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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    New tools in modulating Maillard reaction from model systems to food
    Troise, A.D. - \ 2015
    Wageningen University. Promotor(en): Vincenzo Fogliano, co-promotor(en): Claire Berton-Carabin; P. Vitaglione. - Wageningen : Wageningen University - ISBN 9789462575455 - 129
    maillard-reactie - maillard-reactieproducten - modulatie - controle - inkapselen - olijfolie - melk - emulsies - modellen - voedsel - gereedschappen - maillard reaction - maillard reaction products - modulation - control - encapsulation - olive oil - milk - emulsions - models - food - tools
    New tools in modulating Maillard reaction from model systems to food

    The Maillard reaction (MR) supervises the final quality of foods and occupies a prominent place in food science. The first stable compounds, the Amadori rearrangement products (APs) and Heyns rearrangement products (HPs), represent the key molecules from which a myriad of reactions takes place and each of them contributes to the formation of Maillard reaction end-products (MRPs) or advanced glycation end products (AGEs).

    Several papers have dealt with the control of the MR in foods ranging from the thermal loading reduction, to the use of alternative process technologies, reactants impact or enzymes, as well as to the monitoring of the end-products formation by multiresponse modeling. The strategies used up to now aim at common goals: the reduction of potentially toxic compounds and the promotion of desired molecules formation as well as flavor, aroma, color and texture attributes. In other words the ultimate target is the promotion of food quality by tuning the MR.

    This thesis introduces four alternative strategies that are able to control the final extent of the MR in foods.

    The possibility to segregate reactants by encapsulating some minor components and thus delaying the MR was highlighted in Chapter 2. The encapsulation of sodium chloride, ascorbic acid, PUFA and iron inside hydrophobic capsules was used as a possible example: the core material release over the time delayed the reaction rates.

    The results obtained through the treatment with the enzyme fructosamine oxidase (Faox) I and II which is able to deglycate free Amadori products and capitalize the local unfolding of lysine peptide bound residues were reported in Chapter 3. Data showed that Faox can reduce the formation ofNε-(Carboxymethyl)-L-lysine and bound hydroxymethylfurfural in model system and in low lactose milk.

    The effects obtained with the addition of spray-dried olive oil mill wastewaters in milk was illustrated in Chapter 4. This ingredient acts as a source of phenylethanoids, which can trap a-hydroxycarbonyls and a-dicarbonyls and can form adducts with amino groups after the oxidation of phenolic rings into quinone. The use of this functional ingredient before milk thermal treatment resulted in a reduction of off-flavor, reactive carbonyls species and bound MRPs.

    The possibilities offered by the location of MR reactants in microemulsion was investigated in Chapter 5. The oil/water partition coefficient of amino acids played a key role in the formation of Amadori compounds. The anchoring effect of tricaprylin and Tween 20 toward aliphatic amino acids in microemulsion systems was evaluated and compared to a control aqueous solution of amino acids and glucose. Results confirmed the hypothesis: the higher the partition coefficient the lower the formation of aliphatic amino acids Amadori compounds.

    All of the four proposed strategies involved location and interaction of reagents, reactants, intermediates and final products. As a result each strategy depicted a specific route for the control of the final extent of the MR. Many steps are still necessary to scale up these methodologies into the food production chain, however new ways for obtaining foods of superior quality have been paved.

    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.

    Modelling the formation of heat-induced contaminants during thermal processing of food
    Nguyen, H.T. - \ 2015
    Wageningen University. Promotor(en): Tiny van Boekel, co-promotor(en): Ine van der Fels. - Wageningen : Wageningen University - ISBN 9789462574588 - 172
    voedsel - maillard-reactie - voedselbereiding - acrylamiden - voedselbesmetting - gezondheidsgevaren - modellen - food - maillard reaction - food preparation - acrylamides - food contamination - health hazards - models

    Many of our food products have undergone a heat-treatment before consumption, either at home or at the food industry. Heat treatments not only bring out desired characteristics of the food products such as flavour, texture, taste and safety aspects but also leads to the formation of undesired compounds that may have negative impacts for human health. Such undesired compounds that are generated from the Maillard reaction are neo-formed food contaminants (NFC). NFC are present in many common heat-processed foods, such as potatoes-based products, cereal-based products, baby foods, and dairy products. Therefore, effective mitigation measures are being developed to minimize the generation of such undesired compounds while maintaining the organoleptic attributes of the food products as consumer’s demands. This thesis aimed at understanding the mechanistic pathways for the formation of three neo-formed food contaminants: acrylamide, 5-hydroxymethylfurfural (HMF), and -(carboxymethyl)lysine (CML), using multireponse kinetic modelling.

