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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National Reference Laboratories RIKILT : annual report 2017
Leeuwen, S.P.J. van; Mol, J.G.J. ; Lee, M.K. van der; Gerssen, A. ; Lasaroms, J.J.P. ; Sterk, S.S. ; Raamsdonk, L. aan; Jong, J. de; Scholtens, I.M.J. ; Alewijn, A. ; Silletti, E. ; Ginkel, L. van; Noordam, M.Y. ; Meijer, N. - \ 2018
Wageningen : RIKILT Wageningen University & Research (RIKILT-report 2018.009) - 51
Effect of NaCl and sucrose tastants on proteincomposition of oralfluidanalysed by SELDI-TOF-MS
Silletti, E. ; Bult, J.H.F. ; Stieger, M.A. - \ 2012
Archives of Oral Biology 57 (2012)9. - ISSN 0003-9969 - p. 1200 - 1210.
acquired enamel pellicle - flight-mass-spectrometry - proline-rich proteins - human parotid-saliva - 2-dimensional gel-electrophoresis - human whole - serum biomarkers - ionization-time - tandem ms - identification
During eating, human saliva is secreted into the oral cavity by salivary glands. The relative contribution of different glands to total salivary flow rate depends, among other factors, on the tastants in the food. Few reports indicated that also the salivary proteincomposition depends on the tastant make-up of the food. We studied the influence of sodium-chloride- and sucrose solutions on the presence of proteins in the Mr range 2–20 kDa in whole saliva. Upon oral stimulation with a sodium chloride solution, a sucrose solution or water, we collected whole saliva from 14 volunteers after t = 1 min, t = 11 min and t = 20 min. Saliva protein profiles were analysed by SELDI-TOF-MS. SELDI-TOF-MS intensities of m/z values representing different protein masses were compared between subjects, tastants and time conditions. For subsets of the 33 detected masses, significant effects were observed for all factors, with most masses involved in the Subjects effect: m/zSubjects > m/zTime×Stimulus > m/zStimulus > m/zTime. Most effects on saliva proteincomposition were observed at t = 1 min, whilst almost no effects were observed at t = 11 min and t = 20 min. When considering the Stimulus × Time interaction, we identified four different stimulus–response patterns. Proteins identified in the present study, and attributed to specific glands or tissues in literature, were used to associate stimulus–response patterns with tissue provenances. Observed stimulus–response patterns were not uniquely associated to particular glands and tissues. Hence, there was no evidence of the involvement of particular tissues or glands in tastant-specific protein responses. In conclusion, oral stimulation with different tastants affects salivary proteincomposition in a protein- and stimuli dependent way, which seems not be associated with any specific tissues or glands of origin.
In vitro study of intestinal lipolysis using pH-stat and gas chromatography
Helbig, A. ; Silletti, E. ; Timmerman, E. ; Hamer, R.J. ; Gruppen, H. - \ 2012
Food Hydrocolloids 28 (2012)1. - ISSN 0268-005X - p. 10 - 19.
pancreatic lipase activity - human gastric lipase - fat digestion - bile-salt - stereoselective hydrolysis - emulsion flocculation - droplet sizes - digestibility - triglycerides - absorption
Developing healthy products requires in-depth knowledge of digestion. This study focuses on lipid digestion in relation to emulsion properties typically followed by pH-stat. Although this is a fast and easy method to follow the overall digestion, it provides no details on lipid digestion products. Thus, the aims of the present study were to use gas chromatography (GC) to determine all products present during lipolysis, i.e. monoglycerides (MG), diglycerides (DG) and triglycerides (TG), and to compare this method with the pH-stat method for free fatty acids (FFA). Fine, medium and coarse emulsions stabilized with two different emulsifiers (whey protein isolate (WPI) or gum arabic) were digested under in vitro intestinal conditions. Although the amount of FFA increased for both methods for WPI stabilized emulsions, the amount of FFA was 2–3 times higher when determined by GC compared with pH-stat. GC analysis showed decreasing amounts of MG and DG with increasing droplet size for both emulsions. Molar ratios of FFA/DG and MG/DG were twofold higher for WPI than for gum arabic stabilized emulsions. This indicates that the total production of lipolytic products (i.e. FFA + MG + DG) depends on the droplet size and the emulsifier but their proportions only depend on the emulsifier. Although pH-stat provides a fast measure of FFA release, it is influenced by the emulsifier type at the oil–water interface and therefore care should be taken when interpreting pH-stat results. We suggest combining this method with GC for accurate FFA determination and further evaluation of all lipolytic products.
