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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    Eco-friendly design of scour protection: potential enhancement of ecological functioning in offshore wind farms : Towards an implementation guide and experimental set-up
    Lengkeek, Wouter ; Didderen, K. ; Teunis, M. ; Driessen, F. ; Coolen, J.W.P. ; Bos, O.G. ; Vergouwen, S.A. ; Raaijmakers, T. ; Vries, M.B. de; Koningsveld, M. van - \ 2017
    Culemborg : Bureau Waardenburg (Report / Bureau Waardenburg 17-001) - 98
    The aim of this study is to explore the possibilities to implement ‘Building with North Sea Nature’ in offshore infrastructures in the North Sea by providing guidelines for the eco-friendly design of scour protection structures around monopiles in planned wind farms to enhance ecological functioning.
    The guidelines include specifications on: The type of hard substrate material or products available and how these can potentially enhance ecological functioning (and have added value compared to regular types used); How different types of hard substrates and configurations can be (experimentally) designed to vary spatially, in such a systematic manner that the effect on ecological enhancement can be determined empirically; How the effects of these scour protection structures can be monitored and evaluated; Whether site-specific conditions apply to wind planned farm locations in the Dutch North Sea. Eco-friendly design in this study entails optimising the scour protection of offshore wind farms to enhance its ecological functioning. Enhancement of ecological functioning has been defined as: increasing habitat suitability for species (or communities) occurring naturally in the Dutch North Sea, in particular, for policyrelevant
    (from a conservation perspective) and endangered species, such as those
    listed in the EU Habitats Directive, OSPAR or national red lists (see Annex 2 in Bos et al. in prep.). Where previous work has explored the more general possibility for enhancement of ecological functioning in offshore wind farms (van Duren et al. 2016; Smaal et al. in prep.), this study provides explicit steps towards realising an eco-friendly design of scour protection and a practical field experiment to allow for scientific evaluation. From an analysis of physical conditions in the North Sea that influence both biodiversity and scouring mechanisms at wind farm locations, it is concluded that scour protection will be required in most, or all, future offshore wind farms on the Dutch Continental Shelf. It is also concluded that scour protection design could be altered to benefit the ecology, but that new designs will require additional testing for
    anti-scouring effects. Based on a selection of policy-relevant species for the North Sea, two umbrella species were selected: Atlantic cod (Gadus morhua) and European flat oyster (Ostrea edulis). Focussing design variables and principles on these two umbrella species is expected to result in optimising the habitat for a wide range of native hard substrate biodiversity. Based on existing data from current wind farm scour protection, other artificial hard substrates and natural hard substrates from the North Sea, it is hypothesized that an optimised design of scour protection will yield increased populations of umbrella species or increased native biodiversity in general, including policy-relevant species.
    Based on available knowledge on ecological principles and expert judgement of North Sea hard substrate ecologists, four design variables for optimised scour protection are defined: 1. Adding larger structures than conventional scour protection to create large holes and crevices, to provide adequate shelter / holes for large mobile species. 2. Adding more small-scale structures than conventional scour protection to create more small-scale holes and crevices but also attachment substrate and settlement substrate. 3. Providing or mimicking natural (biogenic) chemical substrate properties to facilitate species. An example is to provide chalk-rich substrate such as concrete with added chalk, or even natural substrate such as shell material. 4. Active introduction of specimens of target species to enhance establishment of new populations. This is to facilitate recruitment at locations where reproduction by naturally occurring adults is These design variables are made practically applicable by providing example
    materials and specifications for implementation in the field and, a cost overview is provided for example materials. Combining the above information, this study provides design guidelines for wind farms with optimised scour protection to enhance ecological functioning. In addition it defines a minimum and a standardized approach for deployment and monitoring of a subset of locations to allow for scientific evaluation. The monitoring techniques that are required to do so, are described and a cost estimate for the monitoring is provided.
    In conclusion, this study provides eco-friendly design principles for scour protection and a first experimental design to implement ‘Building with North Sea Nature’: ecological enhancement by optimising scour protection in offshore wind farms. This is considered as a first step in a process that should result in ‘learning by doing’.
