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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    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.
    Non-starch polysaccharides in barley and malt: a mass balance of flour fractionation.
    Viëtor, R.J. ; Voragen, A.G.J. ; Angelino, S.A.G.F. ; Pilnik, W. - \ 1991
    Journal of Cereal Science 14 (1991). - ISSN 0733-5210 - p. 73 - 83.
    Studies on apple protopectin. 4. Apple xyloglucans and influence of pectin extraction treatments on their solubility.
    Renard, C.M.G.C. ; Voragen, A.G.J. ; Thibault, J.F. ; Pilnik, W. - \ 1991
    Carbohydrate Polymers 15 (1991). - ISSN 0144-8617 - p. 387 - 403.
    Effects of the treatment of apple pulp with liquefying enzymes on the aroma of apple juice.
    Jenniskens, L.H.D. ; Voragen, A.G.J. ; Pilnik, W. ; Posthumus, M.A. - \ 1991
    Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 24 (1991). - ISSN 0023-6438 - p. 70 - 92.
    Characterization of polygalacturonases from yeast and fungi.
    Pasculli, R. ; Geraeds, C. ; Voragen, A.G.J. ; Pilnik, W. - \ 1991
    Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 24 (1991). - ISSN 0023-6438 - p. 63 - 70.
    Studies on apple protopectin. 3. Characterization of the material extracted by pure polysaccharidases from apple cell walls.
    Renard, C.M.G.C. ; Schols, H.A. ; Voragen, A.G.J. ; Thibault, J.F. ; Pilnik, W. - \ 1991
    Carbohydrate Polymers 15 (1991). - ISSN 0144-8617 - p. 13 - 32.
    Comparison between enzymatically and chemically extracted pectins from apple cell walls.
    Renard, C.M.G.C. ; Voragen, A.G.J. ; Thibault, J.F. ; Pilnik, W. - \ 1991
    Animal Feed Science and Technology 32 (1991). - ISSN 0377-8401 - p. 69 - 75.
    Studies on apple protopectin. 2. Apple cell wall degradation by pure polysaccharides and their combinations.
    Renard, C.M.G.C. ; Searle-van Leeuwen, M.J.F. ; Voragen, A.G.J. ; Thibault, J.F. ; Pilnik, W. - \ 1991
    Carbohydrate Polymers 14 (1991). - ISSN 0144-8617 - p. 295 - 314.
    Apple juice and concentrated apple juice manufacture with special consideration of use of enzymes: classical-modern-visions for the future.
    Pilnik, W. - \ 1990
    In: Proc. Int. Fruit Juice Symp. '90, Japan (1990) 26 pp
    Carbohydrates in food and feed.
    Pilnik, W. ; Voragen, A.G.J. - \ 1990
    In: Biological sciences - Towards a carbohydrate-based chemistry / Ellwood, D.C., Sargeant, K., Sergheraert, G., van Bekkum, H., Woelk, H.U., - p. 44 - 75.
    Antimutagenic effects of apple juices: Interference with heat load measurement by microbiological methods.
    Ekasari, I. ; Jongen, W.M.F. ; Pilnik, W. - \ 1990
    Journal of Food Science 55 (1990). - ISSN 0022-1147 - p. 1026 - 1028.
    Optimization of the saccharification of xylan by xylan-degrading enzymes in the bioconversion of biomass.
    Kormelink, F.J.M. ; Searle-van Leeuwen, M.J.F. ; Wood, T.M. ; Voragen, A.G.J. ; Pilnik, W. - \ 1990
    In: Proc. 5th EC Conf. Biomass for energy and industry, Vol. 1: Policy, environment, production and harvesting, G. Grassi, G. Gosse, G. dos Santos (eds.). Lisbon, Potugal, 1989. London-New York (1990) 2.66-2.74
    Use of enzymes in food processing.
    Pilnik, W. ; Voragen, A.G.J. - \ 1990
    In: Proc. Int. Conf. Biotechnology and food, 1989, K. Gierschner, W.P. Hammes, W. Hartmeier (eds.). Food Biotechnology 4,1 - p. 319 - 328.
    A simplified method for the determination of the intrinsic viscosity of pectin solutions by classical viscosimetry.