    First, the topic of the Maillard reaction, occurrence and human exposure to the three NFC in heated foods, and multiresponse kinetic modelling is introduced. Then, scientific literature on analytical methods, formation pathways, occurrence in processed foods, and health impacts of CML was reviewed. Based on the literature, an experiment was set up to understand the formation pathway for CML in caseinate-lactose/glucose solutions, each heated at 120oC and 130oC. According to the best fitting mechanistic model, the formation of CML in the two model solutions originated from the reaction between lactose/glucose and lysine residues via the Amadori rearrangement product formation. Moreover, glucose and lactose were degraded via Lobry de Bruyn-Alberda van Ekenstein (LA) arrangement. CML seems to be not thermally stable, and may thus not be an optimal indicator for heat damage of foods.

    Another experiment was done for gaining insights into the formation of acrylamide and HMF in biscuits during baking at 200oC. Four biscuit recipes were prepared with three sugar types: (1) sucrose (35 g), (2) glucose (17.5 g) and fructose (17.5 g), (3) fructose (17.5 g), and (4) glucose. The molar ratio of total glucose and fructose to asparagine in each type of biscuit was higher than 1. The concentrations of acrylamide and HMF were lowest in the sucrose-prepared biscuits. Kinetic modelling results suggested that during baking of these four kinds of biscuits, acrylamide was formed via the specific amino acid route, i.e., a reducing sugar reacts with asparagine to form the Schiff base without the Amadori product formation (not via Strecker degradation), and that HMF was formed via caramelisation. Fructose played a key role in the formation of both acrylamide and HMF.

    In a similar experiment, the effects of different types of wheat flour on acrylamide and HMF formation in sucrose-prepared biscuits during baking at 200oC were investigated. Four types of wheat flour, which had the most different concentrations of asparagine, and total glucose and fructose (the reducing sugar), were selected for the preparation of four kinds of biscuits. Out of four wheat flour types, two had the molar ratio of reducing sugars to asparagine lower than 1, and the other two had a ratio higher than 1. Results showed that those different molar ratios in wheat flour did not have effects on the pathways leading to the formation of acrylamide and HMF in all four types of biscuits. Acrylamide was formed via the specific amino acid route, and HMF was formed via caramelisation. No clear correlation was found between the concentration of either acrylamide or HMF in biscuits and the concentration of asparagine or the reducing sugars in wheat flour. Asparagine was not a limiting factor for acrylamide generation in biscuits.

    The outcomes of this thesis give insights into the actual reaction pathways for the formation of acrylamide and HMF in biscuits during baking at 200oC and for the formation of CML in the model solutions. These modelling results may help to control the formation of these NFCs in a quantitative way.

