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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    Prediction of spoilage of tropical shrimp (Penaeus notialis) under dynamic temperature regimes
    Dabade, D.S. ; Azokpota, P. ; Nout, M.J.R. ; Hounhouigan, D.J. ; Zwietering, M.H. ; Besten, H.M.W. den - \ 2015
    International Journal of Food Microbiology 210 (2015). - ISSN 0168-1605 - p. 121 - 130.
    shelf-life prediction - bacterial-growth - sensory characteristics - listeria-monocytogenes - pseudomonas-fragi - microbial model - water activity - packed fish - fresh fish - meat
    The spoilage activity of Pseudomonas psychrophila and Carnobacterium maltaromaticum, two tropical shrimp (Penaeus notialis) spoilage organisms, was assessed in cooked shrimps stored at 0 to 28 °C. Microbiological, chemical and sensory analyses were performed during storage. P. psychrophila had a higher growth rate and showed a higher spoilage activity at temperatures from 0 to 15 °C, while at 28 °C, C. maltaromaticum had a higher growth rate. The spoilage activity of P. psychrophila was found to be higher in cooked shrimp than in fresh shrimp. Observed shelf-life data of shrimps stored at constant temperatures were used to validate a previously developed model that predicts tropical shrimp shelf-life at constant storage temperatures. Models predicting the growth of the spoilage organisms as a function of temperature were constructed. The validation of these models under dynamic storage temperatures simulating temperature fluctuation in the shrimp supply chain showed that they can be used to predict the shelf-life of cooked and fresh tropical shrimps.
    Interactions between formulation and spray drying conditions related to survival of Lactobacillus plantarum WCFS1
    Perdana, J.A. ; Fox, M.B. ; Siwei, C. ; Boom, R.M. ; Schutyser, M.A.I. - \ 2014
    Food Research International 56 (2014). - ISSN 0963-9969 - p. 9 - 17.
    glass-transition temperature - membrane phase-behavior - lactic-acid bacteria - flow-cytometry - industrial applications - dairy ingredients - osmotic-stress - water activity - rhamnosus gg - gel phase
    Protective solid carriers are commonly added to probiotic cultures prior to drying. Their formulation is not trivial and depends on the drying conditions applied. In this study, we systematically investigated the influence of formulation parameters on the survival of Lactobacillus plantarum WCFS1 after drying. Low molecular weight carbohydrates (less than 2 kDa) with high glass transition temperatures provided the highest level of protection at both low (25 degrees C) and high (50 degrees C or higher) drying temperatures. Low molecular weight carbohydrates may provide stabilization by closely interacting with the lipid bilayer of the cell membranes. Meanwhile, carbohydrates with high glass transition temperatures probably provide stabilization via fixation of the cells in a glassy powder. Furthermore, adequate amounts of solid carrier are required to sufficiently stabilize the cells during drying. During drying, crystallization of solid carriers may occur. Depending on the crystal geometry, crystallization can be either beneficial (e.g. with mannitol or sorbitol) or detrimental (e.g. with lactose) to cell survival. Finally, the effect of formulation on cell viability during storage was studied. A decimal reduction time of approximately 300 days was observed when spray dried L. plantarum WCFS1 was stored at temperatures below 40 degrees C. The outcome of this study was used as a basis to construct a generalized diagram to indicate the combinations of formulation and drying conditions to maximally retain viability and operate dryers at high efficiency. (C) 2013 Elsevier Ltd. All rights reserved.
    Factors Impeding Enzymatic Wheat Gluten Hydrolysis at High Solid Concentrations
    Hardt, N.A. ; Janssen, A.E.M. ; Boom, R.M. ; Goot, A.J. van der - \ 2014
    Biotechnology and Bioengineering 111 (2014)7. - ISSN 0006-3592 - p. 1304 - 1312.
