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.

    We have a manual that explains all the features 

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    The Role of Academic Spin-Offs Facilitators in Navigation of the Early Growth Stage Critical Junctures
    Khodaei, Hanieh ; Scholten, Victor E. ; Wubben, Emiel F.M. ; Omta, S.W.F. - \ 2020
    IEEE Transactions on Engineering Management (2020). - ISSN 0018-9391 - 13 p.
    Academic spin-off (ASO) - critical junctures - growth stages - stage-gate model

    Academic spin-off facilitators support high-tech academic spin-offs and help them to navigate various barriers and critical junctures during their growth stages. In this article we draw on stage-gate models, the path-dependency, and resource based view to identify start-ups' resource needs as perceived by both facilitators and by entrepreneurs. Using qualitative data based on in-depth interviews with 18 academic spin-off facilitators and nine spin-off founders, from three technical universities in the Netherlands, we explore the critical junctures and key support activities. The results show that founders appreciate milestones and direct interface regarding business support, business plan development, and legal support during the early growth stages. In all stages, in particular during the later stages, founders appreciate different type of network support (e.g., start-up network and industry) and when facilitators act as intermediaries to guide them in the network. This helps spin-offs to gain credibility and reach out to the market. This article adds to current research on academic facilitators and in particular incubators by providing a more comprehensive explanation for the low usage of the incubator's resources. By matching key resources and support activities that can navigate particular critical junctures, we try to promote the successful transition from one stage to the other. Our findings offer significant implications, both theoretical and practical, for academic entrepreneurship literature.

    Cracker shape modifies ad libitum snack intake of crackers with cheese dip
    Eck, Arianne Van; Stratum, Anouk Van; Achlada, Dimitra ; Goldschmidt, Benoît ; Scholten, Elke ; Fogliano, Vincenzo ; Stieger, Markus ; Bolhuis, Dieuwerke - \ 2020
    The British journal of nutrition (2020). - ISSN 0007-1145
    ad libitum snack intake - composite foods - oral processing behaviour - shape - snacks

    Food and energy intake can be effectively lowered by changing food properties, but little is known whether modifying food shape is sufficient to influence intake. This study investigated the influence of cracker shape and cheese viscosity on ad libitum intake of cracker-cheese combinations. Forty-four participants (13 males, 23±3 years, BMI 21±2 kg/m2) participated in four late afternoon snack sessions [2x2 randomized crossover design]. Iso-caloric crackers were baked into flat squares and finger-shape cylindrical sticks and combined with a cheese dip varying in viscosity. Approximately 80 crackers and 500 g cheese dip were served in separate large bowls. Participants consumed crackers with cheese dip ad libitum while watching a movie of 30 minutes. Dipping behaviour and oral processing behaviour were measured simultaneously by hidden balances under the cheese bowls and video recordings. Cracker intake (28±1 crackers) of cracker-cheese combinations was not influenced by cracker shape. Cheese intake of cracker-cheese combinations was 15% higher for flat squared than finger-shape crackers (131 kJ, p=0.016), as a larger amount of cheese was scooped with flat squared crackers (2.9±0.2 vs. 2.3±0.1 g cheese per dip, p<0.001), and showed higher eating rate and energy intake rate (p<0.001). Eating rate over snacking time decreased by reducing bite frequency (p<0.001) while cheese dip size remained fairly constant (p=0.12). Larger energy intake from condiments was facilitated by increased cracker surface, and this did not trigger earlier satiation. Changing food carrier surface may be a promising approach to moderate energy intake of often high energy dense condiments, sauces and toppings.

