Spatial development of transport structures in apple (Malus x domestica Borkh.) fruit

The void network and vascular system are important pathways for the transport of gases, water and solutes in apple fruit (Malus x domestica Borkh). Here we used X-ray micro-tomography at various spatial resolutions to investigate the growth of these transport structures in 3D during fruit development of ‘Jonagold’ apple. The size of the void space and porosity in the cortex tissue increased considerably. In the core tissue, the porosity was consistently lower, and seemed to decrease towards the end of the maturation period. The voids in the core were more narrow and fragmented than the voids in the cortex. Both the void network in the core and in the cortex changed significantly in terms of void morphology. An automated segmentation protocol underestimated the total vasculature length by 9 to 12% in comparison to manually processed images. Vascular networks increased in length from a total of 5 meter at 9 weeks after full bloom, to more than 20 meter corresponding to 5 cm of vascular tissue per cubic centimeter of apple tissue. A high degree of branching in both the void network and vascular system and a complex three-dimensional pattern was observed across the whole fruit. The 3D visualisations of the transport structures may be useful for numerical modeling of organ growth and transport processes in fruit

African-European contacts in the Kongo Kingdom (sixteenth-eighteenth centuries): new archaeological insights from Ngongo Mbata (Lower Congo, DRC)

Ngongo Mbata, the main and most affluent center of the Kongo kingdom’s Mbata province in the 17th century, is well known from the historical sources, but virtually unexplored in archaeological publications. Ngongo Mbata is unique in that it hosted a monumental stone building about which the historical record remains silent. This makes it particularly challenging from the point of view of historical archaeology. In this paper historical data, unpublished excavation results from the 1930s and our own fieldwork undertaken in 2012-2013 are brought together, to tell a new story of early African-European contacts in the interior of West Central Africa

X-ray microtomography provides new insights into vacuum impregnation of spinach leaves

Vacuum impregnation is used in the food industry to facilitate the impregnation of porous products with, e.g. firming, antioxidant, antimicrobial or cryoprotective agents. X-ray micro-tomography (CT) was used to study the process of vacuum impregnation in spinach leaves. Low (300 mbar absolute pressure) and mild vacuum (150 mbar absolute pressure) impregnation protocols were used to impregnate an isotonic solution of trehalose in the leaves and CT was used to make observations of the cross section of the impregnated samples and quantify their porosity. Results revealed that the free volume in the spongy mesophyll is easier to impregnate than the spaces around the palisade mesophyll. The low vacuum impregnation protocol provoked less impregnation close to the edge of the leaf than in its centre, probably accounting for an influence of the tissue structure on impregnation. The vacuum impregnation protocols tested in this investigation drastically decreased the proportion of large pores (>100 m) and increased the proportion of small pores (<50 m). The mild vacuum impregnation protocol, which was designed on the basis of measured apparent porosity, did not achieve full impregnation of the tissue.V. Panarese acknowledges the financial support from the Portuguese Foundation of Science (FCT). F. Gomez Galindo acknowledges the financial support from European Community's Seventh Framework Program (FP7/2007-2013) under grant agreement no. 245280, also known under the acronym PRESERF. Financial support of FWO Vlaanderen (project G.0645.13), the Flemish government agency for Innovation by Science and Technology (project IWT SBO120033 TomFood) and the University of Leuven (project OT 12/055) is gratefully acknowledged. Dennis Cantre is an IRO scholar of KU Leuven. We also acknowledge the Hercules foundation for supporting the X-ray CT facility (AKUL001(HER/09/016))

Nondestructive measurement of fruit and vegetable quality

We review nondestructive techniques for measuring internal and external quality attributes of fruit and vegetables, such as color, size and shape, flavor, texture, and absence of defects. The different techniques are organized according to their physical measurement principle. We first describe each technique and then list some examples. As many of these techniques rely on mathematical models and particular data processing methods, we discuss these where needed. We pay particular attention to techniques that can be implemented online in grading lines

The elusive archaeology of Kongo urbanism: the case of Kindoki, Mbanza Nsundi (Lower Congo, DRC)

We present here results, analyses and an in-depth historical contextualisation of the fieldwork undertaken in 2012 and 2013 at the Kindoki site in the Lower Congo (DRC). This site is linked with Mbanza Nsundi, one of the Kongo Kingdom's provincial capitals, which turns out to be archaeologically 'elusive'. Pinpointing its location proved to be particularly challenging. To this end, a historically-informed excavation methodology was developed that was never implemented in Central Africa before. We combined a strategy of systematic test pits with a large-scale 50 m grid approach. A cemetery was identified on Kindoki Hill with distinct but contemporaneous quarters of a 16th-17thcenturies settlement on both sides. The cemetery itself contains mainly 18th-century burials, in all likelihood of successive Nsundi rulers. The foreign, especially Portuguese, ceramics excavated on the hilltop and the hundreds of Venetian and likely Bavarian beads found in the graves are indicative of Mbanza Nsundi's connection to trade routes linking the Atlantic coast with the Pool region. The most striking discovery is that of a previously unknown type of comb-impressed pottery, from a pit with a calibrated radiocarbon date AD 1294-1393 (2 sigma). This suggests that a settlement had been developing at Kindoki since at least the 14th century, which allows us, for the very first time, to spatially bridge Kongo history and 'prehistory'. For the entire Lower Congo region only three 14C dates posterior to AD 1000 were available before the start of the KongoKing project, twelve have been added for just Kindoki

