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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    Total Fermented Dairy Food Intake Is Inversely Associated with Cardiovascular Disease Risk in Women
    Buziau, Amée M. ; Soedamah-Muthu, Sabita S. ; Geleijnse, Johanna M. ; Mishra, Gita D. - \ 2019
    The Journal of Nutrition 149 (2019)10. - ISSN 0022-3166 - p. 1797 - 1804.
    Australia - cardiovascular disease - cheese - coronary heart disease - dairy - fermented dairy - stroke - type 2 diabetes mellitus - women's health - yogurt

    BACKGROUND: The relation between fermented dairy consumption and type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) in an Australian population remains to be established. OBJECTIVES: The aim of this study was to investigate the association between fermented dairy consumption and T2DM and CVD risk. METHODS: The Australian Longitudinal Study on Women's Health included Australian women (aged 45-50 y) at baseline in 2001, who were followed up through 5 surveys until 2016. Dietary intake was assessed through the use of a validated 101-item FFQ at baseline. Main study outcomes were self-reported physician-diagnosed T2DM and CVD. Logistic regression models adjusted for sociodemographic and lifestyle factors were used to estimate the association between dairy intake and T2DM and CVD risk. RESULTS: Of 7633 women free of diabetes at baseline, 701 (9.2%) developed T2DM during a maximum 15-y follow-up period. Women in the highest tertile of yogurt intake had lower adjusted odds of T2DM than those in the lowest tertile (OR: 0.81; 95% CI: 0.67, 0.99; P = 0.041). This relation became nonsignificant after adjustment for dietary variables and total energy intake (OR: 0.88; 95% CI: 0.71, 1.08; P = 0.21). Of 7679 women free of CVD at baseline, 835 (10.9%) cases of CVD were reported during follow-up. High intake of yogurt and total fermented dairy was associated with lower CVD risk (OR: 0.84; 95% CI: 0.70, 1.00; P = 0.05, 0.80; 0.67, 0.96; 0.017, respectively) than observed in the lowest tertile of dairy product intake. Additional adjustment attenuated the relation (OR: 0.87; 95% CI: 0.72, 1.04; P = 0.13, 0.83; 0.69, 1.00; 0.048, for yogurt and total fermented dairy, respectively). No associations were found with other dairy groups. CONCLUSION: The findings from this population-based study of Australian women suggest an inverse association between total fermented dairy intake and CVD risk, which may partly be accounted for by other dietary components.

    Consumption of dairy foods and diabetes incidence: a dose-response meta-analysis of observational studies
    Gijsbers, L. ; Ding, E.L. ; Malik, Vasanti ; Goede, J. de; Geleijnse, J.M. ; Soedamah-Muthu, S.S. - \ 2016
    American Journal of Clinical Nutrition 103 (2016)4. - ISSN 0002-9165 - p. 1111 - 1124.
    dairy - milk - yoghurt - type 2 diabetes - cheese
    BACKGROUND: A growing number of cohort studies suggest a potential role of dairy consumption in type 2 diabetes (T2D) prevention. The strength of this association and the amount of dairy needed is not clear. OBJECTIVE: We performed a meta-analysis to quantify the associations of incident T2D with dairy foods at different levels of intake. DESIGN: A systematic literature search of the PubMed, Scopus, and Embase databases (from inception to 14 April 2015) was supplemented by hand searches of reference lists and correspondence with authors of prior studies. Included were prospective cohort studies that examined the association between dairy and incident T2D in healthy adults. Data were extracted with the use of a predefined protocol, with double data-entry and study quality assessments. Random-effects meta-analyses with summarized dose-response data were performed for total, low-fat, and high-fat dairy, (types of) milk, (types of) fermented dairy, cream, ice cream, and sherbet. Nonlinear associations were investigated, with data modeled with the use of spline knots and visualized via spaghetti plots. RESULTS: The analysis included 22 cohort studies comprised of 579,832 individuals and 43,118 T2D cases. Total dairy was inversely associated with T2D risk (RR: 0.97 per 200-g/d increment; 95% CI: 0.95, 1.00; P = 0.04; I2 = 66%), with a suggestive but similar linear inverse association noted for low-fat dairy (RR: 0.96 per 200 g/d; 95% CI: 0.92, 1.00; P = 0.072; I2 = 68%). Nonlinear inverse associations were found for yogurt intake (at 80 g/d, RR: 0.86 compared with 0 g/d; 95% CI: 0.83, 0.90; P < 0.001; I2 = 73%) and ice cream intake (at ∼10 g/d, RR: 0.81; 95% CI: 0.78, 0.85; P < 0.001; I2 = 86%), but no added incremental benefits were found at a higher intake. Other dairy types were not associated with T2D risk. CONCLUSION: This dose-response meta-analysis of observational studies suggests a possible role for dairy foods, particularly yogurt, in the prevention of T2D. Results should be considered in the context of the observed heterogeneity.