    Orsay virus infection reduces outcrossing behaviour of Caenorhabditis elegans males
    Sluijs, L. van; Liu, Jie ; Schrama, Mels ; Hamond, Sanne van; Vromans, Sophie ; Scholten, Marèl ; Žibrat, Nika ; Riksen, J.A.G. ; Sterken, M.G. ; Pijlman, G.P. ; Kammenga, J.E. - \ 2020
    Clustering of oil droplets in foods : Implications on rheology, tribology and sensory perception
    Fuhrmann, Philipp L. - \ 2020
    Wageningen University. Promotor(en): E. Scholten; M.A. Stieger, co-promotor(en): G. Sala. - Wageningen : Wageningen University - ISBN 9789463953542 - 214

    Many foods with a high palatability include significant quantities of fat. Fat influences next to the sensory perception and palatability also the microstructure of foods. It is thus challenging to reduce the fat content in many food items without negative impact on texture or perception. Fats and oils are mostly found as droplets in both solid and liquid matrices. Those droplets can be distributed homogeneously or inhomogeneously throughout a system. Previous research has shown that inhomogeneity (clustering) in the distribution of fat, in model systems, changes the fat related sensory perception and changes the mechanical properties. However, so far, the processes to obtain an inhomogeneous (clustered) fat distribution neither allow control over the process nor incorporation into foods.

    Therefore, this research aimed to understand the influence of fat phase inhomogeneity through controlled clustering of oil droplets on physical-chemical properties (rheology, tribology, cluster morphology), in-mouth behaviour and sensory perception of liquid o/w emulsions, emulsion gels and emulsion-filled gels. The findings of this research can help to control the microstructure of foods to design the physicochemical and sensory properties of foods. Further, the insights might help in reducing the fat content of foods without negative impact on mechanical properties and sensory perception. 

    Key conclusions/findings

    Oil droplet cluster size and interaction strength (within oil droplet clusters) can be controlled in liquid o/w emulsions, and semi-solid emulsion filled gels.

    Two methodologies provide good control over the size and interaction strength: hetero-aggregation and clustering with cross-linkers. For hetero-aggregation, the cluster size is controlled by the volume ratio of charged droplets and the strength by the charge of the emulsifier. For chemical clustering, the extent of clustering depends on cross-linker content. With regards to oil droplet inhomogeneity in gels, this process was controlled for overall strongly bound clusters (chemically and strong electrostatic interactions). An alternative approach is the incorporation of oil-rich or oil depleted filler particles into a gel matrix, introducing an inhomogeneity on a larger length scale.

    Inhomogeneity strongly affects rheological/mechanical properties and sensory perception of fat-related attributes.

    Clustering of oil droplets in o/w emulsions significantly increases viscosity due to entrapment of water in the oil droplet cluster leading to an increase in effective volume fraction and improved lubrication, allowing to enhance the perception of fat-related attributes. Emulsions with inhomogeneous oil droplet distribution were shown to be perceived as more thick and creamy. In gels, inhomogeneity mainly affects the modulus but can make gels also more brittle. If strong cluster interactions are present, graininess perception is enhanced. The effects on sensory perception in gels are less distinct. When taking increases in gel stiffness and brittleness into consideration, clustering in gels can be used to reduce the overall fat content. 

    Tribological characterisations of fat containing foods correlate to their sensory properties but depend on the presence of saliva

    When taking interactions between emulsions and saliva into account, tribological parameters correlate stronger with fat-related perception, then without saliva. We developed a new tribological setup to measure the friction properties of intact foods and boli samples.

    Material properties of emulsion gels can be directed by designing droplet-droplet interactions

    The rheological properties at small and large deformations of emulsion gels can be designed to vary between soft glassy and gel-like materials, by increasing the interaction strength between oil droplets.

    Overall, we conclude that by changing the oil droplet distribution in foods and the droplet-droplet interactions, the microstructure, physicochemical and sensory properties can be changed controllably.

    Combine nicely, consume wisely : The role of single food properties in oral processing behavior, intake and sensory perception of composite foods
    Eck, Arianne van - \ 2020
    Wageningen University. Promotor(en): V. Fogliano; M. Stieger, co-promotor(en): E. Scholten. - Wageningen : Wageningen University - ISBN 9789463953467 - 241

    Consumers frequently combine two or more single foods within one bite; for example bread with spread or vegetables with dressing. Such food pairings are called composite foods. This research investigates the effects of food properties on oral processing behavior, intake and sensory perception of composite foods.

