Scientific Research and Essays Vol. 2 (5), 150-158, May 2007          
ISSN 1992-2248 © 2007 Academic Journals

Full Length Research Paper

Advanced fullerene-type texture and further features of the macadamia nutshell as revealed by optical 3D microscopy

Gerd Kaupp and  Maria Kaupp

University of Oldenburg, Faculty Organic Chemistry 1, Diekweg 15, D-26188 Edewecht, Germany.

*Corresponding author. E-mail:  gerd.kaupp@uni-oldenburg.de. Fax: +49 4486 920704.

Accepted 25 April, 2007

Optical three-dimensional digital microscopy with symmetric or asymmetric frontal ring illumination and with composition of images at equidistant focus also for surface reconstruction is used for the study of various qualities of the rough macadamia nut / seed (fat) at various levels of magnification. The almost spherical object with two off-axis poles has an unreported advanced fullerene-like surface structure (polygons and additional stiffeners) at its wooden hard shell that makes the nut extremely resistant against cracking, but also permits the cracking by internal pressure for germination. The structure of the wooden shell is microscopically inves-tigated from cracked particles with sharp rectangular edges and from the depth of incomplete fissures. While SEM assumed isotropy the thin hard shell (160 µm) is connected to (chewable) softer wood (depth 1.5 – 5 mm in the same nut) followed by insulating black (northern hemisphere) and white (southern hemisphere) glossy layers. One of the poles is fibrous and a very long channel down to the black layer could be imaged. The development of cracks starts from the poles (upon external or internal pressure) and from particular sites lacking the stiffeners that are imaged with full depth of focus by the versatile microscopic technique with high contrast. Additional features are hitherto unreported distinct red and green spots that are stable to air and light.

Key words: Advanced fullerene-type texture, bijective illumination, bionics, cracking, fracture toughness, germination, image composition, impact compliance, macadamia nut, surface texture, surface reconstruction, surjective illumination, three-dimensional optical microscopy, wooden shell structure.