How long can you leave hamburger in the refrigerator before it goes bad?
"Color of Beef
Beef muscle meat not exposed to oxygen (in vacuum packaging, for
example) is a burgundy or purplish color. After exposure to the air
for 15 minutes or so, the myoglobin receives oxygen and the meat
turns bright, cherry red.
After beef has been refrigerated about 5 days, it may turn brown
due to chemical changes in the myoglobin. Beef that has turned
brown during extended storage may be spoiled, have an off-odor, and
be tacky to the touch."