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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    Influence of pectin supplementation on feed fermentation characteristics in rats and pigs
    Tian, L. - \ 2016
    Wageningen University. Promotor(en): Harry Gruppen; Henk Schols. - Wageningen : Wageningen University - ISBN 9789462577282 - 142
    pigs - rats - pectins - feed supplements - dietary fibres - digestion - digestive tract - carbohydrates - microbial flora - nutrition physiology - animal nutrition - food chemistry - varkens - ratten - pectinen - voedersupplementen - voedingsvezels - spijsvertering - spijsverteringskanaal - koolhydraten - microbiële flora - voedingsfysiologie - diervoeding - voedselchemie

    The physiological effects of dietary fiber (DFs) depend on several factors including structural features of the DFs, composition and activity of colonic microbiota, and products formed during fermentation. In this thesis, the influence of pectin supplementation to feed fermentation characteristics in rats and pigs was studied. The non-starch polysaccharides (NSP) present in the selected feed ingredient oats were characterized. Distinct populations of arabinoxylans (AXs) were observed in oats, compared to those reported for other cereals like wheat and barley. The fate of cereal AXs and soybean pectin during fermentation and the consequent effects on appetite regulation and fat accumulation were studied in rats as a model. Oat AXs were fermented less rapidly than wheat AXs in the caecum of rats. Soy pectin was fermented more early and efficiently than cereal AXs. A significant inverse correlation between rat retroperitoneal fat-pad weight and concentration and relative SCFA proportion of butyrate was observed. In a following in vivo rat experiment, commercial soy pectin together with three other soluble pectins originating from citrus and sugar beet and differing in their methyl esterification were individually supplemented to the diets. Their effects on the utilization of the different DFs present in the feed and the consequent effect on the microbial community in the colon of rats was studied. All pectins were fermented rapidly and consequently shifted fermentation of other consumed DFs (e.g. cereal AXs) to more distal part of colon, although low-methyl esterified pectin was more efficiently fermented by the microbiota than high-methyl esterified pectin. Results suggested that pectins can confer beneficial health effects through modulation of the gut microbiota. In a last in vivo experiment, citrus pectins together with a hydrothermal treated soybean meal were supplemented to pig diets to study their effect on the digestion and fermentation of carbohydrates in both the small and large intestine. Pectins, and more particularly low-methyl esterified pectin, decreased the ileal digestibility of digestible starch resulting in more starch to be fermentated in the proximal colon of pigs. Consequently, also the fermentation patterns of DFs and the microbiota composition was affected. All pectins tested shaped the colonic microbiota from a Lactobacillus-dominated microbiota to a Prevotella-dominated community, with potential health-promoting effects.

    Alkaline pretreatments of lignin-rich by-products and their implications for enzymatic degradation
    Murciano-Martinez, P. - \ 2016
    Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Mirjam Kabel. - Wageningen : Wageningen University - ISBN 9789462576629 - 156
    degradation - enzymes - pretreatment - byproducts - lignin - food chemistry - delignification - sugarcane bagasse - degradatie - enzymen - voorbehandeling - bijproducten - lignine - voedselchemie - delignificatie - suikerrietbagasse

    The increasing interest in plant biomass based biofuels and chemicals arouses mainly from the increased awareness of a possible finiteness of fuels. The current main challenge to produce such biofuels and biochemicals is economic efficiency, but also knowledge concerning type and effectiveness of both thermally assisted chemical and enzymatic treatments, needed to generate fermentable sugars, is lacking. The subject of this thesis is to gain understanding of the effect of both sulphuric acid and NaOH catalysed pretreatments of sugar cane bagasse and oil palm empty fruit bunches on subsequent enzymatic saccharification, with a focus on the NaOH catalysed pretreatments. The fate of the main polymers present, lignin, cellulose and xylan, was studied and also single-activity xylan degrading enzymes, all from Rasamsonia emersonii, were studied for their mode-of-action.

