Thijs Defraeye

Empa - Swiss Federal Laboratories for Materials Science and Technology | Empa · Department Materials meet Life

Optimising ventilated packaging for fresh horticultural produce will play a key role in making future food cold chains more energy-smart and resource-efficient in a cost-effective way. Package performance analysis currently lacks an integrated approach for simultaneous and quantitative evaluation of product cooling rate, box ventilation, product qu...

During respiratory quotient based dynamic controlled atmosphere (RQ-DCA) storage, the oxygen concentration in the room is reduced until the RQ measured in the air of the room (RQair) increases above a predefined threshold. This increase in RQ indicates an increased extent of fermentation within the fruit. Because of internal gas gradients, the oxyg...

Soft fruits like strawberries are highly perishable and susceptible to postharvest decay caused by fungal infestation. Mold growth is favored by elevated temperatures in the cold chain or when water vapor condenses in the packaging induced by temperature fluctuations at high relative humidity. Optimal packaging for these products is required to imp...

Transdermal fentanyl patches are an effective alternative to the sustained release of oral morphine for chronic pain management. Due to the narrow therapeutic range of fentanyl, the concentration of fentanyl in the blood needs to be carefully monitored. Only then can effective pain relief be achieved while avoiding adverse effects such as respirato...

Currently, there are differences in the quality loss between individual fruit upon arrival at retail. These differences in fruit quality stem from pre-harvest biological variability between individual fruit at harvest and postharvest variations in hygrothermal conditions between refrigerated shipments. The impact of these pre-harvest biological and...

Background Thousands of refrigerated containers transport fresh fruit and vegetables to feed the world yearly. These containers should preserve fresh-food quality as uniformly as possible throughout the cargo. Scope and approach Several simulation studies have suggested the presence of a systematic hot spot in these containers near the supply-air...

SARS-CoV-2 spreads via droplets, aerosols, and smear infection. From the beginning of the COVID-19 pandemic, using a facemask in different locations was recommended to slow down the spread of the virus. To evaluate facemasks' performance, masks' filtration efficiency is tested for a range of particle sizes. Although such tests quantify the blockage...

Large quantities of fresh produce are exported every year to international markets across the world using refrigerated freight containers (RFCs). However, many packaging systems are legacy designs for older shipping technologies. For fruit, more than 10% of the RFC floor area is unused by current packaging systems, and designs often do not facilita...

Horticultural products are prone to high postharvest losses due to their perishability and susceptibility to drivers for food decay, including temperature. A narrow temperature window must typically be maintained to prevent accelerated decay and, at the same time, thermal damage, such as chilling injury. Food simulators or so-called biophysical foo...

Fentanyl transdermal therapy is a suitable treatment for moderate-to-severe cancer-related pain. Patients show inter-individual drug uptake behavior, which leads to a different response to the therapy. This study aims to determine the effect of different physiological features of the patients on the pain relief achieved with the therapy. Therefore,...

Supply chains of fresh fruit must maintain a very narrow window of hygrothermal conditions after harvest. Any excursions outside this range can markedly lower the consumer acceptability of the fruit. However, the loss in fruit quality and marketability largely remains invisible to stakeholders throughout the supply chain. Here we developed a physic...

In light of increasing public pressure, retailers strive to remove plastic packaging as much as possible from fresh fruits and vegetables to reduce the environmental impacts along their supply chains. Plastic packaging, however, also has an important protective function, similar to the fruit's peel. For cucumbers transported from Spain and sold in...

Horticultural packaging is a critical component of the cold chain and influences both the preservation of fresh produce quality as well as the efficiency of cold chain operations. Development and optimisation of packaging designs is a multidisciplinary task. Nevertheless, knowledge and expertise are often not transferred between domain specialists....

In the postharvest chain of fresh horticultural produce, it is often challenging to quantify how much potential measures improve the supply chain. This study compares and quantifies the impact of the different measures in preserving the quality of fresh produce in the cold chain. We employed physics-based digital twins of fresh produce. This digita...

Plants modify the climate and provide natural cooling through transpiration. However, plant response is not only dependent on the atmospheric evaporative demand due to the combined effects of wind speed, air temperature, humidity, and solar radiation, but is also dependent on the water transport within the plant leaf-xylem-root system. These intera...

Controlling the hygrothermal conditions around fresh fruit and vegetables is vital for their preservation. Therefore, cold chain stakeholders often measure temperature along the supply chain of fresh produce. However, the temperature is typically monitored only in one segment of the entire cold chain, namely from the supplier until the distribution...