    Kravtchenko, T.P. ; Pilnik, W. - \ 1990
    In: Proc. 5th Int. Conf., Wrexham, 1989. Gums and stabilisers for the Food Industry 5, G.O. Philips, D.J. Wedlock, P.A. Williams (eds.) - p. 281 - 285.
    Pectin - a many splendoured thing.
    Pilnik, W. - \ 1990
    In: Proc. 5th Int. Conf., Wrexham, 1989. Gums and stabilisers for the Food Industry 5, G.O. Philips, D.J. Wedlock, P.A. Williams (eds.) - p. 209 - 221.
    Characterization of mutagenic compound(s) in heated orange juice.
    Indriati Ekasari, ; Berg, H.E. ; Jongen, W.M.F. ; Pilnik, W. - \ 1990
    Food Chemistry 36 (1990). - ISSN 0308-8146 - p. 11 - 18.
    Studies on apple protopectin: I. Extraction of insoluble pectin by chemical means.
    Renard, C.M.G.C. ; Voragen, A.G.J. ; Thibault, J.F. ; Pilnik, W. - \ 1990
    Carbohydrate Polymers 12 (1990). - ISSN 0144-8617 - p. 9 - 25.
    Die Verbesserung der Impraegnierbarkeit von Fichtenholz mittels chemischer und enzymatischer Vorbehandlung
    Militz, H. - \ 1990
    Agricultural University. Promotor(en): W. Pilnik; A.G.J. Voragen. - S.l. : Militz - 220
    bosbouw - bomen - enzymen - hout - houtchemie - houteigenschappen - vloeistoffen (liquids) - gassen - permeabiliteit - organische verbindingen - houtverduurzaming - enzymologie - fermentatie - toedieningswijzen - picea abies - forestry - trees - enzymes - wood - wood chemistry - wood properties - liquids - gases - permeability - organic compounds - wood preservation - enzymology - fermentation - application methods - picea abies

    Finely ground spruce ( Picea abies (L.) Karst. ) was incubated with different enzyme preparations. The enzyme concentration, incubation time, temperature and buffer concentration were varied. The nature and quantity of uronic acids and neutral sugars released from the cell walls were determined. The most effective enzyme preparations were shown to be those with a broad cellulolytic and hemicellulolytic spectrum of activity. Specific pectinases were found not to be particularly effective. Sapwood and heartwood were broken down in equal degrees. Enzymatic preliminary treatment of intact spruce improved the permeability of the timber. The extent of the improvement was dependent on the enzyme preparation applied, the enzyme concentration, the incubation time, the incubation temperature and the origin of the timber. Enzymatic preliminary treatment was more effective in sapwood than in heartwood. Scanning electron microscopy made it possible to demonstrate the decomposition of the torus and the margo of the bordered pits as well as the decomposition of the pits between tracheids and parenchyma. The compression strength and the modulus of elasticity were not reduced. Preliminary treatment of intact spruce with alkali, acids and chelating agents did not result in improved permeability.

    Optimization of the saccharification of xylan by xylan-degrading enzymes in the bioconversion of biomass.
    Kormelink, F.J.M. ; Searle-van Leeuwen, M.J.F. ; Wood, T.M. ; Voragen, A.G.J. ; Pilnik, W. - \ 1989
    In: Abstracts 5th European Conf. Biomass for energy and industry. Gulbenkian Foundation Lisbon, Portugal (1989)
    FPLC-HPLC: a useful combination for screening hemicellulase activities in technical enzyme preparations.
    Kormelink, F.J.M. ; Searle-van Leeuwen, M.J.F. ; Schols, H.A. ; Voragen, A.G.J. ; Pilnik, W. - \ 1989
    In: Proc. Symp. Food science: basic research for technological progress, Wageningen, 1988. J.P. Roozen, F.M. Rombouts and A.G.J. Voragen (eds.). Pudoc, Wageningen - p. 145 - 149.
    Optimization of the saccharification of hemicelluloses in the bioconversion of biomass.
    Kormelink, F.J.M. ; Voragen, A.G.J. ; Searle-van Leeuwen, M.J.F. ; Schols, H.A. ; Pilnik, W. - \ 1989
    In: Proc. 3rd Contractors' Meeting, Paestum, 1988. Energy from biomass 4, G. Grassi, D. Pirrwitz and H. Zibetta (eds.). London, New York - p. 307 - 315.