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

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

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

    Maillard reaction products in pet foods
    Rooijen, C. van - \ 2015
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Guido Bosch; Peter Wierenga. - Wageningen : Wageningen University - ISBN 9789462575523 - 182
    gezelschapsdieren - huisdierenvoer - maillard-reactie - voedselverwerking - voedingswaarde - diergezondheid - lysine - stoom - omhullen - verteerbaarheid - voedselchemie - voedertechnologie - pets - pet foods - maillard reaction - food processing - nutritive value - animal health - lysine - steam - pelleting - digestibility - food chemistry - feed technology

    Pet dogs and cats around the world are commonly fed processed commercial foods throughout their lives. Often heat treatments are used during the processing of these foods to improve nutrient digestibility, shelf life, and food safety. Processing is known to induce the Maillard reaction, in which a reducing sugar binds to a free reactive amino group of an amino acid. In intact proteins, the ε-amino group of lysine is the most abundant free amino group. The reaction reduces the bioavailability of lysine and results in the formation of advanced Maillard reaction products. The aim of this thesis was to determine the occurrence and progression of the Maillard reaction during the manufacturing of pet foods, the subsequent impact on nutritive value of the food, and the bioavailability of Maillard reaction products in cats.

    In Chapter 2, the scientific literature was reviewed to investigate the current state of knowledge on the Maillard reaction and its potential effect on the nutritive value of pet foods and on pet health. Determination of the difference between total and reactive lysine by chemical methods provides an indication of the Maillard reaction in pet foods. Studies reported that the proportion of reactive lysine is on average 73% (range 39 – 100%) of total lysine, and that foods for growing dogs may be at risk of supplying less lysine than the animals require. The endogenous analogues of Maillard reaction products, advanced glycation end-products, have been associated with age-related diseases in humans, such as diabetes and impaired renal function. In dogs, data indicate higher advanced glycation end-product contents in plasma from dogs suffering from canine diabetes mellitus compared with healthy control animals. In addition, elevated levels of advanced glycation end-products in tissue proteins in dogs were observed for a number of diseases. To date it was unknown to what extent Maillard reaction products were present in pet foods, and whether dietary Maillard reaction products can be associated with the development of diseases such as diabetes and impaired renal function in pet animals. As the Maillard reaction is induced by processing, changing processing conditions should have an influence on the severity of the reaction. However, effects of processing conditions on the difference in total and reactive lysine contents in pet foods were inconsistent and did not always correspond to model systems. Processing temperature was reported to be the most important factor followed by moisture level. In addition, differences between total and reactive lysine were observed in several ingredients commonly used in pet foods. Reviewing the literature indicates that it is unknown to which extent the Maillard reaction occurs and whether Maillard reaction products are present in pet foods. There might be a risk for certain foods not meeting minimal lysine requirements. It is also unknown what the exact effect of processing on the Maillard reaction is in pet foods.

    The experiment described in Chapter 3 was designed to evaluate whether commercial pet foods meet minimal lysine requirements. Sixty-seven extruded, canned and pelleted commercially available dog and cat foods formulated for growth and maintenance were analysed using conventional amino acid analysis and O-methylisourea as reagent for reactive lysine. Sixty out of the 67 foods in this study, regardless of the type of processing technology used, contained a lower reactive lysine than total lysine content. On average, pelleted and extruded foods contain lower reactive to total lysine ratios compared to canned foods (0.85, 0.89, and 0.93, respectively). All cat foods and foods for adult dogs met minimal lysine requirements. However, eight dry foods for growing dogs contained reactive lysine contents between 96 and 138% of the minimal lysine requirement, indicating that reactive lysine has to be between 62 and 104% digestible to meet minimal requirement. Considering the variability in reactive lysine digestibility, these foods could be at risk of not meeting minimal lysine requirements for growing dogs.

    In Chapter 4, the foods from Chapter 3 were used to quantitate the Maillard reaction products fructoselysine (FL), carboxymethyllysine (CML), hydroxymethylfurfural (HMF), and the cross-linked amino acid lysinoalanine (LAL) using UPLC-MS. In all foods, Maillard reaction products and LAL were found but in highly variable amounts. Type of processing seems to be a key factor for the concentration of FL, CML and HMF, with on average higher amounts in canned foods than pelleted and extruded foods (on a dry matter basis). The contents of CML and HMF found in commercial pet foods are, on average, within the range reported in processed human food products. Average daily intake (mg/kg body weight0.75) of HMF was 122 times higher for dogs and 38 times higher for cats than the calculated average intake for adult humans. Average daily intake of CML was comparable to the intake of adult humans.

