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.

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Intracellular & extracellular lipolysis : regulation by the PPAR targets ANGPTL4 & HILPDA
Dijk, Wieneke - \ 2016
Wageningen University. Promotor(en): Sander Kersten. - Wageningen : Wageningen University - ISBN 9789462579460 - 248
foams - foaming - milk products - processing - aggregates - casein - micelles - physical properties - schuim - schuimen - melkproducten - verwerking - bodemdeeltjes - caseïne - micellen - fysische eigenschappen

The body efficiently stores energy in the form of triglyceride (fat) molecules. However, triglycerides cannot directly enter or exit our cells, but first need to be degraded to so-called fatty acids before moving in or out a cell. This degradation process, called lipolysis, is crucial for human physiology and is tightly regulated to prevent the accumulation of fats either within organs or within the bloodstream - hallmarks of diseases such as obesity and cardiovascular disease.

To allow for uptake by underlying organs, triglycerides in the circulation are efficiently broken down by an enzyme called lipoprotein lipase (LPL) that sits in the bloodstream of multiple organs (extracellular lipolysis). In this thesis, we characterized a protein named angiopoietin-like 4 (ANGPTL4) that potently inhibits LPL and, thereby, inhibits the breakdown of triglycerides in the bloodstream. Our data show that by adjusting the tissue expression levels of ANGPTL4, different organs collaborate to ensure that triglycerides are distributed to organs in need of energy. Moreover, we uncovered that, in the fat tissue, ANGPTL4 starts to inhibit LPL before LPL arrives in the bloodstream. By preventing the arrival of LPL in the bloodstream, ANGPTL4 is capable of rapidly adjusting the rates of triglyceride degradation and the concomitant uptake of fatty acids from the circulation to the energy requirements of the underlying organ.

To exit our cells, stored triglycerides, such as present in our fat tissue, need to be broken down to fatty acids. Subsequently, the released fatty acids can fuel other organs in need of energy. To further clarify the mechanisms underlying this process of intracellular lipolysis, we investigated the role of a promising new protein called HILPDA. Our data show, however, that loss of HILPDA did not impact the release of fatty acids from the fat tissue, while a high abundance of HILPDA only had a mild attenuating effect on the release of fatty acids. This suggests that HILPDA is not a major physiological regulator of intracellular lipolysis in fat cells.

In conclusion, in this thesis, we have clarified the regulation of intracellular and extracellular lipolysis by studying the respective roles of the proteins ANGPTL4 and HILPDA. Such efforts are clinically relevant, as regulators of lipolysis are potential therapeutic targets to lower cardiovascular disease risk.

The role of casein micelles and their aggregates in foam stabilization
Chen, Min - \ 2016
Wageningen University. Promotor(en): Erik van der Linden; Toon van Hooijdonk, co-promotor(en): Marcel Meinders; Guido Sala. - Wageningen : Wageningen University - ISBN 9789462579842 - 124
foams - foaming - milk - casein - micelles - physical properties - stabilization - schuim - schuimen - melk - caseïne - micellen - fysische eigenschappen - stabilisatie

Many foam products derived from milk or specific dairy ingredients suffer from drainage, coalescence and/or disproportionation. Previous studies indicated that foam properties of milk are strongly influenced by the composition of the milk as well as by the processing conditions during foam production. The aim of this research was to get a better understanding of these two factors. Interestingly, the presence of aggregates of casein micelles was found to result in very stable foams. The interfacial properties (adsorption speed, adsorption energy, dynamical interfacial tension, interfacial dilatational moduli), thin film stability (rupture time) and foam properties (foamability, drainage, coalescence) of casein micelle dispersions were determined. Based on these data, the very stable foams were concluded to result from properties of the thin films in the foam, which were affected drastically by the presence of the large aggregates of casein micelles.