    Chymosin-induced hydrolysis of caseins: Influence of degree of phosphorylation of alpha-s1-casein and genetic variants of beta-casein
    Bijl, E. ; Valenberg, H.J.F. van; Sikkes, S. ; Jumelet, S. ; Sala, G. ; Olieman, K. ; Hooijdonk, A.C.M. van; Huppertz, T. - \ 2014
    International Dairy Journal 39 (2014)2. - ISSN 0958-6946 - p. 215 - 221.
    capillary-zone-electrophoresis - rennet coagulation properties - bovine alpha-s1-casein - protein-composition - milk-proteins - kappa-casein - secondary structure - individual cows - polyproline-ii - cheese
    The objective of this study was to investigate the impact of natural variations in aS1-casein and b-casein composition of milk on chymosin-induced hydrolysis of these caseins in milk gels and in sodium caseinate solutions. At 50% casein degradation, 15% more of aS1-casein with eight phosphate groups was hydrolysed compared with aS1-casein with nine phosphate groups in chymosin-induced milk gels. Furthermore, in sodium caseinate solutions, >10% more b-casein A2 was degraded compared with bcasein A1 and B at 50% casein degradation. Proteolysis by chymosin was not impacted by natural variation in the aS1-casein/b-casein ratio. Natural variation in aS1-casein/b-casein ratio did not impact upon firmness and gel strength in milk gels. Overall, comparison of sodium caseinate solutions to milk gels showed that differences in either phosphorylation of aS1-casein or amino acid composition of b-casein caused significant differences in degradation by chymosin, possibly due to changes in physical conformation of caseins.
    Verification of fresh grass feeding, pasture grazing and organic farming by FTIR spectroscopy analysis of bovine milk
    Capuano, E. ; Rademaker, J. ; Bijgaart, H. van den; Ruth, S.M. van - \ 2014
    Food Research International 60 (2014). - ISSN 0963-9969 - p. 59 - 65.
    near-infrared spectroscopy - fatty-acid-composition - total mixed ration - geographic origin - edible oils - dairy-cows - fluorescence - cheese - food - differentiation
    In the present study, a total of 116 tank milk samples were collected from 30 farms located in The Netherlands and analysed by Fourier-transform infrared (FTIR) spectroscopy. Samples were collected in April, May and June 2011 and in February 2012. The samples differed in the time spent by the cows on pasture, presence/absence of fresh grass in the daily ration and the farming system (organic/biodynamic or conventional). Classification models based on partial least square discriminant analysis (PLS-DA) of FTIR spectra were developed for the prediction of fresh grass feeding, pasture grazing and organic farming. The PLS-DA model discriminated between milk from cows that had fresh grass in the daily ration and milk from cows that had not fresh grass with sensitivity and specificity values of 88% and 83% in external validation and all the samples from cows that had no fresh grass collected in spring were correctly classified. The PLS-DA model developed for the authentication of pasture grazing showed comparable accuracy when the whole sample set is considered but was less accurate on the spring samples (75% of samples from cows indoors in spring correctly classified). Discrimination of organic and conventional milk was also accomplished with acceptable accuracy with % correct classification of 80% and 94% respectively in external validation. The results suggest that milk FTIR spectra contain valuable information on cows' diet that can be used for authentication purposes.
