Bart Nicolaï

KU Leuven | ku leuven

Tomato ( Solanum lycopersicum L.) is an important model plant whose fleshy fruit consists of well-differentiated tissues. Recently it was shown that these tissues develop hypoxia during fruit development and ripening. Therefore, we employed a combination of metabolomics and isotopic labeling to investigate the central carbon metabolic response of t...

Certain species in the Brassicaceae family exhibit high photosynthesis rates, potentially providing a valuable route toward improving agricultural productivity. However, factors contributing to their high photosynthesis rates are still unknown. We compared Hirschfeldia incana, Brassica nigra, Brassica rapa and Arabidopsis thaliana, grown under two...

Fruit mass and sugar content are important quality attributes of apple and pear fruit. During fruit growth, water and sugars accumulate as a result of the coordination of water and solid fluxes. This causes expansive growth driven by turgor pressure and controlled by cell mechanical properties. To analyse the effect of environmental conditions on f...

Fruit quality traits are determined to a large extent by their metabolome. The metabolite content of climacteric fruit changes drastically during ripening and postharvest storage and has been investigated extensively. However, the spatial distribution of metabolites and how it changes in time has received much less attention as fruit are usually co...

Chloroplasts movement within mesophyll (M) cells in C4 plants is hypothesized to enhance the CO2 concentrating mechanism (CCM), but this is difficult to verify experimentally. A three-dimensional (3-D) leaf model can help analyze how chloroplast movement influences the operation of CCM. The first volumetric reaction-diffusion model of C4 photosynth...

Current experimental design techniques for dynamical systems often only incorporate measurement noise, while dynamical systems also involve process noise. To construct experimental designs we need to quantify their information content. The Fisher information matrix is a popular tool to do so. Calculating the Fisher information matrix for linear dyn...

Botrytis cinerea causing gray mold and Penicillium expansum causing blue mold are the two major pathogens causing postharvest rots in pears. In this study, wounded pears were inoculated with these two pathogens and compared with wounded control and mock infected fruit. Lesion size and pear fruit aroma were monitored for 7 d at 20–22 °C. SIFT-MS and...

In developing countries like Ethiopia, where the time of harvesting coincides with the dry season, farmers cure onion bulbs naturally on the field. Field curing generally takes longer than artificial curing and results in more losses and reduced quality of the bulbs due to increased risks for infestations and uncontrolled suboptimal drying conditio...

Internal gas gradients in pear fruit during controlled atmosphere storage depend on the effective gas diffusivity of the tissue. The diffusivity varies over the fruit organ due to the heterogeneous tissue microstructure across the fruit. This study implemented effective diffusivity maps reflecting the heterogeneous structure to predict internal gas...

Adaptive plasticity requires an integrated suite of functional responses to environmental variation, which can include social communication across life stages. Desert locusts (Schistocerca gregaria) exhibit an extreme example of phenotypic plasticity called phase polyphenism, in which a suite of behavioral and morphological traits differ according...

With its increasing popularity, the need for optimal storage conditions of pointed cabbages becomes more important to meet the year-round demand. Storage of the pointed varieties, however, is more difficult compared to the traditional, round varieties and is limited to a few weeks in normal air. Pointed cabbages are more susceptible to quality loss...

The aim of this study was to determine postharvest loss of tomatoes along the postharvest supply chain in Northwest Ethiopia. The study was conducted on tomato fruits produced in three productive kebeles (Chimba, Gumara, and Kudmi) of Northwest Ethiopia following the FAO load tracking and sampling assessment method. Postharvest losses of tomatoes r...

Improper curing of onion bulbs leads to high losses during storage. The aim of curing is to seal the onion by drying its outer scales and the neck, limiting weight loss. A coupled heat and mass transfer model was established for the prediction of the moisture and temperature distribution inside onion bulbs. A finite element method was used for disc...

Dynamic models based on non-linear differential equations are increasingly being used in many biological applications. Highly informative dynamic experiments are valuable for the identification of these dynamic models. The storage of fresh fruit and vegetables is one such application where dynamic experimentation is gaining momentum. In this paper,...

Many studies have focused on the plant hormone ethylene because of its key role in controlling, among others, climacteric fruit ripening and fruit senescence. These processes can be controlled by applying 1-MCP, which tightly binds to the ethylene receptors thereby blocking the ethylene signaling pathway. 1-MCP is known to inhibit the action of eth...

There is considerable variability in the distribution of porosity within a fruit, hence non-destructive methods to map porosity of the entire fruit are essential. The objective of this study was to use X-ray computed tomography (CT) to map the porosity of ‘Fuji’ apple and help determine the extent to which different fruit morphological and microstr...

Oxygen (O2) diffusion affects respiration of fruit and vegetables and, thus, their behavior under controlled or modified atmosphere storage conditions. The effective gas diffusivity expresses, at a macroscopic level, the overall ability of the tissue to exchange gasses and is determined by the porous structure of the tissue. Variations of the tissu...