    Rijke riffen in de Noordzee : verkenning naar het stimuleren van natuurlijke riffen en gebruik van kunstmatig hard substraat
    Duren, L.A. van; Gittenberger, A. ; Smaal, A.C. ; Koningsveld, M. van; Osinga, R. ; Cado van der Lelij, J.A. ; Vries, M.B. de - \ 2016
    Delft : Deltares - 82
    Sustainable hydraulic engineering through building with nature
    Vriend, H.J. de; Koningsveld, M. van; Aarninkhof, S.G.J. ; Vries, M.B. de; Baptist, M.J. - \ 2015
    Journal of Hydro-environment Research 9 (2015)2. - ISSN 1570-6443 - p. 159 - 171.
    sea-level rise - intertidal habitats - river - protection - wetlands - coastal
    Hydraulic engineering infrastructures are of concern to many people and are likely to interfere with the environment. Moreover, they are supposed to keep on functioning for many years. In times of rapid societal and environmental change this implies that sustainability and adaptability are important attributes. These are central to Building with Nature (BwN), an innovative approach to hydraulic engineering infrastructure development and operation. Starting from the natural system and making use of nature's ecosystem services, BwN attempts to meet society's needs for infrastructural functionality, and to create room for nature development at the same time. By including natural components in infrastructure designs, flexibility, adaptability to changing environmental conditions and extra functionalities and ecosystem services can be achieved, often at lower costs on a life-cycle basis than ‘traditional’ engineering solutions. The paper shows by a number of examples that this requires a different way of thinking, acting and interacting.
    Interactions between globular proteins and procyanidins of different degrees of polymerization
    Prigent, S.V.E. ; Voragen, A.G.J. ; Koningsveld, G.A. van; Baron, A. ; Renard, C.M. ; Gruppen, H. - \ 2009
    Journal of Dairy Science 92 (2009). - ISSN 0022-0302 - p. 5843 - 5853.
    bovine serum-albumin - precipitating capacity - condensed tannins - haze formation - binding - grape - milk - polyphenols - products - quality
    Interactions of proteins with phenolic compounds occur in food products containing vegetable sources, such as cocoa, cereals, or yogurts containing fruit. Such interactions can modify protein digestion and protein industrial properties. Noncovalent interactions between globular proteins (proteins important in industry) and procyanidins (phenolic compounds present in large quantity in fruits) were studied. The affinity constants between procyanidins of various average degrees of polymerization () and lysozyme or -lactalbumin were measured by isothermal titration calorimetry. The effects of these interactions on protein solubility and foam properties were examined using -lactalbumin and BSA. Weak interactions were found with epicatechin and procyanidin dimers. Procyanidins of n = 5.5 and n = 7.4 showed medium (1.5 x 105 M–1) and high (8.69 x 109 M–1) affinities, respectively, for -lactalbumin at pH 5.5, with n the average number of subunits per oligomer. A positive cooperativity of binding at low procyanidin:protein molar ratios was observed. The affinities of -lactalbumin and lysozyme for procyanidins increased when the pH was close to the isoelectric pH. Solubility of lysozyme was strongly decreased by procyanidins of n = 5.5, whereas -lactalbumin and BSA were less affected. Protein solubility in the presence of procyanidins was not affected by increased ionic strength but increased slightly with temperature. Procyanidins of n = 5.5 and n = 7.4 stabilized the average bubble diameter of foam formed with -lactalbumin but had no effect on foam made from BSA. These results indicate that procyanidins of medium can lead to an undesirable decrease of protein solubility, but may play a positive role in foam stability.