    Multifactorial diversity sustains microbial community stability
    Erkus, O. ; Jager, V.C.L. de; Spus, M. ; Alen-Boerrigter, I.J. van; Rijswijck, I.M.H. van; Hazelwood, L. ; Janssen, P.W. ; Hijum, S.A.F.T. van; Kleerebezem, M. ; Smid, E.J. - \ 2013
    ISME Journal 7 (2013)11. - ISSN 1751-7362 - p. 2126 - 2136.
    lactic-acid bacteria - complete genome sequence - lactococcus-lactis - dairy environment - subsp lactis - raw-milk - cremoris - plasmids - cheese - identification
    Maintenance of a high degree of biodiversity in homogeneous environments is poorly understood. A complex cheese starter culture with a long history of use was characterized as a model system to study simple microbial communities. Eight distinct genetic lineages were identified, encompassing two species: Lactococcus lactis and Leuconostoc mesenteroides. The genetic lineages were found to be collections of strains with variable plasmid content and phage sensitivities. Kill-the-winner hypothesis explaining the suppression of the fittest strains by density-dependent phage predation was operational at the strain level. This prevents the eradication of entire genetic lineages from the community during propagation regimes (back-slopping), stabilizing the genetic heterogeneity in the starter culture against environmental uncertainty
    Genome-scale metabolic model for Lactococcus lactis MG1363 and its application to the analysis of flavor formation
    Flahaut, N.A.L. ; Wiersma, A. ; Bunt, B. van der; Martens, D.E. ; Schaap, P.J. ; Sijtsma, L. ; Martins Dos Santos, V.A.P. ; Vos, W.M. de - \ 2013
    Applied Microbiology and Biotechnology 97 (2013)19. - ISSN 0175-7598 - p. 8729 - 8739.
    amino-acid catabolism - streptococcus-lactis - cremoris mg1363 - steady-state - bacteria - growth - reconstruction - networks - systems - cheese
    Lactococcus lactis subsp. cremoris MG1363 is a paradigm strain for lactococci used in industrial dairy fermentations. However, despite of its importance for process development, no genome-scale metabolic model has been reported thus far. Moreover, current models for other lactococci only focus on growth and sugar degradation. A metabolic model that includes nitrogen metabolism and flavor-forming pathways is instrumental for the understanding and designing new industrial applications of these lactic acid bacteria. A genome-scale, constraint-based model of the metabolism and transport in L. lactis MG1363, accounting for 518 genes, 754 reactions, and 650 metabolites, was developed and experimentally validated. Fifty-nine reactions are directly or indirectly involved in flavor formation. Flux Balance Analysis and Flux Variability Analysis were used to investigate flux distributions within the whole metabolic network. Anaerobic carbon-limited continuous cultures were used for estimating the energetic parameters. A thorough model-driven analysis showing a highly flexible nitrogen metabolism, e.g., branched-chain amino acid catabolism which coupled with the redox balance, is pivotal for the prediction of the formation of different flavor compounds. Furthermore, the model predicted the formation of volatile sulfur compounds as a result of the fermentation. These products were subsequently identified in the experimental fermentations carried out. Thus, the genome-scale metabolic model couples the carbon and nitrogen metabolism in L. lactis MG1363 with complete known catabolic pathways leading to flavor formation. The model provided valuable insights into the metabolic networks underlying flavor formation and has the potential to contribute to new developments in dairy industries and cheese-flavor research.
