [S.l.] : S.n. - ISBN 9789085853558
    melk - melkvet - melksamenstelling - genetische variatie - selectie - dierveredeling - selectief fokken - vetzuren - milk - milk fat - milk composition - genetic variation - selection - animal breeding - selective breeding - fatty acids
    In her thesis, Stoop shows that there is considerable genetic variation in milk fat composition, which opens opportunities to improve milk fat composition by selective breeding. Short and medium chain fatty acids had high heritabilities, whereas variation due to herd (mainly feed effects) was moderate. Long chain fatty acids had moderate heritabilities, whereas variation due to herd was high. Several genomic regions (QTL) with effect on short and medium chain, long chain, or both types of fatty acids were identified. Differences in results could be explained by the origin of the fatty acids; short and medium chain fatty acids are predominantly synthesized by the cow in the mammary gland, whereas long chain fatty acid are mainly of dietary origin. Results show that milk fat composition can be improved by selective breeding, which offers opportunities to meet consumers’ demands regarding health and technological aspects.
    Genome-wide scan for short and medium chain milk fatty acids
    Stoop, W.M. ; Schennink, A. ; Visker, M.H.P.W. ; Mullaart, E. ; Arendonk, J.A.M. van; Bovenhuis, H. - \ 2008
    melkvee - zwartbont - melkvet - vetzuren met een lange keten - loci voor kwantitatief kenmerk - merkers - genotyping - genexpressieanalyse - dairy cattle - holstein-friesian - milk fat - long chain fatty acids - quantitative trait loci - markers - genotyping - genomics
    Aim of this research was to identify Quantitative Trait Loci (QTL) for long chain milk fatty acids. Therefore 1905 Dutch Holstein Friesian heifers were phenotyped. One of the conclusions was that the identification of QTL for long chain fatty acids, and in particular for C18:1trans fatty acids, strongly supports the hypothesis of a genetic component for these fatty acids
    DGAT1 underlies large genetic variation in milk-fat composition of dairy cows
    Schennink, A. ; Stoop, W.M. ; Visker, M.H.P.W. ; Heck, J.M.L. ; Bovenhuis, H. ; Poel, J.J. van der; Valenberg, H.J.F. van; Arendonk, J.A.M. van - \ 2007
    Animal Genetics 38 (2007)5. - ISSN 0268-9146 - p. 467 - 473.
    dierveredeling - melkkoeien - melkvee - zwartbont - melksamenstelling - melkvet - vetzuren - lactatie - genetische variatie - genotypen - genetische parameters - heritability - selectief fokken - nederland - animal breeding - dairy cows - dairy cattle - holstein-friesian - milk composition - milk fat - fatty acids - lactation - genetic variation - genotypes - genetic parameters - heritability - selective breeding - netherlands - coa-diacylglycerol acyltransferase - serum-cholesterol - production traits - dietary-fat - bovine - acids - cattle - yield - parameters - disease
    Dietary fat may play a role in the aetiology of many chronic diseases. Milk and milk-derived foods contribute substantially to dietary fat, but have a fat composition that is not optimal for human health. We measured the fat composition of milk samples in 1918 Dutch Holstein Friesian cows in their first lactation and estimated genetic parameters for fatty acids. Substantial genetic variation in milk-fat composition was found: heritabilities were high for short- and medium-chain fatty acids (C4:0¿C16:0) and moderate for long-chain fatty acids (saturated and unsaturated C18). We genotyped 1762 cows for the DGAT1 K232A polymorphism, which is known to affect milk-fat percentage, to study the effect of the polymorphism on milk-fat composition. We found that the DGAT1 K232A polymorphism has a clear influence on milk-fat composition. The DGAT1 allele that encodes lysine (K) at position 232 (232K) is associated with more saturated fat; a larger fraction of C16:0; and smaller fractions of C14:0, unsaturated C18 and conjugated linoleic acid (P <0.001). We conclude that selective breeding can make a significant contribution to change the fat composition of cow¿s milk.
