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Wageningen, Netherlands

Perdana J.,Food Process Engineering Group | Van Der Sman R.G.M.,Food and Biobased Research | Fox M.B.,NIZO food research | Boom R.M.,Food Process Engineering Group | Schutyser M.A.I.,Food Process Engineering Group
Journal of Food Engineering | Year: 2014

Knowledge about moisture diffusivity in solid matrices is a key for understanding drying behaviour of for example probiotic or enzymatic formulations. This paper presents an experimental procedure to determine moisture diffusivity on the basis of thin film drying and gravimetric analysis in a Dynamic Vapour Sorption (DVS) system. The extraction of moisture diffusivity is based on the "regular regime approach". The method was explored and verified for its assumptions. It provided insight in the effect of moisture content and temperature on moisture diffusivity. Moreover, it was found that moisture diffusivity in different carbohydrate systems was similar and decreased with moisture content. The latter was explained by similar molecular interactions in carbohydrate systems and formation of a percolating network at low moisture content that affects water mobility. Subsequently, measured moisture diffusivities were compared to model predictions based on the generalised Darken relation. It was found that predicted moisture diffusivities were in fair agreement with these, including the effect of moisture content and temperature on moisture diffusivity. At low moisture content the model overestimated the sensitivity of moisture diffusivity towards temperature. This was explained by the fact that the different water-solid interactions at lower moisture content (including relaxation behaviour in the glassy state) are not considered in the modelling. Finally, the methodology was successfully evaluated to other solid matrices such as glycerol, skimmed milk and casein, providing different moisture diffusivities as function of moisture content. © 2013 Elsevier Ltd. All rights reserved. Source


Perdana J.,Food Process Engineering Group | Fox M.B.,NIZO food research | Schutyser M.A.I.,Food Process Engineering Group | Boom R.M.,Food Process Engineering Group
Food Chemistry | Year: 2012

Enzymes are often dried for stability reasons and to facilitate handling. However, they are often susceptible to inactivation during drying. It is generally known that temperature and moisture content influence the enzyme inactivation kinetics. However, the coupled effect of both variables on enzyme inactivation over a broad temperature-moisture content range is still not well understood. Therefore, the inactivation of β-galactosidase in maltodextrin matrix is investigated using a newly developed method. An improved kinetic modelling approach is introduced, to predict the inactivation over a large range of temperature-moisture values. The model assumes a two-step inactivation mechanism involving reversible unfolding and irreversible inactivation. The model is able to describe the inactivation kinetics of β-galactosidase accurately, showing the temperature-dependent kinetic transition from reversible unfolding to irreversible inactivation limited. Application of this approach can provide immediate understanding of the effect of processing on enzyme inactivation and indicates the processes' critical points, which offers the possibility for optimisation. © 2011 Elsevier Ltd. All rights reserved. Source


Pelgrom P.J.M.,Food Process Engineering Group | Schutyser M.A.I.,Food Process Engineering Group | Boom R.M.,Food Process Engineering Group
Food and Bioprocess Technology | Year: 2013

Milling and subsequent air classification can be exploited for production of functional protein-enriched fractions from legumes and grains. Fracture behaviour is of large relevance to optimal disentanglement of protein and starch and is determined by the thermomechanical morphology of the seeds. Thermomechanical properties of peas were explored as a function of temperature and moisture content. Differential scanning calorimetry and thermal mechanical compression tests were carried out on pea protein and starch isolates yielding similar glass transition temperatures. Glass transition lines were successfully constructed using the Gordon-Taylor equation. Subsequently, three regions were identified in the state diagram; starch in the glassy and protein in the rubbery state, both components in the glassy state, and both components in the rubbery state. From single pea fracture experiments, it was found that the completely glassy peas fractured at a smaller critical compression distance compared to the peas in the other two regions. This can be explained by the elastic behaviour of the rubbery protein network, having a detrimental effect on the energy efficiency of milling processes. However, from scanning electron microscopy, it appeared that in rough fracture planes, visible when the protein was in the rubbery state, starch granules were present as more separate identities, suggesting increased disentanglement. Disentanglement of protein and starch by milling would then be optimal when protein is in the rubbery state. The latter can be achieved by milling at increased temperature and/or moisture content, which would be an attractive alternative. © 2012 Springer Science+Business Media New York. Source


Perdana J.,Food Process Engineering Group | Fox M.B.,NIZO food research | Schutyser M.A.I.,Food Process Engineering Group | Boom R.M.,Food Process Engineering Group
Food and Bioprocess Technology | Year: 2013

The inactivation of bioactive ingredients during spray drying is often matrix specific. Therefore, the design of new processes or the optimisation of existing spray drying processes is usually highly product specific and requires numerous experiments. Rapid experimentation methods that facilitate fast data generation are therefore desired. A novel method for drying single droplets to mimic spray drying is proposed. The approach involves droplet deposition on a hydrophobic flat surface followed by controlled drying. A heat and mass transfer model is applied to predict the drying history of the single droplets. The approach is successfully evaluated through studying the inactivation of β-galactosidase during drying. The heat and mass transfer model supplemented with inactivation kinetics provided reasonable prediction of the residual enzyme activity after drying. In addition, the inactivation kinetics could be directly extracted from single droplet experiments rather than using the kinetics from separate heating experiments. Finally, it was demonstrated that the inactivation kinetics found with the single-drop experiments could satisfactorily predict the residual activity of β-galactosidase dried with a laboratory-scale spray dryer. © 2012 The Author(s). Source


Wang J.,Food Process Engineering Group | De Wit M.,Food Process Engineering Group | Boom R.M.,Food Process Engineering Group | Schutyser M.A.I.,Food Process Engineering Group
Separation and Purification Technology | Year: 2015

Electrostatic separation is a novel and sustainable process for dry separation of food ingredients. To establish guidelines for electrostatic separation, well-defined charging and separation experiments of model mixtures prepared from wheat gluten and starch were carried out. For this a custom-built bench-scale electrostatic separator was developed. Charging behavior of mixtures improved with decreasing particle concentration and increasing gas flow rate, which was similar compared to charging behavior of single materials. However, the charge of mixtures was not simply the sum of the charge of single materials because particle-particle interactions also largely influence the charging. Separation efficiencies for mixtures were found lower than could be expected on the basis of behavior of single materials in the equipment. This was attributed to formation of agglomerates by particles having opposite charge, which was further confirmed by the observation that dispersibility of the mixtures was poorer than for the single materials. Agglomeration of particles during electrostatic separation can be minimized by using high gas flow velocity, low feed dosing and higher field strength. © 2015 Elsevier B.V. All rights reserved. Source

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