Electrohydrodynamic drying (EHDD) is an energy-efficient and non-thermal technique for dehydrating heat-sensitive biological materials, like fruits, vegetables, or medicinal plants. However, little is known about the relative contribution of the different dehydration mechanisms in EHDD. An accurate understanding of the impact of the different EHD-d...

Electrohydrodynamic (EHD) drying is a novel non-thermal drying method to dry heat-sensitive foods faster and with lower energy. Upscaling EHD drying to dry large amounts of food is the current challenge of this technology. In this regard, we quantify how successful a newly-proposed electrode configuration for EHD dryers is for drying commercial amo...

Drying processes reduce the amount of available essential nutrients in dried plant-based foods to a large extent compared to fresh produce. This reduction is much larger than the differences in the final quality of products dried using various processing parameters and, in most cases, different drying methods. This aspect is, however, rarely highli...

Electrohydrodynamic (EHD) drying is considered a highly efficient technology due to its ability to create powerful convective airflow with low energy consumption. EHD efficiency depends on multiple factors, such as voltage, current, environmental conditions, drying material, and electrodes geometry. This research is exploring the effect of collecti...

Electrohydrodynamic (EHD) drying is a promising technology to better preserve the nutritional content and sensory appeal of dried fruits and vegetables. To successfully scale up this technology, we need to rethink the current EHD dryer designs. There is also a significant potential to further enhance the nutritional content and sensory quality of t...

In light of increasing public pressure, retailers strive to remove plastic packaging as much as possible from fresh fruits and vegetables to reduce the environmental impacts along their supply chains. Plastic packaging, however, also has an important protective function, similar to the fruit's peel. For cucumbers transported from Spain and sold in...

Transdermal drug delivery systems are a key technology to administer drugs with a high first-pass effect in a non-invasive and controlled way. Physics-based modeling and simulation are on their way to become a cornerstone in the engineering of these healthcare devices since it provides a unique complementarity to experimental data and additional in...

Freezing is a standard method to preserve perishable agricultural products such as fruits and vegetables, which increases off-season availability. Nevertheless, freezing of plant tissue with high water content causes cellular damage by the formation of ice crystals. This damage leads to drip loss and decreased firmness, which then reduces the quali...

Solar drying is regarded as a less reliable process compared to continuous hot-air drying due to the intermittency of solar radiation. This problem is mitigated by equipping solar dryers with thermal storage, dehumidifier units, or auxiliary heating that enhances drying continuity during night time. In this study, we combine a mechanistic fruit dry...

Transdermal fentanyl patches are an effective alternative to the sustained-release of oral morphine for chronic pain treatment. Due to the narrow therapeutic range of fentanyl, the fentanyl concentration in the blood needs to be controlled carefully. Only then, effective pain relief can be reached while avoiding adverse effects such as respiratory...

Background Digital twins have advanced fast in various industries, but are just emerging in postharvest supply chains. A digital twin is a virtual representation of a certain product, such as fresh horticultural produce. This twin is linked to the real-world product by sensors supplying data of the environmental conditions near the target fruit or...

South Africa is the second-largest exporter of fresh citrus fruit, which is shipped to various distant markets for extended durations. Rising production quantities and increasingly more stringent phytosanitary requirements have placed considerable pressure on the logistics chain and the availability of precooling facilities. One solution to this ch...

Electrohydrodynamic (EHD) drying is a promising technology to better preserve the nutritional content and sensory appeal of dried fruits and vegetables. To successfully scale up this technology, we need to rethink the current EHD dryer designs. There is also a significant potential to further enhance the nutritional content and sensory quality of t...

Background. Digital twins have advanced fast in various industries, but are just emerging in postharvest supply chains. A digital twin is a virtual representation of fresh horticultural produce. This twin is linked to the real-world product by sensors supplying data of the environmental conditions near the target fruit or vegetable. Statistical and...

Electrohydrodynamic (EHD) drying is a novel technology, which appears to be beneficial for drying of heat-sensitive biomaterials with high moisture contents. Although numerous publications on EHD drying of fruits, vegetables, and other plant-based foods report high energy efficiency and superior product quality, the technology is still not commerci...

Convective drying of fruits leads to microstructural changes within the material as a result of moisture removal. In this study, an upscaling approach is developed to understand and identify the relation between the drying kinetics and the resulting microstructural changes of apple fruit, including shrinkage of cells without membrane breakage (free...

Convective drying of fruits leads to microstructural changes within the material as a result of moisture removal. In this study, an upscaling approach is developed to understand and identify the relation between the drying kinetics and the resulting microstructural changes of apple fruit, including shrinkage of cells without membrane breakage (free...

