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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Editorial Professor Walter Pilnik
Voragen, A.G.J. - \ 2009
Carbohydrate Research : an international journal 344 (2009)14. - ISSN 0008-6215 - p. 1786 - 1787.
Degradation of low molecular weight fragments of pectin and alginates by gamma-irradiation.
Purwanto, Z.I. ; Broek, L.A.M. van den; Schols, H.A. ; Pilnik, W. ; Voragen, A.G.J. - \ 1998
Acta Alimentaria 27 (1998). - ISSN 0139-3006 - p. 29 - 42.
10 Pectins.
Voragen, A.G.J. ; Pilnik, W. ; Thibault, J.F. ; Axelos, M.A.V. ; Renard, C.M.G.C. - \ 1995
In: Food polysaccharides and their applications / Stephen, A.M., - p. 287 - 339.
Ethische vraagstukken voor de levensmiddelentechnoloog bij de verwerking van groente en fruit.
Pilnik, W. - \ 1994
In: Ethiek uit het veld, ervaringen van landbouwkundigen - p. 85 - 90.
Starch and other polysaccharides.
Daniel, J.R. ; Whistler, R.L. ; Voragen, A.G.J. ; Pilnik, W. - \ 1994
In: Ullmann's Encyclopedia of Industrial Chemistry, Vol. A 25 - p. 1 - 62.
Studies on apple protopectin 6: extraction of pectins from apple cell walls with rhamno-galacturonase.
Renard, C.M.G.C. ; Thibault, J.F. ; Voragen, A.G.J. ; Broek, L.A.M. van den; Pilnik, W. - \ 1993
Carbohydrate Polymers 22 (1993). - ISSN 0144-8617 - p. 203 - 210.
Pectic enzymes in fruit and vegetable juice manufacture.
Pilnik, W. ; Voragen, A.G.J. - \ 1993
In: Enzymes in food processing, 3rd Edition / Nagodawithana, T., Reed, G., Academic Press - p. 363 - 399.
Enzymic and chemical degradation of some industrial pectins.
Kravtchenko, T.P. ; Penci, M. ; Voragen, A.G.J. ; Pilnik, W. - \ 1993
Carbohydrate Polymers 20 (1993). - ISSN 0144-8617 - p. 195 - 205.
Characterization of mutagenic compounds in heated orange juice by UV and mass spectra.
Ekasari, I. ; Fokkens, R.H. ; Bonestroo, M.H. ; Schols, H.A. ; Nibbering, N.M.M. ; Pilnik, W. - \ 1993
Food Chemistry 46 (1993). - ISSN 0308-8146 - p. 77 - 79.
Characterisation and enzymic degradation of non-starch polysccharides in lignocellulosic by-products : a study on sunflower meal and palm-kernel meal
Duesterhoeft, E.M. - \ 1993
Agricultural University. Promotor(en): A.G.J. Voragen, co-promotor(en): W. Pilnik. - S.l. : Duesterhoeft - ISBN 9789054850762 - 134
lignocellulose - lignine - zonnebloemolie - asteraceae - plantaardige oliën - palmpitolie - helianthus annuus - zonnebloemen - elaeis guineensis - oliepalmen - fermentatie - voedselbiotechnologie - bijproducten - koolhydraten - cellulose - celmembranen - celwanden - lignocellulose - lignin - sunflower oil - asteraceae - plant oils - palm kernel oil - helianthus annuus - sunflowers - elaeis guineensis - oil palms - fermentation - food biotechnology - byproducts - carbohydrates - cellulose - cell membranes - cell walls

Non-starch polysaccharides (NSP) constitute a potentially valuable part of plant by- products deriving from the food and agricultural industries. Their use for various applications (fuel, feed, food) requires the degradation and modification of the complex plant materials. This can be achieved by enzymatic processes which, in comparison with chemical or physical methods, are regarded as energy-saving and non-polluting. However, a major disadvantage of enzymic processes often is their low effectivity and consequently high costs.

The investigations described in this thesis were conducted to understand the reasons for the low susceptibility to enzymic hydrolysis of such by-products and, in particular, of their non-starch polysaccharides, and to find out whether and how the efficacy of enzymic treatment could be enhanced. The studies should provide information necessary for the development of polysaccharidase-preparations, tailored for the use in different applications.

Sunflower ( Helianthus annuus L.) meal and palm-kernel ( Elaeis guineensis Jacq) meal, by-products from the production of edible oil and used as animal feed compounds, were chosen for our studies.