    Results show that eating behavior of composite foods can be modified by relatively small changes in single food properties. In addition, sensory perception of composite foods is complex, as interactions between foods in mouth imply significant changes in sensory perception. Consequently, consumer sensitivity to discriminate between foods is reduced when a food is assessed together with an accompanying food.

    This thesis provides new insights into how structural transitions of foods contribute to intake and perception of composite foods. This is of particular interest in the design of healthy or environmentally friendly foods, in which assuring excellent sensory quality still poses a challenge.

    Koeien zijn kringloopdieren: Nederlandse landbouw wil inzetten op kringlooplandbouw
    Scholten, Martin - \ 2020
    circular agriculture - feeds - animal health - soil management - technical progress - innovations
    Niet alles kan overal : Eindadvies over structurele aanpak op lange termijn
    Remkes, J.W. ; Dijk, J.J. van; Dijkgraaf, E. ; Freriks, A. ; Gerbrandy, G.J. ; Maij, W.H. ; Nijhof, A.G. ; Post, E. ; Rabbinge, R. ; Scholten, M.C.Th. ; Vet, L.E.M. - \ 2020
    Amersfoort : Adviescollege Stikstofproblematiek - 175
    Het Adviescollege Stikstofproblematiek heeft de opdracht gekregen de minister van Landbouw, Natuur en Voedselkwaliteit te adviseren over hoe om te gaan met de stikstofproblematiek in Nederland. Na het uitbrengen van het eerste advies ‘Niet alles kan’, het tussentijdse advies over ‘Bemesten en beweiden in 2020’ en het ‘Advies Luchtvaartsector’ is het Adviescollege van start gegaan met de tweede fase van de opdracht. Opdracht voor deze tweede fase betreft het adviseren over een structurele aanpak van de stikstofproblematiek op de lange termijn. Dit advies is verwoord in deze eindrapportage.
    Martin Scholten to be WUR's 'Man in Brussels'
    Scholten, Martin - \ 2020
    Alles over kringlooplandbouw met Martin Scholten | Food Hub Colleges
    Scholten, M.C.T. - \ 2020
    Wageningen : Wageningen University & Research
    circular agriculture - farmers - citizens - food policy - returns - climate - energy - agri-environment schemes - soil management - feeds - land-based
    Kringlooplandbouw is de toekomstvisie voor ons toekomstige voedselsysteem. Maar wat is het nou eigenlijk en wat is het niet? Martin Scholten van Wageningen Universiteit en Research vertelt je alles wat je moet weten over kringlooplandbouw. Als boer en als burger.
    Sensitivity of spinach seed germination to moisture is driven by oxygen availability and influenced by seed size and pericarp
    Magnée, Kim ; Scholten, O.E. ; Postma, J. ; Lammerts Van Bueren, E. ; Groot, S.P.C. - \ 2020
    Seed Science and Technology 48 (2020)1. - ISSN 0251-0952 - p. 117 - 131.
    germination, moisture, oxygen, pericarp, seed size, spinach, temperature
    Uniform seedling emergence is crucial for economically viable spinach (Spinacia oleracea) leaf production. However, non-uniform seed germination occurs due to variation in moisture sensitivity between and within spinach seed lots. To test moisture sensitivity, we developed a floating germination system with fixed distances between germination papers and the water table, so that moisture levels could be standardised. We tested germination performance of different cultivar seed lots, with one seed lot fractioned in different seed sizes, and of seeds with an intact, open or removed pericarp. At a high moisture level, smaller seeds germinated better than larger seeds, and seeds without a pericarp or with an open pericarp germinated better than intact seeds. Further, the pericarp of smaller seeds was thinner than the pericarp of larger seeds. A lower temperature or increased oxygen level resulted in higher germination rates for differently-sized seeds at high moisture levels. In conclusion, the sensitivity of spinach seed germination to moisture is influenced by seed size, hence pericarp thickness and intactness, and is driven by the oxygen availability to the seed embryo. To determine the full germination potential of spinach seed lots, we recommend a standardised low moisture level in addition to a temperature of 15 or 20°C.
    Uncovering friction dynamics using hydrogel particles as soft ball bearings
    Rudge, Raisa E.D. ; De Sande, Jesse P.M. Van; Dijksman, Joshua A. ; Scholten, Elke - \ 2020
    Soft Matter 16 (2020)15. - ISSN 1744-683X - p. 3821 - 3831.

