what makes ground beef turn gray
When ground beef is not exposed to oxygen (as in the inside of the packaged meat), the myoglobin turns grayish-brown after a few days. It may look less appetizing but is safe. If the ground meat is gray or brown throughout, however, that could indicate that it's beginning to spoil. If you just bought it, you may want to return it. Spoilage bacteria, though generally harmless, can make meat smell and cause other signs of deterioration.