Ann Schenk - Academia.edu (original) (raw)

Papers by Ann Schenk

Ist International Symposium on CFD Applications in Agriculture, 2013

ABSTRACT CFD models were used to investigate 1-MCP application to apple fruit stored in different... more ABSTRACT CFD models were used to investigate 1-MCP application to apple fruit stored in different bin materials. Cases included in the study are high density polyethylene (HDPE) plastic bins, HDPE plastic bins with plastic sheet covering and wooden bins of slightly-weathered oak. Experiments were conducted for validation of the models. The amount of 1-MCP adsorbed by fruits was similar in HDPE plastic bins and wooden bins, using a dose of of 1 μL L-1. The presence of wood significantly reduced the 1-MCP remaining inside the container. Simulation at reduced dosage indicated lower adsorbed 1-MCP in fruits in wooden bins than fruits in HDPE plastic bins. The relative proportion of wood or other 1-MCP adsorbing agents (other than fruits) in commercial storage rooms for apple is generally smaller than in this experiment and if 1-MCP levels are near the maximum rate recommended (1 μL L-1), it can be concluded that the scavenging effect may not create a serious concern.

Horticultural Science (HORTSCI)

The effects of several pre- and postharvest factors on apple cv. Braeburn browning disorder (BBD)... more The effects of several pre- and postharvest factors on apple cv. Braeburn browning disorder (BBD) incidence using a nine-factor experimental design has been investigated. The design allowed the determination of the effects of single factors as well as their interaction with growing season and storage time. BBD increased in severity with storage duration. BBD incidence was reduced with calcium and potassium fertilizers application, while it was increased when triazoles were used. Delayed controlled atmosphere (DCA) application resulted in less BBD in storage, while treatment with 1-methylcyclopropene (1-MCP) increased BBD incidence. More BBD was observed in fruit stored at above optimal CO2 levels. BBD incidence was increased when O2 concentration in CA was increased from 1 kPa to 3 kPa (optimum CA) or 6 kPa. Finally, the various factors showed a different effect for different growing seasons and storage time. These findings suggest a possible mechanism for the development of BBD. Fu...

Article in a professionally oriented journal. Flanders, Belgium.

Article in a professionally oriented journal. Flanders, Belgium.

Article in a professionally oriented journal. Flanders, Belgium.

Food and Bioprocess Technology, 2015

ABSTRACT The storage potential of apples highly depends on the maturity at harvest. Optical metho... more ABSTRACT The storage potential of apples highly depends on the maturity at harvest. Optical methods have been proposed to measure maturity in a fast, reliable and non-destructive way. However, the signal is often composed of photons with different penetration depths into the material. An attempt to separate these photons might result in more precise correlations with quality attributes, as these could relate to a specific layer/depth into the sample. Therefore, a Vis/NIR spatially resolved laser reflectance setup was used, combining a supercontinuum laser and a monochromator to illuminate samples with a monochrome focused beam in the 550–1000 nm wavelength range. A panchromatic camera was used to obtain diffuse reflectance profiles at each wavelength. In the period starting 50 days before until 11 days after commercial harvest, 320 Braeburn apples were measured. Partial least squares regression models were developed to relate apple maturity/quality to the diffuse reflectance spectra at different distances from the illumination point. The effect of detector size (spatial bandwidth) was also evaluated. A bandwidth of 0.82 mm in combination with a parameter specific illumination-detection distance, gave the best results. Using an internal test set, an R 2 of prediction of 0.98 and 0.93, and a ratio of prediction to performance (RPD) of 5.84 and 3.42, predicting, respectively, the Streif index and starch conversion values was obtained. The predictions of soluble solids content (SSC) (R 2 of 0.81; RPD of 2.04) and firmness (R 2 of 0.65; RPD of 1.66) were less accurate. Also, worse predictions were obtained using an external test set.

The purpose of this research was to model the kinetics of adsorption of 1-Methylcyclopropene (1-M... more The purpose of this research was to model the kinetics of adsorption of 1-Methylcyclopropene (1-MCP) in apple fruit and ‘non-target’ solid materials found in apple storage rooms. A distinction is made between diffusion into the material and the adsorption. The process was therefore described by Fick’s second law of diffusion of the gas through the pores of the material coupled with adsorption of the gas on the material’s binding sites. A finite element formulation of the model, describing the diffusion and adsorption mechanisms separately, was first developed. The values of the relevant parameters were estimated based on head space measurements of the decrease of 1-MCP in dedicated jars with the different materials. The diffusion coefficient, adsorption coefficient and concentration of active site in the various solids were determined and were in the order of 10-9m2/s, 101 m3 mol-1s-1 and 10-4 mol m-3 respectively. The model was validated with separate experimental data.