In chapter 1 an introduction is given to the macroscopic and microscopic structure of the raw materials, to plant cell walls and their constituent polymers. The biodegradation of cell walls and its limitations are briefly reviewed and major non-starch polysaccharide degrading enzymes are summarised. Chapter 1 closes with an outline of the thesis.

For a detailed study of type and structure of the non-starch polysaccharides, cell wall materials (CWM) were prepared from the meals by enzymatic digestion of protein and removal of small amounts of buffer-extractable material ( chapter 2 ). The resulting CWM's were enriched in NSP (55% of sunflower CWM and 75% of palm-kernel CWM) and had a high lignin content. Two different chemical methods, sequential extraction with alkali and sodium chlorite and treatment with 4-methylmorpholine-N-oxide (MMNO) were tested to extract all constituent polysaccharides. Almost complete dissolution could be achieved by a combination of both methods, but the recovery of sugars, especially during MMNO treatment, was low. From the sugar composition of polysaccharide fractions, obtained by sequential chemical extraction, a tentative identification of major polysaccharides was achieved. Their distribution in different botanical fractions of the meals could be deduced by comparison with data from literature (sunflower) or by own experiments (palm-kernel).

The polysaccharide extracts of different purity were further fractionated by graded precipitation with ethanol, size-exclusion or adsorption-chromatography. By determination of the sugar- and glycosidic linkage composition of extracts, (partially) purified subfractions and intact cell wall materials, the identification, partial characterisation and quantification of major non-starch polysaccharides were achieved ( chapter 3 ). In sunflower meal, cellulose (42% of NSP), pectic polysaccharides (24%) and (4-O-methyl)-glucuronoxylans (24%) with about 10% glucuronosyl-substitution were major constituents. Minor amounts of (gluco)mannans (5%) and fucoxyloglucans (4.5%) were also identified. Major polysaccharides in palm-kernel meal were mannans (78% of NSP) with very low degrees of galactose-substitution and of apparently small molecular size (DP 12 to 14), and cellulose (12%). Arabinoxylans (3%) and (4- O -methyl)-glucuronoxylans (3%), deriving from the endocarp fraction of the meal, were present in low amounts in this monocotyledenous material.

For a study of the enzymic hydrolysis of the cell wall materials ( chapter 4 ), three multi-component enzyme preparations were chosen. Solubilisation occurred as a bi-phasic process with high reaction velocities in the first stage of the incubation and only slow progress during extended incubation up to 72h. The solubilisation could markedly be improved by reduction in particle size; partial delignification or increasing enzyme concentration, however, had almost no effect. Maximally 30% of NSP in sunflower meal and 50% in palm-kernel meal could be solubilised from the finely milled CWM's. Although the composition of the enzyme preparations was found to influence the type of reaction products, the extent of their release and, as observed by transmission electron microscopy, the site of enzymic attack in different cell wall layers, our results suggested that substrate accessibility was the major factor limiting enzymic hydrolysis.

A detailed study of the reaction products obtained by incubation with the crude enzyme preparations or fractions thereof (prepared by anion-exchange chromatography) revealed, that pectic compounds and mannose-containing polysaccharides in sunflower CWM were readily degradable ( chapter 5 ). The hydrolysis of mannans in palm-kernel CWM varied from 20% to 50%. In both CWM's, xylans and cellulose were most resistant to hydrolysis. The results indicate the preferential degradation of parenchyma and endosperm tissues and the resistance of hull and endocarp fractions to enzymic hydrolysis. The reaction products formed during all stages of the treatment were of small oligomeric and monomeric size.

The contribution of different enzyme activities to the total solubilisation achieved by the heterogeneous enzyme preparations was studied with (partially) purified subfractions which were prepared by various chromatographic techniques from the crude preparations, and with highly purified enzymes from other microbial sources ( chapter 6 ). In general, the effect of these purified enzyme fractions was low (solubilisation of NSP: 1 % to 5 %). Supplementation of main enzyme fractions with pectolytic, cellulolytic or mannanolytic subfractions did only slightly enhance the total solubilisation. Synergistic action was observed between glucanases and mannanases in palm-kernel incubations and between arabinanases, polygalacturonases and rhamnogalacturonan-degrading enzyme fractions in the hydrolysis of pectic polysaccharides in sunflower CWM. The enzymic hydrolysis of (4- O -methyl)-glucuronoxylans was studied in-situ and with the isolated polysaccharide. The results indicated that the resistance of the xylans to enzymic degradation is not only due to their interlinkage with other polymers and location in the cell wall but also to their primary structure.