    Changes in protein conformation and surface hydrophobicity upon peroxidase-catalyzed cross-linking of apo-a-lactalbumin
    Saricay, Y. ; Wierenga, P.A. ; Vries, R.J. de - \ 2014
    Journal of Agricultural and Food Chemistry 62 (2014)38. - ISSN 0021-8561 - p. 9345 - 9352.
    secondary structure analyses - high hydrostatic-pressure - microbial transglutaminase - horseradish-peroxidase - circular-dichroism - whey proteins - beta-lactoglobulin - maillard reaction - oxygen radicals - dairy-products
    In this study, we explore the effect of peroxidase-catalyzed cross-linking on the molecular conformation of apo-a-lactalbumin (apo-a-LA) and the resulting changes in protein surface hydrophobicity. In studying conformational changes, we distinguish between early stages of the reaction (“partial cross-linking”), in which only protein oligomers (106 Da > Mw = 104 Da) are formed, and a later stage (“full cross-linking”), in which larger protein particles (Mw = 106 Da) are formed. Partial cross-linking induces a moderate loss of a-helical content. Surprisingly, further cross-linking leads to a partial return of a-helices that are lost upon early cross-linking. At the same time, for partially and fully cross-linked apo-a-LA, almost all tertiary structure is lost. The protein surface hydrophobicity first increases for partial cross-linking, but then decreases again at full cross-linking. Our results highlight the subtle changes in protein conformation and surface hydrophobicity of apo-a-LA upon peroxidase-catalyzed cross-linking.
    Modification of Ovalbumin with Fructooligosaccharides: Consequences for Network Morphology and Mechanical Deformation Responses
    Munialo, C.D. ; Ortega, R.G. ; Linden, E. van der; Jongh, H.H.J. de - \ 2014
    Langmuir 30 (2014)46. - ISSN 0743-7463 - p. 14062 - 14072.
    protein gels - rheological properties - beta-lactoglobulin - maillard reaction - pea protein - neutral ph - mixed gels - gelation - aggregation - perception
    The Maillardation of proteins has been used as a natural alternative to improve its functionality by covalent coupling of proteins with saccharides. However, the impact of Maillard reaction on the structural aspects of protein networks and, as a consequence, the mechanical breakdown properties of the gel networks has not been reported. The objective of this study was to evaluate how the attachment of linear oligo-sugar moieties onto ovalbumin affects its aggregation, network morphology, and consequently the mechanical deformation properties including the ability of the networks to elastically store energy in this material. To potentially alter the morphology of the network structure, ovalbumin was modified by conjugating some of its amino groups with fructooligosaccharide (FOS) moieties via the Maillard reaction. It was demonstrated that the attachment of FOS to ovalbumin does not affect the integrity of the secondary and tertiary structure as characterized using circular dichroism and tryptophan fluorescence. Differences in the network morphology were observed by scanning electron microscopy for FOS-modified ovalbumin variants. Upon increased modification, the microstructure of the gels had more and larger pores and had thinner strands than nonmodified variants. Evaluation of the large deformation properties of the gels demonstrated that FOS-modified gels were less strong and less brittle and showed lower stiffness than nonmodified variants. The recoverable energy (elastically stored energy) of gels reduced with an increase in the degree of modification. The results show that the attachment of FOS to ovalbumin alters the structural and mechanical (large) breakdown properties of the protein gels. The consequences of the alteration of the network structure and large deformation properties of FOS-modified ovalbumin offer opportunities to efficiently design food materials with desirable techno-functional applications
    Acrylamide and 5-hydroxymethylfurfural formation during baking of biscuits: NaCl and temperature-time profile effects and kinetics
    Fels, H.J. van der; Capuano, E. ; Nguyen, H.T. ; Mogol, B.A. ; Kocadagli, T. ; Goncuoglu Tas, N. ; Hamzalioglu, A. ; Boekel, M.A.J.S. van; Gokmen, V. - \ 2014
    Food Research International 57 (2014). - ISSN 0963-9969 - p. 210 - 217.
    aberrant crypt foci - maillard reaction - mass-spectrometry - model system - food - glucose - cookies - asparagine - sucrose - cancer
    The present study aimed to investigate the effect of recipe and temperature–time on the formation of acrylamide and 5-hydroxymethylfurfural (HMF) during biscuit baking. Baking experiments were performed with biscuits of two different recipes, with and without NaCl, at 180 °C, 190 °C and 200 °C. Acrylamide and HMF reached highest concentrations at 200 °C for both recipes. The presence of NaCl in the biscuit formulation lowered acrylamide concentrations at 180 °C and 190 °C but not at 200 °C, and led to higher concentrations of HMF at all the tested temperatures. Sucrose hydrolysis was a key step in acrylamide and HMF formation during biscuit baking, even though a significant amount of acrylamide already had formed before the onset of sucrose hydrolysis. A lag phase was observed before sucrose hydrolysis occurred, which might depend on the melting of crystalline sucrose occurring at approximately 180 °C. A mathematical model based on the chemical reaction pathways was developed for the recipe with NaCl baked at 200 °C. The model described the chemical evolution during the last part of biscuit baking, and accurately predicted acrylamide and HMF content at the end of baking. The model showed the significant contribution of the reducing sugars to the formation of both acrylamide and HMF. The model could not be extended to the entire baking period because it was not possible to incorporate the lag phase observed before sucrose hydrolysis. The results reported in this study confirm that the kinetics of acrylamide and HMF formation in real food and dry systems may depend on the physical state of their precursors.
    Quantitation of Acrylamide in Foods by High-Resolution Mass Spectrometry
    Troise, A.D. ; Fiore, A. ; Fogliano, V. - \ 2014
    Journal of Agricultural and Food Chemistry 62 (2014)1. - ISSN 0021-8561 - p. 74 - 79.
    liquid-chromatography - maillard reaction - potato-chips - lc-ms/ms - gc-ms - heated foodstuffs - dietary exposure - kinetic-model - fried potato - coffee
    Acrylamide detection still represents one of the hottest topics in food chemistry. Solid phase cleanup coupled to liquid chromatography separation and tandem mass spectrometry detection along with GC-MS detection are nowadays the gold standard procedure for acrylamide quantitation thanks to high reproducibility, good recovery, and low relative standard deviation. High-resolution mass spectrometry (HRMS) is particularly suitable for the detection of low molecular weight amides, and it can provide some analytical advantages over other MS techniques. In this paper a liquid chromatography (LC) method for acrylamide determination using HRMS detection was developed and compared to LC coupled to tandem mass spectrometry. The procedure applied a simplified extraction, no cleanup steps, and a 4 min chromatography. It proved to be solid and robust with an acrylamide mass accuracy of 0.7 ppm, a limit of detection of 2.65 ppb, and a limit of quantitation of 5 ppb. The method was tested on four acrylamide-containing foods: cookies, French fries, ground coffee, and brewed coffee. Results were perfectly in line with those obtained by LC-MS/MS.