    Covalent interactions between amino acid side chains and oxidation products of caffeoylquinic acid (chlorogenic acid)
    Prigent, S.V.E. ; Voragen, A.G.J. ; Li, F. ; Visser, A.J.W.G. ; Koningsveld, G.A. van; Gruppen, H. - \ 2008
    Journal of the Science of Food and Agriculture 88 (2008)10. - ISSN 0022-5142 - p. 1748 - 1754.
    caffeic acid - polyphenol oxidase - plant phenols - proteins - model - inhibitor - compound - quinone - esters
    BACKGROUND: Physicochemical properties and digestibility of proteins can be modified by covalent interactions with oxidized phenolic compounds, i.e., quinones. In order to control these interactions in food products, the covalent interactions between quinones from caffeoylquinic acid (CQA) and amino acid side chains were studied with mass spectrometry using N-terminally protected amino acids. RESULTS: The addition of two molecules of CQA, presumably in the form of a pre-formed dimer, was observed for lysine, tyrosine, histidine and tryptophan. A monomer of CQA seemed to be able to react with histidine and tryptophan, whereas no interaction with a CQA monomer was observed for lysine and tyrosine. Serine and threonine showed no covalent interactions with CQA. Cross-linking between CQA and the side chains of two molecules of lysine is likely to occur also in proteins. The results show that protein cross-linking may also be expected to occur via two tyrosine residues in the absence of other phenolic substrates. The side chains of lysine and tyrosine are more reactive than that of histidine and tryptophan. CONCLUSIONS: These results show that covalent protein modification by oxidized phenolics occurs preferentially via an initial dimerization and encompasses not only lysine and cysteine residues.
    Preparative chromatographic purification and surfactant properties of individual soyasaponins from soy hypocotyls
    DeCroos, K. ; Vincken, J.P. ; Koningsveld, G.A. van; Gruppen, H. ; Verstraete, W. - \ 2007
    Food Chemistry 101 (2007)1. - ISSN 0308-8146 - p. 324 - 333.
    performance liquid-chromatography - critical micelle concentration - biological-activities - quillaja saponin - structural elucidation - triterpenoid saponins - soybean saponins - soyasapogenol-a - cancer cells - food plants
    The amphipathic character of soyasaponins and their consequent biological and technological properties are well-recognised. However, mainly due to the absence of purified compounds, no data are available on the amphiphilic surfactant properties of individual soyasaponins. In this study we developed a preparative method for the purification of the main soyasaponins species from soy germ. Reversed-phase chromatography (Source 15 RPC) gave a good resolution of the various soyasaponins, and was used for the purification of non- and fully-acetylated soyasaponin Ab, DDMP-conjugated and unconjugated soyasaponins Ba and Bb. For these compounds, the critical micelle concentration (CMC), the minimal attainable surface tension (¿CMC) and the surface density (¿max) were determined using the Wilhelmy plate method. The order of CMC values was as follows: soyasaponin Bb
    The costs of human Campylobacter infections and sequelae in the Netherlands: A DALY and cost-of-illness approach
    Mangen, M.J.J. ; Havelaar, A.H. ; Bernsen, R.A.J.A.M. ; Koningsveld, G.A. van; Wit, G.A. de - \ 2007
    Acta Agriculturae Scandinavica. Section C Food Economics 2 (2007)1. - ISSN 1650-7541 - p. 35 - 51.
    Campylobacter infections and sequelae pose an important public health problem for the Netherlands. With the help of a second order stochastic simulation model (using @Risk), confidence intervals (CI) for the associated disease burden (summing up morbidity and mortality) and the associated costs-of-illness were estimated. Approximately 80,000 persons per year (90% CI 30,000¿160,000) are estimated to experience symptoms of acute gastro-enteritis, of which 30 are fatal cases. Around 18,000 patients visit a doctor and 500 are hospitalized each year. Additionally, each year some 1,400 cases of reactive arthritis, 59 cases of Guillain-Barré syndrome and 10 cases of inflammatory bowel disease are associated with a previous Campylobacter infection. The disease burden is expressed in Disability Adjusted Life Years (DALYs) and was estimated at 1,200 DALYs (90% CI 900¿1,600 DALYs) per year. The associated costs for the Dutch society, using cost estimates for the year 2000, included direct health-care costs, direct non-health-care costs and productivity losses from missed work and were estimated to total ¿21 million (90% CI ¿11 million ¿¿36 million) per year.