In chapter 7 , important aspects concerning the approach and the methodology used are discussed. Implications arising for different fields of application are shown and suggestions for the formulation of enzyme preparations, which merit further research, are made.

Sesquiterpene lactones and inulin from chicory roots : extraction, identification, enzymatic release and sensory analysis
Leclercq, E. - \ 1992
Agricultural University. Promotor(en): W. Pilnik; Æ. de Groot. - S.l. : Leclercq - 137
cichorium intybus - cichorei - diterpenoïden - sesquiterpenoïden - terpenen - etherische oliën - sesquiterpenen - chemie - zetmeel - dextrinen - glycogeen - inuline - versuikering - cichorium intybus - chicory - diterpenoids - sesquiterpenoids - terpenoids - essential oils - sesquiterpenes - chemistry - starch - dextrins - glycogen - inulin - saccharification

Chicory ( Cichorium intybus L.) is one of the many species of the family Compositae. Chicory has been cultivated for the production of leaves or chicons, which have been used as a vegetable since approximately 300 BC, and for its roots, which can be used as a coffee substitute after roasting.

Chicory leaves are appreciated for their slightly bitter taste. Two bitter compounds were known at the start of this project: lactucin (Lc) and lactucopicrin (Lp), both sesquiterpene lactones with a guaiane skeleton. These compounds are also present in the roots, which remain as a waste product after harvesting of the chicons. Chicory roots contain besides bitter substances also inulin, a linear β-(2-1) linked fructose polymer terminated by a sucrose unit residue and the main carbohydrate of the chicory plant.

In Chapter 2 all known constituents of chicory roots are discussed as well as the effect of roasting on these compounds. A survey is given of work carried out on the isolation and identification of bitter principles in Compositae, especially chicory. The aim of this project was to isolate the bitter constitutents and inulin in one step from waste chicory roots. A one step process is only possible when enzymatic liquefaction is applied. Both bitter compounds and inulin will then pass into the liquid phase. The obtained bitter, sweet liquid can be used as a raw material for soft drinks. Quinine eventually could be replaced by the bitter principles from chicory roots.

An isocratic HPLC method was developed for the analysis of the sesquiterpene lactones. Three components were identified in the chicory root extract: Lc, Lp and 8-deoxylactucin (8dLc). Various extraction solvents were tried for the isolation of the sesquiterpene lactones from chicory roots. Polar solvents gave many unknown polar compounds, which eluted at the beginning of the HPLC chromatogram. More apolar solvents gave the sesquiterpene lactones and hardly any of the polar components.

Storage of the roots and further processing, such as drying and milling, affects the amount of sesquiterpene lactones in the roots and thus the composition of the chicory extract (Chapter 4).

The release of bitter compounds and inulin has been studied during enzymatic liquefaction of chicory roots with commercial pectinases and cellulases (Chapter 5 and 7). An increase was seen in the amount of Lc and 8dLc found in the liquid phase during enzymatic liquefaction. After improvement of the HPLC method (gradient elution instead of isocratic method) it was found that the increase of Lc and 8dLc was due to the increase of their dihydro derivatives, which eluted at the same place as Lc respectively 8dLc with the isocratic method.

Endogenous chicory root enzymes have also been studied in this context, because they have proven to be capable to release bitter components as well (Chapter 6). However, the optimum pH and temperature for the performance of endogenous chicory root enzymes are different from those of the commercial enzyme preparations tested, and may therefore not play a role in the release of sesquiterpene lactones during enzymatic liquefaction.

Cichorioside B (glycoside of ll(S),13-dihydro-lactucin), crepidiaside B (glycoside of ll(S),13-dihydro-8-deoxylactucin), cichorioside C (glycoside of a germacranolide), and ll(S),13-dihydrolactucopicrin were identified in chicory roots. Compound N could not be identified, but there are indications that this compound is a diglycoside of dHLc. The presence of the glycoside of Lc is plausible, but to date this compound was not extracted from the chicory roots.

The threshold value of six pure sesquiterpene lactones (Lc, Lp, 8dLc, dHLc, dHLp, dH8dLc) was determined (Chapter 8) and related to the theories on bitterness as discussed in Chapter 3.

The effect of processing and storage on the bitter taste of bitter orange lemonade was investigated. A comparison was made between quinine as bitter substance and chicory root extract as the bitter ingredient.

The storage in daylight of the bitter orange containing quinine caused a tremendous decrease of the bitterness of the beverage. No decrease in bitterness was seen in the beverage with chicory root extract. Pasteurization did not affect the bitter taste of bitter orange with chicory root extract.

