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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    Schets van de voedingsmiddelenindustrie : verleden, heden, perspectief
    Leniger, H.A. - \ 1980
    Unknown Publisher
    Voorlichting in de sector voedings- en voedermiddelenindustrie
    Leniger, H.A. - \ 1980
    Stadsbrink 389, 6707 AC Wageningen : Stichting MPW
    Werving en Selectie van hoger technisch personeel
    Leniger, H.A. - \ 1980
    Stadsbrink 389, 6707 AC Wageningen : Stichting MPW
    Het voedingsmiddelenonderzoek in Nederland: organisatie, aard en omvang
    Leniger, H.A. - \ 1978
    Voedingsmiddelentechnologie 11 (1978)7. - ISSN 0042-7934 - p. 21 - 25.
    Het voedingsmiddelenonderzoek in Nederland : organisatie, aard en omvang
    Leniger, H.A. - \ 1977
    Wageningen : Landbouwhogeschool - 28
    voedsel - voedselsamenstelling - voedselindustrie - voedseltechnologie - voedingsmiddelen - nederland - voedingswaarde - eigenschappen - kwaliteit - onderzoek - food - food composition - food industry - food technology - foods - netherlands - nutritive value - properties - quality - research
    The State of the Art of Food Dehydration
    Leniger, H.A. ; Bruin, S. - \ 1977
    In: COST Industrial Food Technology Seminar. Section Thermal Processing. Dublin, 1977
    Quantification of Quality Attributes for Economic Optimisation
    Leniger, H.A. - \ 1977
    In: Proceedings Seventh European Symposium-Food: Product and Process Selection in the Food Industry. Food Working Party EFCE-IUFOST. Eindhoven, 1977 - p. 146 - 162.
    Concentration by Evaporation
    Leniger, H.A. - \ 1977
    In: Proc. Int. Symp. Phys., Chem. and Biol. Changes in food caused by Thermal Processing, Oslo, 1976, T. Hoyem, O. Kvale (eds), Applied Science Publ., 1977 - p. 54 - 76.
    Water activity in foods
    Berg, C. van den; Leniger, H.A. - \ 1976
    In: Int. Cong. Engng. Food, Aug. 1976
    Simulation of heat and mass transfer in spray drying
    Lijn, J. van der - \ 1976
    Landbouwhogeschool Wageningen. Promotor(en): H.A. Leniger, co-promotor(en): H.A.C. Thijssen. - Wageningen : Centre for Agricultural Publishing and Documentation - ISBN 9789022005958 - 87
    warmtebehandeling - warmtewisselaars - sproeidroging - computersimulatie - simulatie - simulatiemodellen - heat treatment - heat exchangers - spray drying - computer simulation - simulation - simulation models

    A survey is given of heat and mass transfer around droplets in spray dryers and the diffusional transport inside them. A calculational model is developed which includes variable diffusion coefficients in the drying liquid and swelling or shrinking of droplets. Calculations for droplets containing soluble solids show how the drying histories of droplets are influenced by three extreme patterns of air circulation and spray dispersion, and by droplet inflation. The influence of these factors on the properties of spray-dried liquid foods are discussed. Furthermore diffusion equations for binary systems are surveyed and diffusion coefficients for super-saturated aqueous maltose solutions are reported.

    Rede uitgesproken bij de rectoraatsoverdracht op 9 januari 1975
    Leniger, H.A. - \ 1975
    Wageningen : Landbouwhogeschool - 31
    hogere agrarische scholen - universiteiten - hoger onderwijs - onderwijsbeleid - nederland - veluwe - gelderland - organisatie - agricultural colleges - universities - higher education - educational policy - netherlands - veluwe - gelderland - organization
    Het studiejaar 1972 - 1973
    Leniger, H.A. - \ 1973
    Wageningen : Landbouwhogeschool - 39
    hogere agrarische scholen - universiteiten - nederland - veluwe - gelderland - agricultural colleges - universities - netherlands - veluwe - gelderland
    Activity coefficients and plate efficiencies in distillation of multicomponent aqueous solutions
    Bruin, S. - \ 1969
    Wageningen University. Promotor(en): H.A. Leniger; H.A.C. Thijssen. - Wageningen : Veenman - 185
    distillatie - evaporatie - voedseladditieven - technologie - thermische energie - thermodynamica - distillation - evaporation - food additives - technology - thermal energy - thermodynamics - cum laude