    As Chapters 3 and 4 indicated that pelleted foods contain more Maillard reaction products than extruded foods, despite the less severe production process, an experiment was designed to gain insight in the effect of steam pelleting on the Maillard reaction in a dog food (Chapter 5). The aim was to examine the effect of conditioning temperature (65 and 90°C) and die hole length (ø 5 × 45, 65, and 80 mm) during pelleting processing of a standard dry dog food on selected indicators of the Maillard reaction (total lysine, reactive lysine, FL, CML, HMF, LAL), browning development and CIE-Lab colour. Steam pelleting did not cause a significant loss of reactive lysine and change of absorbance values. This indicates that the effect of steam pelleting on the nutritive value of the foods is low. However, steam pelleting did increase the content of Maillard reaction products. The formation of the Maillard reaction products was associated with an increase in temperature and die hole length during the steam pelleting process. The unprocessed ingredient mix already contained a larger difference between reactive and total lysine, and contents of Maillard reaction products than was induced during steam pelleting. Therefore, the choice of the ingredients used in this study mainly determines reactive lysine content and Maillard reaction products in the pet food formulation.

    As it is unknown to which extent extrusion processing influences the Maillard reaction in pet foods, the effect of extrusion processing on selected indicators of the Maillard reaction was determined (Chapter 6). The extrusion parameters temperature (140 and 165°C), moisture content (200 and 300 g/kg) and screw speed (100 and 200 rpm) were applied to two dry dog foods formulated using either intact or hydrolysed proteins. Extrusion processing in general results in a decrease in total and reactive lysine and an increase in FL, CML, HMF and LAL content. However, this effect appeared more pronounced in the diet containing hydrolysed protein. Decreasing temperature and moisture content led to higher total and reactive lysine contents, and less Maillard reaction products in the dog foods. Increasing screw speed had a positive influence on total and reactive lysine, but a negative influence on Maillard reaction products. As was found in Chapter 5, the unprocessed ingredient mixtures in this experiment contained already more Maillard reaction products than was induced during extrusion processing.

    Whether the Maillard reaction products reported in pet foods are physiologically relevant in pet animals depends on the bioavailability of these components. Therefore, urinary excretion was studied in adult cats fed commercial moist and dry foods containing varying amounts of FL, CML and the amino acid LAL (Chapter 7). A pilot study was first conducted to determine the adaptation time required for stable urinary excretion of the Maillard reaction products when changing diets with contrasting contents of Maillard reaction products. An adaptation time of 1 d was deemed sufficient in adult cats. The short adaptation time indicates an effective urinary excretion of Maillard reaction products. In the main study, six commercially processed dry and six moist diets were fed to 12 adult female cats in two parallel randomized, 36-day, balanced Latin square designs. Urine was collected quantitatively and FL, CML and LAL were analysed in foods and collected urine using HPLC-MS. Daily urinary excretion of FL and CML showed a positive relationship with daily intake in the dry and moist foods. For LAL, no significant relationship was observed. The observed increase in urinary excretion with increasing dietary intake indicates that dietary Maillard reaction products are absorbed from the gastro-intestinal tract of cats and excreted in the urine. Minimum apparent absorption based on urinary excretion (assuming 100% of the excreted component originates from the diet) of FL, CML and LAL was found to range between 8 to 23%, 25 to 73% and 6 to 19%, respectively. Urinary recovery (% ingested) showed a negative relationship with daily intake for FL, CML and LAL in the dry foods and for CML and LAL in the moist foods. The observed decrease in urinary recovery with increasing intake suggests a limiting factor in digestion, absorption, metabolism or urinary excretion.

    The studies reported in this thesis are one of the first to determine Maillard reaction products in pet foods and the bioavailability of FL, CML and LAL in cats. In addition, the results highlight the importance of reactive lysine measurement in foods for growing dogs used as weaning diets. Contribution of the absorption of dietary Maillard reaction products to the pathogenesis of various health conditions requires further study, as well as the potential role of restriction of dietary Maillard reaction products in prevention and treatment of long-term health implications. Extrusion and pelleting processing do increase the Maillard reaction, however, choice of ingredients appears to have a larger effect on the content of Maillard reaction products and can, therefore, be a useful strategy for pet food manufacturers that want to decrease the content of Maillard reaction products in their pet foods.

