Iridescence in beef caused by multilayer interference from sarcomere discs

Microscope photometry of raw and cooked iliocostalis was used to test the hypothesis that interference colours in beef may originate from reflections from sarcomere discs. Evidence in support of the hypothesis was, firstly, that interference colours were not altered by rotating a polarizer in the illumination pathway, or by rotating a polarizer in the measuring pathway. But when both pathways contained polarizers, iridescence was completely extinguished when the polarizers were crossed. Secondly, the reflectance spectra of interference colours all showed multiple interference peaks, with a major peak possibly originating from the top sarcomere and minor peaks originating from lower sarcomeres. Thirdly, major peaks were strongly dependent on the angle of measurement. Iridescence in beef is quite rare, but reflections from sarcomere discs may be a ubiquitous source of light scattering in meat.

► Iridescence on roast beef was examined by microscope photometry
► Iridescence was extinguished by crossed polarizers showing it originated from reflectance
► Reflectance was from sarcomere discs with strongest interference from the top disc