    The thermodynamics of vapour liquid equilibria and the calculation of distillation processes of volatile flavours are studied. Various methods of reducing experimental data of equilibria of binary systems to two meaningful parameters are discussed. These parameters are building blocks in a thermodynamic model of multicomponent solutions. Recently ORYE has developed a modified Wilson equation for the excess Gibbs free energy of mixing in a multicomponent solution. In the present study three equations are deduced, using a lattice model of a liquid solution, all of which are applicable to systems showing partial miscibility. One of these equations appeared to be identical to the modified Wilson equation as proposed by Orye. The Enthalpic Λ-equation turns out to be of high accuracy for a number of binary systems investigated.

    An apparatus, employing a gas chromatographic technique, was developed for measuring activity coefficients of volatile organic components in water. At infinite dilution of the volatiles the activity coefficients can be measured simultaneously in a multicomponent system. The apparatus was tested for a number of n-alcoholes and ketones and found to meet the required accuracy. Activity coefficients of some aldehydes and esters were measured with the apparatus.

    A multicomponent distillation calculational procedure (MCDTG-EFF computer programme) especially suited to aroma distillations was developed. This programme takes into account the efficiencies of the individual components. In the calculational scheme the following assumptions are made:
    1. The liquid on each plate is at bubble temperature;
    2. The number of gas phase- and liquid phase transfer units on a plate can be obtained from an empirical correlation;
    3. Complete mixing of the liquid phase occurs on each plate;
    4. The efficiencies are specified for all components in the reboiler;
    5. The Van Laar multicomponent equation relating activity coefficients to composition is applicable;
    6. The liquid phase does not separate into two liquid layers.

    Comparison of calculated results obtained with this programme with the results of a calculation based on ideal plates (MCDTG computer programme) shows large deviations.

    The validity of assumption 5 was checked by experimental determination of activity coefficients in multicomponent mixtures, showing resemblance to complex food flavours.

    A calculational scheme to determine multicomponent plate efficiencies from binary data, using a matrix formulation, is proposed. The theory degenerates consistently to the formulations one can deduce for as well binary systems as for dilute multicomponent solutions.

    Computer programmes (FORTRAN) are given together with a detailed description and block schemes.

    Leniger, H.A. - \ 1968
    Wageningen : Veenman - 17
    voedselindustrie - voedseltechnologie - food industry - food technology
    Rede Wageningen, 1968
    Continuous mixing of solids
    Raouf, M.S. - \ 1963
    Wageningen University. Promotor(en): H.A. Leniger; N.H. Kuiper. - Wageningen : Veenman - 73
    mengers - vermenging - transportvoertuigen - materialen - voorbehandeling - metaalbewerking - mixers - mixing - transporters - materials - pretreatment - metal working
    The most important literature on theoretical aspects of mixing solids was reviewed.

    Only when the mixed materials showed no segregation it was possible to analyse the mixing process quantitatively. In this case the mixture could be described by the 'χ' Square test. Longitudinal mixing could be studied by estimating the spread in residence times.

    In two common types of mixers the mixing was studied of two kinds of granular materials, differing only in colour of granules. (Colour had no influence on mixing.)

    In a continuously operating semi-technical 'Spaans' screw and ribbon mixer the mixing proceeded rapidly but irregularly. The minimal mixer length necessary for apparent completion of mixing decreased at higher speeds of rotation. The performance of a more widely pitched. screw and ribbon element was slightly better. The spread in residence times was appreciable. Longitudinal mixing was slightly more intensive at higher speeds of rotation, wider screw and ribbon pitches and greater mixer lengths.