Foam properties of proteins, low molecular weight surfactants and their complexes
Lech, F.J. - \ 2016
Wageningen University. Promotor(en): Harry Gruppen; Peter Wierenga; Marcel Meinders. - Wageningen : Wageningen University - ISBN 9789462576247 - 122 p.
surfactants - proteins - bovine serum albumin - beta-lactoglobulin - lysozyme - foams - chemical properties - stability - mixtures - food chemistry - oppervlaktespanningsverlagende stoffen - eiwitten - runderserumalbumine - bèta-lactoglobuline - lysozym - schuim - chemische eigenschappen - stabiliteit - mengsels - voedselchemie

This thesis shows the effects that the addition of low molecular weight surfactants (LWMS) to proteins has on the foam stability of the mixture. For this, the bulk, interfacial, thin liquid films and foam properties are determined for different protein-LWMS mixtures at different molar ratios (MR). It was shown that the MR as well as the charge of the protein and LMWS determine the foam stability of the mixtures. For all mixtures it was found that the proteins have a select number of high affinity binding sites. So, the concentration of free LMWS in the solution is 0 until a critical MR (MRcr), at which all high affinity binding sites are saturated. Above this MRcr, part of the LMWS binds to low affinity binding sites of the proteins. The low affinity binding sites have a binding ratio < 1, which determines the concentration of bound and free LMWS. For similarly charged protein-LMWS mixtures (i.e. b-lactoglobulin (BLG) and sodium dodecyl sulphate (SDS) and bovine serum albumin (BSA) and SDS at pH 7) the foam stability typically decreases from the foam stability of the pure protein solution (MR 0) until MRcr is reached. At MR > MRcr the foam stability is dominated by the amount of free LMWS. For oppositely charged protein-LMWS mixtures, the binding of the LMWS to the proteins can be described in a similar way, although the number of high affinity sites and low affinity binding ratio are different. There is also a regime of MRs in which the protein-LMWS complexes form large aggregates. These aggregates were in some cases found to increase foam stability (lysozyme (LYS) and SDS and BLG-SDS at pH 3), while in another case (BLG and cetyltrimethylammonium bromide (CTAB)) they lead to decreased foam stability. Still, in all cases it was found that above MRD the aggregates dissociate and the foam stability becomes dominated by free surfactants, equivalent to what was observed for similarly charged protein-LMWS mixtures.

A multi-scale model was developed to describe the stability of thin liquid films in terms of rupture time and thickness. Initially, the model was used to predict the stability of surfactant free films of water and electrolyte solutions. Later, it was used to predict the foam stability in LYS-SDS mixtures. For that purpose, the model was combined with a foam drainage model to provide theoretical estimations of foam stability. This model is the basis to understand coalescence of bubbles in foam. Finally, the concept of the critical MRs and the free LMWS was introduced. Using this, the foam properties of protein-LMWS mixtures can partly be predicted by relative charge of the components and the binding to both high and low affinity binding sites.