    Microbe-microbe interactions in mixed culture food fermentations
    Smid, E.J. ; Lacroix, C. - \ 2013
    Current Opinion in Biotechnology 24 (2013)2. - ISSN 0958-1669 - p. 148 - 154.
    lactic-acid bacteria - cheese - genomics - growth - propionibacteria - communication - lactobacilli - probiotics - consortia - milk
    Most known natural and industrial food fermentation processes are driven by either simple or complex communities of microorganisms. Obviously, these fermenting microbes will not only interact with the fermentable substrate but also with each other. These microbe–microbe interactions are complex but thought to be crucial for obtaining the desired product characteristics. Microbial interactions are mediated through a variety of molecular and physiological mechanisms. Examples of interaction mechanisms which have an impact on the outcome of food fermentation processes will be discussed. Finally, the technological and scientific challenges associated with the production and propagation of complex mixed starter cultures are briefly addressed. Research on the composition and functionality of complex microbial consortia is gaining momentum and will open new avenues for controlling and improving food fermentation processes, and developing new applications for mixed cultures.
    Inhomogeneous distribution of fat enhances the perception of fat-related sensory attributes in gelled foods
    Mosca, A.C. ; Rocha, J.L. ; Sala, G. ; Velde, F. van de; Stieger, M.A. - \ 2012
    Food Hydrocolloids 27 (2012)2. - ISSN 0268-005X - p. 448 - 455.
    emulsion-filled gels - oil droplet - custard desserts - texture - microstructure - deformation - fracture - cheese
    This study investigated the effect of the spatial distribution of fat on the perception of fat-related sensory attributes using a model system that consisted of layered agar/gelatin gels containing oil-in-water (O/W) emulsion droplets dispersed in the gel matrix. Four layers of gel varying in the amount of emulsion droplets were combined to prepare samples with homogeneous and inhomogeneous distributions of fat (emulsion droplets). The composition of the gels was optimized to obtain samples with comparable mechanical properties. A significant enhancement of mouthfeel attributes such as spreadable and melting was observed in samples with inhomogeneous distributions of fat in a Quantitative Descriptive Analysis (QDA) panel. Inhomogeneous samples with large differences in fat content between layers were perceived more spreadable and melting than the sample in which fat was homogeneously distributed. Creaminess ratings tended to increase as the difference in fat content between layers increased in the inhomogeneous samples. Additionally, the position of the high-fat layers in the sample affected the perception of fat-related attributes. The sample with high-fat layers on the outside had the highest ratings for all mouthfeel and afterfeel attributes. The enhancement of fat-related attributes by an inhomogeneous distribution of fat depended on the overall fat content. The enhancement at 15 wt% fat was larger than that at 5 wt% fat. We suggest that the modulation of the spatial distribution of fat can be used to reduce the fat content of food products without causing undesirable changes in the sensory properties
    Time-resolved genetic responses of Lactococcus lactis to a dairy environment
    Bachmann, H. ; Wilt, L. de; Kleerebezem, M. ; Hylckama Vlieg, J.E.T. van - \ 2010
    Environmental Microbiology 12 (2010)5. - ISSN 1462-2912 - p. 1260 - 1270.
    flavor formation - acid bacteria - lactobacillus-plantarum - stationary-phase - stress responses - regulated genes - amino-acids - expression - cheese - identification
    Lactococcus lactis is one of main bacterial species found in mixed dairy starter cultures for the production of semi-hard cheese. Despite the appreciation that mixed cultures are essential for the eventual properties of the manufactured cheese the vast majority of studies on L. lactis were carried out in laboratory media with a pure culture. In this study we applied an advanced recombinant in vivo expression technology (R-IVET) assay in combination with a high-throughput cheese-manufacturing protocol for the identification and subsequent validation of promoter sequences specifically induced during the manufacturing and ripening of cheese. The system allowed gene expression measurements in an undisturbed product environment without the use of antibiotics and in combination with a mixed strain starter culture. The utilization of bacterial luciferase as reporter enabled the real-time monitoring of gene expression in cheese for up to 200 h after the cheese-manufacturing process was initiated. The results revealed a number of genes that were clearly induced in cheese such as cysD, bcaP, dppA, hisC, gltA, rpsE, purL, amtB as well as a number of hypothetical genes, pseudogenes and notably genetic elements located on the non-coding strand of annotated open reading frames. Furthermore genes that are likely to be involved in interactions with bacteria used in the mixed strain starter culture were identified
    Genetic and nongenetic variation in concentration of selenium, calcium, potassium, zinc, magnesium, and phosphorus in milk of Dutch Holstein-Friesian cows
    Hulzen, K.J.E. van; Sprong, R.C. ; Meer, R. van der; Arendonk, J.A.M. van - \ 2009
    Journal of Dairy Science 92 (2009)11. - ISSN 0022-0302 - p. 5754 - 5759.