    Covalent interactions between proteins and oxidation products of caffeoylquinic acid (chlorogenic acid)
    Prigent, S.V.E. ; Voragen, A.G.J. ; Visser, A.J.W.G. ; Koningsveld, G.A. van; Gruppen, H. - \ 2007
    Journal of the Science of Food and Agriculture 87 (2007)13. - ISSN 0022-5142 - p. 2502 - 2510.
    bovine serum-albumin - physicochemical characterization - proteolytic digestion - polyphenol oxidase - model solutions - caffeic acid - derivatives - tyrosine - systems - peroxidase
    BACKGROUND: The interactions between phenolic compounds and proteins can modify protein properties important in the food industry. To understand the effects of these interactions, the covalent interactions between caffeoylquinic acid (chlorogenic acid, CQA) oxidised by polyphenol oxidase (PPO) at acidic pH 6 (pH 6) and -lactalbumin, lysozyme and bovine serum albumin (BSA) were compared with non-enzymatically induced covalent interactions at alkaline pH (pH 9). The effects of these modifications on protein properties were examined. RESULTS: Both ways of modification seemed to result in protein modification mainly via dimeric rather than monomeric CQA quinones. These modifications led to a decrease in the number of free primary amino groups of the proteins. Modification with CQA alone induced a low degree of protein dimerisation, which also occurred through the action of PPO alone. Modification drastically reduced the solubility of lysozyme over a broad pH range, whereas that of -lactalbumin was strongly reduced only at pH values close to its pI. The solubility of BSA was much less affected than that of the other proteins and only at acidic pH. CONCLUSION: These results indicate some similarities between modifications at pH 6 and 9 and that both modifications clearly change the functional properties of globular proteins.
    Opposite Contributions of Glycinin- and ß-Conglycinin-Derived Peptides to the Aggregation Behavior of Soy Protein Isolate Hydrolysates
    Kuipers, B.J.H. ; Koningsveld, G.A. van; Alting, A.C. ; Driehuis, F. ; Voragen, A.G.J. ; Gruppen, H. - \ 2006
    Food Biophysics 1 (2006)4. - ISSN 1557-1858 - p. 178 - 188.
    heat-induced gelation - soybean proteins - structural characteristics - emulsifying properties - enzymatic-hydrolysis - limited proteolysis - physical-properties - alpha-lactalbumin - gel properties - whey proteins
    The aggregation behavior as a function of pH was studied for hydrolysates obtained by hydrolysis of soy protein isolate (SPI) and glycinin- and ß-conglycinin-rich protein fractions with subtilisin Carlsberg. The substrates were hydrolyzed up to degrees of hydrolysis (DH) of 2.2% and 6.5%. Compared with nonhydrolyzed SPI, a decrease in solubility was observed for the hydrolysates of SPI [0.8% (w/v) protein, I¿=¿0.03 M] around neutral pH. At pH 8.0, glycinin hydrolysates had a much lower solubility (~43% and 60%, respectively, for DH 2.2% and 6.5%) than SPI and ß-conglycinin-derived hydrolysates, which were almost completely soluble. Peptides that aggregated were all larger than 5 kDa, and as estimated by size-exclusion chromatography their composition was almost independent of the aggregation pH. The solubility of hydrolysates of SPIs with a varying glycinin and ß-conglycinin composition showed that glycinin-derived peptides are the driving force for the lower solubility of SPI hydrolysates. The solubility of SPI hydrolysates at pH 8.0 was shown not to be the sum of that of glycinin and ß-conglycinin hydrolysates. Assuming that the separate hydrolysis of glycinin and ß-conglycinin did not differ from that in the mixture (SPI), this indicates that ß-conglycinin-derived peptides have the ability to inhibit glycinin-derived peptide aggregation.
    Expanded bed adsorption as a fast technique for the large-scale purification of the complete isoform pool of Ber e 1, the major allergen from Brazil nuts.