    N -(carboxymethyl)lysine: A Review on Analytical Methods, Formation, and Occurrence in Processed Food, and Health Impact
    Nguyen, Ha T. ; Fels, H.J. van der; Boekel, M.A.J.S. van - \ 2014
    Food Reviews International 30 (2014)1. - ISSN 8755-9129 - p. 36 - 52.
    glycation end-products - n-epsilon-carboxymethyllysine - performance liquid-chromatography - community-dwelling women - maillard reaction - lipid-peroxidation - protein glycation - milk-products - treated foods - diet
    Foods are often heat processed and may contain advanced glycation end products (AGE). One of the most widely studied AGE is Ne-(carboxymethyl)lysine (CML); nevertheless, knowledge on dietary CML is fragmentary. This study aimed to review current scientific knowledge on analytical methods to determine CML contents in food, chemical pathways of CML formation in food, occurrence of CML in food, and health implications of dietary exposure to CML. Chemical analyses of CML in food products are carried out by immunochemical assays and instrumental methods, but the former method may interfere with the food matrix. CML is formed in food through various chemical pathways, depending on food ingredients and processing conditions. The compound is present in many cooked foods, with relatively high concentrations in carbohydrate- rich foods and dairy products. Dietary CML is very likely to impair human health, but full cause-effect evidence is not available yet. More studies on metabolic effects and impact of food-derived CML on human health should be performed. Food production should be optimized to minimize CML concentrations, while maintaining acceptable microbiological safety and organoleptic properties of the final food product. To this end, more insights into effects of food composition and processing conditions on CML formation are necessary.
    What makes protein indigestible from tissue-related, cellular, and molecular aspects?
    Becker, P.M. ; Yu, P.Q. - \ 2013
    Molecular Nutrition & Food Research 57 (2013)10. - ISSN 1613-4125 - p. 1695 - 1707.
    dried distillers grains - amino-acid - enzymatic hydrolysate - nutritional quality - lotus-corniculatus - condensed tannins - maillard reaction - oxidizing lipids - insect cuticle - food proteins
    This paper gives an insight into key factors, which impair enzymatic protein digestion. By nature, some proteins in raw products are already poorly digestible because of structural peculiarities, or due to their occurrence in plant cytoplasmic organelles or in cell membranes. In plant-based protein, molecular and structural changes can be induced by genetic engineering, even if protein is not a target compound class of the genetic modification. Other proteins only become difficult to digest due to changes that occur during the processing of proteinaceous products, such as extruding, boiling, or acidic or alkaline treatment. The utilization of proteinaceous raw materials in industrial fermentations can also have negative impacts on protein digestibility, when reused as fermentation by-products for animal nutrition, such as brewers' grains. After consumption, protein digestion can be impeded in the intestine by the presence of antinutritional factors, which are ingested together with the food or feedstuff. It is concluded that the encircling matrix, but also molecular, chemical, and structural peculiarities or modifications to amino acids and proteins obstruct protein digestion by common proteolytic enzymes in humans and animals.
    Sugars and the formation of acrylamide and 5-hydroxymethylfurfural
    Nguyen, Thi Thu Ha ; Fels, H.J. van der; Peters, R.J.B. ; Boekel, M.A.J.S. van - \ 2013
    hmf - acrylamiden - biscuits - bakken (in de oven) - suikers - maillard-reactie - hmf - acrylamides - biscuits - baking - sugars - maillard reaction
    The objective of this research was: to investigate the role of sugars in the formation of acrylamide and HMF during biscuit baking.
    PTR-MS monitoring of volatiles fingerprint evolution during grape must cooking
    Dimitri, G. ; Ruth, S.M. van; Sacchetti, G. ; Piva, G. ; Alewijn, M. ; Arfelli, G. - \ 2013
    Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 51 (2013)1. - ISSN 0023-6438 - p. 356 - 360.
    reaction-mass-spectrometry - maillard reaction - flavor retention - food - product - consumption - headspace - systems - storage - matrix
    The main aim of this study was to investigate the effect of processing temperature on the evolution of volatiles during grape must concentration upon cooking. The evolution of the volatiles fingerprint of grape must heated at 80, 90, and 100 °C was studied by Proton Transfer Reaction Mass Spectrometry (PTR-MS). The intensity of the heat treatment influenced the volatile molecules generated after the activation of the non enzymatic browning (NEB) reactions during the cooking process. These volatile compounds represent the most important molecules that characterise the aroma of highly cooked and concentrated must. Time and temperature of treatment influenced dramatically the evolution of must volatile compounds, so at the end of the treatment different volatile profiles were observed. Concentration being equal, high temperature-short time treatments limited the accumulation of volatiles associated to NEB while prolonged times of treatment favoured the formation of NEB flavours.
    Effects of pretreatment of wheat bran on the quality of protein-rich residue for animal feeding and on monosaccharide release for ethanol production
    Borne, J.J.G.C. van den; Kabel, M.A. ; Briens, M. ; Poel, A.F.B. van der; Hendriks, W.H. - \ 2012
    Bioresource Technology 124 (2012). - ISSN 0960-8524 - p. 446 - 454.
    cellulosic biomass - maillard reaction - available lysine - reactive lysine - amino-acids - acrylamide - chemistry - kinetics - foods - microbiology
    The effects of hydrothermal conditions for pretreating wheat bran on the quality of residual protein for animal feeding, and on monosaccharide release for ethanol production were studied according to a 4 × 2 × 2 design with the factors, temperature (120, 140, 160, and 180 °C), acidity (pH 2.3 and 3.9), and retention time (5 and 10 min). Temperature affected the quality of residual protein for animal feeding. Pretreatment at 120 and 140 °C did not affect O-methylisourea-reactive lysine in protein-rich wheat bran residue, although total lysine decreased with increasing temperature at pH 2.3. At temperatures higher than 140 °C, reactive lysine decreased and melanoidins, furfural and 5-HMF increased. Lower acidity during pretreatment at 120 and 140 °C increased the digestibility of the residual wheat protein in vitro by 36%. Pretreatment conditions did not substantially affect the release of monomeric xylose and arabinose by hemicellulases, which suggests that arabinoxylans in wheat bran are well accessible for enzymes.