    In a mixer consisting of a simple, rotating, slightly inclined, partially filled, hollow cylinder mixing proceeded more gradually. Mixing was 'diffusive'. The mixing rate increased with increased rotational speed, increased wall roughness and decreasing feed rate. Longitudinal mixing proved to be very limited.

    Onderzoekingen over de warmtedoorgang in een vertikale pijpverdamper
    Veldstra, J. - \ 1960
    Wageningen University. Promotor(en): H.A. Leniger. - Wageningen : [s.n.] - 84
    scheiding - warmtebehandeling - thermodynamica - toestandsverandering - kookpunt - dauwpunt - warmteoverdracht - warmte - transmissie - warmteuitwisseling - separation - heat treatment - thermodynamics - change of state - boiling point - dewpoint - heat transfer - heat - transmission - heat exchange
    The influences were investigated of various operating parameters on beat transmission, i.e. the evaporative capacity, in a single vertical evaporator tube, fed with pure water.

    With natural circulation, temperature level and difference had a pronounced influence, especially at lower values of these parameters (e.g. boiling temperature 40°C, temperature difference 15°C). The heat transmission coefficient k increased for increasing temperature level as well as for increasing temperature difference.

    The influence of the apparent liquid level was very important and was more pronounced for lower temperature levels and smaller differences. For each set of operating temperatures an apparent liquid level existed, for which k was maximum. The apparent liquid level had a very big influence on circulation rate. Forced circulation induced higher values of k only if the forced circulation rate was much higher than the natural one. Because natural circulation was slow for low temperatures and small differences forced circulation was found to be advantageous in these conditions.

    With forced circulation the influence of temperature difference on k was small and sometimes reversed. Due to decreased viscosity, k was higher at higher temperatures. The most important influence on k was exerted by forced circulation rate.

    With flash evaporation k was generally slightly smaller than with forced circulation, except at high circulation rates, where k became equal for both systems.

    De invloed van kneuzen van groenvoeder op het ensilageproces
    Leniger, H.A. ; Wieringa, G.W. - \ 1960
    Wageningen : Instituut voor Bewaring en Verwerking van Landbouwprodukten (Publikatie / Instituut voor Bewaring en Verwerking van Landbouwprodukten no. 33) - 24
    kuilvoer - kuilvoerbereiding - voedergrassen - silage - silage making - fodder grasses
    Technology of soymilk and some derivatives
    Tan Boe Han, - \ 1958
    Wageningen University. Promotor(en): H.A. Leniger. - Wageningen : [s.n.] - 132
    sojamelk - melkvervangers - imitatiemelk - imitatieroom - soya milk - milk substitutes - imitation milk - imitation cream
    The technological aspects of the manufacture of soya milk were studied, with special attention to pretreatment of beans (soaking and various methods of grinding), extraction (influence of extraction rate, pH, temperature, time and method of mixing) and the separation of the milk.

    Preservation of soya milk by pasteurization or sterilization was briefly studied.

    The concentration of soya milk by evaporation was difficult. The heat stability of the milk was influenced by the way of heating before evaporation. By choosing working conditions carefully a fairly high dry matter content could be achieved. A few experiments were made on the manufacture of soya curd and soya yoghurt. Both products had promising applications.

    Onderzoek over het ventileren van vohtige zaden met weinig of niet verwarmde lucht
    Leniger, H.A. ; Poel. A.J. van der, - \ 1954
    Wageningen : Centraal Instituut voor Landbouwkundig Onderzoek (Publikatie van het Droogtechnisch Laboratorium / Centraal Instituut voor Landbouwkundig Onderzoek no. 49) - 17
    Beschouwingen over het onderwijs in de technologie aan de Landbouwhogeschool
    Leniger, H.A. - \ 1951
    Wageningen : Veenman - 16
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