    Carbohydrates in food and feed.
    Pilnik, W. ; Voragen, A.G.J. - \ 1989
    In: Abstracts Symp. Towards a carbohydrate-based chemistry, Amiens, France (1989)
    Effect of enzyme treatment on the quality of processed fruit and vegetables.
    Pilnik, W. ; Voragen, A.G.J. - \ 1989
    ACS symposium series 405 (1989). - ISSN 0097-6156 - p. 250 - 269.
    Pectin-degrading enzymes in fruit and vegetable processing.
    Voragen, A.G.J. ; Pilnik, W. - \ 1989
    In: Proc. 195th Nat. Meeting Am. Chem. Soc., Toronto, Ontario, Canada, 1988. ACS Symposium Series No. 389: Biocatalysis in agricultural biotechnology, J.R. Whitaker and P.E. Sonnet (eds.). Washington, DC - p. 93 - 115.
    Mild isolation of water-insoluble cell-wall material from wheat flour: Composition of fractions obtained with emphasis on non-starch polysaccharides.
    Gruppen, H. ; Marseille, J.P. ; Voragen, A.G.J. ; Hamer, R.J. ; Pilnik, W. - \ 1989
    Journal of Cereal Science 9 (1989). - ISSN 0733-5210 - p. 247 - 260.
    Enzymic studies on the connections between polymers in apple cell walls.
    Renard, C.M.G.C. ; Voragen, A.G.J. ; Thibault, J.F. ; Pilnik, W. - \ 1989
    In: Abstracts 5th Cell Wall Meeting, Edinburgh, UK (1989)
    Pectin - a many splendoured thing.
    Pilnik, W. - \ 1989
    In: Abstracts 5th Int. Conf. and Industrial Exhibition, Gums and stabilisers for the industry. Wrexham, UK (1989)
    Properties of amidated pectins. II. Polyelectrolyte behavior and calcium binding of amidated pectins and amidated pectic acids.
    Racape, E. ; Thibault, J.F. ; Reitsma, J.C.E. ; Pilnik, W. - \ 1989
    Biopolymers 28 (1989). - ISSN 0006-3525 - p. 1435 - 1448.
    Apple protopectin: preliminary study of enzymic extraction.
    Renard, C.M.G.C. ; Voragen, A.G.J. ; Schols, H.A. ; Searle-van Leeuwen, M.F. ; Thibault, J.F. ; Pilnik, W. - \ 1989
    In: Proc. Symp. Food science: basic research for technological progress, Wageningen, 1988. J.P. Roozen, F.M. Rombouts and A.G.J. Voragen (eds.). Pudoc, Wageningen - p. 163 - 170.
    High performance ion exchange chromatography of pectins.
    Schols, H.A. ; Reitsma, J.C.E. ; Voragen, A.G.J. ; Pilnik, W. - \ 1989
    Food Hydrocolloids 3 (1989). - ISSN 0268-005X - p. 115 - 121.
    Enzymic hydrolysis of the 'hairy' fragments of sugarbeet pectins.
    Guillon, F. ; Thibault, J.F. ; Rombouts, F.M. ; Voragen, A.G.J. ; Pilnik, W. - \ 1989
    Carbohydrate Research : an international journal 190 (1989). - ISSN 0008-6215 - p. 97 - 108.
    Analysis of mixtures of pectins and amidated pectins.
    Reitsma, J.C.E. ; Pilnik, W. - \ 1989
    Carbohydrate Polymers 10 (1989). - ISSN 0144-8617 - p. 315 - 319.
    Microbiological methods to evaluate the inner quality of orange juices.
    Ekasari, I. ; Jongen, W.M.F. ; Pilnik, W. - \ 1989
    In: Proc. Symp. Food science: basic research for technological progress, Wageningen, 1988. J.P. Roozen, F.M. Rombouts and A.G.J. Voragen (eds.). Pudoc, Wageningen - p. 97 - 103.
    Mutagenicity and possible occurrence of flavonol aglycones in heated orange juice.
    Ekasari, I. ; Bonestroo, M.H. ; Jongen, W.M.F. ; Pilnik, W. - \ 1989
    Food Chemistry 31 (1989). - ISSN 0308-8146 - p. 289 - 294.