Identification of salivary proteins at oil–water interfaces stabilized by lysozyme and ß-lactoglobulin
Silletti, E. ; Vitorino, R.M.P. ; Schipper, R.G. ; Amado, F.M.L. ; Vingerhoeds, M.H. - \ 2010
Archives of Oral Biology 55 (2010)4. - ISSN 0003-9969 - p. 268 - 278.
acquired enamel pellicle - polyacrylamide-gel-electrophoresis - induced emulsion flocculation - proline-rich proteins - human whole saliva - mucin mg1 - structural features - mass-spectrometry - dental-caries - sds-page
In this research, we investigated the interaction occurring between oil-in-water emulsion droplets, stabilized by different emulsifiers, i.e. lysozyme and ß-lactoglobulin (ß-lg), and salivary proteins (SPs) with a molecular mass (Mr) above about 10 kDa. Different techniques, i.e. infrared spectroscopy, Western blotting, PAS staining and SDS-PAGE coupled to MS, were employed for this purpose. This study demonstrated the interaction between several salivary proteins and the emulsifiers at the oil–water interfaces. In particular, results show that the high Mr mucin MUC5B was strongly bound to lysozyme stabilized emulsions, whereas ß-lg stabilized emulsions associated with MUC7 and, moderately, with MUC5B. Furthermore, we observed that salivary proteins in the range Mr 10–100 kDa associated differently with emulsion droplets. A large majority of SPs was found to interact with lysozyme stabilized emulsion droplets whilst in case of ß-lg stabilized emulsions, the SPs distribute more evenly between the fraction associated and non-associated with the droplets. A clear example is a-amylase (Mr 55 kDa) which predominantly associates with lysozyme stabilized emulsion droplets, but not with ß-lg emulsion droplets. To conclude, our findings indicate that adsorption/association of salivary protein components onto the emulsion droplets is related to the type of emulsifying proteins at the oil–water interfaces and it is probably driven by the overall net charge at the droplet's oil–water interfaces, i.e. positive for lysozyme stabilized emulsions and negative for ß-lactoglobulin stabilized emulsion at neutral pH.
Relating the effect of saliva-induced emulsion flocculation on rheological properties and retention on the tongue surface with sensory perception
Vingerhoeds, M.H. ; Silletti, E. ; Groot, J. de; Schipper, R.G. ; Aken, G.A. van - \ 2009
Food Hydrocolloids 23 (2009)3. - ISSN 0268-005X - p. 773 - 785.
oil-in-water - custard desserts - alpha-amylase - oral texture - creaminess - protein - tannin - model - viscosity - lysozyme
Perception of food emulsions can often not be directly related to the structure of the products before consumption. Taking into account the changing product structure upon oral processing might increase understanding of the relation between perception and product properties. This study aims to gain insight in the effect of saliva-induced flocculation on perception of emulsions at neutral pH. Whey protein (WPI)-stabilized emulsions flocculating in a reversible manner with saliva were compared with lysozyme-stabilized emulsions that irreversible flocculate with saliva. The main emulsion variables, besides the emulsifying protein, were oil content (2.5% oil vs 10% oil), and the effect of emulsion thickening with guar gum (at 10% oil). To relate perception to processes occurring in the oral cavity, the emulsions were characterized before and after oral processing with respect to morphology and rheological properties (viscosity, storage and loss moduli). In addition, insight in retention of emulsion droplets on the tongue surface was obtained by measuring emulsifier and oil content in tongue swabs. Saliva-induced emulsion flocculation clearly shows a large effect on perception of the here studied emulsions. WPI-stabilized emulsions showed little retention on the tongue surface and perception was characterized by creaminess, fattiness and thickness. Guar gum thickening further increased perception of these attributes. On the other hand, for lysozyme-stabilized emulsions perception was largely related to attributes like dryness, roughness and astringency. In addition, a large viscosity increase upon oral processing and clear retention of emulsion droplets on the tongue surface was observed. Guar gum thickening decreased the effects of irreversible flocculation, likely because of its lubricating properties and increased viscosity. Although the amount of mucins recovered from the tongue surface was unaffected by orally processing of lysozyme-stabilized emulsions, the sensory characteristics of these emulsions reminds one of astringency perception of e.g. tannins that precipitate salivary proteins.