    functional-properties - water activity - plastein synthesis - biomass - lignocellulose - inhibition - proteins - softwood
    Enzymatic wheat gluten hydrolysis at high solid concentrations is advantageous from an environmental and economic point of view. However, increased wheat gluten concentrations result in a concentration effect with a decreased hydrolysis rate at constant enzyme-to-substrate ratios and a decreased maximum attainable degree of hydrolysis (DH%). We here identified the underlying factors causing the concentration effect. Wheat gluten was hydrolyzed at solid concentrations from 4.4% to 70%. The decreased hydrolysis rate was present at all solid concentrations and at any time of the reaction. Mass transfer limitations, enzyme inhibition and water activity were shown to not cause this hydrolysis rate limitation up to 50% solids. However, the hydrolysis rate limitation can be, at least partly, explained by a second-order enzyme inactivation process. Furthermore, mass transfer impeded the hydrolysis above 60% solids. Addition of enzyme after 24 h at high solid concentrations scarcely increased the DH%, suggesting that the maximum attainable DH% decreases at high solid concentrations. Reduced enzyme activities caused by low water activities can explain this DH% limitation. Finally, a possible influence of the plastein reaction on the DH% limitation is discussed.
    Moisture Sorption Isotherms of Broccoli Interpreted with the Flory-Huggins Free Volume Theory
    Jin, X. ; Sman, R.G.M. van der; Maanen, J.F.C. van; Deventer, H.C. van; Straten, G. van; Boom, R.M. ; Boxtel, A.J.B. van - \ 2014
    Food Biophysics 9 (2014)1. - ISSN 1557-1858 - p. 1 - 9.
    water activity - glassy-polymers - drying methods - carrot slices - tissue-damage - quality - vegetables - mixtures - heat - pretreatment
    In this work, the Flory Huggins Free Volume theory is used to interpret the sorption isotherms of broccoli from its composition and using physical properties of the components. This theory considers the mixing properties of water, biopolymers and solutes and has the potential to describe the sorption isotherms for varying product moisture content, composition and temperature. The required physical properties of the pure components in food became available in recent years and allow now the prediction of the sorption isotherms with this theory. Sorption isotherm experiments have been performed for broccoli florets and stalks, at two temperatures. Experimental data shows that the Flory Huggins Free Volume (FHFV) theory represents the sorption isotherm of fresh and blanched broccoli samples accurately. The results also show that blanching affects the sorption isotherm due to the change of composition via leaching solutes and the change of interaction parameter due to protein denaturation
    Enzymatic synthesis of oligo- and polysaccharide fatty acid esters
    Broek, L.A.M. van den; Boeriu, C.G. - \ 2013
    Carbohydrate Polymers 93 (2013)1. - ISSN 0144-8617 - p. 65 - 72.
    catalyzed cellulose acetylation - organic media - vinyl esters - regioselective esterification - water activity - lipase - acylation - solvents - transesterification - oligosaccharides
    Amphiphilic oligo- and polysaccharides (e.g. polysaccharide alkyl or alkyl-aryl esters) form a new class of polymers with exceptional properties. They function as polymeric surfactants, whilst maintaining most of the properties of the starting polymeric material such as emulsifying, gelling, and film forming properties combined with partial water solubility or permeability. At present carbohydrate fatty acid esters are generally obtained by chemical methods using toxic solvents and organic and inorganic catalysts that leave residual traces in the final products. Enzymatic reactions offer an attractive alternative route for the synthesis of polysaccharide esters. In this review the state of the art of enzymatic synthesis of oligo- and polysaccharides fatty esters has been described.
    Single droplet drying for optimal spray drying of enzymes and probiotics
    Schutyser, M.A.I. ; Perdana, J.A. ; Boom, R.M. - \ 2012
    Trends in Food Science and Technology 27 (2012)2. - ISSN 0924-2244 - p. 73 - 82.
    acid starter cultures - glass-transition temperature - inactivation kinetics - enthalpy relaxation - water activity - milk droplets - foods - state - mechanisms - stability
    Spray drying is a mild and cost-effective convective drying method. It can be applied to stabilise heat sensitive ingredients, such as enzymes and probiotic bacteria, albeit in industrial practice for example freeze drying or freezing are often preferred. The reason is that optimum drying conditions and tailored matrix formulations are required to avoid severe heat damage leading to loss in enzyme activity or reduced survival of bacteria. An overview is provided on the use of protective carbohydrate-rich formulations in the spray drying of enzymes and probiotics. Subsequently, single droplet drying experimentation methods are reviewed for mapping drying trajectories of individual droplets. The advantage of these is to provide insight in inactivation kinetics of enzymes and probiotics and thus contribute to unravelling of stabilisation mechanisms. Finally, it is shown that detailed modelling of single droplet drying and insight in micro-structural changes during drying can be complementary to the experimental single droplet approaches.