    Design of an electronic performance support system for food chemistry laboratory classes
    Kolk, J. van der - \ 2013
    Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Gerrit Beldman; Rob Hartog. - S.l. : s.n. - ISBN 9789461735058 - 130
    voedselchemie - onderwijsondersteuning - ondersteuningssystemen - laboratoria - laboratoriumproeven - computerondersteund onderwijs - food chemistry - education support - support systems - laboratories - laboratory tests - computer assisted instruction

    The design oriented research described in this thesis aims at designing an realizing an electronic performance support system for food chemistry laboratory classes (labEPSS). Four design goals related to food chemistry laboratory classes were identified. Firstly, labEPSS should avoid extraneous cognitive load caused by the instructional format of the laboratory classes. Secondly, labEPSS should let students prepare for their laboratory experiments. Thirdly, labEPSS should support the communication in the laboratory class between students and between students and supervisors. Fourthly, labEPSS should give students the freedom to plan their experiments, without supervisors losing control and without risking overbooking of equipment. To address these goals, a couple of tools were designed, realized and subsequently used and evaluated in two model food chemistry laboratory classes:

    A web-based laboratory manual, aiming to provide students with just-in-time procedural information (e.g. how an apparatus looks like, where chemicals can be found). A web-based experiment design tool, aiming to let students design their research strategy as a workflow beforehand and support students while carrying out this strategy in the laboratory. A ‘web-app’ for students’ smartphones providing the same functionalities as the digital laboratory manual. A web-based equipment booking system, which is part of the web-based experiment design tool.

    Based on the evaluations it can be concluded that students and supervisors appreciated the tools and that these tools are capable of reaching the design goals. Finally, an overall design of labEPSS is proposed, in which the tools offer an integrated experience. Because labEPSS is highly configurable, it can be used in many different laboratory classes throughout curricula.

    Microorganisms in Foods 8: Use of Data for Assessing Process Control and Product Acceptance
    Swanson, K.M.J. ; Buchanan, R.L. ; Cole, M.B. ; Cordier, J.L. ; Flowers, R.S. ; Gorris, L.G.M. ; Taniwaki, M.H. ; Tompkin, R.B. ; Zwietering, M.H. - \ 2011
    New York : Springer Science + Business Media - ISBN 9781441993731 - 400
    chemie - voedselchemie - voedselwetenschappen - chemistry - food chemistry - food sciences
    Contains wealth of information on food microbiology and food safety Provides guidance on the appropriate testing of food processing environments Presents ways to improve the microbiological safety of food Continuing the ICMSF series, Microorganisms in Foods 8 provides practical guidance on appropriate testing of food processing environments, processing lines, shelf life and finished product to enhance the safety and microbiological quality of the food supply. Part I, Principles of Using Data in Microbial Control, summarizes the principles of Microorganisms in Foods 7: Microbiological Testing in Food Safety Management (2002), which illustrates how HACCP and Good Hygienic Practices (GHP) provide greater assurance of safety than microbiological testing, and also identifies circumstances where microbiological testing may play a useful role. Part II, Applications of Principles to Product Categories, updates and expands Part II of Microorganisms in Foods 2: Sampling for Microbiological Analysis: Principles and Specific Applications (1986) and builds on Microorganisms in Foods 6: Microbial Ecology of Food Commodities (2nd edition, 2005) with recommended tests and specific criteria for 19 food product categories to evaluate the effectiveness of controls. Microorganisms in Foods 8 is intended for anyone using microbiological testing or engaged in setting microbiological criteria including government, food processors and the customers they supply. This book provides actionable information for food quality assurance professionals, food microbiologists, food technologist, veterinarians, public health workers and regulatory officials. This peer reviewed book was prepared by the International Commission on Microbiological Specifications for Foods (ICMSF), with assistance from a limited number of consultants. The ICMSF was formed in response to the need for internationally acceptable and authoritative guidance on microbiological limits for foods in international commerce. Currently the membership consists of 17 food microbiologists and public health professionals from eleven countries, drawn from government, universities, and food processing and related industries.
    Maillard-reactie door model beheersbaar
    Roost, M. van - \ 2006
    Elsevier Voedingsmiddelen Industrie 2006 (2006)1. - ISSN 1570-6907 - p. 22 - 23.
    voedselchemie - voedseltechnologie - maillard-reactie - bruinkleuring - simulatiemodellen - pigmenten - ph - zuurgraad - suikers - eiwitten - kwaliteit - smaak - productieprocessen - food chemistry - food technology - maillard reaction - browning - simulation models - pigments - ph - acidity - sugars - proteins - quality - taste - production processes
    Gewenste en ongewenste bruinkleuring van levensmiddelen door een Maillard-reactie is vaak lastig te beheersen. Wageningse onderzoekers ontwikkelden een simulatiemodel, waarmee producentenmeer inzicht krijgen in de Maillard-reactie, en zo ook de kleur van het eindproduct beter kunnen beheersen tijdens het productieproces en de opslag. Met schematische weergave van de Maillard-reactie
    Design and evaluation of digital activating learning materials for Food Chemistry education.
    Diederen, J. - \ 2005
    Wageningen University. Promotor(en): Harry Gruppen; Fons Voragen, co-promotor(en): Rob Hartog. - Wageningen : - ISBN 9789085042716 - 160
    voedselchemie - onderwijs - lesmaterialen - ontwerp - computerondersteund onderwijs - food chemistry - education - teaching materials - design - computer assisted instruction
    Food chemistry is amongst others about the components and chemical reactions that are part of food products, about the effect of chemical reactions on the quality and about the techniques used to research food products. To support students in acquiring the knowledge and skills of food chemistry, in this design research it is investigated whether, but especially also how, digital learning materials can be developed. The biggest advantage of digital material opposed to non-digital material is that students can be activated easily. The computer can respond directly to an answer of the student for a question (feedback). The computer can also give a hint how to solve the question. Different kinds of learning materials were designed: 1. material with which students independently can solve a quantitative problem 2. material with which students can acquire knowledge in an active and efficient manner, and 3. material with which students learn how to design experiments. From evaluations with students a positive appreciation of these materials was noticed. Furthermore, it can be concluded from this research that giving feedback, just-in-time information and visual information is of importance for the success of digital learning materials.
    Physical chemistry of foods
    Walstra, P. - \ 2003
    New York [etc.] : Marcel Dekker (Food science and technology 121) - ISBN 9780824793555 - 807
    fysische chemie - fysische eigenschappen - voedsel - fysica - voedselchemie - voedselwetenschappen - studieboeken - physical chemistry - physical properties - food - physics - food chemistry - food sciences - textbooks
    Exploring the structure and physical and chemical properties of solutions, dispersions, soft solids, fats, and cellular systems, this text describes the physicochemical principles essential to the comprehension and prediction of reactions and conversions that occur during the manufacture, handling, and storage of foods. The book contains practical examples of starch gelatinization and retrogradation, protein denaturation, lipid crystallization, foam and emulsion formation, colloidal interactions, glass transitions, and food freezing and structure, etc.
    Structural characteristics of polysaccharides from olive fruit cell walls in relation to ripening and processing
    Vierhuis, E. - \ 2002
    Wageningen University. Promotor(en): A.G.J. Voragen; H.A. Schols. - S.l. : S.n. - ISBN 9789058085948 - 135
    voedselchemie - olijven - celwandstoffen - polysacchariden - rijp worden - voedselverwerking - food chemistry - olives - cell wall components - polysaccharides - ripening - food processing