    Boxtel, E.L. van; Koningsveld, G.A. van; Koppelman, S.J. ; Broek, L.A.M. van den; Voragen, A.G.J. ; Gruppen, H. - \ 2006
    Molecular Nutrition & Food Research 50 (2006)3. - ISSN 1613-4125 - p. 275 - 281.
    bertholletia-excelsa hbk - sulfur-rich protein - 2s albumin - expression - peanut
    A new, fast, large-scale purification method for Ber e 1, the major allergen from Brazil nuts, using expanded bed adsorption (EBA) chromatography, is presented. Using EBA, crude extracts can be applied to a fluidized column, which allows the unhindered passage of particulate impurities, thereby avoiding time-consuming centrifugation or filtration steps. With this new purification method, 2.8 g of Ber e 1 was obtained from 85 g defatted Brazil nut meal, essentially within 1 day. Various structural as well as immunochemical characteristics of the purified protein were determined, and compared to those of Ber e 1 purified using conventional chromatographic techniques. The complete pool of Ber e 1 isoforms was collected using EBA. The most abundant isoforms were observed to have pI around 8 and heterogeneity was observed in both the large and the small subunit of the heterodimeric protein. Ber e 1 has a highly ordered secondary structure. No apparent differences in immune reactivity were observed between EBA purified Ber e 1 and conventionally purified Ber e 1, using IgE-binding experiments. Thus, using EBA, Ber e 1 can be purified fast and on gram-scale, while having purity equal to that of conventionally purified Ber e 1.
    Peptide-peptide and protein-peptide interactions in mixtures of whey protein isolate and whey protein isolate hydrolysates
    Creusot, N.P. ; Gruppen, H. ; Koningsveld, G.A. van; Kruif, C.G. de; Voragen, A.G.J. - \ 2006
    International Dairy Journal 16 (2006)8. - ISSN 0958-6946 - p. 840 - 849.
    bovine alpha-lactalbumin - beta-lactoglobulin - induced gelation - scanning calorimetry - induced aggregation - identification - functionality - denaturation - fractions - glu
    The extent of aggregation in whey protein isolate (WPI) hydrolysates induced by Bacillus licheniformis protease was quantified as a function of degree of hydrolysis (DH), temperature and ionic strength. The capacity of the hydrolysates to aggregate added intact protein was also studied. The amount of aggregated material and the size of the aggregated peptides were measured by nitrogen content and size exclusion chromatography, respectively. Aggregation increased with DH up to the practical end point of hydrolysis (DH 6.8%). The aggregates formed under the various conditions studied consisted of peptides with masses ranging from 1.4 to 7.5 kDa. The hydrolysates were also able to aggregate added WPI. The additional amount of aggregated material increased with increasing DH. Peptides involved in peptide¿peptide interactions were also involved in protein¿peptide interactions. It is hypothesized that hydrophobic interactions dominated peptide¿peptide interactions, while protein¿peptide interactions depended on the balance between hydrophobic attraction and electrostatic repulsion.
    Effects of Protein Composition and Enzymatic Activity on Formation and Properties of Potato Protein Stabilized Emulsions
    Koningsveld, G.A. van; Walstra, P. ; Voragen, A.G.J. ; Kuijpers, I.J. ; Boekel, M.A.J.S. van; Gruppen, H. - \ 2006
    Journal of Agricultural and Food Chemistry 54 (2006)17. - ISSN 0021-8561 - p. 6419 - 6427.