    Why coarse toasted rusk rolls are crispier than fine ones
    Castro-Prada, E.M. ; Meinders, M.B.J. ; Primo-Martin, C. ; Hamer, R.J. ; Vliet, T. van - \ 2012
    Journal of Texture Studies 43 (2012)6. - ISSN 0022-4901 - p. 421 - 437.
    water activity - potato-chips - snack food - instrumental parameters - perceived crispness - acoustic properties - sensory crispness - auditory cues - deformation - texture
    Toasted rusk rolls with a coarser structure are sensed crispier than those with a fine structure, at the same water activity (aw). The present paper shows that this difference in crispness perception is related to differences in fracture behavior and accompanying acoustic emission. Both sensory and instrumentally determined crispness decreased gradually with increasing aw in roughly the same manner for both coarse and fine products. Nevertheless, the coarse rusk roll was perceived as being crispier than the fine one. Typically, in the coarse structure the measured “Number of Force Drops” of a relatively large size and the “Number of Sound Events per cross section area” of relatively large intensity were more numerous than in the fine one. Our data show that relatively large force drops and sound events are related to the more intense crispness perception and stronger sound sensation for the coarse structure toasted rusk roll. We propose the “Total Sound Energy per cross section area” and the “Mean Sound Event Intensity” to be primarily responsible for the higher crispness perception of the coarse rusk over the whole aw range.
    Modelling mycotoxin formation by Fusarium graminearum in maize in The Netherlands
    Asselt, E.D. van; Booij, C.J.H. ; Fels-Klerx, H.J. van der - \ 2012
    Food Additives & Contaminants. Pt. A, Chemistry, Analysis, Control, Exposure & Risk Assessment 29 (2012)10. - ISSN 1944-0049 - p. 1572 - 1580.
    water activity - deoxynivalenol content - agricultural practices - zearalenone formation - fumonisin b-1 - zea-mays - ear rot - temperature - growth - corn
    The predominant species in maize in temperate climates is Fusarium graminearum, which produces the mycotoxins deoxynivalenol and zearalenone. Projected climate change is expected to affect Fusarium incidence and thus the occurrence of these mycotoxins. Predictive models may be helpful in determining trends in the levels of these mycotoxins with expected changing climatic conditions. The aim of this study was to develop a model describing fungal infection and subsequent growth as well as the formation of deoxynivalenol and zearalenone in maize in The Netherlands. For this purpose, a published Italian model was used as a starting point. This model is a mixed empiric–mechanistic model that describes fungal infection during silking (based on wind speed and rainfall) and subsequent germination, growth and toxin formation (depending on temperature and water availability). Model input uses weather parameters and crop management factors, such as maize hybrid, sowing date, flowering period and harvest date. Model parameter values were obtained by fitting these parameters to deoxynivalenol and zearalenone measurements in Dutch maize, using national mycotoxin data from the years 2002–2007. The results showed that the adapted model is capable of describing the trend in average deoxynivalenol and zearalenone levels over these years. Validation with external data is needed to verify model outcomes. It is expected that the current model can be used to estimate the effect of projected climate change on trends in deoxynivalenol and zearalenone levels in the coming years.
    Immobilization to prevent enzyme incompatibility with proteases
    Vossenberg, P. ; Beeftink, H.H. ; Cohen Stuart, M.A. ; Tramper, J. - \ 2011
    Biocatalysis and Biotransformation 29 (2011)6. - ISSN 1024-2422 - p. 288 - 298.