A heat and mass transfer model of apple fruit, based on reaction-diffusion equations, was develop... more A heat and mass transfer model of apple fruit, based on reaction-diffusion equations, was developed in Comsol Multiphysics (Comsol AB, Stockholm, Sweden) in the Matlab environment (The Mathworks Inc, Natick, USA). The model accepts as inputs the air temperature and the air velocity and predicts the product temperature and gas composition during different stages of the apple cold chain. Software code for predicting quality changes as a function of storage time, temperature and gas composition was written in Matlab. The software for the developed heat and mass transfer model was coupled to the software for the quality kinetic models: the predicted product temperatures and gas concentrations are applied as inputs to the different quality models, resulting in the prediction of apple quality under different temperature scenarios during storage. Simulation of changes in apple quality along a reference cold chain of apple in Belgium was carried out.

Postharvest Biology and Technology, 2007

Food and Bioprocess Technology, 2013

Abstract 1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to ... more Abstract 1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to delay ripening of fruits. 1-MCP (SmartFresh TM ) is applied in gaseous form (as a fumi- gant) in the cool store room. This paper uses a porous medium computational fluid dynamics model to numerically analyze the distribution of 1-MCP in cool store rooms for apple fruit. The effects of air circulation, room shape, and bin material were investigated. Dose calculation based on filling density was explored. The 1-MCP distribution in commercial cool stores,underroom cooling condition, was uniform irrespective of room shape. Rooms filled with fruit in wooden bins deplete 25 % more of the active substance than rooms filled with fruit in plastic bins. The calculated dose increases linearly with the amount of fruit in the cool store (filling density). Hence, this study suggests that dose prescription based on filling density is feasible. Keywords Fruit storage . Computational fluid dynamics . Diffusion – adsorption . Porous medium . Simulation

Food and Bioprocess Technology, 2013

Postharvest Biology and Technology, 2002

Postharvest Biology and Technology, 2013

ABSTRACT A permeation diffusion reaction model was applied to study the internal metabolic gas co... more ABSTRACT A permeation diffusion reaction model was applied to study the internal metabolic gas concentration inside apple fruit cv. ‘Kanzi’, ‘Jonagold’ and ‘Braeburn’ under controlled atmosphere (CA) conditions. A new criterion for the local O2 partial pressure beyond which there is a risk of cell death due to energy shortage was established as the local O2 partial pressure at which the oxidative ATP production becomes smaller than the maximal ATP production by fermentation. The Michaelis–Menten constant (Km,O2)(Km,O2) of oxidative respiration of apple tissue at 1 °C was within 0.13–0.17 kPa. At an O2 partial pressure of 0.46–0.78 times the Km,O2Km,O2 at a storage temperature of 1 °C, energy production for cell maintenance could be still secured in the three cultivars. The effect of natural variability of the maximal respiration rate and tissue gas diffusivities inside apple fruit was further studied by means of a Monte Carlo analysis. The simulations confirm that ‘Jonagold’ has large potential for storage under low O2 partial pressure, while ‘Kanzi’ and ‘Braeburn’ need to be stored at higher O2 partial pressure, in line with commercial practices.

Postharvest Biology and Technology, 2005

Mathematical and Computer Modelling of Dynamical Systems, 2004

ABSTRACT At present, mathematical models to predict the change of fruit quality attributes during... more ABSTRACT At present, mathematical models to predict the change of fruit quality attributes during apple maturation are deterministic and do not take into account the large natural variability of fruit quality attributes during the growing season. In this work a stochastic system approach was developed to describe the quality evolution of fruit. The basic dynamics of fruit quality evolution was represented by means of a stochastic system, in which the initial conditions and the model parameters were specified as random variables together with their probability density functions. A fundamental approach from stochastic systems theory was used to compute the propagation of the probability density functions of fruit quality attributes, which requires the numerical solution of the Fokker–Planck equation.

