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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    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.

    Ervaringen en perspectieven van zaadcoating met pesticiden
    Ester, A. ; Huiting, H. ; Putter, H. de - \ 2005
    Gewasbescherming 36 (2005)4. - ISSN 0166-6495 - p. 159 - 164.
    pesticiden - zaden - zaadbehandeling - omhullen - gewasbescherming - insecticiden - gezondheidsbescherming - plantenziektebestrijding - milieubescherming - penen - preien - aardappelen - brassica oleracea var. gemmifera - slasoorten - vollegrondsgroenten - pesticides - seeds - seed treatment - pelleting - plant protection - insecticides - health protection - plant disease control - environmental protection - carrots - leeks - potatoes - brassica oleracea var. gemmifera - lettuces - field vegetables
    Zaadbehandeling is doorgaans een uitgelezen kans om gebruik van gewasbeschermingsmiddelen fors terug te dringen. Coating van het zaad met insecticiden kan in een aantal situaties een effectieve bestrijdingsmethode zijn. Doordat de volvelds-, kweekplaat-, plantvoetbehandeling en soms een gewasbehandeling bij de start van de teelt kan vervallen, kan zo een grote besparing op het gebruik van middel verkregen worden. Bij coating wordt zaad voorzien van een dun laagje lijmstof. Dit voorkomt verstuiving van insecticiden, maar het vookomt ook dat de mens met het (giftige) middel in aanraking komt. Bij zaadbehandeling met insecticiden is coating dan ook verplicht. De voordelen van zaadcoating op een rij
    Jasje moet zaad beschermen tegen kiemplantenziekte
    Derkx, M.P.M. ; Brouwer, J. - \ 2004
    De Boomkwekerij 17 (2004)51. - ISSN 0923-2443 - p. 14 - 15.
    zaden - plantmateriaal - zaadbehandeling - omhullen - voorbehandeling - bescherming - boomkwekerijen - chemische bestrijding - bestrijdingsmethoden - seeds - planting stock - seed treatment - pelleting - pretreatment - protection - forest nurseries - chemical control - control methods
    Kiemplantenziekte kan dramatische gevolgen hebben in zaadbedden. Het zaad direct bij uitzaai een goede bescherming meegeven, kan veel ellende besparen. PPO denkt dat een coating met daarin gewasbeschermingsmiddelen perspectief biedt voor de bos- en haagplantsoenteelt
    Biological nitrogen fixation of soybean in acid soils of Sumatra, Indonesia
    Waluyo, S.H. - \ 2000
    Agricultural University. Promotor(en): W.M. de Vos; L. 't Mannetje; L.T. An. - S.l. : S.n. - ISBN 9789058082954 - 151
    glycine max - sojabonen - bodembiologie - stikstoffixatie - stikstofbindende bacteriën - rhizobium - bradyrhizobium - inoculatie - entstof - biochemische technieken - dna-fingerprinting - stamverschillen - stammen (biologisch) - zaadbehandeling - omhullen - zure gronden - bodemaciditeit - bekalking - sumatra - indonesië - glycine max - soyabeans - soil biology - nitrogen fixation - nitrogen fixing bacteria - rhizobium - bradyrhizobium - inoculation - inoculum - biochemical techniques - dna fingerprinting - strain differences - strains - seed treatment - pelleting - acid soils - soil acidity - liming - sumatra - indonesia

    The aim of this study is to improve soybean cultivation in transmigration areas, especially in Sitiung, West Sumatra. However, these soils are very acid, and have a high P-fixing capacity. To reduce the amounts of fertilisers, normally 5 - 7 ton lime ha -1 and 100 kg P as TSP, seed, pelleted with lime (60 kg ha -1 ) and TSP (10 kg ha -1 ), was introduced. In this way only 2 ton lime ha -1 are required.

    Soybean can fix nitrogen (BNF) in symbiosis with ( Brady ) Rhizobium bacteria. However, these acid soils in general, have low numbers of ( Brady ) Rhizobium . By inoculating the soils with ( Brady ) Rhizobium , BNF of soybean, and yield, were considerably improved.