    candida-antarctica - peptide-synthesis - organic-synthesis - crystal-structure - water activity - lipase-b - deactivation - improvement - autolysis - proteins
    Enzyme incompatibility is a problem in multi-enzyme processes that involve a non-specific protease, such as Alcalase. An example is the one-pot enzymatic synthesis of peptides catalyzed by a lipase and a protease. The incompatibility between lipase B from Candida antarctica (CalB) and Alcalase was studied. To what extent immobilization of both or either CalB or Alcalase onto macroporous beads helps to prevent hydrolysis of CalB by Alcalase was evaluated. The rate of activity loss of native and immobilized CalB in the absence and presence of native and immobilized Alcalase was calculated from the rate of triacetin hydrolysis. Immobilization of both or either CalB or Alcalase onto macroporous beads was found to be effective in largely preventing hydrolysis of CalB by Alcalase
    Regio- and stereoselective glucosylation of diols by sucrose phosphorylase using sucrose or glucose 1-phosphate as glucosyl donor
    Renirie, R. ; Pukin, A. ; Lagen, B. van; Franssen, M.C.R. - \ 2010
    Journal of Molecular Catalysis. B, Enzymatic 67 (2010)3-4. - ISSN 1381-1177 - p. 219 - 224.
    enzymatic-synthesis - catalyzed synthesis - bifidobacterium-adolescentis - water activity - glycosides
    Previously it has been shown that glycerol can be regioselectively glucosylated by sucrose phosphorylase from Leuconostoc mesenteroides to form 2-O-alpha-D-glucopyranosyl-glycerol (Coedl et al., Angew. Chem. Int. Ed. 47 (2008) 10086-10089). A series of compounds related to glycerol were investigated by us to determine the scope of the alpha-glucosylation reaction of sucrose phosphorylase. Both sucrose and glucose 1-phosphate (GIP) were applied as glucosyl donor. Mono-alcohols were not accepted as substrates but several 1,2-diols were readily glucosylated, proving that the vicinal diol unit is crucial for activity. The smallest substrate that was accepted for glucosylation appeared to be ethylene glycol, which was converted to the monoglucoside for 69%. Using high acceptor and donor concentrations :up to 2.5 M), sucrose or GIP hydrolysis (with H2O being the 'acceptor') can be minimised. In the study cited above, a preference for glucosylation of glycerol on the 2-position has been observed. For 1,2-propanediol however, the regiochemistry appeared to be dependent on the configuration of the substrate. The (R)enantiomer was preferentialy glucosylated on its 1-position (ratio 2.5:1), whereas the 2-glucoside is the major product for (S)-1,2-propanediol (1:4.1). d.e.(p)s of 71-83% were observed with a preference for the (S)-enantiomer of the glucosides of 1,2-propanediol and 1,2-butanediol and the (R)-enantiomer of the glucoside of 3-methoxy-1,2-propanediol. This is the first example of stereoselective glucosylation of a non-natural substrate by sucrose phosphorylase. 3-Amino-1,2-propanediol, 3-chloro-1,2-propanediol, 1-thioglycerol and glyceraldehyde were not accepted as substrates. Generally, the glucoside yield is higher when sucrose is used as a donor rather than GIP. due to the fact that the released phosphate is a stronger inhibitor of the enzyme (in case of Cl P) than the released fructose (in case of sucrose). Essentially the same results are obtained with sucrose phosphorylase from Blfidobacterium adolescentis.
    Performance of cellulose derivates in deep-fried battered snacks: Oil barrier and crispy properties
    Primo Martin, C. ; Sanz, T. ; Steringa, D.W. ; Salvador, A. ; Fiszman, S.M. ; Vliet, T. van - \ 2010
    Food Hydrocolloids 24 (2010)8. - ISSN 0268-005X - p. 702 - 708.
    hydroxypropyl methylcellulose - methyl-cellulose - water activity - carrot slices - fat - behavior - fracture - quality - sounds - crust
    The performance of batters containing cellulose derivatives (methylcellulose(A4M), three hydroxypropylmethyl celluloses (E4M, F4M and K4M) with different degree of hydroxypropyl and/or methyl substitution and carboxymethyl cellulose (CMC)) to produce crispy deep-fried snacks crusts was studied by using a deep-fried crust model. Their performance was compared in terms of their ability to retain moisture content, to decrease oil content and the effect on crispness. Thermogelation properties of the cellulose derivatives depended on the type and degree of substitution. All increased the water content and decreased the oil content of the deep-fried crusts, except for CMC, which does not thermogelate and did not increase the amount of water retained in the crust, although a decrease in the oil content was found. The highest oil reduction and the lowest water retention were found for the cellulose with the lowest level of methyl substitution (K4M). The sound emitted during fracture of K4M crusts had higher intensity than the other cellulose derivatives indicating a crispier crust
    Permeability of crust is key to crispness retention
    Hirte, A. ; Hamer, R.J. ; Meinders, M.B.J. ; Primo-Martin, C. - \ 2010
    Journal of Cereal Science 52 (2010)2. - ISSN 0733-5210 - p. 129 - 135.