Sonication–Microfluidics for Fabrication of Nanoparticle-Stabilized Microbubbles
Chen, H. ; Li, J. ; Zhou, W. ; Pelan, E.G. ; Stoyanov, S.D. ; Arnaudov, L.N. ; Stone, H.A. - \ 2014
Langmuir 30 (2014)15. - ISSN 0743-7463 - p. 4262 - 4266.
flow-focusing device - contrast agents - foams - emulsions - delivery - bubbles
An approach based upon sonication–microfluidics is presented to fabricate nanoparticle-coated microbubbles. The gas-in-liquid slug flow formed in a microchannel is subjected to ultrasound, leading to cavitation at the gas–liquid interface. Therefore, microbubbles are formed and then stabilized by the nanoparticles contained in the liquid. Compared to the conventional sonication method, this sonication–microfluidics continuous flow approach has unlimited gas nuclei for cavitation that yields continuous production of foam with shorter residence time. By controlling the flow rate ratios of the gas to the liquid, this method also achieves a higher production volume, smaller bubble size, and less waste of the nanoparticles needed to stabilize the microbubbles.
Non-linear surface dilatational rheology as a tool for understanding microstructures of air/water interfaces stabilized by oligofructose fatty acid esters
Kempen, S.E.H.J. van; Schols, H.A. ; Linden, E. van der; Sagis, L.M.C. - \ 2013
Soft Matter 9 (2013)40. - ISSN 1744-683X - p. 9579 - 9592.
air-water-interface - monolayers - layers - shear - viscoelasticity - adsorption - systems - foams
In this paper, the rheological response of air/water interfaces, stabilized by various oligofructose fatty acid esters, to oscillatory dilatational deformations was studied and compared to the response of interfaces stabilized by sucrose esters. We have followed a traditional approach to surface rheology, where the development of the modulus as a function of time is studied as well as the frequency dependence of the modulus. We also adopted a different approach where we investigate in detail the amplitude dependence of the modulus. Finally, we studied the temperature dependence. We show that for an accurate characterization of the dilatational rheology of fluid-fluid interfaces with a complex microstructure, a protocol should be used that not only involves variations of surface pressure, frequency, and temperature, but also establishes amplitude dependence. We show that Lissajous plots of surface pressure versus deformation can be useful tools to help interpret surface dilatational behavior in terms of interfacial microstructure. The rheological response of interfaces stabilized by oligofructose esters differed significantly from the response of those stabilized by sucrose esters. Sucrose esters behaved like typical low molecular weight surfactants, and gave interfaces with relatively low moduli, a frequency scaling of the dilatational modulus with an exponent close to 0.5, and displayed no asymmetries in Lissajous plots. In contrast, the oligofructose esters gave, depending on the fatty acid tail, relatively high moduli, almost independent of frequency. Significant asymmetries were observed in the Lissajous plots, with strain hardening during compression and strain softening during extension. Our results suggest that the unusual rheological properties of interfaces stabilized by oligofructose esters may be the result of the formation of a two-dimensional soft glass phase by the oligofructose part of the ester.
Coalescence and compression in centrifuged emulsions studied with in situ optical microscopy
Krebs, T. ; Ershov, D.S. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2013
Soft Matter 9 (2013)15. - ISSN 1744-683X - p. 4026 - 4035.
hydrocarbon-water interfaces - stability - dispersions - separation - kinetics - droplets - gravity - foams