    Possible causes of variation in acrylamide concentration in French fries prepared in food service establishments: an observational study
    Sanny, M.A.I. ; Jinap, S. ; Bakker, E.J. ; Boekel, M.A.J.S. van; Luning, P.A. - \ 2012
    Food Chemistry 132 (2012)1. - ISSN 0308-8146 - p. 134 - 143.
    techno-managerial approach - mu-g/kg acrylamide - maillard reaction - risk-assessment - quality - potatoes - asparagine - chips - fat - glucose
    Acrylamide is a probable human carcinogen, and its presence in a range of fried and oven-cooked foods has raised considerable health concern world-wide. Dietary intake studies observed significant variations in acrylamide concentrations, which complicate risk assessment and the establishment of effective control measures. The objective of this study was to obtain an insight into the actual variation in acrylamide concentrations in French fries prepared under typical conditions in a food service establishment (FSE). Besides acrylamide, frying time, frying temperature, and reducing sugars were measured and the actual practices at receiving, thawing and frying during French fries preparation were observed and recorded. The variation in the actual frying temperature contributed most to the variation in acrylamide concentrations, followed by the variation in actual frying time; no obvious effect of reducing sugars was found. The lack of standardised control of frying temperature and frying time (due to inadequate frying equipment) and the variable practices of food handlers seem to contribute most to the large variation and high acrylamide concentrations in French fries prepared in a restaurant type of FSE as compared to chain fast-food services, and institutional caterers. The obtained insights in this study can be used to develop dedicated control measures in FSE, which may contribute to a sustainable reduction in the acrylamide intake.
    Effect of Heating and Glycation on the Allergenicity of 2S Albumins (Ara h 2/6) from Peanut
    Vissers, Y.M. ; Blanc, F. ; Stahl Skov, P. ; Johnson, P.E. ; Rigby, N.M. ; Przybylski-Nicaise, L. ; Bernhard, H. ; Wal, J.M. ; Ballmer-Weber, B. ; Zuidmeer-Jongejan, L. ; Szepfalusi, Z. ; Ruinemans-Koerts, J. ; Jansen, A.P.H. ; Savelkoul, H.F.J. ; Wichers, H.J. ; Mackie, A.R. ; Mills, E.N.C. ; Adel-Patient, K. - \ 2011
    PLoS ONE 6 (2011)8. - ISSN 1932-6203 - 9 p.
    ige-binding epitopes - t-cell responses - lipid transfer protein - in-vitro assay - maillard reaction - food allergens - cytokine production - major allergen - b-cell - digestion
    Background Peanut allergy is one of the most common and severe food allergies, and processing is known to influence the allergenicity of peanut proteins. We aimed to establish the effect of heating and glycation on the IgE-binding properties and biological activity of 2S albumins (Ara h 2/6) from peanut. Methodology/Principal Findings Native Ara h 2/6 was purified from raw peanuts and heated in solution (15 min, 110°C) in the presence or absence of glucose. Ara h 2 and 6 were also purified from roasted peanut. Using PBMC and sera from peanut-allergic patients, the cellular proliferative potency and IgE reactivity (reverse EAST inhibition) and functionality (basophil degranulation capacity) of allergens were assessed. Heating Ara h 2/6 at 110°C resulted in extensive denaturation, hydrolysis and aggregation of the protein, whilst Ara h 2 and 6 isolated from roasted peanut retained its native conformation. Allergen stimulation of PBMC induced proliferation and Th2 cytokine secretion which was unaffected by thermal processing. Conversely, IgE reactivity and functionality of Ara h 2/6 was decreased by heating. Whilst heating-glycation further reduced the IgE binding capacity of the proteins, it moderated their loss of histamine releasing capacity. Ara h 2 and 6 purified from roasted peanut demonstrated the same IgE reactivity as unheated, native Ara h 2/6. Conclusions/Significance Although no effect of processing on T-cell reactivity was observed, heat induced denaturation reduced the IgE reactivity and subsequent functionality of Ara h 2/6. Conversely, Ara h 2 and 6 purified from roasted peanut retained the structure and IgE reactivity/functionality of the native protein which may explain the allergenic potency of this protein. Through detailed molecular study and allergenicity assessment approaches, this work then gives new insights into the effect of thermal processing on structure/allergenicity of peanut proteins.
    Effect of roasting on the allergenicity of major peanut allergens Ara h 1 and Ara h 2/6: the necessity of degranulation assays
    Vissers, Y.M. ; Iwan, M. ; Adel-Patient, K. ; Stahl Skov, P. ; Rigby, N.M. ; Johnson, P.E. ; Mandrup Muller, P. ; Przybylski-Nicaise, L. ; Schaap, M. ; Ruinemans-Koerts, J. ; Jansen, A.P.H. ; Mills, E.N.C. ; Savelkoul, H.F.J. ; Wichers, H.J. - \ 2011
    Clinical and Experimental Allergy 41 (2011)11. - ISSN 0954-7894 - p. 1631 - 1642.
    plant food allergens - ige-binding - enzyme immunoassays - maillard reaction - cooking methods - protein - children - ara-h-1 - purification - reactivity
    Background - Peanuts are often consumed after roasting, a process that alters the three-dimensional structure of allergens and leads to Maillard modification. Such changes are likely to affect their allergenicity. Objective - We aimed to establish the effect of thermal treatment mimicking the roasting process on the allergenicity of Ara h 1 and a mix of 2S albumins from peanut (Ara h 2/6). Methods - Ara h 1 and Ara h 2/6 were purified from raw peanuts and heated in a dry form for 20 min at 145 °C in the presence (R+g) or absence (R-g) of glucose, and soluble proteins were then extracted. Sera obtained from 12 well-characterized peanut-allergic patients were used to assess the IgE binding and degranulation capacities of the allergens. Results - Extensive heating at low moisture resulted in the hydrolysis of both Ara h 1 and Ara h 2/6. However, in contrast to Ara h 2/6, soluble R+g Ara h 1 formed large aggregates. Although the IgE-binding capacity of R+g and R-g Ara h 1 was decreased 9000- and 3.6-fold, respectively, compared with native Ara h 1, their capacity to elicit mediator release was increased. Conversely, both the IgE-binding capacity and the degranulation capacity of R-g Ara h 2/6 were 600–700-fold lower compared with the native form, although the presence of glucose during heating significantly moderated these losses. Conclusions - and Clinical Relevance Extensive heating reduced the degranulation capacity of Ara h 2/6 but significantly increased the degranulation capacity of Ara h 1. This observation can have important ramifications for component-resolved approaches for diagnosis and demonstrates the importance of investigating the degranulation capacity in addition to IgE reactivity when assessing the effects of food processing on the allergenicity of proteins.
