Microstructure characterization of higuerilla seed (Ricinus communis) by microscopy techniques and image analysis

Microscopy Techniques (MT) have been important tools for qualitative characterization of the morphology, composition and structure on fresh plant tissue, while Image Analysis (IA) is useful to evaluate quantitatively the size, shape and texture from microscopy images. When IA and MT are joined, become helpful tools to understand the relationship between structure-property- functionality of biomaterials. The aim of this work was to carry out an extensive microstructure study of Ricinus communis ("higuerilla seed"). It is an alternative non-edible oil source to obtain biodiesel. A structural study was achieved using histological methods and Light Microscopy (LM), stereomicroscopy, CLSM and ESEM. A microchemical elemental analysis of seeds was carried out by means of Energy Dispersive X-ray spectroscopy. The images obtained by MT were used to extract different geometric parameters by IA. The seeds showed an ellipsoid shape with 13 mm long × 9 mm wide × 6 mm thick. Testa is brittle and has a complex brown pattern, the internal structure shows an endosperm, and this structure is formed by two cotyledons. The microstructure of the epidermis, cell wall, lipid bodies, protein bodies and cytoplasm were characterized. EDS X-ray spectrum and compositional mapping showed mainly microelements contained in the endosperm (P, Mg, S and K), these elements are mineral reserves of endosperm. Cells have isodiametric shape with cellular size of 44.01±8.05μm and lipid bodies present spherical morphology and 12.63±1.30μm of average diameter. This study could be helpful for the processing in the food industry and biofuel production of this seed.