We report an experimental method to investigate droplet dynamics in centrifuged emulsions and its application to study droplet compression and coalescence. The experimental setup permits in situ monitoring of an ensemble of droplets in a centrifuged monolayer of monodisperse emulsion droplets using optical microscopy. We studied a hexadecane-in-water emulsion stabilized by the ionic surfactant sodium-n-dodecyl sulfate as a model system. With a microfluidic T-junction emulsion droplets of 97 mm diameter are produced which are subsequently inserted into a rectangular glass chamber of 100 mm height. Using an emulsion which is stable against coalescence, we measured the steady-state oil volume fraction in the compressed layer as a function of the compressive force induced by centrifugation, and quantified the deformation of droplets upon compression. To induce coalescence, we decreased the SDS bulk concentration by dilution of the continuous phase with water before the start of centrifugation. The growth rate of the separated oil phase, which forms on top of the emulsion, and the extent of drop–drop coalescence in the droplet layer upon centrifugation were evaluated as a function of the radial acceleration. The potential of the method for studies in emulsion science and possible improvements of the experimental setup are discussed.
Jatropha seed protein functional properties for technical applications
Lestari, D. ; Mulder, W.J. ; Sanders, J.P.M. - \ 2011
Biochemical Engineering Journal 53 (2011)3. - ISSN 1369-703X - p. 297 - 304.
soy protein - antinutritional factors - curcas - films - concentrate - interfaces - extraction - oilseed - plant - foams
Jatropha press cake, by-product after oil expression from Jatropha seeds, contains 24–28% protein on dry basis. Objectives of this research were to investigate functional properties, such as solubility, emulsifying, foaming, film forming, and adhesive properties, of Jatropha press cake proteins and compared those with relevant industrial proteins. From our study, we found that protein extracted from press cake proteins had a solubility of about 90% above pH 9. Emulsifying properties of press cake protein were comparable to sodium caseinates and reached the highest value at pH 9–10. Jatropha proteins formed films with tensile strength of 0.4–1.8 MPa with 10–75% elongation, which were below soy protein or wheat-gluten. Further oil removal from press cake decreased emulsifying properties, while increased foaming and adhesive properties of the extracted proteins. Protein extracted from de-oiled press cake showed better foaming properties than sodium caseinate at pH 10, but lower than egg white protein at all pH. Furthermore, press cake protein showed better adhesive properties than casein adhesives at the same dry matter content. Based on these results, Jatropha press cake protein showed most promising results on adhesive and emulsifying properties, which indicate the potential of Jatropha press cake protein as emulsifier or paper adhesive.
Peroxidase-mediated cross-linking of bovine a-lactalbumin
Heijnis, W.H. - \ 2010
Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Willem van Berkel; Peter Wierenga. - S.l. : s.n. - ISBN 9789085858324 - 120
alfa-lactalbumine - peroxidase - schuimen - schuim - enzymatische cross-linking - alpha-lactalbumin - foaming - foams - enzymatic cross-linking
The research presented in this thesis aimed at controlling the horseradish peroxidase-catalyzed cross-linking of bovine α lactalbumin and the implications of this cross-linking for the foam stabilizing properties. Attention is also given to microreactors and their potential to control the enzymatic cross-linking of proteins.
The proportion of cross-linked α lactalbumin dimers, oligomers and polymers could be directed by variations in ionic strength, pH, H2O2, and temperature.
Covalent α lactalbumin dimers were proteolytic digested. FTMS analysis of the peptide mixture resulted in the unambiguous identification of a Tyr18 Tyr50 dityrosine cross-link. Structural modeling of the α lactalbumin dimer indicated that favorite electrostatics direct the selectivity of the cross-linking reaction and, hence, the formation of an intermolecular cross-link. The formation of the Tyr18-Tyr50 cross-link suggests that further cross-linking of α lactalbumin dimers enables the formation of linear polymers.
A microreactor system was set up to obtain control over the reaction conditions to cross-link proteins. The enzymatic cross-linking of α lactalbumin was analyzed as a function of enzyme and substrate(s) feed. The increase in absorption at 318 nm due to dityrosine formation was found to be directly correlated to the decrease in monomeric α lactalbumin and was shown to be a good tool to monitor the cross-linking reaction.
The α lactalbumin oligomers produced were investigated for their foam stabilizing properties. Cross-linked α lactalbumin oligomers did not stabilize foams, whereas α lactalbumin polymers acted as an anti-foam, destabilizing other protein films.