Identification of salivary peptides and proteins interacting with lysozyme and beta-lactoglobulin stabilized emulsions
Silletti, E. ; Vitorino, R.M.P. ; Schipper, R.G. ; Groot, J. de; Vingerhoeds, M.H. ; Amado, F.M.L. - \ 2008
Rheological Behavior of Food Emulsions Mixed with Saliva: Effect of Oil Content, Salivary Protein Content, and Saliva Type
Silletti, E. ; Vingerhoeds, M.H. ; Aken, G.A. van; Norde, W. - \ 2008
Food Biophysics 3 (2008)3. - ISSN 1557-1858 - p. 318 - 328.
in-water emulsions - transmission electron-microscopy - human glandular salivas - micelle-like structures - stabilized emulsions - depletion-flocculation - beta-lactoglobulin - sodium caseinate - oral behavior - polysaccharide
In this paper, we studied the effect of saliva on the rheological properties of ß-lactoglobulin- and lysozyme-stabilized emulsions, prepared at pH¿=¿6.7 in relation to variation of emulsions- and saliva-related parameters. The effect of oil¿volume fraction (2.5% w/w to 10% w/w), salivary protein concentration (0.1 to 0.8 mg ml¿1), and the use of both stimulated and unstimulated saliva was investigated. Viscosity and storage modulus were measured before (¿ emul and G¿emul, respectively) and after addition of saliva (¿ mix and G¿mix). To better estimate the changes due to saliva-induced flocculation of the emulsions, the ratios ¿ mix/¿ emul, G¿mix/G¿emul were calculated. In addition, tan ¿ (=the ratio of the loss and storage moduli) was investigated to evaluate the viscoelastic behavior of the emulsion/saliva mixtures. Increasing the oil¿volume fraction and salivary protein concentration resulted in an increase in ¿ mix/¿ emul and G¿mix/G¿emul, while a decrease in tan ¿ of the emulsion/saliva mixtures is occurring. When compared with unstimulated saliva, mixing ß-lactoglobulin-stabilized emulsions with stimulated saliva led to a reduction in ¿ mix/¿ emul and G¿mix/G¿emul, and an augment of tan ¿ at all measured deformations. In case of lysozyme-stabilized emulsions, the use of stimulated saliva increased G¿mix/G¿emul for ¿¿
When emulsions meet saliva : a physical-chemical, biochemical and sensory study
Silletti, E. - \ 2008
Wageningen University. Promotor(en): Willem Norde, co-promotor(en): G.A. van Aken; Monique Vingerhoeds. - S.l. : s.n. - ISBN 9789085048213 - 243
emulsies - eigenschappen - sensorische evaluatie - speeksel - uitvlokking - lysozym - eiwitexpressieanalyse - emulsions - properties - sensory evaluation - saliva - flocculation - lysozyme - proteomics
Keywords: Emulsion, flocculation, bridging, saliva, salivary protein, salivary peptides, lysozyme, -lactoglobulin, complex formation, LC-MS, SELDI-TOF-MS, proteomics.