    The inner quality of orange juice and apple juice : assessment by the use of microbiological methods
    Ekasari, I. - \ 1989
    Agricultural University. Promotor(en): W. Pilnik; W.M.F. Jongen. - S.l. : Ekasari - 119
    appelsap - sinaasappelsap - voedingsmiddelen - voedselkwaliteit - kwaliteitscontroles - apple juice - orange juice - foods - food quality - quality controls

    A modified Salmonella mutagenicity assay and a cytotoxicity test were developed to. determine the concentration of sensorially inactive Maillard Intermediate Products (MIP) in fruit juices. The formation of MIP is initiated by heat treatments necessary for pasteurization and thermal concentration. In industrial and laboratory prepared orange juices their concentration was seen to be related to the intensity of the heat treatment and to allow a shelf-life prediction in relation to non-enzymatic browning (inner quality). The microbial MIP assay(s) are therefore useful for orange juice manufactures to select concentrated juices for reconstitution and packing and to test equipment and processes. The modification of the tests involve preincubation with the tester bacteria for 4 hr at pH 7.4 and 37°C. Under natural acidic condition orange juice is not mutagenic.

    It was further seen that the heat treatments did not hydrolyze orange glycosides to mutagenic aglycones which could have influenced the assay. MIP were characterized to be polar, non volatile compounds which carry no charge and have a molecular weight from 200 to 700 daltons. Automation of the mutagenicity assay by a turbidometric assay system was seen to be only possible for gel filtration and HPLC fractions of juice; in whole orange juice endogenous growth factors and cytotoxicity disturbed the assay. on the other hand measurement of cytotoxicity of whole juice could be carried out conveniently by a kinetic conductance method. Heat treated laboratory prepared apple juice also contained mutagenic fractions but the whole juice had a positive antimutagenic balance. There was a heat load and dose related reduction of the mutagenicity of MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) and 4-NQO (4-nitroquinoline-N-oxide) in the presence of apple juice. These findings give new aspects to apple juice as a healtly food.

    Prof. Walter Pilnik: a life dedicated to food science.
    Rombouts, F.M. ; Roozen, J.P. ; Voragen, A.G.J. - \ 1989
    In: Abstract Symp. Food science: basic research for technological progress, Wageningen, 1988. J.P. Roozen, F.M. Rombouts and A.G.J. Voragen (eds.). Pudoc, Wageningen (1989)
    Food science: basic research for technological progress. Proceedings of the symposium in honour of Professor W. Pilnik, Wageningen, 1988.
    Roozen, J.P. ; Rombouts, F.M. ; Voragen, A.G.J. - \ 1989
    Wageningen : Pudoc - ISBN 9789022009925 - 184
    voedselindustrie - voedseltechnologie - onderzoek - food industry - food technology - research
    Chufa (Cyperus esculentus): A new source of dietary fibre.
    Linssen, J.P.H. ; Cozijnsen, J.L. ; Pilnik, W. - \ 1989
    Journal of the Science of Food and Agriculture 49 (1989). - ISSN 0022-5142 - p. 291 - 296.
    Enzymatic conversion of potato arabinogalactans by endo-arabinanase and endo-galactanase from Aspergillus niger.
    Vis, J.W. van de; Searle-van Leeuwen, M.J.F. ; Schols, H.A. ; Voragen, A.G.J. ; Pilnik, W. - \ 1988
    In: Proc. Euroforum New Energies Congr. Vol. 3. H.S. Stephens & Ass., Saarbrücken, FRG - p. 555 - 557.
    Measurement of heat load in orange juices: use of microbiological methods.
    Ekasari, I. ; Jongen, W.M.F. ; Vermunt, A.E.M. ; Pilnik, W. - \ 1988
    Food Technology 45 (1988). - ISSN 0015-6639 - p. 124 - 128.
    The arabinanases of Aspergillus niger; purification and characterisation of two _-L-arabinofuranosidases and an endo-1,5-_-L-arabinanase.
    Rombouts, F.M. ; Voragen, A.G.J. ; Searle-van Leeuwen, M.F. ; Geraeds, C.C.J.M. ; Schols, H.A. ; Pilnik, W. - \ 1988
    Carbohydrate Polymers 9 (1988). - ISSN 0144-8617 - p. 25 - 47.
    Communications to the Editor. Synergism in cellulose hydrolysis by endoglucanases and exoglucanases purified from Trichoderma viride.