    lipid acyl hydrolase - emulsifying properties - tuber protein - patatin - oil - solubility - water - purification - selectivity - expression
    In the present study emulsions were made with various potato protein preparations, which varied in protease inhibitor and patatin content. These emulsions were characterized with respect to average droplet size, plateau surface excess, and the occurrence of droplet aggregation. Droplet aggregation occurred only with potato protein preparations that contained a substantial amount of protease inhibitors and could be prevented only at pH 3. The average droplet size of the emulsions made with potato proteins appeared to be related to the patatin content of the preparation used. Average droplet size was found to be dominated by the patatin-catalyzed lipolytic release of surface active fatty acids and monoglycerides from the tricaprylin oil phase during the emulsification process. Addition of monoglycerides and especially fatty acids, at concentrations representative of those during emulsification, was shown to cause a stronger and much faster decrease of the interfacial tension than that with protein alone and to result in a drastic decrease in droplet size. The patatin used was shown to have a lipolytic activity of 820 units/g with emulsified tricaprylin as the substrate. Because of the droplet aggregating properties of the protease inhibitors, the patatin-rich potato preparations seem to be the most promising for food emulsion applications over a broad pH range, provided the lipolytic activity can be diminished or circumvented
    Stability of pea DDMP saponin and the mechanism of its decomposition
    Heng, L. ; Vincken, J.P. ; Hoppe, K. ; Koningsveld, G.A. van; DeCroos, K. ; Gruppen, H. ; Boekel, M.A.J.S. van; Voragen, A.G.J. - \ 2006
    Food Chemistry 99 (2006)2. - ISSN 0308-8146 - p. 326 - 334.
    pisum-sativum-l - performance liquid-chromatography - soyasaponin-i - structural elucidation - soybean seed - quantification - food
    DDMP saponin can be converted to saponin B by the loss of its DDMP group (2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one). The stability of DDMP saponin from pea was investigated under various conditions (temperature, ethanol concentration, pH). DDMP saponin in water was observed to be unstable at acidic and alkaline pHs, and to have an optimal stability around pH 7. In water, DDMP saponin became unstable at temperatures >30 °C. The presence of ethanol, however, had a stabilizing effect on the DDMP group. The loss of the DDMP group at 65 °C could be completely prevented at >30% (v/v) ethanol. The breakdown reaction of DDMP saponin and the subsequent formation of saponin B was modelled using a multi-response modelling approach and was found to be best described by a first-order reaction. The activation energy was estimated to be 49 kJ/mol, indicating a chemical reaction with moderate temperature dependence. A mechanism of DDMP saponin decomposition is proposed, consisting of a fast protonation or deprotonation, followed by a rate-determining step in which maltol is the leaving group.
    Bitterness of saponins and their content in dry peas
    Heng, L. ; Vincken, J.P. ; Koningsveld, G.A. van; Legger, A. ; Gruppen, H. ; Boekel, M.A.J.S. van; Roozen, J. ; Voragen, A.G.J. - \ 2006
    Journal of the Science of Food and Agriculture 86 (2006)8. - ISSN 0022-5142 - p. 1225 - 1231.
    pisum-sativum-l - soyasaponin-i - soybean seed - biological-activities - undesirable taste - trypsin-inhibitor - plant saponins - serum-albumin - 13 varieties - perception
    The bitterness of a saponin mixture (containing saponin B and DDMP (2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one) saponin in a ratio of 1:4) and saponin B obtained from dry peas were established by a trained panel using line scaling. Both saponins were found to be bitter. However, the saponin mixture, and hence DDMP saponin, was found to be significantly more bitter than saponin B. The bitterness perceived correlated with the saponin concentration. In addition to saponin bitterness, the saponin content and composition of 16 dry pea varieties were also investigated. In two varieties, DDMP saponin was the only saponin present whereas, in the rest of the varieties, DDMP saponin was more abundant than saponin B. The pea varieties investigated differed significantly in saponin content. The amounts of DDMP saponin ranged from 0.7 to 1.5 g kg-1 (dry matter), whereas those of saponin B ranged from 0 to 0.4 g kg-1. As saponins are bitter, pea varieties with lower saponin contents would be preferred for use in food production
    Enzymatic hydrolysis as a means of expanding the cold gelation conditions of soy proteins
    Kuipers, B.J.H. ; Koningsveld, G.A. van; Alting, A.C. ; Driehuis, F. ; Gruppen, H. ; Voragen, A.G.J. - \ 2005
    Journal of Agricultural and Food Chemistry 53 (2005)4. - ISSN 0021-8561 - p. 1031 - 1038.