    Rolling ball bearings are widely known and applied to decrease friction between two surfaces. More recently, hydrogel-hydrogel tribopairs have also revealed good but rather complex lubrication properties. Here, we use hydrogels as ball bearings to elucidate that soft spherical particles have nontrivial rate-dependent lubrication behavior. Unlike Newtonian lubrication or dry solid friction, hydrogel particles in suspension transition through four frictional regimes as a function of sliding velocity. We relate the different regimes to the deformation of the particles at different gap sizes, which changes the effective contact area between the sliding surfaces. By systematically varying the particle characteristics and the surface properties of the sliding surfaces, we assign potential mechanisms for each of the different lubricating regimes as a function of velocity: (I) relatively high friction due to particle flattening and direct contact between interacting bodies (II) decrease of friction owing to the presence of rolling particles (III) large inflow of particles in a confined space leading to compressed particles and (IV) the formation of a thick lubricating layer. Using these suspensions with soft, deformable particles as a ball bearing system, we provide new insights into soft material friction with applications in emulsions, powders, pastes or other granular materials.

    Comparison of conditioned Latin hypercube and feature space coverage sampling for predicting soil classes using simulation from soil maps
    Ma, Tianwu ; Brus, Dick J. ; Zhu, Xing A. ; Zhang, Lei ; Scholten, Thomas - \ 2020
    Geoderma 370 (2020). - ISSN 0016-7061
    Calibration sampling - K-means - Random forest - Similarity-based predictive soil mapping - Simulated annealing - Soil sampling

    This study investigates sampling design for mapping soil classes based on multiple environmental features associated with the soil classes. Two types of sampling design for calibrating the prediction models are compared: conditioned Latin hypercube sampling (CLHS) and feature space coverage sampling (FSCS). Simple random sampling (SRS), which does not utilize the environmental features, is added as a reference design. The sample sizes used are 20, 30, 40, 50, 75, and 100 points, and at each sample size 100 sample sets were drawn using each of the three types of design. Each of these sample sets was then used to calibrate three prediction models: random forest (RF), individual predictive soil mapping (iPSM), and multinomial logistic regression (MLR). These sampling designs were compared based on the overall accuracy of predicted soil class maps obtained by these three prediction methods. The comparison was conducted in two study areas: Ammertal (Germany) and Raffelson (USA). For each of these two areas a detailed legacy soil class map is available. These soil class maps were used as references in a simulation study for the comparison. Results of both study areas show that on average FSCS outperforms CLHS and SRS for all three prediction methods. The difference in estimated medians of overall accuracy with CLHS and SRS was marginal. Moreover, the variation in overall accuracy among sample sets of the same size was considerably smaller for FSCS than that for CLHS. These results in the two study areas suggest that FSCS is a more effective sampling design.

    How addition of peach gel particles to yogurt affects oral behavior, sensory perception and liking of consumers differing in age
    Aguayo-Mendoza, Monica ; Santagiuliana, Marco ; Ong, Xian ; Piqueras-Fiszman, Betina ; Scholten, Elke ; Stieger, Markus - \ 2020
    Food Research International 134 (2020). - ISSN 0963-9969
    Chewing - Composite foods - Eating rate - Mechanical contrast - Oral processing - Particles - Texture perception