    Beldman, G. ; Voragen, A.G.J. ; Rombouts, F.M. ; Pilnik, W. - \ 1988
    Biotechnology and Bioengineering 31 (1988). - ISSN 0006-3592 - p. 173 - 178.
    Specific and nonspecific glucanases from Trichoderma viride.
    Beldman, G. ; Voragen, A.G.J. ; Rombouts, F.M. ; Pilnik, W. - \ 1988
    Biotechnology and Bioengineering 31 (1988). - ISSN 0006-3592 - p. 160 - 167.
    From traditional ideas to modern fruit juice winning processes.
    Pilnik, W. - \ 1988
    In: Proc. Int. Congr. Fruit juices. Orlando, Florida, USA - p. 159 - 179.
    Effect of light, solvents and commercial enzymes on the solubility and stability of sesquiterpene lactones from chicory roots.
    Leclercq, E. ; Voragen, A.G.J. ; Brugging, L.M. ; Pilnik, W. - \ 1988
    Zeitschrift für Lebensmittel-Untersuchung und -Forschung. A, Food research and technology 187 (1988). - p. 440 - 443.
    Non-enzymatic browning of oligogalacturonides in apple juice models.
    Voragen, A.G.J. ; Schols, H.A. ; Pilnik, W. - \ 1988
    Zeitschrift für Lebensmittel-Untersuchung und -Forschung. A, Food research and technology 187 (1988). - p. 315 - 320.
    Comparison of chufa and olive oils.
    Linssen, J.P.H. ; Kielman, G.M. ; Cozijnsen, J.L. ; Pilnik, W. - \ 1988
    Food Chemistry 28 (1988). - ISSN 0308-8146 - p. 279 - 285.
    III. Vorwiegend kohlenhydrathaltige Lebensmittel. 27 Pektine.
    Pilnik, W. - \ 1988
    In: Lebensmitteltechnologie - p. 228 - 234.
    Book review: H.-D. Belitz, W. Grosch (translation D. Hadzieyev): Lebensmittelchemie (Food chemistry). Springer Verlag, Berlin etc. 1987.
    Pilnik, W. - \ 1988
    Zeitschrift für Lebensmittel-Untersuchung und -Forschung. A, Food research and technology 186 (1988). - p. 39 - 39.
    The arabinanase complex for complete saccharification of arabinans.
    Voragen, A.G.J. ; Rombouts, F.M. ; Searle-van Leeuwen, M.J.F. ; Pilnik., W. - \ 1987
    In: Proc. 4th Eur. Conf. Biomass for energy and industry. Orleans, France - p. 264 - 265.
    Conversion of arabinans by the arabinanases of Aspergillus niger.
    Voragen, A.G.J. ; Rombouts, F.M. ; Searle-van Leeuwen, M.J.F. ; Geraeds, C.C.J.M. ; Schols, H.A. ; Pilnik, W. - \ 1987
    In: Proc. 4th Eur. Conf. Biomass for energy and industry. Orleans, France - p. 737 - 744.
    Degradation of arabinans by endo-arabinanase and arabino-furanosidases purified from Aspergillus niger.
    Voragen, A.G.J. ; Rombouts, F.M. ; Searle-van Leeuwen, M.F. ; Schols, H.A. ; Pilnik, W. - \ 1987
    Food Hydrocolloids 2 (1987). - ISSN 0268-005X - p. 423 - 437.
    Liquefaction power of technical enzyme preparations.
    Siliha, H.A. ; Voragen, A.G.J. ; Pilnik, W. - \ 1987
    Unknown Publisher - 44 p.
    Screening of technical enzyme preparation and the influence of arabinanase and galactanase on juice yields from apples.
    Kroef, T. ; Pilnik, W. ; Voragen, A.G.J. - \ 1987
    Unknown Publisher - 11 p.
    An HPGPC method for assaying endo-arabinanases in the presence of exo-arabinanases.
    Kroef, T. ; Schols, H.A. ; Pilnik, W. ; Voragen, A.G.J. - \ 1987
    Unknown Publisher - 15 p.
    Voortgangsrapport enzymatische veevoeder ontsluiting.
    Dusterhoft, E.M. ; Voragen, A.G.J. ; Pilnik, W. - \ 1987
    Unknown Publisher - 15 p.
