Ground beef has gone bad if it emits a rancid odor and if the outer layer is brown or gray in color. Spoiled ground beef can lead to serious food poisoning, so it is always important for people to use the product by its "use by" date or freeze by its "freeze by" date. Refrigerating or freezing the beef as soon as possible after purchase helps to ensure its freshness.
The outer layer of fresh ground beef is red in color, and while a gray to brown outer layer indicates spoilage, a brown to gray tint to the internal portion is normal. This is due to the fact that the internal portion of the beef is not exposed to air. Ground beef perishes faster than whole cuts of beef, and it is more prone to picking up bacteria during the preparation process. Preparing ground beef on a sanitized surface helps to minimize the chance of cross-contamination.
When storing fresh ground beef in the refrigerator, it is important to use the beef within three days of refrigeration. For ground beef that is stored in the freezer, wrapping the product in tin foil prior to freezing helps to preserve its freshness and minimizes the chance of freezer burn.