    Key words: Olive fruit; olive oil; pectic polysaccharides; xyloglucans; xylans;

    enzyme preparations; phenolic compounds; processing; ripening

    Technical enzyme preparations can be used as processing aids in the olive oil industry to obtain a higher yield and a better quality of the oil. These technical enzyme preparations degrade the plant cell wall, thus enhancing the permeability for oil. However, still very little is known about the specific role of the various constituent enzymes present in the preparations towards the polysaccharides in the plant cell wall. This study deals with this subject and describes the structural characteristics of the polysaccharides in the cell wall of olive fruit in relation to processing for oil extraction.

    The major polysaccharides in the cell wall of olive fruit were found to be the pectic polysaccharides and the hemicellulosic polysaccharides xyloglucan and xylan. The pectic polysaccharides were highly methyl esterified and rich in arabinose. The xyloglucans had a backbone with three out of four glucose residues substituted with xylose residues and had a very specific substitution pattern, because galactose as well as arabinose residues could be linked to the xylose residues. The presence of arabinose residues linked to xylose residues is a common feature of xyloglucans produced by solanaceous plants, but has not been demonstrated for other dicotylodonous plants. Incubation of the cell wall material from olive fruit with pectin degrading enzymes in combination with endo-glucanases revealed that O -acetyl groups were not only linked to pectic material in olive fruit but also to xyloglucan. It was established that the arabinose residues of the xyloglucan could carry one or two O -acetyl groups. The cell wall material of olive fruit contained besides xyloglucan also considerable amounts of the hemicellulose xylan. These xylans appeared to be very low in substitution. Less than 10% of the xylose residues were mono substituted, mainly with 4- O -methyl-glucuronic acid residues.