Journal of Food Engineering, 2013

Journal of Food Engineering, 2013

ABSTRACT 1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to ... more ABSTRACT 1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to delay ripening of fruits. The substance is applied in gas form (as a fumigant) in the storage room. In long term postharvest cold storage, fruit are placed in boxes (usually plastic or wooden bins) and stacked in a specific pattern. The top of the boxes are frequently covered with a thin plastic sheet for the purpose of reducing fruit moisture loss. Wooden boxes, card linings and other plant based porous materials used in bins have 1-MCP adsorption capacity. Plastic covers affect the airflow and with that the 1-MCP transport. In this paper, the influence of box materials and plastic cover on the distribution of 1-MCP in cold storage was studied using validated CFD models. Reynolds Average Navier–Stokes equations with the SST k–ω turbulence model were used to calculate the airflow. Diffusion, convection and adsorption of 1MCP were modeled to obtain 3D spatial and temporal distributions of 1-MCP inside a storage container, boxes and fruit. Time dependent profiles of calculated 1-MCP concentrations in the air in the container agreed well with measurement data. The plastic cover imposed no effect on the adsorption of 1-MCP. Wooden boxes notably adsorbed 1-MCP from the treatment atmosphere and may reduce the efficacy and uniformity of the treatment.

Journal of Food Engineering, 2012

Postharvest treatments of fruits in storage rooms using a fogging system is a recent development ... more Postharvest treatments of fruits in storage rooms using a fogging system is a recent development that offer a promising means to reduce the use of fungicides in the orchards, where ecological and environmental risks are higher than in the closed environment of the ...

Journal of Food Engineering, 2012

ABSTRACT To study the operation of postharvest storage fungicide fogging systems, a CFD model was... more ABSTRACT To study the operation of postharvest storage fungicide fogging systems, a CFD model was used. The modelling was based on an Eulerian–Lagrangian multiphase flow model. The effect of air circulation rate, circulation interval, bin design, stacking pattern and room design on deposition of fungicide was investigated. Air circulation rates of 0 m3 h�1 (no circulation), 2100 and 6800 m3 h�1 were used. Interval circulation of air was also investigated. The highest fungicide deposition was observed during fogging without circulation while the lowest deposition corresponded to fogging with the highest circulation rate. For the considered on/off combination times, the effect of circulation interval on overall average deposition and uniformity was not significantly different from the case of fogging with continuous air circulation. Bin with higher vent hole ratio and the presence of air deflector increased the amount and uniformity of deposition. Good agreement was found between measured and predicted results of deposition of fungicide particles.

Ist International Symposium on CFD Applications in Agriculture, 2013

ABSTRACT CFD models were used to investigate 1-MCP application to apple fruit stored in different... more ABSTRACT CFD models were used to investigate 1-MCP application to apple fruit stored in different bin materials. Cases included in the study are high density polyethylene (HDPE) plastic bins, HDPE plastic bins with plastic sheet covering and wooden bins of slightly-weathered oak. Experiments were conducted for validation of the models. The amount of 1-MCP adsorbed by fruits was similar in HDPE plastic bins and wooden bins, using a dose of of 1 μL L-1. The presence of wood significantly reduced the 1-MCP remaining inside the container. Simulation at reduced dosage indicated lower adsorbed 1-MCP in fruits in wooden bins than fruits in HDPE plastic bins. The relative proportion of wood or other 1-MCP adsorbing agents (other than fruits) in commercial storage rooms for apple is generally smaller than in this experiment and if 1-MCP levels are near the maximum rate recommended (1 μL L-1), it can be concluded that the scavenging effect may not create a serious concern.

Horticultural Science (HORTSCI)

The effects of several pre- and postharvest factors on apple cv. Braeburn browning disorder (BBD)... more The effects of several pre- and postharvest factors on apple cv. Braeburn browning disorder (BBD) incidence using a nine-factor experimental design has been investigated. The design allowed the determination of the effects of single factors as well as their interaction with growing season and storage time. BBD increased in severity with storage duration. BBD incidence was reduced with calcium and potassium fertilizers application, while it was increased when triazoles were used. Delayed controlled atmosphere (DCA) application resulted in less BBD in storage, while treatment with 1-methylcyclopropene (1-MCP) increased BBD incidence. More BBD was observed in fruit stored at above optimal CO2 levels. BBD incidence was increased when O2 concentration in CA was increased from 1 kPa to 3 kPa (optimum CA) or 6 kPa. Finally, the various factors showed a different effect for different growing seasons and storage time. These findings suggest a possible mechanism for the development of BBD. Fu...

Article in a professionally oriented journal. Flanders, Belgium.

Article in a professionally oriented journal. Flanders, Belgium.

Article in a professionally oriented journal. Flanders, Belgium.