    bread crust - sensory crispness - water activity - food-products - deformation - model - fracture - starch
    Bread loses crispness rapidly after baking because water originating from the wet crumb accumulates in the dry crust. This water accumulation might be increased by the dense and low permeable character of the bread crust. Our objective was to investigate the influence of permeability of the crust on water uptake in the crust and on crispness retention. To achieve this objective, we increased the permeability of the control bread crust by creating small channels through the crust. The water vapour permeability of the crust with and without channels was measured using a newly developed method for brittle materials. Two further properties were measured over time: crispness of bread by analysing acoustic properties and water content of the crust. Control bread crust had low water vapour permeability and functioned as a barrier, leading to increased uptake of water in the crust. Water uptake was halved, however, if the water vapour permeability of the crust was doubled. As a consequence, crispness retention increased eight-fold; breads stored for four hours were as crispy as control breads stored for 30 min. We can conclude, therefore, that permeability of crust is key to crispness retention.
    Comparison of two optical-density-based methods and a plate count method for estimation of growth parameters of Bacillus cereus
    Biesta-Peters, E.G. ; Reij, M.W. ; Joosten, H. ; Gorris, L.G.M. ; Zwietering, M.H. - \ 2010
    Applied and Environmental Microbiology 76 (2010)5. - ISSN 0099-2240 - p. 1399 - 1405.
    listeria-monocytogenes - inoculum size - lag times - enterobacter-sakazakii - pseudomonas-fragi - pasteurized milk - gamma hypothesis - carbon-dioxide - water activity - shelf-life
    Quantitative microbiological models predicting proliferation of microorganisms relevant for food safety and/or food stability are useful tools to limit the need for generation of biological data through challenge testing and shelf-life testing. The use of these models requires quick and reliable methods for the generation of growth data and estimation of growth parameters. Growth parameter estimation can be achieved using methods based on plate counting and methods based on measuring the optical density. This research compares the plate count method with two optical density methods, namely, the 2-fold dilution (2FD) method and the relative rate to detection (RRD) method. For model organism Bacillus cereus F4810/72, the plate count method and both optical density methods gave comparable estimates for key growth parameters. Values for the maximum specific growth rate (µmax) derived by the 2FD method and by the RRD method were of the same order of magnitude, but some marked differences between the two approaches were apparent. Whereas the 2FD method allowed the derivation of values for lag time () from the data, this was not possible with the RRD method. However, the RRD method gave many more data points per experiment and also gave more data points close to the growth boundary. This research shows that all three proposed methods can be used for parameter estimation but that the choice of method depends on the objectives of the research
    Bread crispness and morphology can be controlled by proving conditions
    Primo Martin, C. ; Dalen, G. van; Meinders, M.B.J. ; Don, A. ; Hamer, R.H. ; Vliet, T. van - \ 2010
    Food Research International 43 (2010)1. - ISSN 0963-9969 - p. 207 - 217.
    water activity - moisture migration - mechanical-properties - food-products - cereal foods - solid food - crust - gluten - crumb - redistribution
    Bread crust crispness is lost when water migrates from crumb to crust during storage. To what extent water migration is influenced by morphology is not known. Therefore, the effect of crispy rolls morphology on crust crispness was studied. Crispy rolls were prepared at three proving volumes: 300 mL (short proving), 500 mL (control) and 800 mL (long proving). X-ray microtomography was used to characterize morphology. Water transport from crumb to crust was determined. Short proved crispy rolls showed lower rate of crust water uptake while longer proved rolls showed faster uptake during cooling down. Sensory analysis revealed higher crispness for short proved crispy rolls after the same storage time at low RH. We hypothesize that shorter proved crispy rolls with finer crumb morphology, more closed structure, smaller gas cells with less gas cells interconnections and a thicker crust have a significant positive effect on water uptake kinetics and crispness retention.