    production traits - dairy-cows - parameters - cheese - plasma - supplementation - transport - proteins - minerals - elements
    Minerals found in milk, such as Se, Ca, K, Zn, Mg, and P, contribute to several vital physiological processes. The aim of this study was to quantify the genetic variation in levels of Se, Ca, K, Zn, Mg, and P in milk and to quantify the between-herd variation in the levels of these minerals in milk. One morning milk sample from each of 1,860 Dutch Holstein-Friesian cows from 388 commercial herds in the Netherlands was used. Concentration of minerals was determined by inductively coupled plasma-atomic emission spectrometry. Variance components were estimated using an animal model with covariates for days in milk and age at first calving; fixed effects for season of calving and effect of test or proven bull; and random effects for animal, herd, and error. Heritability and proportion of phenotypic variation that can be explained by herd were estimated using univariate analysis. The intraherd heritability for Se was low (0.20) whereas herd explained 65% of the total variation in Se. Variation between herds most likely results from variation in Se content in the feed, which partly reflects variation in Se levels in the soil. Intraherd heritabilities for Ca, K, Zn, Mg, and P were moderate to high and were 0.57, 0.46, 0.41, 0.60, and 0.62, respectively. For Ca, K, Zn, Mg, and P, the proportions of phenotypic variation that could be explained by herd were low (0.13–0.24). This study shows that there are possibilities for altering the mineral composition of milk. For Ca, K, Zn, Mg, and P, there are good prospects for selective breeding whereas, for Se, measures at farm level may be more effective
    Regulatory phenotyping reveals important diversity within the species Lactococcus lactis
    Bachmann, H. ; Starrenburg, M. ; Dijkstra, A. ; Molenaar, D. ; Kleerebezem, M. ; Rademaker, J.L.W. ; Hylckama Vlieg, J.E.T. van - \ 2009
    Applied and Environmental Microbiology 75 (2009)17. - ISSN 0099-2240 - p. 5687 - 5694.
    escherichia-coli - flavor formation - streptococcus-cremoris - natural diversity - gene inactivation - parallel changes - acid bacteria - cheese - evolution - subsp
    The diversity in regulatory phenotypes among a collection of 84 Lactococcus lactis strains isolated from dairy and nondairy origin was explored. The specific activities of five enzymes were assessed in cell extracts of all strains grown in two different media, a nutritionally rich broth and a relatively poor chemically defined medium. The five investigated enzymes, branched chain aminotransferase (BcaT), aminopeptidase N (PepN), X-prolyl dipeptidyl peptidase (PepX), alpha-hydroxyisocaproic acid dehydrogenase (HicDH), and esterase, are involved in nitrogen and fatty acid metabolism and catalyze key steps in the production of important dairy flavor compounds. The investigated cultures comprise 75 L. lactis subsp. lactis isolates (including 7 L. lactis subsp. lactis biovar diacetylactis isolates) and 9 L. lactis subsp. cremoris isolates. All L. lactis subsp. cremoris and 22 L. lactis subsp. lactis (including 6 L. lactis subsp. lactis biovar diacetylactis) cultures originated from a dairy environment. All other cultures originated from (fermented) plant materials and were isolated at different geographic locations. Correlation analysis of specific enzyme activities revealed significantly different regulatory phenotypes for dairy and nondairy isolates. The enzyme activities in the two investigated media were in general poorly correlated and revealed a high degree of regulatory diversity within this collection of closely related strains. To the best of our knowledge, these results represent the most extensive diversity analysis of regulatory phenotypes within a single bacterial species to date. The presented findings underline the importance of the availability of screening procedures for, e.g., industrially relevant enzyme activities in models closely mimicking application conditions. Moreover, they corroborate the notion that regulatory changes are important drivers of evolution
    Salt Reduction in Foods Using Naturally Brewed Soy Sauce
    Kremer, S. ; Mojet, J. ; Shimojo, R. - \ 2009
    Journal of Food Science 74 (2009)6. - ISSN 0022-1147 - p. S255 - S262.