    Brouweigenschappen van sorghum: Isolatie en karakterisering van NSP uit geslepen sorghum en effecten van chemische en enzym. behandelingen op NSP fracties.
    Roersma, E.S. ; Voragen, A.G.J. ; Pilnik, W. - \ 1987
    Unknown Publisher - 20 p.
    Winning van inuline en fructose uit de aardpeer (Helianthus tuberosis) door enzymatische vervloeiing.
    Birtantie, I.R.K. ; Voragen, A.G.J. ; Pilnik, W. ; Fuchs, A. - \ 1987
    In: Verslagen van de tweede themadag inuline : gehouden op 30 oktober 1987 in het Internationaal Agrarisch Centrum, Wageningen / Fuchs, A., - p. 50 - 58.
    Polysaccharides in food technology.
    Rombouts, F.M. ; Voragen, A.G.J. ; Pilnik, W. - \ 1987
    In: Carbohydrate, F.W. Lichtenthaler and K.H. Neff (eds.). Gesellsch. Deutscher Chemiker, Frankfurt (1987) D8
    Optimization of the enzymatic saccharification of hemicelluloses in the bioconversion of biomass.
    Voragen, A.G.J. ; Rombouts, F.M. ; Pilnik, W. - \ 1987
    In: Energy from biomass -1-. Proc. First Contractors' Meeting, G. Grassi and H. Zilbetta (eds.). Brussels, 1986. Elsevier Applied Science Publ - p. 241 - 246.
    Adsorption and kinetic behavior of purified endoglucanases and exoglucanases from Trichoderma viride.
    Beldman, G. ; Voragen, A.G.J. ; Rombouts, F.M. ; Searle-van Leeuwen, M.F. ; Pilnik, W. - \ 1987
    Biotechnology and Bioengineering 30 (1987). - ISSN 0006-3592 - p. 251 - 257.
    Studies on pectin degradation.
    Deventer-Schriemer, W.H. van; Pilnik, W. - \ 1987
    Acta Alimentaria 16 (1987). - ISSN 0139-3006 - p. 143 - 153.
    Effects of iota carrageenan, carboxymethyl cellulose and xanthan gum on the stability of formulated minced fish products.
    Ponte, D.J.B. Da; Roozen, J.P. ; Pilnik, W. - \ 1987
    International Journal of Food Science and Technology 22 (1987). - ISSN 0950-5423 - p. 123 - 133.
    Polysacchariden in de levensmiddelentechnologie.
    Pilnik, W. ; Voragen, A.G.J. - \ 1987
    Koolhydraten in Nederland 2 (1987). - p. 5 - 8.
    Cyperus esculentus: voedingsmiddel of onkruid.
    Linssen, J.P.H. ; Olderen, J.D. van; Pilnik, W. - \ 1987
    Voedingsmiddelentechnologie 20 (1987)5. - ISSN 0042-7934 - p. 4 - 26.
    Detection of maillard intermediary product in orange juice by bacterial mutagenicity assay.
    Ekasari, I. ; Jongen, W.M.F. ; Pilnik, W. - \ 1987
    In: Proc. Symp. Internationale Fruchtsaft/Union - p. 409 - 417.
    Use of a bacterial mutagenicity assay as a rapid method for the detection of early stage of Maillard reaction in orange juices.
    Ekasari, I. ; Jongen, W.M.F. ; Pilnik, W. - \ 1986
    Food Chemistry 21 (1986). - ISSN 0308-8146 - p. 125 - 131.
    Pectinases and other cell-wall degrading enzymes of industrial importance.
    Rombouts, F.M. ; Pilnik, W. - \ 1986
    Symbiosis 2 (1986). - ISSN 0334-5114 - p. 79 - 90.