    whey proteins - rheological properties - beta-lactoglobulin - globular-proteins - food proteins - heat - protease - gels - aggregation - isolate
    Acid-induced cold gelation of soy protein hydrolysates was studied. Hydrolysates with degrees of hydrolysis (DH) of up to 10% were prepared by using subtilisin Carlsberg. The enzyme was inhibited to uncouple the hydrolysis from the subsequent gelation; the latter was induced by the addition of glucono--lactone. Visual observations, confocal scanning laser microscopy images, and the elasticity modulus showed that hydrolysates gelled at higher pH values with increasing DH. The nonhydrolyzed soy protein isolate gelled at pH ~6.0, whereas a DH = 5% hydrolysate gelled at pH ~7.6. Gels made from hydrolysates had a softer texture when manually disrupted and showed syneresis below a pH of 5-5.5. Monitoring of gelation by measuring the development of the storage modulus could be replaced by measuring the pH onset of aggregate formation (pHAggr-onset) using turbidity measurements. The rate of acidification was observed to also influence this pHAggr-onset. Changes in ionic strength (0.03, 0.2, and 0.5 M) had only a minor influence on the pHAggr-onset, indicating that the aggregation is not simply a balance between repulsive electrostatic and attractive hydrophobic interactions, but is much more complex.
    Structure and stability of the potato cysteine protease inhibitor group (Cv. Elkana)
    Pouvreau, L.A.M. ; Kroef, C.H.M. ; Gruppen, H. ; Koningsveld, G.A. van; Broek, L.A.M. van den; Voragen, A.G.J. - \ 2005
    Journal of Agricultural and Food Chemistry 53 (2005)14. - ISSN 0021-8561 - p. 5739 - 5746.
    circular-dichroism spectra - molten-globule state - plasminogen-activator - proteinase-inhibitor - conformation - denaturation - fluorescence - spectroscopy - binding - family
    The conformational stability of potato cysteine protease inhibitor (PCPI), the second most abundant protease inhibitor group in potato tuber, was investigated at ambient temperature and upon heating using far- and near-UV circular dichroism spectroscopy, fluorescence spectroscopy, and differential scanning calorimetry (DSC). The PCPI isoforms investigated have a highly similar structure at both the secondary and the tertiary level. PCPI isoforms show structural properties similar to those of the potato serine protease inhibitor group and the Kunitz type soybean trypsin inhibitor, a known -II protein. Therefore, PCPI isoforms are also classified as members of the -II protein subclass. Results show that the thermal unfolding of PCPI isoforms does not follow a two-state mechanism and that at least one intermediate is present. The occurrence of this intermediate is most apparent in the thermal unfolding of PCPI 8.3 as indicated by the presence of two peaks in the DSC thermogram. Additionally, the formation of aggregates (>100 kDa), especially at low scan rates, increases the apparent cooperativity of the unfolding
    Interactions of phenolic compounds with globular proteins and their effects on food-related functional properties
    Prigent, S.V.E. - \ 2005
    Wageningen University. Promotor(en): Fons Voragen; Harry Gruppen, co-promotor(en): G.A. van Koningsveld. - Wageningen : - ISBN 9789085042679 - 132
    globulinen - eiwitten - fenolverbindingen - chlorogeenzuur - interacties - fysicochemische eigenschappen - fysische eigenschappen - voedsel - globulins - proteins - phenolic compounds - chlorogenic acid - interactions - physicochemical properties - physical properties - food
    In order to modulate the functional properties of food proteins, the interactions between globular proteins and the monomeric phenolic, caffeoylquinic acid (CQA, chlorogenic acid), and the oligomeric phenolics, procyanidins, were characterized and investigated for their effect on protein functional properties. Non-covalent interactions between proteins and CQA involved a low affinity and did not affect protein solubility. Proteins show a medium affinity for procyanidins of an average degree of polymerization (DP) of 5.5, but weakly interacted with smaller procyanidins. Procyanidins of DP 5.5 strongly decreased protein solubility. Covalent interactions between proteins and CQA oxidised by polyphenol oxidase (PPO) or oxidised at alkaline pH resulted in protein modification mainly via dimeric CQA quinones. The covalent modifications of proteins with CQA strongly reduced protein solubility. Lysine, tyrosine, histidine and tryptophan were able to interact with CQA quinones. It can be concluded that for food non-covalent interactions are restricted to oligomeric phenolic.