    A study was made of the indigenous ( Brady ) Rhizobium population in view of the following:

      Although at the beginning the numbers may be low, by repeated soybean cultivation, the numbers will increase, and they may interfere with inoculation of effective ( Brady ) Rhizobium strains.These indigenous ( Brady ) Rhizobium are adapted to local stress conditions, and they may be useful for the improvement of strains, to be used as inoculants.

    Using molecular techniques, indigenous strains derived from soil samples from old soybean areas (Java) and from new soybean areas (Sumatra) were classified in more detail. Most likely B. japonicum is the dominant strain in Java while in Sumatra B. elkanii is more present. A Sinorhizobium fredii -like strain was isolated from one soil sample from Java.

    Salmonella in mengvoeders
    Driessen-van Lankveld, W. ; v. Velzen, H. ; Broex, N. - \ 1981
    Wageningen : RIKILT (Verslag / RIKILT 82.02)
    mengvoer - omhullen - salmonella - dierziektepreventie - compound feeds - pelleting - salmonella - animal disease prevention
    In het kader van het veelomvattende salmonella-vraagstuk is het plan opgevat om alle mengvoeders te pelleteren. De monsters werden na pelleteren aangeboden en onderzocht op aanwezigheid van salmonella volgens de zogenaamde 'methode Cornelisse'. Doel hiervan is na te gaan of het pelleteerprocédé van mengvoeders voldoende effectief is om de aanwezigheid van salmonella in mengvoeders te reduceren.
    Herschikking van stortgoederen door tanden van grondbewerkingswerktuigen
    Kouwenhoven, J.K. - \ 1979
    Landbouwhogeschool Wageningen. Promotor(en): H. Kuipers. - Wageningen : Veenman - 17
    bewerking als stortgoed - verandering - componenten - cultivators - uitrusting - bewerking - eggen - omhullen - bolletjes - poeders - zaaibedbereiding - bodemstructuur - grondbewerking - gereedschappen - transport - machines - bulk handling - change - components - cultivators - equipment - handling - harrows - pelleting - pellets - powders - seedbed preparation - soil structure - tillage - tools - transport - machines
    4. 1. INTRODUCTION

    During tillage operations, soil aggregates and other bulk solids such as seeds, fertilizers, stones, tubers (left by the potato harvester) and roots, are often displaced from one layer to another by a sorting process causing the larger particles to be displaced into higher layers and smaller particles into lower layers. This process is influenced by particle properties and handling factors, and is counteracted by mixing.

    The influence of particle properties and handling factors on mixing and sorting was studied in the laboratory both qualitatively and quantitatively.

    4.2. METHODS

    Most of the experiments were done in a model soil bin filled with glass spheres and worked with normal and model tines. Localization of the processes and flow of the particles around the (model) tines were determined by filming and measuring the displacement of coloured markers, whereas mixing and sorting intensity and the sorting degree were determined by sieving or by counting the markers from different layers after working the bulk solid with normal harrow tines.

    Tines were used in three positions: Forward facing, straight and backward facing; travelling speeds were: 0.01, 0.10, 0.45 and 0.80 m/s. Four fractions of bulk solid were used, monosized and polysized. The influence of particle properties on angularity and fractional solids content were determined. Dilatancy and relief were measured by means of a micro-reliefmeter; positions were determined using a position indicator.

    4.3. RESULTS

    4.3.1. Rearrangement of soil aggregates by tines (I)

    With respect to seedbed and seedbed preparation, experiments were started using dry soil aggregates as the bulk solid, that was accompanied by interparticle percolation. Sorting was characterized by sorting degree and sorting intensity and mixing by mixing intensity. It became apparent that mixing mainly occurs behind the tine and is influenced by the type and inclination of the tine and by tine travelling speed. The direct connection between particle size and mixing intensity was probably caused in front of the tine. Wider and more backward facing tines increased mixing intensity. Sorting mainly occurred in front of the tine. The greater the amount of material moved and the greater the difference in size of the particles involved, the higher was the sorting intensity.