    Tomato juices and tomato juice concentrates : a study of factors contributing to their gross viscosity
    Heutink, R. - \ 1986
    Landbouwhogeschool Wageningen. Promotor(en): W. Pilnik; A.G.J. Voragen. - Wageningen : Heutink - 200
    vloeistofmechanica - frictie - vruchtensappen - solanum lycopersicum - tomaten - viscosimeters - viscositeit - groentesappen - fluid mechanics - friction - fruit juices - solanum lycopersicum - tomatoes - viscometers - viscosity - vegetable juices
    The gross viscosity of tomato juice and tomato juice concentrates was found to be determined primarily by the water insoluble solids (WIS) content. The serum viscosity did not contribute to gross viscosity. The WIS consisted of whole tomato cells, vascular bundles and skin fragments. In general the WIS could be fractionated into 40-45% pectin, 25-30% hemicellulose and 30-35% cellulose. Highly branched as well as more linear pectin fragments were found to be present in tomato WIS. Xylans, arabinans and (arabino)galactans were involved in the attachment of pectic substances to the cell wall matrix. The presence of xylans, xyloglucans, (gluco)mannans and a limited amount of galactan in the hemicellulose was indicated. Pectin fragments, characterized by a low content of arabinose and galactose containing side chains, and esterified in such a way that they were degraded by both PG and PL, made an important contribution to gross viscosity. Cellulose was found to make a relatively smaller contribution to gross viscosity than these pectin fragments. The rigidity of the cell walls, caused by the cellulosic structure, seemed to influence gross viscosity at higher WIS concentrations. The differences which exist naturally in WIS composition were found to be too small to cause large differences In gross viscosity. Higher hot break temperatures were found to result in a more effective removal of WIS from skin material. The influences of hot break temperature, finisher temperature and size of finisher screen opening on the finisher operation were closely related to the efficiency of the finisher. The concentration of a tomato juice by evaporation resulted in a loss in gross viscosity, after dilution of the paste to the original strength. The causes for this "dilution-loss" were studied and could be related to the simultaneous concentration of tomato cells and, presumably, ions. The centrifugation-serum-concentration method resulted in a significantly decreased "dilution-loss".

    The cellulases of Trichoderma viride : mode of action and application in biomass conversion
    Beldman, G. - \ 1986
    Landbouwhogeschool Wageningen. Promotor(en): W. Pilnik; A.G.J. Voragen. - Wageningen : Beldman - 109
    amylasen - cellulase - fermentatie - voedselbiotechnologie - o-glycoside hydrolasen - biomassaconversie - amylases - cellulase - fermentation - food biotechnology - o-glycoside hydrolases - biomass conversion
    Beet pulp and potato fibre were liquefied and saccharified with a combination of cellulase from Trichodermaviride and pectinase from Aspergillusniger . Cell wall polysaccharides were hydrolysed extensively. The application of a packed column reactor, connected with a hollow fibre ultrafiltration unit was investigated for the enzymatic hydrolysis of beet pulp. A high degree of polysaccharide hydrolysis of spent grain by the action of cellulases was obtained after pretreatment with sulfuric acid or sodium hydroxyde. Essentially only monomeric sugars were present in the enzyme digest of the acid pretreated material . Six endoglucanases, three exoglucanases and a β-glucosidase were purified from a commercial cellulase preparation of T . viride origin. These enzymes were characterized with respect to their activities on several cellulosic substrates as well as chemical and physical properties. The β-glucosidase showed no cellobiase activity . Random and less random acting endoglucanases were distinguished. Adsorption, kinetic and synergistic behaviours of these enzymes were investigated on crystalline cellulose. It was shown that an optimal ratio of endoglucanase to exoglucanase was needed in order to obtain a maximal degree of synergism. This ratio could be related to the adsorption behaviours of the cellulases, suggesting that synergism between endoglucanases and exoglucanases takes place in very close cooperation at the surface of the cellulose particle . From activity experiments on xylan specific and nonspecific glucanases could be demonstrated. However, the non-specific glucanases prefer to hydrolyse β-1,4-glucosidic linkages over β-1,4-xylosidic bonds.

    Structural studies of apple pectins with pectolytic enzymes.
    Vries, J.A. de; Voragen, A.G.J. ; Rombouts, F.M. ; Pilnik, W. - \ 1986
    In: Recent advances in the chemistry and function of pectins, M.L. Fishman & J.J. Jen, (eds.). ACS Symp. Series 310 - p. 38 - 48.
    Structural features of the neutral sugar side chains of beet pulp pectins.
    Guillon, F. ; Thibault, J.F. ; Rombouts, F.M. ; Voragen, A.G.J. ; Pilnik, W. - \ 1986
    In: Proc. 4th. Cell Wall meeting, B. Vian, D. Reis, R. Goldberg (eds.). Univ. P. et M. Curie, Paris - p. 112 - 115.