    Cross-Linking Behavior and Foaming Properties of Bovine a-Lactalbumin after Glycation with Various Saccharides
    Haar, R. ter; Westphal, Y. ; Wierenga, P.A. ; Schols, H.A. ; Gruppen, H. - \ 2011
    Journal of Agricultural and Food Chemistry 59 (2011)23. - ISSN 0021-8561 - p. 12460 - 12466.
    maillard reaction - beta-lactoglobulin - formation pathways - proteins - stability - pentoses - hexoses - food
    a-Lactalbumin was glycated via the Maillard reaction in the dry state using various mono- and oligosaccharides. The reaction resulted not only in coupling of the saccharides to a-lactalbumin but also in cross-linked proteins. The glycation rate and the extent of cross-link formation were highly dependent on the saccharide used. Glycation by arabinose and xylose led to a very fast protein cross-link formation, whereas glucose showed a relatively low protein cross-linking ability. The stability of foams, created using the various glycated protein samples, depended on the type of saccharide used, the extent of glycation, and possibly the amount of cross-linked protein. Compared to nonmodified a-lactalbumin, glycation with rhamnose and fucose improved foam stability, whereas application of glucose, galacturonic acid, and their oligosaccharides did not exert a clear effect. Mass spectrometric analysis revealed that dehydration of the Amadori products is an indicator of the formation of protein cross-links.
    Fate in digestion in vitro of several food components, including some toxic compounds coming from omega-3 and omega-6 lipids
    Goicoechea, E. ; Brandon, E.F.A. ; Blokland, M.H. ; Guillén, M.D. - \ 2011
    Food and Chemical Toxicology 49 (2011). - ISSN 0278-6915 - p. 115 - 124.
    maillard reaction - sunflower oil - acyl-groups - oxidation - aldehydes - peroxidation - products - model - acids - n-3
    In this study it was proved the formation of oxygenated alpha,beta-unsaturated aldehydes (OaßUAs) of 6, 7, 9 and 10 carbon atoms during the thermal treatment (190 °C with aeration) of a commercial vegetable oil rich in omega-3 and omega-6 acyl groups, which also contained small amounts of added proteins and carbohydrates to produce barbecue aroma when heated. The OaßUAs detected by Solid Phase Microextraction (SPME) followed by Gas Chromatography/Mass Spectrometry (GC/MS) were: 4-hydroxy-2-hexenal, 4-oxo-2-hexenal and 4,5-epoxy-2-heptenals, coming from omega-3 acyl groups; and 4-hydroxy-2-nonenal, 4-oxo-2-nonenal and 4,5-epoxy-2-decenals, coming from omega-6 acyl groups. Mixtures of this oil, either thermodegraded or not, with standard food were submitted to an in vitro digestion model. The study of the digestion products obtained revealed that OaßUAs remained unaltered, being bioaccessible in the gastrointestinal tract and so able to reach the systemic circulation. Besides, it was evidenced that during digestion Maillard, esterification and oxidation reactions take place.
    Lipid oxidation promotes acrylamide formation in fat-rich model systems
    Capuano, E. ; Oliviero, T. ; Açar, Ö. ; Gökmen, V. ; Fogliano, V. - \ 2010
    Food Research International 43 (2010)4. - ISSN 0963-9969 - p. 1021 - 1026.
    maillard reaction - phenylalanine - antioxidant - products - foods - oils
    Lipid oxidation is one of the major chemical reactions occurring during food processing or storage and may have a strong impact on the final quality of foods. A significant role of carbonyl compounds derived from lipid oxidation in acrylamide formation has been recently proposed. In this work, the effect of lipid oxidation level on acrylamide formation was investigated by thermal treatment of differently formulated fat-rich model systems. Results showed that lipid oxidation positively influenced the formation of acrylamide. The effect was more evident in sugar-free system where lipid become the main sources of carbonyls. Catechins reduced acrylamide formation presumably by trapping carbohydrates and/or preventing lipid oxidation. More acrylamide was formed in model systems composed with sunflower oil than in those containing palm oil which is less susceptible to oxidation. In systems containing higher amount of water, acrylamide formation was delayed due to evaporative cooling. In these systems, the effect of catechin was more pronounced and the effect of lipid oxidation became detectable only after a prolonged reaction time. These findings suggested that lipid oxidation could become a relevant factor for acrylamide formation, particularly for dry foods with low carbohydrate content.
    Bioavailability of lysine in heat-treated foods and feedstuffs
    McArtney Rutherfurd, S. - \ 2010
    Wageningen University. Promotor(en): Wouter Hendriks; Martin Verstegen, co-promotor(en): P.J. Moughan. - [S.l. : S.n. - ISBN 9789085856825 - 139
    lysine - biologische beschikbaarheid - voer - voedingsmiddelen - melkproducten - huisdierenvoer - ontbijtgranen - warmtebehandeling - maillard-reactie - maillard-reactieproducten - verteerbaarheid - lysine - bioavailability - feeds - foods - milk products - pet foods - breakfast cereals - heat treatment - maillard reaction - maillard reaction products - digestibility
    During the processing of foodstuffs, lysine can react with other compounds present to form nutritionally unavailable derivatives, the most common example of which are Maillard products. Maillard products can cause serious problems when determining the available lysine content of processed foods or feedstuffs as they can revert to lysine during amino acid analysis. Several methods have been developed to determine the dietary lysine available for the metabolic processes of animals including animal growth-based assays, reactive lysine chemical methods and digestibility assays. However, growth-based assays are laborious, highly variable and tend to determine utilization rather than availability. Chemically reactive lysine assays do accurately determine the unmodified lysine in a food or feedstuff, but do not determine available lysine as they incorrectly assume that reactive lysine digestion and absorption is 100%. Ileal digestibility assays measure digestible total lysine rather than digestible reactive lysine (available lysine) and so are inaccurate, especially when applied to processed protein sources. This thesis describes the development of a true ileal digestible reactive lysine assay for determining dietary (bio)available lysine. This assay couples the guanidination reaction, for determining reactive lysine, with a true ileal digestibility assay. The resulting apparent digestibility estimate is corrected to a true digestibility value by accounting for the endogenous ileal lysine flow.