X-ray CT to detect internal structures in apple fruit. From high-resolution 3D microstructure imaging towards fast screening tools

Pome fruit is often stored up to 10 months at a low temperature (-0.5 &#176; C to 3 &#176; C), in combination with reduced O2 and elevated CO2 partial pressures. Storage at low temperature, combined with 'Controlled Atmosphere' (CA) is used to reduce the respiration activity of the fruit thereby minimising the associated quality changes, and thus extending the storage time. The gas composition is of great importance as physiological defects like internal browning and void formation can occur at suboptimal conditions. Also during the growth phase, various defects can occur, as watercore in apple with hard, glassy zones near the core. A major problem is that these symptoms are not externally observable, and affected fruit cannot be easily distinguished from healthy. Internal fruit quality is typically evaluated based on visual inspection of a randomly selected sample of fruit. Only after cutting the fruit, and thus destroying it, an assessment can be made. When the sampled fruit are affected, the whole batch is rejected and destroyed. The scientific objective of this research project is a better understanding of the development of the symptoms of internal defects in apple and pear. The technological objective is the development of a non-destructive and rapid image-based method for evaluating internal fruit quality. This should lead to a better sorting of fruit with less losses in the sector and a high, uniform fruit quality on the market as a result. Fruit of Braeburn , Kanzi and Conference were stored under defect-inducing CA conditions through which internally brown and hollow fruit were successfully obtained. Cultivars Ascara , Tempera , Rebellón and Verde doncella were delivered from Spain, where a higher risk of watercore is present because of the climatic conditions. These internal defects are generally characterised by a change in density of the affected tissue. Previous research has shown that X-ray radiography and tomography are particularly suited to detect these internal problems both at the micro- and macroscale. With the help of X-ray micro-CT a large number of fruit samples was scanned such that a complete characterisation of these physiological defects was obtained, in different stages of development, for the different cultivars. Preliminary tests on the whole fruit with X-ray radiography and CT have shown that these technologies are able to detect quality defects in different gradations. Additional high-resolution micro-CT measurements will be performed on tissue pear to complete the microstructural evaluation of internal quality. In an extensive experiment, large numbers of affected and non-affected fruit are scanned so that the detection success of X-ray CT and radiography can be assessed. By fine-tuning measurement conditions and optimise the imaging and processing, this should ultimately lead to the development of a test rig in which affected and healthy fruit are sorted on-line, based on the internal fruit quality.1 Introduction 1 1.1 Problem statement 1 1.2 Objectives and outline 2 1.3 References 3 2 Essentials of computed tomography and image processing 5 2.1 Principle 6 2.2 History of X-ray Computed Tomograhpy 8 2.3 Acquisition of CT data 10 2.3.1 X ray source 10 2.3.2 X-ray attenuation 14 2.3.3 Detection 16 2.3.4 Reconstruction 16 2.3.5 X-ray CT systems 18 2.4 Quality of X-ray CT images, challenges and limitations 22 2.4.1 Spatial resolution and sample size limitations 22 2.4.2 Density resolution 23 2.4.3 Artefacts 23 2.5 X-ray CT image processing 26 2.5.1 Fundamental concepts of image processing 26 2.5.2 Image enhancement 28 2.5.3 Image segmentation 30 2.5.4 Morphological operations 30 2.5.5 3D image visualisation and analysis using dedicated software 31 2.5.6 3D image parameters 32 2.6 Applications of X-rays for online sorting of agricultural products 38 2.7 Conclusions 39 2.8 References 40 3 Automatic analysis of the 3D microstructure of plant parenchyma tissue based on X-ray micro-CT 43 3.1 Introduction 44 3.2 Materials and methods 45 3.2.1 Apple and pear samples 45 3.2.2 X-ray CT scans 45 3.2.3 Tissue anatomy analysis algorithm 46 3.3 Results 51 3.3.1 Cell analysis of apple and pear cultivars 51 3.3.2 Void networks 54 3.3.3 Relation to functional properties of tissue 56 3.4 Discussion 60 3.4.1 Automated analysis of 3D microstructure of tissue of bulky plant organs is possible 60 3.4.2 3D tissue structure varies considerably among species and cultivars 62 3.4.3 Functional properties relate to specific fruit tissue anatomy parameters 64 3.5 Conclusion 65 3.6 Acknowledgements 65 3.7 References 66 4 Characterisation of ‘Braeburn’ browning disorder by means of X-ray micro-CT 69 4.1 Introduction 70 4.2 Materials and methods 72 4.2.1 Apple fruit and samples 72 4.2.2 X-ray computed (micro) tomography 74 4.2.3 Image processing 74 4.2.4 Statistical analysis 75 4.3 Results 77 4.3.1 Image segmentation 77 4.3.2 3D analysis of microstructure 77 4.3.3 Effect of storage time on microstructure of optimally stored fruit 82 4.3.4 Microstructural changes during BBD development 84 4.4 Discussion 90 4.5 Conclusion 92 4.6 Acknowledgements 92 4.7 References 93 5 3D multiscale model for simulating gas transport in apple 95 5.1 Introduction 96 5.2 Materials and methods 97 5.2.1 Apple fruit 97 5.2.2 X-ray computed tomography 97 5.2.3 Image processing 98 5.2.4 Multiscale modeling 99 5.3 Results 100 5.3.1 Development and microstructure of BBD 100 5.3.2 Apparent gas diffusivity of BBD tissues 102 5.3.3 Gas concentration profiles in BBD apple fruit 103 5.4 Discussion 106 5.5 Conclusion 107 5.6 Acknowledgements 107 5.7 References 108 6 Development of 3D architecture of transport structures in apple fruit 109 6.1 Introduction 110 6.2 Materials and Methods 112 6.2.1 Apple fruit 112 6.2.2 X-ray micro-CT 113 6.2.3 Image processing 114 6.3 Results 117 6.3.1 Development of air voids in apple fruit 118 6.3.2 Development of vascular bundles in apple fruit 123 6.4 Discussion 130 6.4.1 Implications of the distinct void architectures in core and cortex tissue 130 6.4.2 On the development of voids 130 6.4.3 Extensive vascular networks conduct sap flow 131 6.5 Conclusion 133 6.6 References 134 7 Comparison of X-ray CT and MRI of watercore disorder of different apple cultivars 137 7.1 Introduction 138 7.2 Materials and methods 139 7.2.1 Apple fruit 139 7.2.2 MRI 141 7.2.3 X-ray CT 141 7.2.4 Image processing 142 7.3 Results 145 7.3.1 X-ray CT and MRI of healthy and watercore apples 145 7.3.2 Microstructure analysis of healthy and watercore affected tissue 149 7.3.3 Histogram analysis of X-ray CT and MRI images of watercore apples 150 7.3.4 Automatic segmentation of watercore from X-ray CT and MRI images 153 7.4 Discussion 156 7.4.1 X-ray CT and MRI visualise complementary features of watercore apples related to their microstructure 156 7.4.2 Watercore has distinct characteristics in different cultivars 156 7.4.3 Classification of watercore is feasible based on MRI/X-ray CT histogram analysis and segmentation 157 7.5 Conclusion 158 7.6 Acknowledgements 158 7.7 References 159 8 General conclusions and future perspectives 161 8.1 General conclusions 162 8.2 Remarks for future research 164   Supplemental data 167 Tissue anatomy analysis algorithm 167 Multiscale models for gas exchange in fruit 173 Microscale gas exchange model 173 Macroscale gas exchange model 175 References 176 List of publications 177 Articles in internationally reviewed academic journals 177 Articles in academic books 178 Papers at international scientific conferences and symposia, published in full in proceedings 178 Meeting abstracts, presented at international scientific conferences 179nrpages: 180status: publishe