    The growth limits of a large number of Listeria monocytogenes strains at combinations of stresses show serotype- and niche-specific traits
    Veen, S. van der; Moezelaar, R. ; Abee, T. ; Wells-Bennik, M.H.J. - \ 2008
    Journal of Applied Microbiology 105 (2008)5. - ISSN 1364-5072 - p. 1246 - 1258.
    osmolyte transporters betl - food-borne pathogen - comparative genomics - dairy-products - water activity - inoculum size - lactic-acid - heat-shock - scott-a - low ph
    Aims: The aim of this study was to associate the growth limits of Listeria monocytogenes during exposure to combined stresses with specific serotypes or origins of isolation, and identify potential genetic markers. Methods and Results: The growth of 138 strains was assessed at different temperatures using combinations of low pH, sodium lactate, and high salt concentrations in brain heart infusion broth. None of the strains was able to grow at pH ¿ 4·4, aw ¿ 0·92, or pH ¿ 5·0 combined with aw ¿ 0·94. In addition, none of the strains grew at pH ¿ 5·2 and NaLac ¿ 2%. At 30°C, the serotype 4b strains showed the highest tolerance to low pH and high NaCl concentrations at both pH neutral (pH 7·4) and mild acidic conditions (pH 5·5). At 7°C, the serotype 1/2b strains showed the highest tolerance to high NaCl concentrations at both pH 7·4 and 5·5. Serotype 1/2b meat isolates showed the highest tolerance to low pH in the presence of 2% sodium lactate at 7°C. ORF2110 and gadD1T1 were identified as potential biomarkers for phenotypic differences. Conclusions: Differences in growth limits were identified between specific L. monocytogenes strains and serotypes, which could in some cases be associated with specific genetic markers. Significance and Impact of the Study: Our data confirm the growth limits of L. monocytogenes as set out by the European Union for ready-to-eat foods and provides an additional criterion. The association of L. monocytogenes serotypes with certain stress responses might explain the abundance of certain serotypes in retail foods while others are common in clinical cases.
    Fracture behaviour of bread crust: Effect of bread cooling conditions
    Primo Martin, C. ; Beukelaer, H.J. de; Hamer, R.J. ; Vliet, T. van - \ 2008
    Journal of Food Engineering 89 (2008). - ISSN 0260-8774 - p. 285 - 290.
    snack food-products - water activity - cereal foods - crispness - crunchy - industry - technology
    The effect of air and vacuum cooling on the fracture behaviour and accompanying sound emission, moisture content and crispness of bread crust were investigated. Vacuum cooling resulted in rapid evaporative cooling of products that contained high moisture content. Fracture experiments showed a clear dependence of fracture properties on the way the bread was cooled. Vacuum cooling gave breads with a lower moisture content in the crust than the air cooled breads. Both fracture behaviour and sound emission by bread crust were affected by vacuum cooling. An increase in the number of force and sound events was found which correlated well with the increase in crispness. This treatment also resulted in better retention of crust crispness. Breads stored for 4 h at 22 C and 50% RH showed only force and sound events when vacuum was employed.
    Fracture behaviour of bread crust: Effect of ingredient modification
    Primo-Martin, C. ; Beukelaer, H.J. de; Hamer, R.J. ; Vliet, T. van - \ 2008
    Journal of Cereal Science 48 (2008)3. - ISSN 0733-5210 - p. 604 - 612.
    food crushing sounds - water activity - crispness - texture - quality
    The influence of the formulation on the crispness of bread crust was studied. Crispness is a relevant sensory attribute that depends on several factors particularly the plasticizer content (water), the mechanical properties of the solid matrix and the morphological architecture of the bread. Enzymes and additives were used to modify the bread formulation. This resulted in a modification of the bread characteristics. Crust and crumb had higher porosity than the control breads and a decreased water content of the bread crust was found. Instrumental crispness was evaluated by simultaneous analysis of the fracture behaviour and sound emission while breaking the crust. Addition of lipase, amylase, glucose oxidase and hydroxypropyl methylcellulose (HPMC) increased the number of force and sound events, indicative of higher crispness. The number of fracture and sound events correlated negatively with the water content and positively with the porosity of the crust. Both properties are affected by the use of enzymes/additives. Whether the observed positive effect of the enzymes and additives on the number of force and sound events is due to a direct effect on the flour components properties or interactions or to an indirect effect via structure-water migration properties is still open to discussion.