    Addition of particles to foods, such as fruit pieces to dairy products or vegetable pieces to soup, is a convenient approach to alter nutritional composition, appearance, perception and acceptance. The aim of this study was to investigate the effect of addition of peach gel particles to yogurt on oral behavior, sensory perception and liking of consumers differing in age. One homogeneous yogurt and seven yogurts with peach gel particles were prepared. The added peach gel particles varied in size, fracture stress, or concentration. Oral behavior of n = 62 healthy Dutch, young adults (21 ± 2 years) and n = 62 healthy Dutch elderly (70 ± 5 years) participants was characterized by video recordings. Yogurts’ sensory properties and liking were scored on nine-point scales. Elderly consumed yogurts with higher number of chews and longer consumption time leading to lower eating rate than young adults. Addition of particles, regardless of characteristics, increased number of chews, consumption time, and decreased eating rate up to 60% for both consumer groups, with an average decrement of 110 g/min for young and of 63 g/min for elderly consumers. With increasing peach gel hardness and concentration, the number of chews and consumption time increased while eating rate decreased. Peach gel particle size did not affect oral behavior. Sensory perception of yogurts with added peach gel particles was similar for healthy young adult and healthy elderly. Only small differences in sensory perception were observed between the young adults and elderly for flavor attributes, crumbliness, juiciness, and perceived particle size. Similarly, minor differences in liking of a few yogurts with peach pieces were observed between both consumer groups. Thus, healthy ageing seems to affect sensory perception of semi-solid foods to a limited extent only. We conclude that changes in food texture by addition of particles can be used as a strategy to steer eating rate and potentially impact food intake of young adult and elderly consumers while maintaining or enhancing food palatability. Additionally, particle characteristics can be modified to target specific consumer groups that might differ in eating capabilities.

    Influence of clustering of protein-stabilised oil droplets with proanthocyanidins on mechanical, tribological and sensory properties of o/w emulsions and emulsion-filled gels
    Fuhrmann, Philipp L. ; Sala, Guido ; Scholten, Elke ; Stieger, Markus - \ 2020
    Food Hydrocolloids 105 (2020). - ISSN 0268-005X
    Flow behaviour - Gel properties - Oil droplet clustering - Sensory perception

    This study aimed to determine the effect of clustering of protein-stabilised oil droplets with proanthocyanidins on mechanical, tribological and sensory properties of o/w emulsions and emulsion-filled gels. Whey protein-stabilised oil droplets in o/w emulsions were crosslinked with proanthocyanidins, which led to the controlled formation of dense clusters of strongly-interacting oil droplets, in a size range from 2 to 110 μm. With increasing degree of clustering of oil droplets, the viscosity of o/w emulsions increased by up to three orders of magnitude. Clustering of oil droplets decreased friction coefficients. Clustering led to an increase in perceived creaminess, coating and thickness intensity. The changes in fat-related sensory perception were an interplay of both flow- and friction behaviour. In emulsion-filled gelatine gels, crosslinking of oil droplets increased Young's modulus and decreased fracture strain and stress. With increasing cluster size, gels were perceived as harder and more grainy than emulsion-filled gels with non-clustered oil droplets. Creaminess of emulsion-filled gels did not increase upon clustering, as hardness also increased. When Young's modulus and perceived hardness of the gels were matched, gels containing clustered oil droplets tended to be perceived more creamy (not significant, p = 0.07) and significantly less watery than gels with non-clustered oil droplets. We relate these effects to the role of the emulsion droplets as structuring agents and an increase of the effective volume fraction by clustering of oil droplets. We conclude that clustering of protein-stabilised oil droplets with proanthocyanidins in o/w emulsions and emulsion-filled gels can be used to modify flow- and texture properties with positive effects on perception of fat-related sensory attributes.

