It makes me happy that there are people in the world who, when I idly wonder about something, have already done the research.
The iridescence you see sometimes see in meat, especially bacon, is likely caused by alternating muscle layers acting as a photonic crystal.
This is different to a more obvious interference related hypothesis that it's just striation on the surface acting a bit like a diffraction grating.
https://academic.oup.com/ijfst/article/56/1/250/7806371
Update: also see https://ift.onlinelibrary.wiley.com/doi/10.1111/1541-4337.13191