    monosodium glutamate - sodium content - processed foods - meat-products - taste - nacl - chloride - cheese - acid - kcl
    In recent years, health concerns related to salt/sodium chloride consumption have caused an increased demand for salt-reduced foods. Consequently, sodium chloride (NaCl) reduction in foods has become an important challenge. The more so, since a decrease in NaCl content is often reported to be associated with a decrease in consumer acceptance. The objective of the present study was to investigate whether or not it would be possible to reduce the NaCl content in standard Western European foods by replacing it with naturally brewed soy sauce. Three types of foods were investigated: salad dressing (n = 56), soup (n = 52), and stir-fried pork (n = 57). In the 1st step, an exchange rate (ER) by which NaCl can be replaced with soy sauce without a significant change in the overall taste intensity was established per product type, by means of alternative forced choice tests. In the 2nd step, the same consumers evaluated 5 samples per product type with varying NaCl and/or soy sauce content on pleasantness and several sensory attributes. The results showed that it was possible to achieve a NaCl reduction in the tested foods of, respectively, 50%, 17%, and 29% without leading to significant losses in either overall taste intensity or product pleasantness. These results suggest that it is possible to replace NaCl in foods with naturally brewed soy sauce without lowering the overall taste intensity and to reduce the total NaCl content in these foods without decreasing their consumer acceptance.
    Energy storage controls crumbly perception in whey proteins/polysaccharide mixed gels
    Berg, L. van den; Carolas, A.L. ; Vliet, T. van; Linden, E. van der; Boekel, M.A.J.S. van; Velde, F. van de - \ 2008
    Food Hydrocolloids 22 (2008)7. - ISSN 0268-005X - p. 1404 - 1417.
    property relationships - large-deformation - foods - microstructure - proteins - gelation - texture - cheese - ph
    This paper describes the relation between crumbliness of whey proteins/polysaccharide mixed gels and their physical properties. Crumbly sensation relates strongly to the breakdown behaviour of the gels, which is primarily determined by their viscoelastic properties. These properties result from the balance between elastically stored energy and energy dissipation during deformation. The stored energy is determined as the percentage of the recoverable energy in a compression¿decompression test. Gels breaking readily via a free-running crack (i.e. high recoverable energy) were perceived as the most crumbly ones. Gels showing slow, yielding-like breakdown (i.e. high energy dissipation) were sensed as the least crumbly by assessors during quantitative descriptive analysis (QDA). Serum release from the gels contributed to a large extent to the energy dissipation and thus decreased crumbliness. Microstructure affects serum release and therefore indirectly microstructure affected the crumbly sensation. The relations between crumbly sensation and physical and structural properties of the gels are, to our knowledge, reported here for the first time and can be applied to control and engineer crumbliness of semi-solid foods.
    Identification of plant proteins in adulterated skimmed milk powder by high-performance liquid chromatography-mass spectrometry
    Luykx, D.M.A.M. ; Cordewener, J.H.G. ; Ferranti, P. ; Frankhuizen, R. ; Bremer, M.G.E.G. ; Hooijerink, H. ; America, A.H.P. - \ 2007
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1164 (2007)1-2. - ISSN 0021-9673 - p. 189 - 197.