    On the biosynthesis of auxin in the potato cyst nematode Globodera pallida
    Oosterbeek, Matthijs - \ 2020
    Firm characteristics, business environment, and performance of non-traditional agricultural SME exporters in Ghana
    Abban, Rita - \ 2020
    Wageningen University. Promotor(en): S.W.F. Omta; J.B.K. Aheto, co-promotor(en): V.E. Scholten. - Wageningen : Wageningen University - ISBN 9789463951012 - 198

    The contribution of Africa’s agricultural exports to world trade is less than 15%, although agriculture employs close to 60% of the work force in Africa and contributes on average 30% of gross domestic product. And the foreign revenues generated so far could not stimulate Africa’s further development. This is associated with the fact that Sub Saharan Africa (SSA) economies do not control world market prices, not much investments went into agriculture, and exports had little added value. In the last three decades, two strategic interventions by the Africa Union (AU) stand out, namely, improving the agriculture and agribusiness environment and diversification of export portfolios. This has been done in a number of ways, such as promoting export diversification (programmes/strategies) of non-traditional exports including agricultural exports. Ghana is no exception. In 2017, Ghana was listed in the World Development indicators as one of the best performing countries in Africa. In 2019, the International Monetary Fund (IMF) discussing the fastest growing SSA economies (per GDP growth %) stated Ghana (7.6%) as one of the top three, behind Ethiopia (8.5%) and Rwanda (7.8%).  So it is interesting to investigate how Ghana as one of the fastest growing SSA economy stimulates non-traditional agricultural exports (NTAE). The thesis focuses on small and medium enterprises (SMEs) because these constitute about 85.3% of all the NTAE companies.

    Though there is a pile of literature on Ghana’s export and SMEs, a theoretical gap still exists that needs to be explored to identify which factors at NTAE SME level itself, and the general business environment stimulate or hinder NTAE performance. The thesis starts out using the resource based view (RBV) but it acknowledge criticisms that the RBV is much focused on the internal capabilities of the firm. The criticisms of the RBV suggest that resources alone do not fully explain firm performance. The unexplained link can be better explained by application of other theoretical concepts. For this reason, the network and supply chain management (SCM) theories are used together with the RBV to better link resources and networks to performance.   A mixed method combining a quantitative and a qualitative approach has been used. The cross-sectional analyses are based on a sample of 152 NTAE SMEs located in the coastal, forest and savannah zones of Ghana, with 83% of the cases located in the coastal zone. Partial Least Squares Structural Equation Modelling (PLS SEM) analyses was applied.  The overall objective of this study is to identify the internal and external factors that facilitate or hinder NTAE SME export performance. This knowledge is used to provide suggestions towards a more effective policy framework to support NTAE SMEs’ operations. The thesis addresses the following central research question, within the theoretical context of the Resource Based View (RBV), Supply Chain Management (SCM), and network theories, which characteristics (specifically internal capabilities, resources and network relationships) of NTAE SMEs and their business environment are positively related to their export performance?

    The results show that performance is highest for those SMEs where the CEO has received tertiary level education and has export experience for over five years, exports directly (no use of traders/agents), makes extensive use of Ghana’s export institutions, use export contracts and is a member of SME associations. The network relations in the upstream processes are mostly based on relational embeddedness, based on trust (unwritten agreements) which has led to strong bonds over time. The scenario downstream is a little different. The networks are dense for NTAE SMEs who belonged to an association and sparse for those who did not. Export knowledge, corporate governance, product development, and professional and technical support are positively related to export performance. Interestingly, export mode is negatively related to export performance. The reason for this finding might be that in the case of Ghanaian NTAE SMEs the export mode is restricted.

    The general findings suggest that the macro state level policy is not adequately aligned with micro level policy/factors. Empirical results show that the upstream network linkages are poor between NTAE SMEs and extension services. Further the downstream network coordination is equally poor as either the certification processes/controls are not effective enough, export regulations are not strictly adhered to, leading loss of export market (reject of goods).  The weak institutional support also leads to that the NTAE SMEs are handicapped to build capacity to strengthen their resource bases. From an RBV perspective, NTAE SMEs have to build resources to strengthen their entrepreneurial and innovation capacity. This can be done through continuous innovation and safeguarding knowledge build up. It is crucial where there is/are no national sub-sector policy(s) and regulator(s) because chain operations are seriously affected increasing costs of coordination. Agribusiness financing is perceived to be inadequate, with urgings for more government prioritization to support this. The findings also suggest that export knowledge and good organization of the upstream supply chain relations will help NTAE SMEs to gain better performance when competing in international markets. The type of export product is a determining factor for downstream costs. Implications of the study suggest that NTAE SMEs could improve their social networks through building groups or associations for exporting with strong monitoring and enforcement of rules.