    Conformational stability of the potato serine protease ihibitor group
    Pouvreau, L.A.M. ; Gruppen, H. ; Koningsveld, G.A. van; Broek, L.A.M. van den; Voragen, A.G.J. - \ 2005
    Journal of Agricultural and Food Chemistry 53 (2005)8. - ISSN 0021-8561 - p. 3191 - 3196.
    differential scanning calorimetry - molten-globule state - circular-dichroism - alpha-lactalbumin - side-chains - cv elkana - proteins - form
    The thermal unfolding of potato serine protease inhibitor (PSPI), the most abundant protease inhibitor group in potato tuber, was measured using far UV CD spectroscopy, fluorescence spectroscopy, and DSC. The results indicate that the thermal as well as the guanidinium-induced unfolding of PSPI occurs via a non-two-state mechanism in which at least one stable intermediate is present. Additionally, the occurrence of aggregation, especially at low scan rates, increases the apparent cooperativity of the unfolding and makes the system kinetically rather than thermodynamically controlled. Aggregate formation seems to occur via a specific mechanism of which PSPI in a tetrameric form is the end product and which may involve disulfide interchanges.
    Formation and Stability of Foams Made with Sunflower (Helianthus annuus) Proteins
    Gonzalez-Perez, S. ; Vereijken, J.M. ; Koningsveld, G.A. van; Gruppen, H. ; Voragen, A.G.J. - \ 2005
    Journal of Agricultural and Food Chemistry 53 (2005)16. - ISSN 0021-8561 - p. 6469 - 6476.
    seed storage proteins - functional-properties - defatted sunflower - oilseed proteins - chlorogenic acid - soy glycinin - albumin - meal - isolate - whey
    Foam properties of a sunflower isolate (SI), as well as those of helianthinin and sunflower albumins (SFAs), were studied at various pH values and ionic strengths and after heat treatment. Less foam could be formed from helianthinin than from SFAs, but foam prepared with helianthinin was more stable against Ostwald ripening and drainage than foam prepared with SFAs. Foams made with SFAs suffered from extensive coalescence. The formation and stability of foams made from reconstituted mixtures of both proteins and from SI showed the deteriorating effect of SFAs on foam stability. Foam stability against Ostwald ripening increased after acid and heat treatment of helianthinin. Partial unfolding of sunflower proteins, resulting in increased structural flexibility, improved protein performance at the air/water interface. Furthermore, it was observed that the protein available is used inefficiently and that typically only ~20% of the protein present is incorporated in the foam.
    Emulsion properties of sunflower (Helianthus annuus) proteins
    Gonzalez-Perez, S. ; Koningsveld, G.A. van; Vereijken, J.M. ; Merck, K.B. ; Gruppen, H. ; Voragen, A.G.J. - \ 2005
    Journal of Agricultural and Food Chemistry 53 (2005)6. - ISSN 0021-8561 - p. 2261 - 2267.
    seed storage proteins - functional-properties - physicochemical properties - emulsifying properties - charge heterogeneity - globulin fraction - chlorogenic acid - soy proteins - albumin - meal
    Emulsions were made with sunflower protein isolate (SI), helianthinin, and sunflower albumins (SFAs). Emulsion formation and stabilization were studied as a function of pH and ionic strength and after heat treatment of the proteins. The emulsions were characterized with respect to average droplet size, surface excess, and the occurrence of coalescence and/or droplet aggregation. Sunflower proteins were shown to form stable emulsions, with the exception of SFAs at neutral and alkaline pH values. Droplet aggregation occurred in emulsions made with SI, helianthinin, and SFAs. Droplet aggregation and subsequent coalescence of emulsions made with SFAs could be prevented at pH 3. Calcium was found to cause droplet aggregation of emulsions made with helianthinin, at neutral and alkaline pH values. Treatments that increase conformational flexibility of the protein molecule improved the emulsion properties of sunflower proteins.
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