    fast atom bombardment - electrospray-ionization - reversed-phase - capillary-electrophoresis - perfusion chromatography - soybean proteins - dairy-products - pea - biomolecules - cheese
    The EU subsidises the use of skimmed-milk powder (SMP) in compound feeding stuffs. There are indications of falsified SMP content due to the addition of plant proteins. These proteins are not allowed in SMP and cannot be identified by the official reference method. Since soy and pea proteins are most likely to be added to SMP, manufactured SMP containing 1 and 5% of these plant proteins was used to develop a sensitive protein identification method based on mass spectrometry (MS). The method included a pre-fractionation step to enrich for plant proteins by using a borate buffer. A very fast perfusion liquid chromatography method including sensitive and selective intrinsic fluorescence detection was developed for monitoring and quantifying the efficiency of the pre-fractionation and screening for plant proteins. After tryptic digestion of the enriched fraction from manufactured adulterated SMP, numerous peptides originating from the major seed proteins of soy (glycinin, ß-conglycin) and pea (legumin, vicilin) could be identified by MS/MS analysis on a quadrupole time-of-flight MS instrument.
    Felinine stability in the presence of selected urine compounds
    Rutherfurd, S.M. ; Kitson, T.M. ; Woolhouse, A.D. ; McGrath, M.C. ; Hendriks, W.H. - \ 2007
    Amino Acids 32 (2007)2. - ISSN 0939-4451 - p. 235 - 242.
    carbamylation - identification - cheese - flavor - serum - acid - urea
    The stability of felinine, an amino acid present in feline urine, was investigated. Synthetic felinine was unstable in the urine of a selection of mammals. Felinine was found to stable in feline urine in which urea had been degraded. Synthetic felinine was found to react specifically with urea and did not react with urea analogues such as biuret or thiourea or other nucleophilic compounds such as ammonia which is more nucleophilic or acetamide and water which are less nucleophilic than urea. The reaction of urea and felinine was independent of pH over the range of 3¿10. Urea did not react with N-acetyl-felinine suggesting a felinine N-terminal interaction with urea. Mass spectral analysis of the reaction products showed the presence of carbamylated felinine and fragmentation ions derived from carbamyl-felinine. The physiological relevance of felinine carbamylation is yet to be determined.
    Serum release: The hidden quality in fracturing composites
    Berg, L. van den; Vliet, T. van; Linden, E. van der; Boekel, M.A.J.S. van; Velde, F. van de - \ 2007
    Food Hydrocolloids 21 (2007)3. - ISSN 0268-005X - p. 420 - 432.
    whey proteins - starch gels - gelation - systems - polysaccharides - microstructure - rheology - cheese - tests - model
    Release of serum is important for many food systems such as meat products and its replacers, gels, vegetables and fruit, where serum release plays a clear role in the perception of juiciness. Nevertheless, this phenomenon and its consequences for large deformation and fracture behaviour have not been studied extensively for semi-solid food systems. It has been avoided in the experimental setup or it even has been neglected in analysis of the data. In this study mixed whey protein isolate/gellan gum gels were used as model systems. Gels were subjected to uniaxial compression and evaluated sensorically by a quantitative descriptive analysis panel. The latter showed that serum release was a dominant factor in sensory perception of the gels regarding mouthfeel attributes as slippery and watery. Compression experiments showed that serum release is related to microstructural characteristics of the gels. The serum release can be described by flow through a porous medium, starting from the Darcy's equation. It was demonstrated that the large deformation mechanical properties of the gels can be described better by correcting for the effect of serum release. Moreover, a relation between serum release, gel microstructure and sensory evaluation was established
    Improving farm management by modeling the contamination of farm tank milk with butyric acid bacteria
    Vissers, M.M.M. ; Driehuis, F. ; Giffel, M.C. te; Jong, P. de; Lankveld, J.M.G. - \ 2006
    Journal of Dairy Science 89 (2006)3. - ISSN 0022-0302 - p. 850 - 858.