    Some policy intervention include encouraging public private partnerships where government shortfalls in NTAE support are identified. Incentives made available to private sector actors in agri supply chains would strengthen their resource base, so more services can be provided. The provision of export hubs in the forest and savannah zones, with the same facilities as those found in the coastal zone will ensure equitable spread of opportunities to NTAE SMEs. An alternative could be extending services through e-information, e-training and capacity building at reduced costs. It would be helpful for future studies to go more in-depth into the different sub-sectors using a longitudinal approach to support this cross sectional study. Also a larger sample of NTAE SMEs could be captured for the forest and savannah zones.

    Strategies to compensate for undesired gritty sensations in foods
    Santagiuliana, Marco ; Broers, Layla ; Marigómez, Inés Sampedro ; Stieger, Markus ; Piqueras-Fiszman, Betina ; Scholten, Elke - \ 2020
    Food Quality and Preference 81 (2020). - ISSN 0950-3293
    Composite foods - Grittiness - Microparticles - Multiparticulate - TDS - Texture perception

    This study investigated whether the addition of macroparticles or fat can be used to compensate for negative texture sensations in quark. Cellulose beads were added as model microparticles (1.5% w/w; average size: 263 µm) to quark (0% fat) to induce unpleasant gritty sensations. The addition of microparticles to quark significantly increased grittiness and dryness, while creaminess and liking decreased. Three strategies were explored to reduce the impact of unpleasant gritty sensations on consumer perception: two strategies involved the addition of macroparticles (granola or peach gel pieces); the third one consisted of increasing the fat content of the quark (4.4 and 8.8% w/w). For all three strategies, grittiness caused by microparticles did not significantly decrease when macroparticles or fat were present. Addition of peach gel pieces to quark with microparticles did not increase liking. When granola pieces were added to quark containing microparticles, liking increased significantly despite that grittiness was still perceived. Temporal Dominance of Sensations (TDS) revealed that addition of granola pieces caused prolonged dominance of positive, crunchy sensations and minimized dominance of negative, gritty sensations. The addition of fat did not lead to a significant increase in liking of quark, although when a medium amount of fat was added (4.4%), it also did not decrease liking significantly. This was probably due to an effective hedonic compensation triggered by more positive sensations (i.e. sweetness). We conclude that addition of crunchy granola pieces or fat can be used as strategies to shift and increase dominance of positive and liked attributes, leading to an increase of overall liking, although negative sensations (grittiness) caused by microparticles are still perceived. This approach could be used to compensate for undesired texture sensations in different types of foods, such as high protein foods.

    Natural and induced surface roughness determine frictional regimes in hydrogel pairs
    Rudge, Raisa E.D. ; Scholten, Elke ; Dijksman, Joshua A. - \ 2020
    Tribology International 141 (2020). - ISSN 0301-679X
    Asperity size - Friction - Hydrogels - Surface roughness

    Hydrogels display extremely complex frictional behavior with surprisingly slippery surfaces. We measure the sliding behavior of hydrogels submerged in water using a custom-made tribotool. Samples with an imposed surface roughness give two distinct frictional regimes. Friction coefficients in the first regime change with asperity sizes and Young's moduli. Under increased normal force, a second frictional regime emerges likely due to smoothening of asperities. Friction coefficients in the second regime remain constant across length scales of roughness and appear to be material specific. The hydrogel polymer network also directly influences the surface topography, and with that, the frictional behavior of hydrogels. We highlight the tribological importance of surface roughness at different length scales, which provides potential to engineer functional frictional behavior.