    AKK-Witte Motor op Groene Brandstof
    Jeddens, M. ; Elgersma, A. ; Boschma, S. - \ 2005
    Den Bosch / Wageningen : AKK - 14
    zuivelonderzoek - kazen - melk - melkvet - onverzadigde vetzuren - kaaskwaliteit - begrazing - veevoeder - productontwikkeling - innovaties - duurzame ontwikkeling - agro-industriële ketens - voeding en gezondheid - dairy research - cheeses - milk - milk fat - unsaturated fatty acids - cheese quality - grazing - fodder - product development - innovations - sustainable development - agro-industrial chains - nutrition and health
    CONO Kaasmakers (zuivelproducent), De Heus Brokking Koudijs (diervoederproducent) en Barenbrug Holland BV (grassenveredelingsbedrijf) willen gezamenlijk duurzame melk met een betere vetzuursamenstelling produceren om gezondere kaas te ontwikkelen en in de markt te introduceren. Dit doen zij vanuit een eigen duurzaamheidsvisie en een marktgerichte oriëntatie. Er vindt wetenschappelijk onderzoek plaats naar een optimale samenstelling van voer om jaarrond melk te produceren met voldoende en de juiste onverzadigde vetzuren. Op het onderzoek volgt het selecteren en beproeven van maatregelen om de optimale kwaliteit te realiseren. Tenslotte wordt een marktconcept ontwikkeld om de verbeterde producten in de markt te positioneren. Een belangrijk resultaat is verbetering van de kwaliteit en het imago van melkvet wat gunstig kan uitwerken voor de melkveehouderij en de zuivelindustrie. Verbetering van de kaaskwaliteit (smaak, gezondheid, duurzame productie) is relevant voor de internationale concurrentiepositie
    Zuurtegraad van het melkvet en vaker melken
    Slaghuis, B.A. ; Jong, O. de; Bos, K. ; Wemmenhove, H. ; Koning, C.J.A.M. de - \ 2005
    ZuivelZicht 97 (2005)7. - ISSN 0165-8573 - p. 20 - 21.
    melken - machinaal melken - melkvet - zuurgraad - vetbolletjes - melkmachines - milking - machine milking - milk fat - acidity - fat globules - milking machines
    Dinds de invoering van het automatisch melken is er gemiddeld een stijging te zien van de zuurtegraad van het melkvet. Het is een gevolg van een toename van de vetsplitsing in de melk, die een aantal oorzaken heeft
    Vetsplitsing - Zuurtegraad melkvet hoger bij automatisch melken
    Slaghuis, B.A. - \ 2004
    Veeteelt 21 (2004)9. - ISSN 0168-7565 - p. 67 - 68.
    melkveehouderij - machinaal melken - robots - melkkwaliteit - melkvet - zuurgraad - vetbolletjes - agrarische bedrijfsvoering - dairy farming - machine milking - robots - milk quality - milk fat - acidity - fat globules - farm management
    Sinds de invoering van het automatisch melken is er gemiddeld genomen een stijging te zien van de zuurtegraad van het melkvet. Deze stijging is het gevolg van een toename van de vetsplitsing in melk, veroorzaakt door verschillende factoren die hier in het kort worden weergegeven
    Oorzaak vetsplitsing in melk niet altijd duidelijk
    Slaghuis, B.A. - \ 2003
    Praktijkkompas. Rundvee 17 (2003)2. - ISSN 1570-8586 - p. 14 - 15.
    melken - machinaal melken - robots - automatisering - melkkwaliteit - melkveehouderij - melkvet - vetbolletjes - zuurgraad - landbouwkundig onderzoek - milking - machine milking - robots - automation - milk quality - dairy farming - milk fat - fat globules - acidity - agricultural research
    Omdat de oorzaken niet duidelijk zijn, gaat het PV nader onderzoek uitvoeren naar vetsplitsing.
    EU-project Automatisch Melken (3); melkkwaliteit & hygiene
    Vorst, Y. van der; Koning, K. de - \ 2002
    Praktijkkompas. Rundvee 16 (2002)3. - ISSN 1570-8586 - p. 18 - 19.
    melken - machinaal melken - automatisering - robots - melkkwaliteit - melkveehouderij - melk - kwaliteit - melkhygiëne - kiemgetal - bacteriëntelling - zuurgraad - ph - melkvet - melkveebedrijven - onderzoeksprojecten - celgetal - milking - machine milking - automation - robots - milk quality - dairy farming - milk - quality - milk hygiene - bacterial count - bacterial counting - acidity - ph - milk fat - dairy farms - research projects - somatic cell count
    Ditmaal is dat de melkkwaliteit. De kwaliteit is goed te noemen, maar de zuurtegraad van het melkvet is een punt van aandacht.