    The use of technical enzyme preparations during processing affected only a relatively small part of the polysaccharides in the cell wall. About 8-10% of the cell wall polysaccharides were extracted with cold and hot buffer and appeared to be modified during enzymatic processing. The changes of the buffer soluble pectic material were reflected by an increase in yield, a change in molecular weight distribution, a decrease in methyl esterification and a degradation of the (1®4)-linked galactan chains. No differences were observed in the composition of the arabinan chains during enzymatic processing. Analysis of the olive oil revealed that the use of enzyme preparations increased the concentration of phenolic compounds in the oil. Especially, the contents of secoiridoid derivatives such as the dialdehydic form of elenolic acid linked to 3,4-dihydroxyphenylethanol and an isomer of oleuropein aglycon increased significantly. These two phenolic compounds have high antioxidant activities.

    The effect of enzyme treatment during the mechanical extraction of olive oil depends on the stage of maturity of the olive fruit. From this perspective the structural characteristics of the cell wall polysaccharides during ripening have also been investigated. During ripening the degree of methyl esterification and acetylation decreased and the solubility of the pectic polymers in buffer markedly increased. No distinct differences could be noticed with regard to the sugar composition and the profile of the molecular weight distribution of the pectic and hemicellulosic polymers during fruit development.

    Hapklare fysica?
    Linden, E. van der - \ 1999
    Wageningen : Wageningen Universiteit - 22
    fysica - fysische chemie - voedsel - voedselwetenschappen - voedselchemie - physics - physical chemistry - food - food sciences - food chemistry
    Chemisch, microscopisch en microbiologisch onderzoek van schepklare salades
    Cazemier, G. ; Herstel, H. - \ 1992
    Wageningen : DLO-Rijks-Kwaliteitsinstituut voor Land- en Tuinbouwprodukten (Rapport / RIKILT-DLO 92.17) - 15
    salades - voedingswaarde - voedselsamenstelling - voedselkwaliteit - kwaliteitscontroles - voedselmicrobiologie - voedselchemie - salads - nutritive value - food composition - food quality - quality controls - food microbiology - food chemistry
    In december 1990 werden 25 monsters schepklare salades, die werden ingekocht bij slagers, poeliers en supermarkten, chemisch, microscopisch en microbiologisch onderzocht. Het onderzoek werd uitgevoerd in zeven monsters vleessalade, zeven monsters kipsalade, zeven monsters tonijnsalade, drie monsters garnalensalade en één monster selderijsalade.
    Microbiologisch, chemisch en microscopisch onderzoek van gekoelde kant- en klaar maaltijden
    Cazemier, G. ; Herstel, H. - \ 1991
    Wageningen : DLO-Rijks-Kwaliteitsinstituut voor Land- en Tuinbouwprodukten (Rapport / RIKILT-DLO 91.26) - 16
    maaltijden - voedingswaarde - voedselmicrobiologie - voedselsamenstelling - voedselchemie - voedselkwaliteit - kwaliteitscontroles - borden - keukengerei - meals - nutritive value - food microbiology - food composition - food chemistry - food quality - quality controls - dishes - cooking utensils
    Chemisch onderzoek van slagroomgebak en tompoezen
    Kamp, H.J. van der; Herstel, H. - \ 1991
    Wageningen : DLO-Rijks-Kwaliteitsinstituut voor Land- en Tuinbouwprodukten (Rapport / RIKILT-DLO 91.46) - 8
    zoetwaren - biscuits - geslagen room - cakes - voedselsamenstelling - voedselchemie - chemische samenstelling - confectionery - biscuits - whipped cream - cakes - food composition - food chemistry - chemical composition
    Op verzoek van Konsumenten Kontakt zijn in januari 1991 20 monsters tompoezen en 20 monsters slagroomgebak onderzocht. Het slagroomgebak bestond uit 13 monsters gebakjes en 7 monsters schnitten (rechthoekige slagroomtaart).
    Literatuurstudie naar het voorkomen van flavonolen in voedingsmiddelen en de mogelijkheden tot isoleren van flavonolen uit voedingsmiddelen
    Venema, D.P. ; Hollman, P.C.H. - \ 1991
    Wageningen : RIKILT (Rapport / RIKILT 91.05) - 21
