Some diners posted on the internet that while eating, they noticed strange metallic rainbow colours on the surfaces of some meat products such as roast beef slices and ham. They suspected that the meat products had gone bad.
Rainbow Colour Appearance on Meat is a Physical Phenomenon
Shiny metallic colours with a rainbow or green appearance can sometimes be observed on the surfaces of meat products because the striated structures and fibres of meat muscles can cause diffraction when light shines onto their surfaces, creating a rainbow that may split into various colours. This physical phenomenon may occur in raw or cooked meats and meat products.
Rainbow Meat Does Not Imply Spoilage or Food Safety Issues
Overseas food safety authorities have stated that the aforementioned colour phenomenon on meat does not imply that it has spoiled or has food safety issues, so members of the public need not be overly concerned.