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See detailThe swelling behaviour of wheat starch granules during isothermal and non-isothermal treatments
Malumba Kamba, Paul ULg; Jacquet, Nicolas ULg; Delimme, Guy ULg et al

in Journal of Food Engineering (2013), 114(2), 199-206

The size of wheat starch granules was measured during isothermal and non-isothermal treatments and fitted using mathematical models in order to elucidate the time–temperatures dependence of the swelling ... [more ▼]

The size of wheat starch granules was measured during isothermal and non-isothermal treatments and fitted using mathematical models in order to elucidate the time–temperatures dependence of the swelling phenomenon and to improve our understanding of the mechanism followed by granules during gelatinization. Upon the onset temperature of gelatinization, starch granules size increase rapidly and tend to reach equilibrium values that depend on the temperature and heating rate applied. The most accurate fitting of granule size observed overall isothermal treatments was obtained with the third-order kinetic and the Weibull empirical models. The activation energy of swelling calculated for isothermal treatment varied between 41 and 318 kJ mol 1, depending on the mathematical model considered. Therefore, without a consensus on the mechanism and order of reaction followed during gelatinization, the meaningful of kinetic parameters calculated using mathematical models seems highly questionable. During non-isothermal treatments at lower heating rate, it seems like a limitation of the swelling capacity of granules was induced. This phenomenon was attributed to restructuration occurred inside of granules. So, forecasting the swelling behaviour of starch granules during non-isothermal treatment has to consider both the time–temperature and the heating rate applied. [less ▲]

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See detailInfluence of drying and hydrothermal treatment of corn on the denaturation of salt-soluble proteins and color parameters
Odjo, Sylvanus; Malumba Kamba, Paul ULg; Dossou, Joseph et al

in Journal of Food Engineering (2012), 109(3), 561-570

The effect of heat treatments (drying and hydrothermal treatment) on the extractability of salt-soluble protein (SSP) was assessed using Promatest methodology for corn kernels heated between 60 C and 120 ... [more ▼]

The effect of heat treatments (drying and hydrothermal treatment) on the extractability of salt-soluble protein (SSP) was assessed using Promatest methodology for corn kernels heated between 60 C and 120 C. During drying, the evolution of the grain moisture content is fitted using the analytical solution of Fick equation developed by Crank (1979) for spherical material. The decrease of extractible salt-soluble protein during heating is forecasted using a first and a second order ordinary differential equation. It was found that temperature; moisture content and time of processing greatly influence the kinetic denaturation of SSP of corn kernels. The evolution of extractible SSP content of corn kernels during drying at high temperature is more correctly described with second order kinetic than with the first order kinetic reaction. The Hunterlab color parameters of corn also vary during drying. Lightness and color intensity decrease while yellowness, redness, chroma and hue angle increase through drying time. Most of these Hunterlab color parameters are highly correlated with the salt-soluble proteins content and therefore could be used as indicators of excessive heat treatment and denaturation of salt-soluble proteins in corn kernels [less ▲]

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See detailModelling dehydration and quality degradation of maize during fluidized-bed drying
Janas, Sébastien ULg; Boutry, Sébastien; Malumba Kamba, Paul ULg et al

in Journal of Food Engineering (2010), 100(3), 527-534

At harvest time, maize (Zea mays L.) has a moisture content too high to be stored, and has to be dried. To control the previous termdryingnext term impact on maize characteristics, it is necessary to ... [more ▼]

At harvest time, maize (Zea mays L.) has a moisture content too high to be stored, and has to be dried. To control the previous termdryingnext term impact on maize characteristics, it is necessary to accurately know the spatial distribution of temperature and moisture content in the kernel, and the kinetics of quality loss in relation to these two factors. To this end, a physical model of heat and mass transfer in a maize kernel was designed. The Fick and Fourier equations were solved by the finite element method (FEM). The real 3D geometry of maize was obtained by NMR imaging and then used to build the mesh needed for the FEM computations. The model correctly describes the evolutions of maize moisture and salt-soluble protein content during fluidized-bed previous termdryingnext term with a constant previous termdryingnext term air temperature between 50 °C and 100 °C. [less ▲]

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See detailMultifractal properties of pore-size distribution in apple tissue using X-ray imaging
Mendoza, Fernando; Verboven, Pieter; Ho, Quang Tri et al

in JOURNAL OF FOOD ENGINEERING (2010), 99(2), 206-215

The pore-size distribution (PSD) has an important influence on the complex gas transport phenomena (02 and CO(2)) that occur in apple tissue during storage under controlled atmosphere conditions. It ... [more ▼]