Food and Bioprocess Technology, 2015

ABSTRACT The storage potential of apples highly depends on the maturity at harvest. Optical metho... more ABSTRACT The storage potential of apples highly depends on the maturity at harvest. Optical methods have been proposed to measure maturity in a fast, reliable and non-destructive way. However, the signal is often composed of photons with different penetration depths into the material. An attempt to separate these photons might result in more precise correlations with quality attributes, as these could relate to a specific layer/depth into the sample. Therefore, a Vis/NIR spatially resolved laser reflectance setup was used, combining a supercontinuum laser and a monochromator to illuminate samples with a monochrome focused beam in the 550–1000 nm wavelength range. A panchromatic camera was used to obtain diffuse reflectance profiles at each wavelength. In the period starting 50 days before until 11 days after commercial harvest, 320 Braeburn apples were measured. Partial least squares regression models were developed to relate apple maturity/quality to the diffuse reflectance spectra at different distances from the illumination point. The effect of detector size (spatial bandwidth) was also evaluated. A bandwidth of 0.82 mm in combination with a parameter specific illumination-detection distance, gave the best results. Using an internal test set, an R 2 of prediction of 0.98 and 0.93, and a ratio of prediction to performance (RPD) of 5.84 and 3.42, predicting, respectively, the Streif index and starch conversion values was obtained. The predictions of soluble solids content (SSC) (R 2 of 0.81; RPD of 2.04) and firmness (R 2 of 0.65; RPD of 1.66) were less accurate. Also, worse predictions were obtained using an external test set.

The purpose of this research was to model the kinetics of adsorption of 1-Methylcyclopropene (1-M... more The purpose of this research was to model the kinetics of adsorption of 1-Methylcyclopropene (1-MCP) in apple fruit and ‘non-target’ solid materials found in apple storage rooms. A distinction is made between diffusion into the material and the adsorption. The process was therefore described by Fick’s second law of diffusion of the gas through the pores of the material coupled with adsorption of the gas on the material’s binding sites. A finite element formulation of the model, describing the diffusion and adsorption mechanisms separately, was first developed. The values of the relevant parameters were estimated based on head space measurements of the decrease of 1-MCP in dedicated jars with the different materials. The diffusion coefficient, adsorption coefficient and concentration of active site in the various solids were determined and were in the order of 10-9m2/s, 101 m3 mol-1s-1 and 10-4 mol m-3 respectively. The model was validated with separate experimental data.

A heat and mass transfer model of apple fruit, based on reaction-diffusion equations, was develop... more A heat and mass transfer model of apple fruit, based on reaction-diffusion equations, was developed in Comsol Multiphysics (Comsol AB, Stockholm, Sweden) in the Matlab environment (The Mathworks Inc, Natick, USA). The model accepts as inputs the air temperature and the air velocity and predicts the product temperature and gas composition during different stages of the apple cold chain. Software code for predicting quality changes as a function of storage time, temperature and gas composition was written in Matlab. The software for the developed heat and mass transfer model was coupled to the software for the quality kinetic models: the predicted product temperatures and gas concentrations are applied as inputs to the different quality models, resulting in the prediction of apple quality under different temperature scenarios during storage. Simulation of changes in apple quality along a reference cold chain of apple in Belgium was carried out.

Postharvest Biology and Technology, 2007

Food and Bioprocess Technology, 2013

Abstract 1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to ... more Abstract 1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to delay ripening of fruits. 1-MCP (SmartFresh TM ) is applied in gaseous form (as a fumi- gant) in the cool store room. This paper uses a porous medium computational fluid dynamics model to numerically analyze the distribution of 1-MCP in cool store rooms for apple fruit. The effects of air circulation, room shape, and bin material were investigated. Dose calculation based on filling density was explored. The 1-MCP distribution in commercial cool stores,underroom cooling condition, was uniform irrespective of room shape. Rooms filled with fruit in wooden bins deplete 25 % more of the active substance than rooms filled with fruit in plastic bins. The calculated dose increases linearly with the amount of fruit in the cool store (filling density). Hence, this study suggests that dose prescription based on filling density is feasible. Keywords Fruit storage . Computational fluid dynamics . Diffusion – adsorption . Porous medium . Simulation