    Effect of structure in the sensory characterization of the crispness of toasted rusk roll
    Primo-Martin, C. ; Castro-Prada, E.M. ; Meinders, M.B.J. ; Vereijken, P.F.G. ; Vliet, T. van - \ 2008
    Food Research International 41 (2008)5. - ISSN 0963-9969 - p. 480 - 486.
    snack food-products - water activity - mechanical-properties - breakfast cereals - acoustic-emission - crunchy - texture - sounds - perception - model
    Crispness is a salient textural attribute of toasted foods strongly related to their preference. Crispness is affected by water content, mechanical properties and morphology of the food. Sound emission and force characteristics during food crushing play a key role in crispness. The aim was to assess the effect of product morphology on sensory crispness grading of toasted rusk roll, a cellular solid food. Products with coarse and fine structures were studied. Additionally, the effect of water on crispness was studied by using samples with water activities from 0.30 to 0.8. The sensory test showed that upon absorption of water the product became tough and soft and lost its crispness. The morphology of the product had a significant effect on crispness intensity. Coarse products were rated crispier than those with a fine crumb grain. Deterioration of crispness (Aw10%) started at 0.46 and 0.50 water activity (6.2% and 7.1% H2O) for the fine and coarse structure product, respectively. The critical water activity (Awc) at which the products lost 50% of the crispness was 0.57 and 0.59 (9.1% and 9.7% H2O), respectively for the fine and coarse structure product
    Kinetic Modeling of Food Quality: A Critical Review
    Boekel, T. van - \ 2008
    Comprehensive Reviews in Food Science and Food Safety 7 (2008)1. - ISSN 1541-4337 - p. 144 - 158.
    optimal experimental-design - time-temperature indicators - reversible chemical-reaction - heat sterilization processes - optimum designs - water activity - shelf-life - chlorophyll degradation - thermal inactivation - molecular dimensions
    ABSTRACT: This article discusses the possibilities to study relevant quality aspects of food, such as color, nutrient content, and safety, in a quantitative way via mathematical models. These quality parameters are governed by chemical, biochemical, microbial, and physical changes. It is argued that the modeling of such quality aspects is in fact kinetic modeling. Therefore, attention is paid to chemical kinetics, and its possibilities and limitations are discussed when applied to changes occurring in foods. The discussion is illustrated with examples from the literature. A major difficulty is that principles from chemical kinetics are strictly speaking only valid for simple elementary reactions, and foods are all but simple. Interactions in the food matrix and variability are 2 complicating factors. It is discussed how this difficulty can be tackled, and research priorities are suggested to come to better models in food science, and thereby to a better control of food quality.
    Molecular mobility in crispy bread crust
    Nieuwenhuijzen, N.H. van - \ 2008
    Wageningen University. Promotor(en): Rob Hamer, co-promotor(en): Ton van Vliet; R.H. Tromp. - [S.l.] : S.n. - ISBN 9789085048565 - 133
    brood - broosheid - aw-waarde - wateropname (planten) - sensorische evaluatie - moleculaire fysica - levensmiddelenfysica - bread - brittleness - water activity - water uptake - sensory evaluation - molecular physics - food physics
    The aim of the PhD study on molecular mobility was to analyse the molecular grounds for the deterioration of crispy/crunchy characteristics of cellular solid foods. A fresh baguette for example has a crispy crust and a moist and soft interior. Moisture migrates from crumb to crust. Already at a water content of 9% (crumb contains around 45% water) the crispness of the crust decreases. During the study methods were developed to measure the speed of water uptake to test different ingredients on their potential to prolong crispness. Also the glass transition (which means an increase in mobility of the protein and starch molecules in the crust) and its relation with sensorial loss of crispness was investigated. The history of the crust in terms of water content and water activity as well as the morphology of the crust was found to be important for crispness and crispness retention.
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