    Selected reaction conditions for the guanidination of lysine in a heated lactose/casein mixture and digesta of rats fed unheated casein and heated lactose/casein was examined. Overall, suitable reaction conditions were 0.6 M O-methylisourea for 7 d in a shaking waterbath at 21 ± 2 °C with an O-methylisourea to lysine ratio of 1000 and a reaction mixture pH of 10.6 for casein and heated lactose/casein and 11.0 for digesta. The accuracy of the guanidination method for determining reactive lysine in a range of “ready-to-eat ” cereal-based breakfast foods and selected feedstuffs was tested by comparison with the reactive lysine content of the same protein sources when determined using the fluorodinitrobenzene method. Overall, there was excellent agreement between the two methods. The accuracy of the newly developed bioassay for determining digestible reactive (available) lysine for predicting lysine deposition was also tested using a heated skim milk powder. The true ileal total and reactive lysine digestibilities were determined for the heated skim milk powder which was then fed to pigs, along with two control diets which were formulated based on either total lysine digestibility or reactive lysine digestibility. All diets were limiting in lysine. The pigs fed the heated skim milk powder deposited the same (P > 0.05) amount of lysine (9.1 g d-1) as the pigs fed the control diet that was formulated based on reactive lysine digestibility (9.1 g d-1) but deposited significantly (P < 0.05) more than the pigs fed the control diet that was formulated based on total lysine digestibility (5.4 g d-1). Consequently for the heated skim milk powder at least, the true ileal digestible reactive lysine assay accurately determined the available lysine content.



