血红蛋白（尤其是牛肉的）氧化后就是鲜红色，所以表面是红的。不是什么色素。

血红蛋白（尤其是牛肉的）氧化后就是鲜红色，所以表面是红的。不是什么色素。

至于salmon的颜色，请看Kroger website 的解释："Many suppliers add supplements to the food given to their farm-raised salmon and trout," said Keith Neer, Vice President of Corporate Food Technology and Regulatory Compliance, in a release explaining the company's decision to add the labels. "These additives, which are substantively identical to those naturally occurring in the diets of many wild salmon and trout, enhance the pigmentation of the farm-raised fish. While the supplements do not affect the taste or nutritional value of the fish, we are modifying the product labels to share this information with our customers."