Antioxidative activity and emulsifying properties of cuttlefish skin gelatin modified by oxidised phenolic compounds
Aewsiri, T. ; Benjakul, S. ; Visessanguan, W. ; Eun, J.B. ; Wierenga, P.A. ; Gruppen, H. - \ 2009
Food Chemistry 117 (2009)1. - ISSN 0308-8146 - p. 160 - 168.
in-water emulsions - whey-protein isolate - stability - collagen - surfactant - foams - acids - assay - gum
Antioxidative activity and emulsifying properties of cuttlefish skin gelatin modified by different oxidised phenolic compounds including caffeic acid, ferulic acid and tannic acid at different concentrations were investigated. Oxidised phenolic compounds were covalently attached to gelatin as indicated by the decrease in amino groups. Fourier transform infrared spectroscopic studies indicated the presence of an aromatic ring and a hydroxyl group in gelatin after modification. Modified gelatin had the increased antioxidative activity but the decreased surface hydrophobicity. Gelatin modified with 5% oxidised tannic acid had no change in emulsifying properties. Emulsion stability and oxidative stability of menhaden oil-in-water emulsion stabilised by 0.5% and 1.0% gelatin without and with modification by 5% oxidised tannic acid were studied. Both gelatins at a higher concentration (1.0%) yielded an emulsion with a smaller particle size. Modified gelatin inhibited the formation of TBARS in the emulsion more effectively than the control gelatin throughout the 12 days of storage.
Schuimvorming op mest : eindrapportage
Starmans, D.A.J. ; Blanken, K. ; Kupers, G.C.C. ; Timmerman, M. - \ 2009
Lelystad : Wageningen UR, Livestock Research (Rapport / Wageningen UR, Livestock Research 288) - 40
varkenshouderij - varkens - mest - ontschuimen - schuim - mestverwerking - pig farming - pigs - manures - defoaming - foams - manure treatment
This report deals with the chemistry behind foam formation on liquid manure and the abatement of this foam in practical farm operations
Glasschuim evenaart productie in steenwol
Bouwman-van Velden, Pieternel ; Blok, C. - \ 2009
Onder Glas 6 (2009)9. - p. 5 - 7.
proeven op proefstations - teelt onder bescherming - schuim - substraten - voedingsstoffen - groenteteelt - pythium - siliciummeststoffen - glastuinbouw - groenten - station tests - protected cultivation - foams - substrates - nutrients - vegetable growing - silicon fertilizers - greenhouse horticulture - vegetables
Proeven bij Wageningen UR Glastuinbouw hebben aangetoond dat planten op glasschuim de productie op steenwol evenaren. Glasschuim bevat onder alle groeiomstandigheden 40% lucht en weinig vrij water. Naast een sterk generatieve groei heeft dit ook gevolg voor minder Pythium bij komkommers en minder neusrot bij tomaat
Branden, heet water en heet schuim: energieverbruik en capaciteit verschilt
Kurstjens, D.A.G. - \ 2004
Tuin en Park Techniek 11 (2004)1. - ISSN 1380-3212 - p. 28 - 29.
onkruidbestrijding - bestrating - wegen - bestrijdingsmethoden - warmtebehandeling - heetwaterbehandeling - verbranden - schuim - schuimen - capaciteit - energiegebruik - brandstofverbruik - watergebruik - gebruiksefficiëntie - gebruikswaarde - weed control - pavements - roads - control methods - heat treatment - hot water treatment - burning - foams - foaming - capacity - energy consumption - fuel consumption - water use - use efficiency - use value
Voor onkruidbestrijding op verhardingen is het vanuit milieuoverwegingen belangrijk om effectieve en betaalbare alternatieven voor chemische bestrijding te vinden. Wageningen UR vergeleek drie thermische methoden van onkruidbestrijding op energieverbruik, capaciteit en bestrijdingseffect (bij verschillende rijsnelheden). Een Hoaf Weedstar 100 onkruidbrander, een zelfrijdende heetwatermachine en een Herbifoam-installatie voor heet schuim werden ingezet op proefvelden ingezaaid met gele mosterd en Engels raaigras. Op gele mosterd was de brander het zuinigst en snelst; bij gras de heetwatermachine
Mechanical and conformational aspects of protein layers on water
Martin, A.H. - \ 2003
Wageningen University. Promotor(en): Martien Cohen Stuart, co-promotor(en): M.A. Bos; Ton van Vliet. - [S.I.] : S.n. - ISBN 9058088103 - 126
bovenlagen - moleculaire structuur - schuim - eiwitten - schuifsterkte - reologie - surface layers - molecular conformation - foams - proteins - shear strength - rheology
Physico-chemical and functional properties of sunflower proteins
Gonzalez-Perez, S. - \ 2003
Wageningen University. Promotor(en): Fons Voragen, co-promotor(en): Harry Gruppen; A.L.J. Vereijken. - [S.l.] : S.n. - ISBN 9058089045 - 145
zonnebloemeiwit - fysicochemische eigenschappen - denaturatie - oplosbaarheid - schuimen - schuim - emulgeren - emulsies - sunflower protein - physicochemical properties - denaturation - solubility - foaming - foams - emulsifying - emulsions
Effects of stress relaxation in soy glycinin films on bubble dissolution and foam stability
Meinders, M.B.J. ; Bos, M.A. ; Lichtendonk, W.J. ; Vliet, T. van - \ 2003
In: Food Colloids, Biopolymers and Materials / Dickinson, E., van Vliet, T., Cambridge UK : Royal Society of Chemistry - ISBN 0854048715 - p. 156 - 164.
sojaeiwit - schuim - schuimen - soya protein - foams - foaming
Failure behaviour of adsorbed protein Layers: consequences for emulsion and foam stability
Vliet, T. van; Aken, G.A. van; Bos, M.A. ; Martin, A.H. - \ 2003
In: Food Colloids, Biopolymers and Materials. - Cambridge UK : Royal Society of Chemistry - ISBN 0854048715 - p. 176 - 191.
schuim - emulsies - eiwitten - reologische eigenschappen - foams - emulsions - proteins - rheological properties
Entering and spreading of protein-stabilized emulsion droplets at the expanding air-water interface
Hotrum, N.E. ; Cohen Stuart, M.A. ; Vliet, T. van; Aken, G.A. van - \ 2003
In: Food Colloids, Biopolymers and Materials / Dickinson, E., van Vliet, T., Cambridge : Royal Society of Chemistry - ISBN 0854048715 - p. 192 - 199.