The pore-size distribution (PSD) has an important influence on the complex gas transport phenomena (02 and CO(2)) that occur in apple tissue during storage under controlled atmosphere conditions. It defines the apple tissue microstructure that is correlated to many other apple properties. In this article multifractal analysis (MFA) has been used to study the multiscale structure of the PSD using generalized dimensions in three varieties of apples (Jonagold, Greenstar, and Kanzi) based on X-ray imaging technology (8.5 mu m resolution). Tomographic images of apple samples were taken at two positions within the parenchyma tissue: close to the peel and near to the core. The images showed suitable scaling properties. The generalized dimensions were determined with an R(2) greater than 0.98 in the range of moment orders between -1 and +10. The variation of D(q) with respect to q and the shape of the multifractal generalized spectrum revealed that the PSD structure of apple tissue has properties close to multifractal self-similarity measures. Comparisons among cultivars showed that, in spite of the complexity and variability of the pore space of these apple samples, the extracted generalized dimensions from PSD were significantly different (p < 0.05). The generalized dimensions D(0), D(1), D(2), and the quantity D(0)-D(2) could be used to discriminate tissue samples from different positions or cultivars. Also, high correlations were found between these parameters and the porosity (R(2) >= 0.935). These results demonstrate that MFA is an appropriate tool for characterizing the internal pore-size distribution of apple tissue and thus may be used as a quantitative measure to understand how tissue microstructure affects important physical properties of apple. (C) 2010 Elsevier Ltd. All rights reserved. [less ▲]

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See detailMicrotomographic investigation of a yeast grain porous structure
Debaste, Frédéric; Léonard, Angélique ULg; Halloin, Véronique et al

in Journal of Food Engineering (2010), 97

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See detailInfluence of drying temperature on the wet-milling performance and the proteins solubility indexes of corn kernels
Malumba Kamba, Paul ULg; Janas, Sébastien ULg; Masimango, Thaddée et al

in Journal of Food Engineering (2009), 95

The effects of air drying temperature on the wet-milling performance and the proteins solubility indexes were investigated for corn kernels dried between 54°C and 130°C. It was observed that when the ... [more ▼]

The effects of air drying temperature on the wet-milling performance and the proteins solubility indexes were investigated for corn kernels dried between 54°C and 130°C. It was observed that when the drying temperature increases, the starch yield drops significantly. The gluten recovered increased abruptly for drying temperatures up to 80 C. The albumin, globulin and zein solubility indexes decreased continuously when corn drying temperatures increased. According to the temperatures used, the starch yield, the gluten recovered and the salt-soluble proteins solubility indexes were adjusted satisfactorily by using a two asymptotic logistic model. This model has the advantage of supplying information on the dynamic of the variation of described parameters. The solubility index of total salt-soluble proteins was shown to be a suitable indicator of the severity of the drying treatment in regard to the corn wet-milling performance. [less ▲]

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See detailFlow rate dependency of critical wall shear stress in a radial-flow cell
Detry, Jean G; Jensen, Bo Boye Busk; Sindic, Marianne ULg et al

in Journal of Food Engineering (2009), 92(1), 86-99

In the present work, a radial-flow cell was used to study the removal of starch particle aggregates from several solid substrates (glass, stainless steel, polystyrene and PTFE) in order to determine the ... [more ▼]

In the present work, a radial-flow cell was used to study the removal of starch particle aggregates from several solid substrates (glass, stainless steel, polystyrene and PTFE) in order to determine the critical wall shear stress value for each case. The particle aggregates were formed by aspersion of a water or ethanol suspension of starch granules on the surfaces. Depending on the substrate and on the suspending liquid, the aggregates differed in size and shape. Aggregate removal was studied at two flow rates. At the lower flow rate (Re-inlet = 955), the values of critical wall shear stress for the different surfaces suggested that capillary forces were, for all of them, playing an important role in aggregate adhesion since aqueous based aggregates were always more difficult to remove. At the higher flow rate (Re-inlet = 2016) the critical wall shear stress increased as a result of the change in the flow pattern in the vicinity of the aggregates and not because of changes in the type of particle adhesion. This raises the importance of the experimental conditions on assessing the critical wall shear stress since this parameter may not be always only directly related to the soil adhesion strength. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

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See detailSilo flow-pattern diagnosis using the tracer method
Job, Nathalie ULg; Dardenne, Albert; Pirard, Jean-Paul ULg

in Journal of Food Engineering (2009), 91(1), 118-125

The storage silo of a sugar refinery was designed by its manufacturer for a plug-flow pattern of sugar ingots in order to ensure effective drying of the sugar introduced at the top of the silo. Because of ... [more ▼]