Pome fruit stored under a controlled atmosphere (CA) often suffers hypoxia due to the mismatch of O2 level in the storage rooms and the fruit’s O2 consumption. Fruit response-based O2 sensing and control could be an efficient approach to reduce the hypoxia-related physiological disorders and therefore increase the shelf life of stored fruit. This r...

The short shelf-life of dragon fruit is one of the inhibiting factors for the export of Vietnamese dragon fruit to distant markets. This study aimed at finding an optimal controlled atmosphere (CA) storage condition for dragon fruit by studying the effect of CA storage on fruit quality and its volatile organic compounds profile. Dragon fruit were s...

Bulk optical properties, in terms of absorption (μa) and reduced scattering coefficients (μ′s), can be used for the non-destructive monitoring of fruit quality during ripening. In this study, the performance of time-resolved (TRS) and spatially-resolved (SRS) spectroscopy were compared by analyzing ‘Braeburn’ apples over a 21 d period of ripening....

BACKGROUND The ripening of mango involves changes in texture, flavor, and color, affecting the quality of the fruit. Previous studies have investigated the physiology on the evolution of quality during ripening but only a few have looked at microstructural changes during ripening. None of them has provided an insight into the relationhip between 3‐...

A three-compartment non-equilibrium gas transport model of ‘Conference’ pear fruit under controlled atmosphere (CA) storage was developed. The model fruit tissue consists of cells, in which the concentrations of respiratory gasses can show gradients, and intercellular space, in which gasses are uniformly distributed. Non-equilibrium of gas concentr...

The application of controlled atmosphere and modified atmosphere packaging to extend the shelf life of dragon fruit requires insight into the respiration behaviour of the fruit under different storage conditions. To this end, this study focused on characterising the respiration kinetics of dragon fruit using a dynamic closed depletion system. An in...

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...

In developing apple fruit, metabolic compartmentation is poorly understood due to the lack of experimental data. Distinguishing subcellular compartments in fruit using non-aqueous fractionation has been technically difficult due to the excess amount of sugars present in the different subcellular compartments limiting the resolution of the technique...

After harvest, fruit remain metabolically active and continue to ripen. The main goal of postharvest storage is to slow down the metabolic activity of the detached fruit. In many cases, this is accomplished by storing fruit at low temperature in combination with low oxygen (O2) and high carbon dioxide (CO2) partial pressures. However, altering the...

Computational tools that allow in silico analysis of the role of cell growth and division on photosynthesis are scarce. We present a freely available tool that combines a virtual leaf tissue generator and a two-dimensional microscale model of gas transport during C3 photosynthesis. A total of 270 mesophyll geometries were generated with varying deg...

The success of long-term storage of apples under controlled atmosphere (CA) depends, amongst others, on the gas exchange properties of the fruit. As gas exchange is effectively dictated by the microstructure of the fruit, the ability to obtain microstructure data becomes critical to improve storage solutions. The current study complements scatterin...

Vibrational spectroscopy methods are widely investigated as fast and non-destructive alternatives for postharvest quality evaluation. As these methods measure spectral responses at a large number of wavebands correlated to the quality traits of interest, multivariate calibration equations have to be built to estimate the quality traits from the acq...

Fruit that is stored in sub-optimal controlled atmosphere (CA) condition is susceptible to internal disorders and off-flavours. Understanding spatial variation in fruit respiration and gas exchange in the storage environment may aid in developing more robust and dynamic storage protocols that prevent unfavourable conditions. A computational fluid d...

This study has focussed on the effect of low temperature storage on the postharvest ripening of green tomatoes; more specifically, on the ethylene signal transduction in relation to the ethylene biosynthesis pathway. To this end, the first elements of the ethylene signal transduction, ethylene receptors, CTR and EIN2 have been analysed in tomatoes...

Methods using gas exchange measurements to estimate respiration in the light (day respiration Rd) make implicit assumptions about reassimilation of (photo)respired CO2; however, this reassimilation depends on the positions of mitochondria. We used a reaction‐diffusion model without making these assumptions to analyse datasets on gas exchange, chlor...

Models based on mass balances and Michaelis-Menten respiration kinetics are increasingly used to determine optimal storage conditions of fresh fruits and vegetables. The model parameters are usually estimated from respiration experiments at different, but fixed, gas conditions according to a response surface design. This is a tedious procedure that...

Precooling has been questioned as a suitable step in the process of beef carcass cooling. Model‐based optimization was performed to identify optimum operating conditions for different heavy‐muscled beef carcass cooling practices in slaughterhouses with both precooling and cooling stages. The study was conducted using a validated computational fluid...

Bruise damage in fruit results from cell wall failure and inter-cellular separation. Despite the importance of micro-mechanics of plant tissue with respect to its integrity, it remains largely unquantified and...