emulsies - schuim - schuimen - eiwitten - caseïnaten - grensvlak - mechanische eigenschappen - emulsions - foams - foaming - proteins - caseinates - interface - mechanical properties
Colloids and interfaces in life sciences
Norde, W. - \ 2003
New York; Basel : Marcel Dekker - ISBN 0824709969 - 433
colloïden - colloïdale eigenschappen - grensvlak - oppervlaktespanning - emulsies - schuim - reologische eigenschappen - studieboeken - oppervlaktechemie - colloids - colloidal properties - interface - surface tension - emulsions - foams - rheological properties - textbooks - surface chemistry
Composition of thin films between emulsion droplets stabilized by protein, as measured in highly concentrated emulsions
Aken, G.A. van; Zoet, F.D. ; Diederen, J. - \ 2002
Colloids and Surfaces. B: Biointerfaces 26 (2002)3. - ISSN 0927-7765 - p. 269 - 279.
air-water-interface - rheology - coalescence - foams - tool
Oil-in-water emulsions stabilized by whey protein and ß-lactoglobulin are extremely stable to coalescence, provided a saturated adsorbed protein layer is present at the droplet surfaces. If this is the case, these emulsions can be concentrated to stable highly concentrated emulsions, in which the droplets are in continuous contact and separated by thin films. The water content in these highly concentrated emulsions could be lowered to such an extent that almost all of the protein in the emulsion was present in the adsorbed layers at both sides of the thin films separating the emulsion droplets. Therefore, these systems are convenient for determination of the composition and mechanical properties of adsorbed protein layers in thin films between emulsion droplets. At the lowest water content obtained by us, the mobility of water was strongly reduced as measured by NMR, suggesting that hardly any water was present in the Plateau borders and that most of the remaining water was held within the adsorbed protein layer in the thin film regions between the emulsion droplets. The amount of protein and water remaining in the highly concentrated emulsion corresponded well with compositions of adsorbed protein layers as described in the literature, suggesting that these thin films are composed of two layers of adsorbed protein
Biochemical and functional characterisation of casein and whey protein hydrolysates : a study on the correlations between biochemical and functional properties using multivariate data analysis
Ven, C. van der - \ 2002
Wageningen University. Promotor(en): A.G.J. Voragen; Harry Gruppen; D.B.A. de Bont. - S.l. : S.n. - ISBN 9789058086532 - 155
melkeiwitten - caseïnehydrolysaat - wei-eiwit - eiwithydrolysaten - peptiden - multivariate analyse - vloeistofchromatografie met omgekeerde fase - gelfiltratiechromatografie - infraroodspectroscopie - molecuulgewicht - emulsies - schuim - oplosbaarheid - bitterheid - milk proteins - casein hydrolysate - whey protein - protein hydrolysates - peptides - multivariate analysis - reverse phase liquid chromatography - gel filtration chromatography - infrared spectroscopy - molecular weight - emulsions - foams - solubility - bitterness
<p>Whey protein and sodium caseinate were hydrolysed with commercially available enzyme preparations. The resulting hydrolysates were characterised using several analytical characterisation methods and by determination of several functional properties. Subsequently, correlations between the biochemical characteristics themselves and between biochemical and functional properties were studied using multivariate regression analysis.</p><p>Biochemical characteristics of hydrolysates were determined using unifactorial methods like the degree of hydrolysis, and by multifactorial methods, <em>i.e</em> . reversed phase (RPC) and size exclusion chromatography (SEC), and Fourier transform infrared (FTIR) spectroscopy. FTIR spectroscopy appeared to discriminate most effectively between hydrolysates made from different protein sources and classes of proteolytic enzymes, followed by RPC and SEC.</p><p>Emulsion and foam properties of hydrolysates were similar or inferior to those of the parental proteins. Casein hydrolysates generally showed better emulsion and foam forming ability than whey protein hydrolysates. Foam forming ability of whey protein hydrolysates was correlated to the molecular weight distribution (MWD) of the peptides, showing that especially peptides with MW of 3-5 kDa contributed to foam forming ability.</p><p>Concerning prevention of emulsion instability due to coalescence it was shown that peptides with a molecular weight larger than 2 kDa are needed. Foam stabilising ability of casein hydrolysates also depended on the MWD of hydrolysates, but higher molecular weight peptides, <em>i.e.</em> larger than 7 kDa, were needed to obtain good foam stability.</p><p>The ability of the three multifactorial characterisation methods (SEC, RPC, FTIR spectroscopy) to predict functional properties was investigated. It appeared that SEC profiles were able to predict emulsion and foam stability of all hydrolysates, as well as foam forming ability, Angiotensin Converting Enzyme (ACE) inhibiting ability and bitterness of whey hydrolysates. RPC profiles were also able to predict these properties and additionally predicted solubility and bitterness of casein hydrolysates. FTIR spectra were best suited to predict a variety of hydrolysate properties, since apart from the before-mentioned properties, the spectra can also be used to predict emulsion forming ability and to improve prediction of bitterness of hydrolysates.</p><p>Finally, the influence of hydrolysis process conditions on ACE inhibiting ability of whey hydrolysates was investigated, showing that ACE inhibiting activity could be optimised by using process optimisation techniques like experimental design and response surface optimisation.
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