Food and Bioprocess Technology, 2013

Postharvest Biology and Technology, 2002

Postharvest Biology and Technology, 2013

ABSTRACT A permeation diffusion reaction model was applied to study the internal metabolic gas co... more ABSTRACT A permeation diffusion reaction model was applied to study the internal metabolic gas concentration inside apple fruit cv. ‘Kanzi’, ‘Jonagold’ and ‘Braeburn’ under controlled atmosphere (CA) conditions. A new criterion for the local O2 partial pressure beyond which there is a risk of cell death due to energy shortage was established as the local O2 partial pressure at which the oxidative ATP production becomes smaller than the maximal ATP production by fermentation. The Michaelis–Menten constant (Km,O2)(Km,O2) of oxidative respiration of apple tissue at 1 °C was within 0.13–0.17 kPa. At an O2 partial pressure of 0.46–0.78 times the Km,O2Km,O2 at a storage temperature of 1 °C, energy production for cell maintenance could be still secured in the three cultivars. The effect of natural variability of the maximal respiration rate and tissue gas diffusivities inside apple fruit was further studied by means of a Monte Carlo analysis. The simulations confirm that ‘Jonagold’ has large potential for storage under low O2 partial pressure, while ‘Kanzi’ and ‘Braeburn’ need to be stored at higher O2 partial pressure, in line with commercial practices.

Postharvest Biology and Technology, 2005

Mathematical and Computer Modelling of Dynamical Systems, 2004

ABSTRACT At present, mathematical models to predict the change of fruit quality attributes during... more ABSTRACT At present, mathematical models to predict the change of fruit quality attributes during apple maturation are deterministic and do not take into account the large natural variability of fruit quality attributes during the growing season. In this work a stochastic system approach was developed to describe the quality evolution of fruit. The basic dynamics of fruit quality evolution was represented by means of a stochastic system, in which the initial conditions and the model parameters were specified as random variables together with their probability density functions. A fundamental approach from stochastic systems theory was used to compute the propagation of the probability density functions of fruit quality attributes, which requires the numerical solution of the Fokker–Planck equation.

Journal of Food Engineering, 2013

Journal of Food Engineering, 2013

ABSTRACT 1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to ... more ABSTRACT 1-Methylcyclopropene (1-MCP) is a synthetic plant growth regulator used commercially to delay ripening of fruits. The substance is applied in gas form (as a fumigant) in the storage room. In long term postharvest cold storage, fruit are placed in boxes (usually plastic or wooden bins) and stacked in a specific pattern. The top of the boxes are frequently covered with a thin plastic sheet for the purpose of reducing fruit moisture loss. Wooden boxes, card linings and other plant based porous materials used in bins have 1-MCP adsorption capacity. Plastic covers affect the airflow and with that the 1-MCP transport. In this paper, the influence of box materials and plastic cover on the distribution of 1-MCP in cold storage was studied using validated CFD models. Reynolds Average Navier–Stokes equations with the SST k–ω turbulence model were used to calculate the airflow. Diffusion, convection and adsorption of 1MCP were modeled to obtain 3D spatial and temporal distributions of 1-MCP inside a storage container, boxes and fruit. Time dependent profiles of calculated 1-MCP concentrations in the air in the container agreed well with measurement data. The plastic cover imposed no effect on the adsorption of 1-MCP. Wooden boxes notably adsorbed 1-MCP from the treatment atmosphere and may reduce the efficacy and uniformity of the treatment.

Journal of Food Engineering, 2012

Postharvest treatments of fruits in storage rooms using a fogging system is a recent development ... more Postharvest treatments of fruits in storage rooms using a fogging system is a recent development that offer a promising means to reduce the use of fungicides in the orchards, where ecological and environmental risks are higher than in the closed environment of the ...

Journal of Food Engineering, 2012

ABSTRACT To study the operation of postharvest storage fungicide fogging systems, a CFD model was... more ABSTRACT To study the operation of postharvest storage fungicide fogging systems, a CFD model was used. The modelling was based on an Eulerian–Lagrangian multiphase flow model. The effect of air circulation rate, circulation interval, bin design, stacking pattern and room design on deposition of fungicide was investigated. Air circulation rates of 0 m3 h�1 (no circulation), 2100 and 6800 m3 h�1 were used. Interval circulation of air was also investigated. The highest fungicide deposition was observed during fogging without circulation while the lowest deposition corresponded to fogging with the highest circulation rate. For the considered on/off combination times, the effect of circulation interval on overall average deposition and uniformity was not significantly different from the case of fogging with continuous air circulation. Bin with higher vent hole ratio and the presence of air deflector increased the amount and uniformity of deposition. Good agreement was found between measured and predicted results of deposition of fungicide particles.