    Stijging gehalte vrije vetzuren bij automatisch melken
    Slaghuis, B. ; Koning, K. de - \ 2001
    Rundvee praktijkonderzoek 14 (2001)1. - ISSN 1569-805X - p. 8 - 9.
    melkmachines - machinaal melken - melken - melkinterval - robots - automatisering - melkkwaliteit - melkvet - zuurgraadwaarde - vetzuren - zuurgraad - melkveehouderij - milking machines - machine milking - milking - milking interval - robots - automation - milk quality - milk fat - acid degree value - fatty acids - acidity - dairy farming
    Sinds de invoering van de melkrobot op bedrijven is te zien dat het gemiddelde gehalte aan vrije vetzuren omhoog gaat. Sommige bedrijven kampen zelfs met een korting voor vrije vetzuren.
    Vergelijkend vetgehalte onderzoek tussen melk geconserveerd met sublimaat en met natriumazide
    Polanen, A. van; Werdmuller, G.A. ; Oortwijn, H. - \ 1982
    Wageningen : RIKILT (Verslag / RIKILT 82.38) - 3
    melk - melkproducten - natriumazide - kwikoxide - conservering - melkvet - bepaling - voedselanalyse - milk - milk products - sodium azide - mercuric oxide - conservation - milk fat - determination - food analysis
    In de regio Drente-Groningen hebben sommige zuivelbedrijven een negatieve vetbalans. Men schreef dit toe aan de door het melkcontrolestation te hoog bepaalde vetgehalten, veroorzaakt door conservering van de melk met natriumazide. Door middel van de butyrometrische methode van Gerber (NEN 962) werd nagegaan of er verschillen zijn in het vetgehalte van monsters melk geconserveerd met sublimaat en monsters melk geconserveerd met natriumazide. Een vierhonderdtal monsters melk respectievelijk geconserveerd met sublimaat en met natriumazide werden onderzocht op het vetgehalte, waarvan 16 monsters op het RIKILT. De rest werd op het M.C.S. Drente- Groningen in samenwerking met de Algemene Inspectiedienst onderzocht, om de praktijkomstandigheden te evenaren.
    Referentiemateriaal voor de bepaling van de vetzuursamen-stelling van melkvet
    Kamp, H.J. van der; Muuse, B.G. - \ 1982
    Wageningen : RIKILT (Verslag / RIKILT 82.42) - 9
    triacylglycerolen - gaschromatografie - boterzuur - melkvet - triacylglycerols - gas chromatography - butyric acid - milk fat
    Vaststellen van de vetzuursamenstelling van een monster botervet om te komen tot een in Nederland geaccepteerd referentiemonster. De samenstelling van enkele synthetische mengsels van triglyceriden werd berekend. De triglyceriden werden tevoren afzonderlijk gecontroleerd op zuiverheid aan de hand van correctiefactoren en gaschromatografische analysen. Met behulp van de triglyceride-mengsels werd de vetzuursamenstelling van een monster botervet vastgesteld. Dit resultaat werd vergeleken met de NIZO-uitkomst.
    Aantonen van gefraktioneerd botervet
    Muuse, B.G. ; Kamp, H.J. van der; Oortwijn, H. - \ 1982
    Wageningen : RIKILT (Verslag / RIKILT 83.3)
    melkvet - vetzuren - sterolen - triacylglycerolen - fractionering - voedselanalyse - analytische methoden - milk fat - fatty acids - sterols - triacylglycerols - fractionation - food analysis - analytical methods
    Doel van het onderzoek was het verkrijgen van methoden voor het aantonen van gefraktioneerd botervet, puur en na verwerking in levensmiddelen. In het kader van een ringonderzoek van de studiegroep gefraktioneerd botervet, werd in 5 x 3 monsters het gehalte c .q. de samenstelling bepaald van: vetzuren, 2 positie vetzuren, triglyceriden, sterolen. De ringtestmonsters bestonden uit normaal botervet (uitgangsmateriaal) en resp. de harde en zachte fraktie daarvan.
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