    flavonolen - voedselchemie - literatuuroverzichten - flavonols - food chemistry - literature reviews
    Dit rapport bevat een literatuuronderzoek naar het voorkomen van flavonalen in voedingsmiddelen en naar de extractie- en hydrolysemogelijkheden.
    Intercomparison of methods for the determination of vitamins in foods : first interlaboratory trial
    Hollman, P.C.H. ; Slangen, J.H. ; Struijs - van de Putte, H.M. van der; Essers, M.L. - \ 1991
    Wageningen : State Institute for Quality Control of Agricultural Products (Report / State Institute for Quality Control of Agricultural Products 91.11) - 106
    vitaminen - voedselchemie - kwaliteitscontroles - analytische scheikunde - vitamins - food chemistry - quality controls - analytical chemistry
    In order to assess the state of the art of vitamin analysis in foods, an intercomparison of methods was set up. Eighteen laboratmies in Europe specialised in vitamin analysis participated in this trial. Each Iabaratory received samples of dry foods in the farm of homogeneaus powders, milk powder, freeze-dried park muscle and haricots verts beans. The food samples presently to be certified for major nutrients, had proved to be homogeneaus with respect to these compounds.
    Verslag van werkbezoek aan het Central Food Research Institute in Boedapest van 16-26 november 1986
    Frankuizen, R. ; Herstel, H. - \ 1987
    Wageningen : RIKILT (Rapport / RIKILT 87.73) - 16
    voedselindustrie - voedselonderzoek - voedseltechnologie - voedselchemie - levensmiddelenfysica - onderzoeksinstituten - food industry - food research - food technology - food chemistry - food physics - research institutes
    In het kader van de samenwerkingsovereenkomst tussen de Hongaarse en Nederlandse Ministeries van Landbouw werd van 16 - 26 november 1986 een werkbezoek gebracht aan het Central Food Research Institute (Keki) in Boedapest. Doel van het bezoek was het uitwisselen van informatie en het uitvoeren van experimenten op het terrein van Nabij Infrarood Reflectie en Transmissie Spectroscopie (Food Physics Division). Onderzoek werd o.a. verricht naar de mogelijkheden van de bepaling van voosheid bij radijs , meligheid bij verduurzaamde doperwten en soortelijk gewicht, alcohol- en suikergehalte van likeur. Bezoeken werden afgelegd aan de afdelingen Food Chemical Division, Food Biology Division en Food Enzymology Division. Op 25 november werd een bezoek gebracht aan Labor HIM o.a . leverancier van de Hongaarse Infrapid (NIRS-instrument) en Contiflo Automatic Analyzers. Door een storing in het meest geavanceerde NIR-systeem van het Keki Instituut, de Neotec-6450 en het hoge bezettingspercentage van de overige NIRS-apparatuur konden een aantal werkzaamheden niet of niet geheel worden uitgevoerd. Ook het ontbreken van moderne computers en software voor data acquisitie, een gevolg van de Amerikaanse boycot op de export van high tech apparatuur, lag hieraan ten grondslag. Het één en ander werd echter voor een groot deel gecompenseerd door de veelheid aan informatie, die met name dr. K. Kaffka, dr I. Conczy en zijn medewerkers verstrekten op het gebied van niet-destructieve analyse aan fruit en groente. Opvallend was de samenwerking met andere afdelingen waar het gaat om positieve kwaliteitskenmerken. Veelvuldig wordt niet alleen gekeken naar chemische parameters maar ook naar fysische en sensorische. Bij laatstgenoemde techniek lijken aroma's een steeds belangrijker rol te gaan spelen. Het bezoek aan het bedrijf Labor MIM o.a. leverancier van de Hongaarse Infrapid analyzer en Contiflo Automatic Analyzers verliep enigszins stroef. Naast genoemde apparatuur produceert het bedrijf apparatuur voor de Hongaarse defensie, hetgeen waarschijnlijk de reden is waarom ik maar een beperkte rondleiding kreeg. Voor de West Europese consument is deze apparatuur echter weinig interessant in verband met het gebruik van sterk verouderde computertechnieken. Zowel de bezoeken aan de verschillende afdelingen, de uitwisseling van informatie als de uitgevoerde experimenten hebben veel kennis opgeleverd omtrent het gebruik van Nabij Infrarood Spectroscopie in het algemeen en voor het onderzoek van fruit en groente in het bijzonder.