The bitterness of the various chicory root extracts made for sensory analysis differed in bitter intensity in spite of standardisation of the Lc content.

Bitter intensities of chicory root extract before and after incubation with pectolytic and cellulolytic enzymes were determined. Thus the bitterness of the precursors was compared with that of the aglycons. However, no judgement could be given on whether the enzyme treatment of the chicory root extractcould be given on whether the enzyme treatment of the chicory root extract gave rise to a more bitter taste. About half of the panellists judged the extract with the glycosides more bitter than the extract with the aglycons, the other half could not taste any difference between these samples.

Studies on the intermolecular distribution of industrial pectins by means of preparative ion-exchange chromatography.
Kravtchenko, T.P. ; Voragen, A.G.J. ; Pilnik, W. - \ 1992
Carbohydrate Polymers 19 (1992). - ISSN 0144-8617 - p. 115 - 124.
Studies on the intermolecular distribution of industrial pectins by means of preparative size exclusion chromatography.
Kravtchenko, T.P. ; Berth, G. ; Voragen, A.G.J. ; Pilnik, W. - \ 1992
Carbohydrate Polymers 18 (1992). - ISSN 0144-8617 - p. 253 - 263.
Improvement of the selective depolymerization of pectic substances by chemical ß-elimination in aqueous solution.
Kravtchenko, T.P. ; Arnould, I. ; Voragen, A.G.J. ; Pilnik, W. - \ 1992
Carbohydrate Polymers 19 (1992). - ISSN 0144-8617 - p. 237 - 242.
Analytical comparison of three industrial pectin preparations.
Kravtchenko, T.P. ; Voragen, A.G.J. ; Pilnik, W. - \ 1992
Carbohydrate Polymers 18 (1992). - ISSN 0144-8617 - p. 17 - 25.
Studies on the structure of industrial high methoxyl pectins
Kravtchenko, T.P. - \ 1992
Agricultural University. Promotor(en): W. Pilnik; A.G.J. Voragen. - S.l. : Kravtchenko - 173
pectinen - polychloorbifenylen - chemische structuur - pectins - polychlorinated biphenyls - chemical structure

The chemical structure of three industrial high methoxyl pectins (one extracted from apple pomace and two from lemon peels) has been extensively investigated. The apple pectin differs from the lemon ones by having a higher apparent molecular size, a higher neutral-sugar content, present either as covalently-linked side chains or as free neutral polysaccharides, a higher acetyl content and a higher phenolic content but a lower protein content. The lemon pectins appear to be very similar to each other except for their calcium cation content. Preparative size exclusion chromatography and ion exchange chromatography show that pectin samples are not homogeneous and that within one pectin preparation, the composition of pectin molecules varies with their molecular size or ionic charge. The lemon pectin sample richer in calcium cations contains a higher proportion of molecules with low degree of esterification, probably explaining its higher tendancy to form aggregates in the presence of calcium. Enzymic degradation of the pectin samples and subsequent analysis of the resulting fragments showed that at least part of the non-esterified carboxylic acids are grouped in blocks. However, such blocks are more numerous in the lemon pectin that is richer in calcium cations than in the apple or the other lemon pectin. Their presence explains the higher calcium-sensitivity of certain pectins and thus strongly influences their physical behaviour on application.

The significance of endogenous and exogenous pectic enzymes in fruit and vegetable processing.
Pilnik, W. ; Voragen, A.G.J. - \ 1991
In: Food enzymology, Vol. 1 / Fox, P.F., - p. 303 - 336.
The use of an automated system for mutagenicity testing to assess the innerquality of heat-treated orange juices.
Ekasari, I. ; Hoenderboom, C.J.M. ; Jongen, W.M.F. ; Pilnik, W. - \ 1991
Food Chemistry 42 (1991). - ISSN 0308-8146 - p. 203 - 212.
Wirkung der Enzymbehandlung auf die Qualität von verarbeiteten Früchten und Gemüse.
Pilnik, W. ; Voragen, A.G.J. - \ 1991
Flüssiges Obst 58 (1991). - p. 422 - 427.
Studies on apple protopectin. 5. Structural studies on enzymatically extracted pectins.
Renard, C.M.G.C. ; Voragen, A.G.J. ; Thibault, J.F. ; Pilnik, W. - \ 1991
Carbohydrate Polymers 16 (1991). - ISSN 0144-8617 - p. 137 - 154.
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