Upon consumption food emulsions undergo various structural and compositional changes in the mouth. One of these changes is that mixing of an emulsion with saliva induces droplet flocculation
In the study described in this thesis we investigated the influence of saliva on emulsions properties, the mechanism of flocculation and the role in sensory perception. Firstly, we started with evaluating the effect of parameters related to emulsions on flocculation (i.e. differently charged surfactants and proteins such as -lactoglobulin and lysozyme used as emulsifiers and oil-volume fraction). Among the obtained results, we observed that the sign and the density of the charge on the surface of the droplets determine the (ir-)reversibility of flocculation upon dilution with water and shearing. Secondly, the effect of saliva-related parameters was analyzed. Among other aspects, it appeared that an increase in salivary protein concentration increased emulsion flocculation, and that extensive flocculation is typically found for unstimulated saliva. This approach shows that both emulsion and saliva properties affect the flocculation behavior of emulsions/saliva mixtures.
To investigate the nature of the flocculation, we characterized the salivary protein composition in both the continuous phase of the emulsion/saliva mixture and on the emulsion droplets. Different physical-chemical and biochemical techniques were used. For this approach, we focused on -lactoglobulin and lysozyme stabilized emulsions, which flocculated reversibly and irreversibly, respectively, upon mixing with saliva. A large number of salivary proteins and peptides in the molecular mass (Mr) range between 0.8 kDa and 100 kDa and the salivary mucins MUC5B and MUC7 (Mr > 200 kDa) associated with emulsion droplets of the emulsions. The results also indicate that the emulsifying protein at the oil-water interface determines which salivary components associate with the droplets in the flocs. A hypothesis is formulated that emulsion flocculation is mainly driven by a complex formation involving specific interactions and electrostatic attraction between salivary peptides/proteins and the emulsifying proteins at the droplets surface.
The importance of the saliva-induced droplet flocculation was demonstrated with a sensory paneling study. Emulsions stabilized by whey protein isolate, (predominantly composed of -lactoglobulin) showed reversible flocculation and were perceived as creamy. In contrast, emulsions stabilised by lysozyme showed irreversible flocculation and were perceived as dry, rough and astringent.
To conclude, this thesis shows that saliva-induced emulsion flocculation is driven mainly by association of salivary peptides and proteins to the droplets surface. Because of this, flocculation is determined by the composition of the droplet interface as well as the composition of the saliva, and can be controlled by variation of emulsion parameters (charge, pH, ionic strength). This interaction between emulsions and saliva may help to improve our understanding an control the sensory perception of emulsions.

Saliva-induced emulsion flocculation: role of droplet charge
Silletti, E. ; Vingerhoeds, M.H. ; Norde, W. ; Aken, G.A. van - \ 2007
In: Food Colloids: Self Assembly and Material Science / Dickinson, E., Leser, M., Cambridge : Royal Society - ISBN 9781847557698 - p. 463 - 472.
Food Colloids: Self-Assembly and Material Science describes new developments in the theory and practice of the formulation of food emulsions, dispersions, gels and foams. Particular emphasis is placed on the self-assembly of surfactants and biopolymers in food. Topics include colloid science in food nutrition and the relationship of texture to sensory perception of food materials, the exploitation of surfactant mesophases for nanoscale encapsulation, the interfacial rheological properties of mixed interfaces, and the electrostatic interactions of proteins with polysaccharides. This authoritative book will serve as a guide and reference to researchers in the field of food colloids.
Complex formation in mixtures of lysozyme-stabilized emulsions and human saliva
Silletti, E. ; Vingerhoeds, M.H. ; Norde, W. ; Aken, G.A. van - \ 2007
Journal of Colloid and Interface Science 313 (2007)2. - ISSN 0021-9797 - p. 485 - 493.
transmission electron-microscopy - phase-ordering kinetics - micelle-like structures - high-pressure treatment - bovine serum-albumin - egg-white lysozyme - rheological properties - beta-lactoglobulin - ionic-strength - whey proteins
In this paper, we studied the interaction between human unstimulated saliva and lysozyme-stabilized oil-in-water emulsions (10 wt/wt% oil phase, 10 mM NaCl, pH 6.7), to reveal the driving force for flocculation of these emulsions. Confocal scanning laser microscopy (CSLM) showed formation of complexes between salivary proteins and lysozyme adsorbed at the oil¿water interface and lysozyme in solution as well. To assess the electrostatic nature of the interaction in emulsion/saliva mixtures, laser-diffraction and rheological measurements were conducted in function of the ionic strength by adding NaCl to the mixture in the range between 0 and 168 mM. Increasing the ionic strength reduced the ability of saliva to induce emulsion flocculation as shown by the decreased floc size and the effect on the viscosity. Turbidity experiments with varying pH (3¿7) and ionic strength also showed decreased complex formation in mixtures between saliva and lysozyme in solution upon NaCl addition up to 200 mM. Decreasing the pH increased the turbidity, in line with the increase of the positive net charge on the lysozyme molecule. We conclude that electrostatic attraction is the main driving force for complex formation between saliva components and lysozyme adsorbed at the oil droplets and in solution.