Convective heat and mass exchange at surfaces of horticultural products: a microscale CFD modelling approach

Knowledge of the convective heat and mass exchange of horticultural products and other plant organs (e.g., leaves) with the environment is of interest for several pre- and postharvest technologies and for plant microclimate analysis. Although these exchange processes often occur at the microscale (e.g. at lenticels, cracks, droplets or stomata, 10−4 to 10−2m), they are still often assessed on a macroscale level. In this study, the convective passive scalar (i.e., heat) transfer from a single spherical product is investigated with computational fluid dynamics (CFD). For this purpose, the product is placed in a virtual wind-tunnel environment, thus not in its natural environment, e.g. on a tree. A sphere is used as reference system; an apple fruit is considered as model system. CFD validation is performed for a sphere, indicating a very good performance of the Reynolds-averaged Navier–Stokes shear stress transport k-ω turbulence model for the drag coefficient, Nusselt number, separation angle and recirculation length over a large Reynolds number range (10–3×104). These quantities compare well for sphere and apple. The impact of discretely distributed microscopic scalar sources on the product surface on the convective transfer is analysed by explicitly modelling them. Such sources are representative for moisture loss through lenticels and cracks in the product's cuticle and evaporation of water or pesticide droplets at the surface. As scalar transfer is assumed only to occur locally at these sources, the active surface area is reduced. In this study, it is found that even at rather low surface coverage ratios, relatively large convective flow rates are found, indicating a non-linear dependency on the active surface area. This dependency is a function of coverage ratio, the Reynolds number and the source size. The proposed computational methodology for investigating the effects of these microscopic scalar sources shows a good performance, by which it is a viable alternative for experiments, which are very challenging at such small scales.status: publishe