    clostridium-tyrobutyricum - bacillus-cereus - grass-silage - cheese - growth - spores - food
    Control of contamination of farm tank milk (FTM) with the spore-forming butyric acid bacteria (BAB) is important to prevent the late-blowing defect in semi-hard cheeses. The risk of late blowing can be decreased via control of the contamination level of FTM with BAB. A modeling approach was applied to identify an effective control strategy at the farm level. The simulation model developed was based on a translation of the contamination pathway into a chain of unit operations. Using various simulations, the effects of factors related to feed quality, feed management, cattlehouse hygiene, and milking practices on the contamination level of FTM were evaluated. Contamination level of silage was found to be the most important factor. When silage contains on average less than 3 log(10) BAB/g, a basic pretreatment of udder teats before milking (similar to 75% removal of attached spores) is sufficient to assure an FTM contamination level below 1 BAB/mL. When silage contains more than 5 log(10) BAB/g, it should not be fed, because it then becomes almost impossible to assure an FTM contamination level below 1 BAB/mL. Measures aimed at improving cattlehouse hygiene, the contamination via soil, and the contamination level of other feeds contribute only marginally to the control of the contamination of FTM with BAB. Application of the modeling methodology could be beneficial for the control of the contamination of FTM with other microorganisms such as Bacillus cereus.
    Fast biosensor immunoassays for the detection of cows' milk in the milk of ewes and goats
    Haasnoot, W. ; Smits, N.G.E. ; Voncken, A.E.M. ; Bremer, M.G.E.G. - \ 2004
    Journal of Dairy Research 71 (2004)3. - ISSN 0022-0299 - p. 322 - 329.
    linked-immunosorbent-assay - bovine beta-casein - monoclonal-antibodies - polyclonal antibodies - liquid-chromatography - k-casein - cheese - elisa - proteins - ovine
    Two monoclonal antibodies (MAb) raised against bovine K-casein were developed and applied in an automated optical biosensor (Biacore 3000) to create easy and fast direct and inhibition biosensor immunoassays (BIA) for the detection of cows' milk in the milk of ewes and goats. With both assay formats, low limits of detection (350 tests); and the wide measurement range (0·1 to 10% cows' milk). Despite these advantages, the inhibition BIA (using K-casein immobilized on the chip) was preferred because of the possible application of non-purified Mab, the higher responses, the higher sensitivity at relevant low percentages of cows' milk and its robustness (>800 cycles per chip)
    Effect of NaCl on textural changes and protein and lipid degradation during the ripening stage of sufu, a Chinese fermented soybean food
    Han, B. ; Wang, J.H. ; Rombouts, F.M. ; Nout, M.J.R. - \ 2003
    Journal of the Science of Food and Agriculture 83 (2003)9. - ISSN 0022-5142 - p. 899 - 904.
    glycine-max curds - soya bean curd - volatile components - ethanol - cheese - yield - tofu
    Sufu is made by solid state fungal fermentation (using Actinomucor elegans) of tofu, followed by salting and maturation in dressing mixtures containing salt, alcohol and various other ingredients. NaCl in dressing mixtures strongly affected the changes in textural properties and the hydrolysis of protein and lipid of sufu. Higher salt contents (14% w/w) resulted in increased hardness (+100%) and elasticity (+18%) and reduced adhesiveness (-30%). Hardness and elasticity could be used to judge the extent of sufu ripening. SDS-PAGE showed the disappearance of all protein subunits at 80 and 110 g kg(-1) salt content; however, some protein subunits were still detectable at 140 g kg(-1) salt content after 60 days of ripening. Higher ratios of free amino nitrogen to total nitrogen (FAN/TN = 0.4-0.45) and free amino acids to crude protein (FAA/CP = 0.24-0.26) were observed in sufu with lower (80 g kg(-1)) salt content. FAN/TN and FAA/CP in white sufu (obtained with dressing mixtures containing only salt and alcohol) were higher than those in red sufu (obtained with dressing mixtures containing angkak or kojic red rice) owing to different dressing mixture compositions. Increases in free fatty acids (FFA) were also observed during ripening. FFA levels in sufu with lower salt content increased rapidly during the first 30-40 days and then increased slowly, probably resulting from the formation of fatty acid esters. Lowering the salt content (80 g kg(-1)) can shorten the ripening time to 40 days, which is of benefit to manufacturers. However, sufu will spoil, ie undergo souring, during the ripening stage at salt contents of SO g kg(-1) or lower. (C) 2003 Society of Chemical Industry.
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