Saliva as research material: Biochemical, physicochemical and practical aspects
Schipper, R.G. ; Silletti, E. ; Vingerhoeds, M.H. - \ 2007
Archives of Oral Biology 52 (2007)12. - ISSN 0003-9969 - p. 1114 - 1135.
human whole saliva - proline-rich proteins - human-parotid-saliva - performance liquid-chromatography - 2-dimensional gel-electrophoresis - submandibular-sublingual saliva - micelle-like structures - transmission electron-microscopy - secretory immunoglobulin-a
Whole saliva is a complex mixture of proteins and other molecules which originate from several sources. The biochemical and physicochemical properties of saliva contribute to the numerous functions of saliva in, e.g., speech, maintaining oral and general health, and food processing. Interest in saliva has increased in the last few years for its potential to diagnose viral, bacterial and systemic diseases. The use of saliva as research material may pose particular problems due to its inherent variability and instability. This review describes practical aspects of salivary as research material with emphasis on protein biochemistry and physical chemistry.
The role of electrostatistics in saliva-induced emulsion flocculation
Silletti, E. ; Vingerhoeds, M.H. ; Norde, W. ; Aken, G.A. van - \ 2007
Food Hydrocolloids 21 (2007)4. - ISSN 0268-005X - p. 596 - 606.
in-water emulsions - human glandular salivas - human whole saliva - depletion flocculation - mucin mg1 - complex coacervation - food hydrocolloids - beta-lactoglobulin - protein-components - whey proteins
Upon consumption food emulsions undergo different processes, including mixing with saliva. It has been shown that whole saliva induces emulsion flocculation [van Aken, G. A., Vingerhoeds, M. H., & de Hoog, E. H. A. (2005). Colloidal behaviour of food emulsions under oral conditions. In E. Dickinson (Eds.), Food colloids 2004: Interactions, microstructure and processing (pp. 356¿366). Cambridge: The Royal Society of Chemistry; Vingerhoeds, M. H., Blijdenstein, T. B. J., Zoet, F. D., & van Aken, G. A. (2005). Emulsion flocculation induced by saliva and mucin. Food Hydrocolloids, 19, 915¿922]. It was hypothesized that depletion flocculation was responsible for the observed flocculation. To further unravel the mechanism, we investigated the role of electrostatics on the behavior of emulsion/saliva mixtures. Emulsions stabilized with differently charged surfactants and proteins were mixed with saliva. Strongly negatively charged emulsions (SDS and Panodan) do not flocculate, likely because the electrostatic repulsion between the droplets overcomes the attractive depletion and van der Waals interactions. Neutral and weakly negatively charged emulsions (Tween 20 and ß-lactoglobulin pH 6.7) undergo flocculation, which is reversible upon dilution with water. This is probably due to depletion interactions, induced by large salivary protein like mucins, in combination with the van der Waals interaction and the sufficiently low electrostatic repulsion between the droplets. Positively charged emulsions (CTAB, lysozyme and ß-lactoglobulin pH 3.0) show irreversible flocculation leading to rapid phase separation. These findings point to a role of electrostatic attraction between the negatively charged proteins present in saliva and the positively charged surfaces of the emulsion droplets. The results indicate that the sign and the density of the charge on the surface of the droplets contribute significantly to the behavior of an emulsion when mixed with saliva. Depending on the charge, saliva-induced emulsion flocculation is driven by two different main mechanisms: depletion flocculation and electrostatic attraction.
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