Three-dimensional pore space quantification of apple tissue using X-ray computed microtomography

BIOSYST, MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, W. de Croylaan 42, 3001 Leuven, Belgium.
Planta (Impact Factor: 3.38). 08/2007; 226(3):559-70. DOI: 10.1007/s00425-007-0504-4
Source: PubMed

ABSTRACT The microstructure and the connectivity of the pore space are important variables for better understanding of the complex gas transport phenomena that occur in plant tissues. In this study, we present an experimental procedure for image acquisition and image processing to quantitatively characterize in 3D the pore space of apple tissues (Malus domestica Borkh.) for two cultivars (Jonagold and Braeburn) taken from the fleshy part of the cortex using X-ray computer microtomography. Preliminary sensitivity analyses were performed to determine the effect of the resolution and the volume size (REV, representative elementary volume analysis) on the computed porosity of apple samples. For comparison among cultivars, geometrical properties such as porosity, specific surface area, number of disconnected pore volumes and their distribution parameters were extracted and analyzed in triplicate based on the 3D skeletonization of the pore space (medial axis analysis). The results showed that microtomography provides a resolution at the micrometer level to quantitatively analyze and characterize the 3D topology of the pore space in apple tissue. The computed porosity was confirmed to be highly dependent of the resolution used, and the minimum REV of the cortical flesh of apple fruit was estimated to be 1.3 mm(3). Comparisons among the two cultivars using a resolution of 8.5 mum with a minimum REV cube showed that in spite of the complexity and variability of the pore space network observed in Jonagold and Braeburn apples, the extracted parameters from the medial axis were significantly different (P-value < 0.05). Medial axis parameters showed potential to differentiate the microstructure between the two evaluated apple cultivars.

Download full-text


Available from: Fernando A Mendoza, Sep 09, 2014
  • Source
    • "Biol. (2014), cated software now available for the tomographic reconstructions and interpretations (Mendoza et al., 2007; Verboven et al., 2012, 2013). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Floods can completely submerge terrestrial plants but some wetland species can sustain O2 and CO2 exchange with the environment via gas films forming on superhydrophobic leaf surfaces. We used high resolution synchrotron X-ray phase contrast micro-tomography in a novel approach to visualise gas films on submerged leaves of common cordgrass (Spartina anglica). 3D tomograms enabled a hitherto unmatched level of detail regarding the micro-topography of leaf gas films. Gas films formed only on the superhydrophobic adaxial leaf side (water droplet contact angle, Φ = 162°) but not on the abaxial side (Φ = 135°). The adaxial side of the leaves of common cordgrass is plicate with a longitudinal system of parallel grooves and ridges and the vast majority of the gas film volume was found in large ∼180 μm deep elongated triangular volumes in the grooves and these volumes were connected to each neighbouring groove via a fine network of gas tubules (∼1.7 μm diameter) across the ridges. In addition to the gas film retained on the leaf exterior, the X-ray phase contrast micro-tomography also successfully distinguished gas spaces internally in the leaf tissues, and the tissue porosity (gas volume per unit tissue volume) ranged from 6.3 to 20.3% in tip and base leaf segments, respectively. We conclude that X-ray phase contrast micro-tomography is a powerful tool to obtain quantitative data of exterior gas features on biological samples because of the significant difference in electron density between air, biological tissues and water.
    Journal of Structural Biology 10/2014; 188(1). DOI:10.1016/j.jsb.2014.08.003 · 3.23 Impact Factor
  • Source
    • "This has been demonstrated for the ripening of climacteric fruits like; tomato (Kelly and Saltveit 1988; Saltveit and Sharaf 1992; McDonald et al. 1996) and apple (Pesis et al. 1994; Pesis 1995). Besides this, levels of volatiles are also found to be associated with storage disorders of apple fruit like; scald (Huelin and Coggiola 1968) and internal browning (Mendoza et al. 2007). The ripening and quality of non-climacteric fruits such as; grapes, orange and strawberries were also influenced by these volatiles (Saltveit and Ballinger 1983; Ke and Kader 1990; Ke et al. 1991). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Concentrations of different gases and volatiles present or produced inside a fruit are determined by the permeability of the fruit tissue to these compounds. Primarily, surface morphology and anatomical features of a given fruit determine the degree of permeance across the fruit. Species and varietal variability in surface characteristics and anatomical features therefore influence not only the diffusibility of gases and volatiles across the fruits but also the activity and response of various metabolic and physiological reactions/processes regulated by these compounds. Besides the well-known role of ethylene, gases and volatiles; O2, CO2, ethanol, acetaldehyde, water vapours, methyl salicylate, methyl jasmonate and nitric oxide (NO) have the potential to regulate the process of ripening individually and also in various interactive ways. Differences in the prevailing internal atmosphere of the fruits may therefore be considered as one of the causes behind the existing varietal variability of fruits in terms of rate of ripening, qualitative changes, firmness, shelf-life, ideal storage requirement, extent of tolerance towards reduced O2 and/or elevated CO2, transpirational loss and susceptibility to various physiological disorders. In this way, internal atmosphere of a fruit (in terms of different gases and volatiles) plays a critical regulatory role in the process of fruit ripening. So, better and holistic understanding of this internal atmosphere along with its exact regulatory role on various aspects of fruit ripening will facilitate the development of more meaningful, refined and effective approaches in postharvest management of fruits. Its applicability, specially for the climacteric fruits, at various stages of the supply chain from growers to consumers would assist in reducing postharvest losses not only in quantity but also in quality.
    Journal of Food Science and Technology -Mysore- 07/2014; DOI:10.1007/s13197-011-0583-x · 2.02 Impact Factor
  • Source
    • "For image processing the following steps were applied (Herremans et al., 2013) using CTAn software (Bruker microCT, Kontich, Belgium): the datasets were cropped on all sample edges (0.8 mm) to remove approximately 4–5 outer cell layers that are potentially damaged by sample preparation. The final tissue volume for analysis measured 55 mm 3 , well above the 1.3 mm 3 limit that has been shown to representatively describe apple tissue microstructure in terms of its porosity (Mendoza et al., 2007). The grey scale images were median-filtered with a kernel of 2 pixels radius in 3D to reduce noise and subsequently binarised by means of Otsu thresholding. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Watercore is an internal disorder that appears as water-soaked, glassy regions near the core in apples. Fast and non-destructive solutions for sensing watercore would be readily accepted in the postharvest industry. X-ray CT and MRI were compared as potential imaging technologies for detecting this particular disorder. After matching the 3D datasets of X-ray CT and MRI, the images that were obtained on identical fruit were compared quantitatively. Both MRI and CT were able to detect watercore, however the contrast in MRI images was superior. High-resolution micro-CT images showed the microstructural changes in watercore fruit: the intercellular spaces of the affected apple tissue are filled with water. This explained the higher density that is detected here by the X-rays and the higher water content in the MRI. Mean and variance of the frequency distribution of MRI and X-ray CT intensity appeared to be a parameter that allows the identification of healthy apples from affected fruit. Automatic image processing based on thresholding the images resulted in comparable watercore classification accuracy of up to 89% for X-ray CT and 79% for MRI data, despite the better contrast in the MRI images.
    Postharvest Biology and Technology 01/2014; 87:42-50. DOI:10.1016/j.postharvbio.2013.08.008 · 2.63 Impact Factor
Show more