    The new assay demonstrated that for a range of milk protein-based foods, there was little difference between digestible total lysine and digestible reactive lysine for most of the milk products tested. In contrast, for a range of “ready-to-eat” cereal-based breakfast foods, available lysine was 5 – 50% lower than that determined using the traditional assay, which is of concern given that breakfast cereals are perceived to be “healthy” foods. Similarly, the available lysine content of a range of moist and dry commercial cat foods was significantly (P < 0.05) lower (15-55% lower) than previously estimated using the traditional true ileal digestible total lysine assay. The assay was also used to examine the effect of storage for extended periods at elevated temperatures on a hydrolysed-lactose skim milk powder and overall, there was a significant decrease in the available lysine content over time, as much as 60% over 6 mth when the powder was stored at 40 °C. In addition, the decrease in available lysine content of the hydrolysed-lactose skim milk powder was 2 – 5.5 times greater than observed for a normal skim milk powder depending on the storage time and temperature. Overall, foods and feedstuffs that have undergone processing often contain lower amounts of available lysine than thought previously. This new assay not only highlights the inaccuracy of the traditional true ileal digestible total lysine assay as a method for determining available lysine in processed protein sources, but permits the accurate assessment of the available lysine content of processed foods and feedstuffs.


    Impact of control behaviour on unacceptable variation in acrylamide in French fries
    Sanny, M.A.I. ; Luning, P.A. ; Marcelis, W.J. ; Jinap, S. ; Boekel, M.A.J.S. van - \ 2010
    Trends in Food Science and Technology 21 (2010)5. - ISSN 0924-2244 - p. 256 - 267.
    techno-managerial approach - mu-g/kg acrylamide - food safety - risk-assessment - model system - formation/elimination reactions - multiresponse approach - processing conditions - foodborne disease - maillard reaction
    Various studies have identified high concentrations of acrylamide in French fries and they emphasised that there is much uncertainty about actual concentrations in French fries upon consumption. The aim of this study was to get insight in technological as well as people related factors that contribute to variable and high acrylamide concentrations in French fries prepared under typical food service establishment circumstances. The literature study indicated that glucose and fructose, and actual frying conditions (time-temperature) are the dominant technological factors in acrylamide formation and inadequate control of these factors can result in variable and high concentrations in French fries upon consumption. Analysis of the common control situation in FSE revealed that control decisions on resources by management (i.e. appropriate suppliers, specified raw materials, adequate frying equipment, competent personnel) can be effective in lowering acrylamide formation, but are restricted in practice. However, even under appropriate technological (advanced equipment, low reducing sugars in raw materials) and managerial conditions (competent people, appropriate procedures, etc), it is expected that daily control of food handlers (at receipt and during frying) may be still a major factor contributing to variable concentrations in acrylamide. Article Outline
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