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Visualization of β-carotene and starch granules in plant cells using CARS and SHG microscopy

Authors

  • Christian Brackmann,

    1. Department of Chemical and Biological Engineering, Molecular Microscopy, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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  • Anton Bengtsson,

    1. Department of Chemical and Biological Engineering, Food Science, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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  • Marie Larsson Alminger,

    1. Department of Chemical and Biological Engineering, Food Science, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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  • Ulf Svanberg,

    1. Department of Chemical and Biological Engineering, Food Science, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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  • Annika Enejder

    Corresponding author
    1. Department of Chemical and Biological Engineering, Molecular Microscopy, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
    • Department of Chemical and Biological Engineering, Molecular Microscopy, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
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Abstract

Information on the content and bioavailability of provitamin A carotenoids, such as β-carotene, in plant foods is of great interest due to the widespread vitamin A deficiency in developing countries. While the amount of β-carotene can readily be quantified with analytical techniques, there is limited information on β-carotene morphology in native plant materials. Here, we introduce nonlinear microscopy for three-dimensional, label-free imaging of carotenoids in fresh and thermally treated plant tissues, providing quantitative information at single-aggregate level and detailed insight into their distribution. Carotenoids in orange-fleshed sweet potato (OFSP), carrot, and mango were visualized by coherent anti-Stokes Raman scattering (CARS) microscopy and, in the case of OFSP, related to the plant-matrix morphology by simultaneous second-harmonic generation (SHG) microscopy of starch granules. Sizes, shapes, densities, and location of different types of carotenoid bodies were quantified. While OFSP and carrot showed heterogeneous rod-shaped bodies with high carotenoid densities indicated by higher CARS signals, the carotenoid-filled lipid droplets in mango appeared as homogeneous low-density aggregates of rounded shape. In addition, β-carotene densities and morphologies in OFSP were studied after thermal processing, showing that the bodies remain intact despite significant changes of the surrounding starch granules. Copyright © 2010 John Wiley & Sons, Ltd.

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