The storage silo of a sugar refinery was designed by its manufacturer for a plug-flow pattern of sugar ingots in order to ensure effective drying of the sugar introduced at the top of the silo. Because of the excessive moisture content of the extracted ingots, the quality of flow within the silo was called into question. The silo flow-pattern was thus studied by introducing sugar lumps as a tracer at the top of the silo filled with ingots. The tracer weight percentage was measured at the outlet. Results show that the silo flow-pattern is not of the plug-flow type in its whole volume: after formation of a crater, only the central volume flows, while the outer residual volume remains motionless. The tracer test also enabled the detection of preferential flow patterns. The tracer method was found to be quite useful as a diagnosis method for such a device in normal functioning. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

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See detailUltrasonic internal defect detection in cheese
Leemans, Vincent ULg; Destain, Marie-France ULg

in Journal of Food Engineering (2009), 90(3), 333-340

Different ultrasonic signals and detection techniques were used and compared to detect internal foreign bodies present in semi-soft cheeses. The signals were a pulse or a chirp and the detection was ... [more ▼]

Different ultrasonic signals and detection techniques were used and compared to detect internal foreign bodies present in semi-soft cheeses. The signals were a pulse or a chirp and the detection was carried out by using either correlation with a reference signal or a wavelet decomposition. The principle of the detection consisted in measuring the time of flight of the transmitted signals and of the echoes, the latter in the absence of foreign body should be the double of the former. The presence of a foreign object affected this pattern in several ways. In order to assess the method, a small plastic cylindrical object of 3 mm in diameter was introduced in one half of the cheese and was tested for detection, the second half being used as reference for the control cheese. The results showed that the two signals and the two detection methods were able to localise the transmitted signals and the echo from the opposite face of the cheese under all circumstances. For the foreign body detection, the correlation method gave superior results, in term of signal to noise ratio as well as in term of error rate, while the two signals gave similar results. The analysis of the mean and standard deviation of the signal to noise ratio of the object echo showed that some samples presented peak values close to those due to the noise. Nevertheless, the object was detected in 90% of the tests. There was no significant effect of temperature on the detection technique. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

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See detailThe role of sugar and fat in sugar-snap cookies: Structural and textural properties
Pareyt, Bram; Talhaoui, Faisal; Kerckhofs, Greet ULg et al

in JOURNAL OF FOOD ENGINEERING (2009), 90(3), 400-408

The impact of sugar (17.6-31.2%) and fat (8.7-15.8%) levels on cookie structure was studied. Cookie diameter increased and its height decreased with increasing sugar or fat levels. X-ray microfocus ... [more ▼]

The impact of sugar (17.6-31.2%) and fat (8.7-15.8%) levels on cookie structure was studied. Cookie diameter increased and its height decreased with increasing sugar or fat levels. X-ray microfocus computed tomography porosities and cell sizes increased with fat level, but cell size distribution, cell wall thickness and distribution were not affected by fat level, indicating that fat primarily incorporates air. In contrast, the sugar level influenced porosity, cell size, cell wall thickness and their relative distributions. Thus, the sucrose level, probably by affecting dough viscosity during baking, largely influences the baked cookie structure. Cell and cell wall anisotropy measurements indicated that the inn-or orientation of cells and cell walls probably depends on the horizontal spread behaviour, rather than oil the maximum cookie height and collapse. Finally, the surface cracking pattern was determined by sugar level, rather than by structural collapse at the end of baking. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

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See detailEffect of far-infrared radiation assisted drying on microstructure of banana slices: An illustrative use of X-ray microtomography in microstructural evaluation of a food product
Léonard, Angélique ULg; Blacher, Silvia ULg; Nimmol, Chatchai et al

in Journal of Food Engineering (2008), 85(1), 154-162

X-ray microtomography coupled with image analysis represents a non-destructive technique, which allows scanning an entire sample to obtain such information as total pore volume and pore size distribution ... [more ▼]

X-ray microtomography coupled with image analysis represents a non-destructive technique, which allows scanning an entire sample to obtain such information as total pore volume and pore size distribution without the need of serial cuts as in the case of scanning electron microscopy (SEM). The technique has been applied successfully to obtain reliable microstructural information of many products undergoing different physical and chemical processes. However, the technique has still found limited use in food processing. To illustrate the use of X-ray microtomography the technique was applied to investigate the effect of far-infrared radiation (FIR) assisted drying on microstructure of a food product viz. banana. Two representative drying techniques, i.e., low-pressure superheated steam drying (LPSSD) and vacuum drying (VACUUM) were tested. Banana slices were dried by LPSSD-FIR at two different temperatures (80 and 90 degrees C) at a fixed pressure of 7 kPa. The total pore volume and pore size distribution of dried banana slices were then determined using X-ray microtomography. The results were also compared with those of products dried by LPSSD without FIR. Far-infrared radiation was found to modify the structure of the dried bananas by increasing their final porosity. The same effect of FIR was also observed in the case of vacuum drying with FIR (VACUUM-FIR). An increase of the drying temperature was also found to globally lead to an increase in the final porosity of the products. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailSurvival and preservation after freeze-drying process of thermoresistant acetic acid bacteria isolated from tropical products of Subsaharan Africa
Ndoye, Bassirou; Weekers, Frederic; Diawara, Brehima et al

