One of the frequent questions we have received from consumers over the years is this one: “Why is my package of ground beef red on the outside, but brown in the middle?” We have had this question and answer on the Meat Science web page for years and have received many notes from retailers who have thanked us for providing this response to a question they have received many times from skeptical consumers.
In steaks and roasts packaged in overwrap film, the color of the outside of the cut is bright red. Within the cut, it is purple because there is no oxygen to cause the meat to “bloom” (term used in industry to signify the conversion from the purple state to the red state in the presence of oxygen).
In making ground beef, some air is introduced into the meat in the grinding process. When ground beef is packaged in overwrap film, plenty of oxygen is available to generate the bright red color of lean on the surface. Because there is some, but not enough oxygen deep within the product, it causes the meat to turn brown. When the product is allowed to come in contact with oxygen, it usually will bloom to the bright red color like the surface.