Stand-alone and portable lab-on-chips (LOC) can be obtained by exploiting capillary flow in porous media. Poly-methyl methacrylate (PMMA) platforms obtained through powder-based 3D printing are appropriate for capillarity-driven LOCs. However, fluid flow in such platforms needs to be characterized well. For this purpose a 3D pore-network (PN) was e...

Fruit tissue microstructure affects gas diffusivity, and, therefore, also hypoxia related physiological disorders such as browning disorders in pome fruit stored in controlled atmosphere conditions. Recent results have shown that the microstructure is quite heterogeneous across the fruit. To enhance our understanding of gas exchange during storage...

Attention of both producers and consumers is growing towards improved food quality and safety, which can be conveniently investigated by means of biosensors. Miniaturization of biosensors resulting in microfluidic lab-on-chips leads to an enormous reduction of analysis costs and times. When developing a new biosensor, optimization is recommended. C...

Ethylene, the plant ripening hormone of climacteric fruit, is perceived by ethylene receptors which is the first step in the complex ethylene signal transduction pathway. Much progress has been made in elucidating the mechanism of this pathway, but there is still a lot to be done in the proteomic quantification of the main proteins involved, partic...

List of unlabeled peptides tested for the assay development. The ones marked in yellow were the identified and quantified peptides (labeled peptides were order afterwards for these ones). The ones in green were promisingly identified but labeled peptide for them were not obtained.

Absolute quantification (fmol of target protein/μg of total membrane proteins) of the peptides of SlETR1-SlETR7, SlCTR1-SlCTR3 and SlEIN2 during tomato fruit ripening. MG, mature green; BR, breaker; OR, orange; R, red tomatoes. Error bars represent the standard error of the mean based on six biological replicates. Different uppercase letters indica...

Dilution curves for the PRM analysis of 0–200 fmol/μL of the selected heavy labeled peptides for the proteins SlETR1-SlETR7, SlCTR1-SlCTR3 and SlEIN2 and linearity expressed by coefficient of determination (R2).

Correlation between protein and gene expression levels of the SlETR1-SlETR7, SlCTR1-SlCTR3 and SlEIN2. Significant correlations are represented with an asterisk in the chart title and non-significant correlation with the letters N.S. The protein, gene expression data and their standard errors were normalized for visualization.

Selected results output of the use of the mProphet algorithm of the targeted peptide identifications trained with the second best peak option.

Cluster alignment of Q9S814 (AtEIN2) and Q6Q2C1 (SlEIN2) with the alignment tool of Uniprot. The C-terminal part of AtEIN2 is highlighted in green based on the results of Qiao et al. (2012). The two peptides of SlEIN2 identified and quantified in this work are highlighted in yellow.

Amino acid sequences of the proteins SlETR1-SlETR7, SlCTR1-SlCTR3 and SlEIN2 obtained from Uniprot (Bateman et al., 2015). Their Uniprotannotated transmembrane domains are underlined, their possible phosphorylation sites are highlighted in green and their GAF domain, kinase domain and response regulatory domains are represented in green, blue and o...

RT-qPCR primers for the 12 ethylene signaling and 3 reference genes used in this study. Primers were designed with the Primer3 web tool (http://bioinfo.ut.ee/primer3/). Primer specificity was checked by BLAST-ing against all tomato EST’s and known cDNA sequences.

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...

Multisensor inspection allows for inline detection of internal defects of products with variable shapes, such as fruit and vegetables, by combining X-ray radiography with 3D shape recognition and modelling. For products with a complex internal structure such as apple fruit, inspection must also account for the corresponding internal density gradien...

Apple quality after freezing is affected by temperature fluctuations during cold storage. Ice re-crystallization and sublimation occur slowly at a constant temperature over a long period of storage, and more rapidly during fluctuating temperatures. These phenomena impact fruit quality, thus reducing storage life. To this end, apple tissue samples w...

To ensure profitable margins, European pear fruit producers are forced to explore more and more distant overseas markets. After controlled atmosphere storage, however, pear fruit is susceptible to relatively fast quality loss if conditions during packaged transport are sub-optimal. Both excessive water loss (causing weak necks and shrivelling) and...

A method was developed to correct real-time measurements of the respiratory quotient (RQ) of pome fruit for gas leakage of a cool room. The method is based on a general leakage model that was simplified by performing sensitivity analysis of the contribution of the pressure driven and concentration driven gas transport terms. The analysis showed tha...

The respiration rate of plant tissues decreases when the amount of available O2 is reduced. There is, however, a debate on whether the respiration rate is controlled either by diffusion limitation of oxygen or through regulatory processes at the level of transcriptome. We used experimental and modelling approaches to demonstrate that both diffusion...

Dragon fruit (Hylocereus undatus) is a subtropical fruit, which has recently been grown in many provinces in Vietnam. It is one of the most valuable fruit because of its delicious taste and excellent nutritional properties. At present, the fruit is mainly consumed in fresh while huge quantity is harvested in short period, making its postharvest los...