in Journal of Food Engineering (2007), 79(4), 1374-1382

Two thermoresistant acetic acid bacteria (TAAB) were previously isolated and selected for a sustainable development of vinegar fermentation in Subsaharan Africa. Their use as a starter culture in vinegar ... [more ▼]

Two thermoresistant acetic acid bacteria (TAAB) were previously isolated and selected for a sustainable development of vinegar fermentation in Subsaharan Africa. Their use as a starter culture in vinegar manufactures in such regions could reduce considerably water cooling expenses. For optimising biomass preservation, the effect of 20% w/w mannitol as cryoprotectant on the cells viability after freeze-drying process and during storage was evaluated. Results showed that freeze-dried cells could be conserved at 4 degrees C for at least 6 months without loss of viability. The main reasons were that cryoprotectant tends to lower the water activity (a(w)) and to maintain a temperature of product weaker than that of the glass transition temperature T-g. Furthermore, the heat resistance of freeze-dried cells during storage was all the more increased that strains were cryoprotected. In addition, intrinsically, an increase of saturated fatty acids with the temperature is the essential modification in the lipidome level of membrane cells when the fermentation occured at a temperature of 30 degrees C. Tolerance to heat during storage was significantly enhanced under such mechanisms. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailNumerical simulation of drying under variable external conditions: application to solar drying of seedless grapes
Bennamoun, Lyes ULg; Belhamri, Azeddine

in Journal of Food Engineering (2006), 76(2), 179-187

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See detailDevelopment of a multi-spectral vision system for the detection of defects on apples
Kleynen, Olivier; Leemans, Vincent ULg; Destain, Marie-France ULg

in Journal of Food Engineering (2005), 69(1), 41-49

A method to sort 'Jonagold' apples based on the presence of defects was proposed. A multi-spectral vision system including four wavelength bands in the visible/NIR range was developed. Multi-spectral ... [more ▼]

A method to sort 'Jonagold' apples based on the presence of defects was proposed. A multi-spectral vision system including four wavelength bands in the visible/NIR range was developed. Multi-spectral images of sound and defective fruits were acquired tending to cover the whole colour variability of this bicolour apple variety. Defects were grouped into four categories: slight defects, more serious defects, defects leading to the rejection of the fruit and recent bruises. Stem-ends/calyxes were detected using a correlation pattern matching algorithm. The efficiency of this method depended on the orientation of the stem-end/calyx according to the optical axis of the camera. Defect segmentation consisted in a pixel classification procedure based on the Bayes' theorem and non-parametric models of the sound and defective tissue. Fruit classification tests were performed in order to evaluate the efficiency of the proposed method. No error was made on rejected fruits and high classification rates were reached for apples presenting serious defects and recent bruises. Fruits with slight defects presented a more important misclassification rate but those errors fitted however the quality tolerances of the European standard. Considering an actual ratio of sound fruits of 90%, less than 2% of defective fruits were classified into the sound ones. (c) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailA Real-Time Grading Method Of Apples Based On Features Extracted From Defects
Leemans, Vincent ULg; Destain, Marie-France ULg

in Journal of Food Engineering (2004), 61(1),

This paper presents a hierarchical grading method applied to Jonagold apples. Several images covering the whole surface of the fruits were acquired thanks to a prototype grading machine. These images were ... [more ▼]

This paper presents a hierarchical grading method applied to Jonagold apples. Several images covering the whole surface of the fruits were acquired thanks to a prototype grading machine. These images were then segmented and the features of the defects were extracted. During a learning procedure, the objects were classified into clusters by k-mean clustering. The classification probabilities of the objects were summarised and on this basis the fruits were graded using quadratic discriminant analysis. The fruits were correctly graded with a rate of 73 %. The errors were found having origins in the segmentation of the defects or for a particular wound, in a confusion with the calyx end. [less ▲]

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See detailDesign and simulation of a solar dryer for agriculture products
Bennamoun, Lyes ULg; Belhamri, Azeddine

in Journal of Food Engineering (2003), 59(2-3),

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