    Characterisation of friction behaviour of intact soft solid foods and food boli
    Fuhrmann, Philipp L. ; Aguayo-Mendoza, Monica ; Jansen, Bas ; Stieger, Markus ; Scholten, Elke - \ 2020
    Food Hydrocolloids 100 (2020). - ISSN 0268-005X

    Methodologies to quantify friction forces between soft solid foods or food boli and (model) oral surfaces are desired to better understand how changes in food properties during oral processing affect sensory perception. In this short communication, friction forces (FF) occurring between polydimethylsiloxane (PDMS) surfaces and intact soft solid foods/boli were quantified. As models for intact foods, we used gelatine gels varying in composition and particle size, and sausages were used as an example for real foods. Friction forces measured during the relative motion of intact foods against a rough PDMS surface (“oral surface”), strongly depended on the composition of the food. Friction forces were significantly lower for PDMS against emulsion-filled gels, than for PDMS against unfilled gels, likely due to the lubricating effect of released oil from the gel. Moreover, sausages, displayed significantly higher friction forces than gelatine gels when moving against the PDMS probe, presumably linked to differences in the surface of the foods. The friction forces observed for the PDMS probe moving against food boli were dependent on particle size and saliva quantity; boli with larger particle sizes showed significantly lower friction forces, whereas the addition of saliva to food boli first increased friction forces, but with increasing amount decreased the friction forces significantly. We conclude that the presented methodology is able to quantify the friction behaviour of intact soft solid foods and boli directly, taking into account (i) the effect of composition and added fillers, (ii) serum or oil release and (iii) bolus particle size.

    Effect of oil droplet inhomogeneity at different length scales on mechanical and sensory properties of emulsion-filled gels: Length scale matters
    Fuhrmann, P.L. ; Sala, G. ; Stieger, M. ; Scholten, E. - \ 2020
    Food Hydrocolloids 101 (2020). - ISSN 0268-005X
    Emulsion-filled gels - Fat-related perception - Oil distribution - Oil droplet clustering

    We studied the effect of inhomogeneity in oil droplet distribution at different length scales on the mechanical and sensory properties of emulsion-filled food gels. Two approaches were followed to obtain an inhomogeneous distributions at different length scales: (1) clustering of o/w-emulsions by hetero-aggregation and subsequent gelation to obtain inhomogeneity at μm-scale, and (2) incorporating particles of emulsion-filled gels into emulsion-filled gel matrices with a different volume fraction of oil droplets to obtain gel-in-gels with inhomogeneity at mm-scale. Upon clustering of oil droplets at μm-scale, the Young's modulus of the gels increased by up to 60%, whereas fracture stress and strain depended on emulsifier-matrix interactions. Clustering of oil droplets affected mainly the perception of texture-related sensory attributes, such as hardness, but did not significantly affect the perception of fat-related sensory attributes. Fat-related sensory attributes, such as creaminess and melting, were dominated by emulsifier matrix interactions. For gel-in-gels, the inhomogeneous distribution of oil droplets at mm-scale did not affect Young's modulus or fracture strain. The incorporation of particles decreased the fracture stress of the gels, independently of the droplet distribution. The perception of fat-related sensory attributes changed significantly. Oiliness was lower in samples with lower oil content in the outer phase of the gel than in the inner dispersed particles, whereas coating perception increased in samples in which the oil droplet distribution was inhomogeneous, independently on whether the outer phase or the inner gel particles contained a higher oil volume fraction. Creaminess was only slightly affected. We conclude that oil droplet clustering at μm-scale can be used to modify mechanical properties and texture-related perception of emulsion-filled gels, whereas inhomogeneity at mm-scale allows altering fat-related sensations. Sensory perception can be controlled by modifying the interactions between dispersed oil droplets and matrix using different emulsifiers and by incorporating inhomogeneity in the oil droplet distribution of emulsion-filled gels at different length scales.

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