Food safety is the most critical aspect of cooking, particularly when you are preparing meat. In addition to the pathogens that can render a steak unsafe to eat, marinating it potentially exposes it to other contaminants as well. Several telltale signs of spoilage indicate a steak is not safe to eat. In many cases, you can determine a steak is bad by smell or how it looks or feels. Sight and smell are not foolproof, and it's vital you always adhere to food safety guidelines.

The first sign an uncooked steak has spoiled is its color. A vacuum-sealed marinated steak may be burgundy or purple. Most steaks are exposed to oxygen during the butchering process, which makes them vibrant shades of red. As beef ages, the red hue becomes less vibrant and eventually turns brown. Brown beef is not necessarily spoiled, but it is best to buy marinated steaks that are still red or burgundy. And you should likewise marinate fresh steaks while they are still red. The marinade should not affect the color of the meat significantly.

It is best to freeze a raw steak if you are not going to cook it within five days of its sell-by date. If a thawed steak has grayish-white spots, the discolored patches are likely freezer burn. It is safe to cook and eat a marinated steak that has freezer burn as long as the other qualities of the steak indicate it is safe. Trim the discolored portion off the steak after you thaw it.

For most people, the most unmistakable sign of spoilage is the steak’s odor. The smell of bad beef can range from slightly “off” to rancid. Metallic, chemical or bad cheese scents are all warning signs the beef may be spoiled. The odor may be sour, or it may have a vinegary smell. Keep the ingredients of your marinade in mind if the steak smells sour or vinegary. Acidic ingredients, such as citrus juice, balsamic vinegar or wine, may give off these smells. If you marinate the steak yourself, smell the meat before you apply the marinade, then soak the steak for a short period of time in the refrigerator to ensure that you can correctly attribute the cause of any sour smells.

Steak that is slimy, sticky or tacky may be bad. Marinades may obscure these, but they are generally accompanied by unpleasant odors, which marinades should not hide. The oil in a marinade may give a steak a slightly slick or greasy quality. The meat should be firm but tender when you touch it. It should not feel soft or mushy, the way ground hamburger meat feels. It should not feel too firm, as though it is already cooked well done, either. If the marinade contains an acidic ingredient and the steak marinated for more than two hours, the acid may have had an adverse effect on the proteins. Raw meat that is overexposed to acid is not spoiled or unsafe to eat, but it is unpleasantly tough and dry after you cook it, and it may be inedible.

It is possible for a spoiled or contaminated steak to appear perfectly safe. The best way to protect yourself from foodborne illness is to follow food safety guidelines. Keep raw and cooked meat covered at all times -- even in the refrigerator -- unless you are handling or cooking it. It is safe to marinate a covered steak at room temperature up to two hours. If you marinate the steak longer than two hours, refrigerate it while it soaks. It's safe to marinade a steak in the refrigerator up to five days. Discard used marinade. If you want to baste the steak with the marinade or use it as a sauce, boil it before reapplying it to the meat. Steaks and marinades must reach 145 degrees Fahrenheit to be safe to eat.