Electrohydrodynamic (EHD) drying is a novel drying technology, suitable for food and non-food materials. Most of the previously published research was conducted using a single needle/wire discharge electrode and a solid metal plate. This research was focused on the optimization of multiple needle discharge electrode using three types of needles and...

Drying is one of the most energy-intensive processes in the multiple industries, due to the high latent heat required to evaporate the water, which is often done by employing hot-air drying. Electrohydrodynamic (EHD) drying is an alternative, innovative drying technology with large potential for industrial application and a lower energy consumption...

Electrohydrodynamic (EHD) drying is a promising way to dehydrate food and other materials. The driving forces of the moisture removal from the product are, however, not yet completely understood. Therefore, a unique experimental setup with a grounded metal mesh collector was designed to separately evaluate the electrical and convective effects of E...

Food process modeling has matured with the development of multiscale, multiphase and multi-physics approaches. More comprehensive numerical tools and software platforms for improving insights and optimizing designs and processes have emerged. In the context of industrial digitalization and the advent of the Internet of Things, the concept of the di...

Proper postharvest temperature management is required to maintain the quality of fresh fruit such as pears. Understanding and evaluating the cooling process is crucial. In this context, numerical modelling techniques such as computational fluid dynamics (CFD) can provide complementary insights to experimental measurements. Fruit come in a variety o...

Refrigerated transport and storage of mango fruit are essential to maintain quality, reduce food waste and the associated embodied energy losses. Refrigeration is also key to enable successful transcontinental export to distant markets. To minimize the environmental impact of the cold chain and to optimize logistics, a better knowledge of the fruit...

Refrigeration is vital in fresh-produce supply chains for minimizing food losses. However, it requires energy and impacts the environment. To optimize the control and logistics of postharvest cold chains, we need to better identify trade-offs between maintaining fruit quality and reducing environmental impacts. Therefore, we propose a novel computa...

Optimizing fresh fruit supply chains is essential to reduce food losses and the associated environmental impact, as large amounts of energy and natural resources are embodied in these lost products. Proper refrigeration of these perishable items is essential here, and the used ventilated packaging design and cold chain scenario play a key role. Thi...

Single-use ventilated corrugated cardboard boxes are commonly used in the postharvest apple cold chain but pose significant challenges for optimizing cooling efficiency while reducing energy use. The cooling performance of typical corrugated boxes (standard type ‘Mk4’) was compared to that of an alternative reusable plastic crate (RPC). Cooling rat...

A good understanding of the microstructural changes due to dehydration is critical to optimize fruit drying processes. By using X-ray micro-computed tomography, we quantified the changes in porosity, pore diameter, cell sphericity, cell diameter and cell elongation of apple parenchyma tissue during multiple convective drying scenarios: natural conv...

Plant response is not only dependent on the atmospheric evaporative demand due to the combined effects of wind speed, air temperature, humidity, and solar radiation, but is also dependent on the water transport within the leaf-xylem-root system. Therefore, a detailed understanding of such dynamics is key to the development of appropriate mitigation...

This study presents a novel methodology to model the cooling processes of horticultural produce using realistic product shapes rather than commonly used simplified 3D shapes, such as spheres. Variable 3D apple and pear models were created by means of a validated geometric model generator based on X-ray computed tomography images. The fruit were ran...

Corrugated fibreboard packages (cartons) must support considerable mechanical loads during long term transport of fresh produce in refrigerated freight containers (RFCs). Fresh produce are transported under high relative humidity to reduce fruit moisture loss and preserve quality. However, these conditions can progressively reduce carton mechanical...

The influence of trees in urban areas is typically assessed using urban microclimate models. These models rely on wind tunnel experiments using small-scale tree models to verify and validate their predictions of the flow field. However, it is not known sufficiently to which extent small model trees used in wind tunnel studies can recreate the behav...

Electrohydrodynamic (EHD) drying is a promising, non-thermal drying technology, based on ionic wind generation between an emitter and a collector electrode. This simulation-based study evaluates impact of various emitter-collector configurations for EHD drying in order to assess their potential towards industrial upscaling. The conventional wire-to...

An accurate understanding of the dehydration kinetics of biological materials is essential to optimize their dehydration processes and to produce high-quality dried products. For a soft, cellular material like fruit, the underlying mass transport and deformation mechanisms at the cellular scale play a key role here. To improve our insight into the...

Electrohydrodynamic (EHD) drying is a non-thermal technology with promising perspectives to dehydrate heat-sensitive materials such as foods. With EHD drying, corona discharge is used to generate airflow, which enhances convective drying of the food product. Further development and upscaling of this technology are hindered by a lack of insight in b...