    Structural features of the hemicellulose polymers of apples.
    Voragen, A.G.J. ; Schols, H.A. ; Pilnik, W. - \ 1986
    Zeitschrift fur lebensmittel-untersuchung und-forschung 183 (1986). - ISSN 0044-3026 - p. 105 - 110.
    Screening of technical enzyme preparations.
    Kroef, T. ; Pilnik, W. ; Voragen, A.G.J. - \ 1986
    Unknown Publisher - 12 p.
    Properties of amidated pectins. I. Preparation and characterization of amidated pectic acids.
    Reitsma, J.C.E. ; Thibault, J.F. ; Pilnik, W. - \ 1986
    Food Hydrocolloids 1 (1986)2. - ISSN 0268-005X - p. 121 - 127.
    Investigations in the B5 Maillard system and determination of Maillard volatile compounds.
    Siliha, H.A.I. ; Voragen, A.G.J. ; Pilnik, W. ; Roozen, J.P. - \ 1986
    Unknown Publisher
    Het gebruik van een bacteriele mutageniteitstest als een snelle methode voor de detectie van vroege Maillard reactie producten in sinaasappelsap.
    Ekasari, I. ; Jongen, W.M.F. ; Pilnik, W. - \ 1986
    Voeding 47 (1986). - ISSN 0042-7926 - p. 233 - 233.
    Enzymic lysis of pectic substances in cell walls: Some implications for fruit juice technology.
    Voragen, A.G.J. ; Schols, H.A. ; Siliha, H.A.I. ; Pilnik, W. - \ 1986
    In: Recent advances in the chemistry and function of pectins, M.L. Fishman & J.J. Jen (eds.). ACS Symp. Series 310 - p. 230 - 247.
    Effects of additions, irradiation and heating on the activity of trimethylamine oxidase in frozen stored minced fillets of whiting.
    Ponte, D.J.B. Da; Roozen, J.P. ; Pilnik, W. - \ 1986
    Journal of food technology 21 (1986). - ISSN 1684-8462 - p. 33 - 43.
    Effect of irradiation on the stability of minced cod, with and without hydrocolloids during frozen storage.
    Ponte, D.J.B. Da; Roozen, J.P. ; Pilnik, W. - \ 1986
    Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 19 (1986)2. - ISSN 0023-6438 - p. 167 - 171.
    Effect of hydrocolloids and pretreatments on the keeping quality of minced fillets of whiting and cod during frozen storage
    Ponte, D.J.B. da - \ 1986
    Landbouwhogeschool Wageningen. Promotor(en): W. Pilnik, co-promotor(en): J.P. Roozen. - Wageningen : Da Ponte - 167
    dierlijke producten - kabeljauw - vis - visverwerkende industrie - visproducten - voedselbewaring - voedingsmiddelen - invriezen - gadidae - schelvis - houdbaarheid (kwaliteit) - conserven - koudeopwekking - animal products - cod - fish - fish industry - fish products - food preservation - foods - freezing - gadidae - haddock - keeping quality - preserves - refrigeration
    The present study examines the effects of additions of hydrocolloids and pretreatments (precooking and irradiation) on the stability of minced fillets of whiting and cod during frozen storage (-18°C).

    Some hydrocolloids (Xanthan gum, alginates, carboxymethyl celluloses and Iota and Lambda carrageenan) increase the water holding capacity and have a cryoprotective effect on the texture of the fish minces during frozen storage.

    Irradiation (300 krad, -20°C) can be applied to the fish minces for decreasing the number of viable microorganisms, without affecting the keeping quality of the fish minces in the post-irradiation frozen storage. Precooking the fish minces up to an internal temperature of 80°C or higher, for short periods of time (about 1 minute), prevents the production of dimethyIamine and formaldehyde in the fish minces during subsequent frozen storage. Both precooking and irradiation can be used in combination with additions of hydrocolloids in the fish minces with beneficial effects.

    Hydrocolloids can be used as additives in the manufacture of minced fish products, decreasing the weight loss on cooking, stabilizing the texture and in certain cases increasing significantly the acceptability of the fish products during frozen storage. Iota carrageenan and under certain conditions carboxymethyl cellulose decrease the fat uptake of battered and breaded minced fish products during frying.

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