    Onderzoek naar samenstelling en kwaliteit van loempia's
    Jong, W.J.H.J. de; Herstel, H. - \ 1986
    Wageningen : RIKILT (Rapport / RIKILT 86.19)
    snacks - voedselsamenstelling - voedselkwaliteit - voedselchemie - voedselmicrobiologie - sensorische wetenschappen - snacks - food composition - food quality - food chemistry - food microbiology - sensory sciences
    Het verkrijgen van een indruk van de samenstelling en de kwaliteit van een aantal verschillende loempia's door chemisch, microscopisch, microbiologisch en sensorisch onderzoek. In mei 1985 werden van de Consumentenbond 33 monsters loempia voor onderzoek ontvangen. Het betrof 19 monsters diepvriesloempia's (merkartikelen) en 14 monsters ongebakken loempia's afkomstig uit chinese restaurants. Het chemisch onderzoek betrof de bepaling van het gehalte aan vocht, ruw eiwit, natrium en glutaminezuur. Voor wat betreft het onderzoek naar eventuele vetopname bij het frituren werden de 19 diepvriesmonsters gefrituurd en werden in het gebakken produkt eveneens ruw vet en vocht bepaald. Microscopisch werd onderzoek verricht naar de verhouding korst/vulling, de gebruikte grondstoffen en/of ingrediënten, met name naar de identiteit van de vleesfraktie en eventuele verontreinigingen. Het microbiologisch onderzoek betrof een bepaling van het kiemgetal van Staphylocoscus aureus, Salmonella en gist- en bacteriekiemgetal. Sensorisch werden de 19 diepvriesprodukten beoordeeld. Daartoe werden de loempia's gebakken en werden korst en vulling apart beoordeeld op diverse sensorische aspekten. De Consumentenbond publiceerde een gedeelte van de resultaten in de Consumentengids van januari 1986.
    Microscopisch onderzoek op samenstelling van een aantal vleessalades
    Jong, W.J.H.J. de; Herstel, H. - \ 1982
    Wageningen : RIKILT (Verslag / RIKILT 82.28) - 19
    vlees - salades - microscopie - voedselchemie - meat - salads - microscopy - food chemistry
    Door middel van microscopisch onderzoek nagaan welke verschillen in samenstelling er bestaan tussen een aantal verschillende monsters vleessalade. 24 monsters vleessalade werden onderzocht op samenstellende bestanddelen. Microscopisch werd de identiteit en/of de samenstelling van deze bestanddelen bepaald.
    Literatuuronderzoek omtrent polycyclische aromaten
    Haasnoot, W. ; Tuinstra, L.G.M.Th. - \ 1981
    Wageningen : RIKILT (Verslag / RIKILT 81.70) - 13
    polycyclische aromatische koolwaterstoffen - verbranding - micro-organismen - microbiële besmetting - vloeistofchromatografie met omgekeerde fase - voedselchemie - polycyclic aromatic hydrocarbons - combustion - microorganisms - microbial contamination - reverse phase liquid chromatography - food chemistry
    Dit verslag heeft tot doel een literatuuroverzicht te geven omtrent het voorkomen van polycyclische aromaten en methoden voor het aantonen en bepalen van deze in relevante produkten. Polycyclische aromaten (PCA) zijn algemeen verspreid in het milieu en kunnen carcinogeen, syncarcinogeen of cocarcinogeen zijn. Zij ontstaan door de onvolledige verbranding van organisch materiaal en kunnen door bepaalde microorganismen worden gesynthetiseerd. Voedingsmiddelen kunnen door luchtstof of door "roken" met PCA verontreinigd worden. De door luchtstof verontreinigde grootbladerige groentesoorten, zoals groenekool bevatten in het algemeen grotere hoeveelheden aan PCA dan b.v . gerookte vis. In vergelijking met lucht en water bevat slib, uit zuiveringsinstallaties, enorm grote hoeveelheden aan PCA (mg/kg niveau). In Duitsland geldt voor gerookte vleesprodukten een tolerantie van 1 ug Benzo(a)pyreen per kg vlees en uit onderzoek is gebleken dat deze grens vele malen werd overschreden. Reversed phase vloeistofchromatografie met fluorescentie- en U.V. detectie is de meest geschikte combinatie voor het bepalen van PCA. Voor de bevestiging kunnen dunnelaagchromatografie of capillaire gaschromatografie met een FID of een massaspectrometer gebruikt worden.
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