    The final effect of the rearrangement of bulk solids by tines as a result of sorting and mixing actions could only be understood if the various processes were studied separately.

    4.3.2. Rearrangement of glass spheres by tines (II; IV)

    Because of the necessity for high demands on uniformity of the bulk solid used, especially on the narrow limits of particle size (at mixing), dry soil aggregates were replaced by glass spheres. The sizes of glass spheres were chosen so that interparticle percolation did not occur, allowing the possibility of studying the flow of particles around the tine.

    The experiments revealed that mixing occurs by a strong downward displacement of a small number of spheres behind the tine and by a small sideways and upward displacement of a large number of spheres alongside of the tine. Mixing intensity increases with a decreasing travelling speed, more backward facing inclination of the tines and larger particle diameters.

    Both backward facing tine inclination and low travelling speeds had a similar effect on the mixing intensity. Differences in mixing intensity of monosized bulk solids mainly originated from differences in dispersion in front of the tine; dispersion was stronger with increasing particle size.

    Even without interparticle percolation, sorting mainly occurred in front of the tine, strongest with low travelling speeds and backward facing tines. Sorting intensity decreased with an increase in travelling speed and a more backward facing inclination of the tines.

    In the equilibrium state, the bulk solid was found to be sorted to a higher degree after working with a high travelling speed and forward facing tines. A high sorting degree was characterized by small vertical displacements at a pass of the tine, by a strong stratification and so by a relatively pronounced dilatancy.

    When interparticle percolation was absent, sorting intensity was determined by the smallest fraction. Forward facing tines were accompanied by a relatively high sorting intensity and a high sorting degree.

    4.3.3. Particle properties and handling factors (III; V)

    Particle properties like size, shape, surface roughness and apparent particle density and handling factors such as size ratios, moisture content and travelling speed, influenced bed properties and sorting results: relatively large, oblong, rough and light particles were displaced into higher layers and vice versa. The proces is accelerated, when the bulk solid is dry and worked at a low travelling speed.

    For glass spheres, the diameter was the predominating particle property determining the results of the experiments. With an increasing sphere diameter, bed properties such as fractional solids content and angularity increased. In order to obtain reproducible beds for mixing experiments, the depth of the inserted layers was related to the diameter of the spheres involved. Tapping increased fractional solids content by an average of about 6 per cent.

    Bed properties can only be determined significantly if determination methods are standardized. For standardized methodology large containers with sufficiently roughened bottoms and very smooth walls, low speeds and tapping to improve reproducibility, are advised. The 2-dimensional angle of repose, α d2 , is the one that can be determined easily and objectively. The angles of repose increased and so flowability decreased, with an increasing particle size, surface roughness and apparent particle density. The fractional solids content of a cultivated layer is inversely related to the size ratio of the particles (and to the sorting degree).

    4.3.4. Rearrangement of bulk solids in the field(V)

    Particle properties are more varied in the field than in the model experiments; handling factors such as moisture content and travelling speed are higher.

    Throwing and sorting by interparticle percolation normally occur in the field. Throwing offers the possibility of killing weed seedlings by covering them with soil and of incorporating granulated chemicals and broadcasted seeds superficially._

    Sorting in the field is of paramount importance: fine soil aggregates, seeds and granulated chemicals are placed into or near the seed placement zone, clods and stones are transported upward with respect to erosion control and rhizomes are brought to the surface as a measure of mechanical weed control. When draught animals are used, sorting is predominant; when tractors are applicated, throwing becomes more important as the travelling speed increases.

    Sorting intensity in the field is highest for forward facing and wide or widened tines and tine-like tools, when moisture content is low, with a great variation of flowability of the particles involved and with low ( < 1 m/s) travelling speeds.

    The effects of tined tillage tools in the field could largely be explained from model experiments using dry soil aggregates and glass spheres.

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