How long is it safe to marinate meat?
I started marinating some almost-thawed chicken and skirt steak in the refrigerator on Monday. It's Saturday, and I still haven't gotten around to cooking the meat. Is the meat still safe to cook and eat?
I made several different marinades consisting of lime juice, red wine vinegar, soy sauce, garlic, and pepper. I'm not sure if that makes a difference.
I can't see any reason for the marinating itself to make any difference. If it's safe to leave the (un-marinated) meat in the same conditions for the same length of time, then it's safe to marinate it for that long.
Five days in the refrigerator is definitely stretching it for chicken - usually no more than a few days is recommended, and that's assuming it was fresh when you bought it (not a day before the sell-by date). Even if it's safe, it's not going to be very good. I've accidentally left raw chicken in the refrigerator and forgotten about it before, and it started to smell "off" after about 4 days. I hate to say it, but I wouldn't use it at this point.
As for the steak, you're probably okay, because you only have surface bacteria, but I would cook it well and right away. Again, most cooks I know will recommend no more than a few days in the fridge.
P.S. I've heard people say that weak acids such as lime juice "preserve" the meat, but never from a reliable source; even if it worked, every marinade is different and it would be nearly impossible to predict the exact amount of time it preserves for. You have no idea how much bacteria existed at the outset, and even if the marinade somehow helped to inhibit growth of new bacteria, the "spoiled-ness" of raw meat doesn't come from the bacteria itself but from the toxins they leave behind. It's not a requirement for the bacteria to multiply in order for the food to spoil, if enough existed in the first place.
Unless somebody has it on good authority that marinating makes any significant difference, I refuse to put any stock in that bit of folk wisdom and recommend that others be equally skeptical.
Salt and other substances that raise osmotic pressure kill bacteria. The concentration determines the efficacy. Lemon juice and vinegar are more than strong enough to kill bacteria at full strength. Alton Brown recommends them for cleaning cutting boards after handling chicken. But you are correct, the efficacy is determined by concentration, and that will differ with each marinade.
Even if you had enough salt and acid to avoid danger, after a week you'd be closer to *pickled* meat than marinated. Fine if you're making a stew, I suppose...
@Adam: Yes, they kill bacteria, but *how much*? To get the concentration you're referring to, the "marinade" would basically have to be a brine or pickling liquid, as Knives points out. No marinade is strong enough to do that. Concentrated lemon juice might, as would concentrated vinegar, but those things aren't marinades.
While health concerns for storing meat are very real, in the scope of this question it's actually not an issue. No amount of time you are going to marinate something that will yield a good result is going to pose a health hazard unless your meat is near expiration to begin with. Consider the following:
For most marinades, you will get very little difference flavor-wise from 20 minutes or several hours. In fact, you will get the most flavor by doing a short marinating right before cooking, then reapplying a coating of the marinade just before the food is done cooking.
For marinades that are meant to soak for more than a few hours, they generally call for about 24 hours. This is not an unsafe length of time. Longer than 24 hours is going to have no positive effects on your food...
UNLESS you happen to be brining the meat. For brining you may be leaving your meat sitting for much longer, but it is in solution specifically designed to preserve the meat and kill bacteria.
So all in all, as long as you follow general health and safety principles with your food, you'll be just fine.
Just to clarify #1: Don't reuse the same marinade! Reserve some from before you marinate the raw meat, then reapply the reserved portion.
... or, alternatively, cook the already-used marinade (e.g., bring it to a simmer in a saucepan, stirring to make sure the heating is even). Then you can use it safely for #1, assuming you follow the normal rules (e.g., don't leave the marinade—before or after cooking—sitting out on the counter for hours while a roast cooks; keep it in the fridge). But often @Aaronut's suggestion will taste better.
if you have too much soy sauce then the salt in it will start to preserve the meat, and if you marinate it for too long it will end up like eating peat bog man. I've had this just overnight from a soy and ginger marinade with beef.
In general though I would think that the beef will be ok, but I would be less certain about the chicken. It probably depends on how fresh the meat was in the first place.
Smell it and look at it. If it looks and smells ok, then its probably good. Any doubts and bin it.
You were keeping your meat cold in a high-salt, high-acid environment, so I wouldn't be too worried about pathogens. This doesn't mean you're absolutely safe -- there are no absolutes in food safety, even with fresh-killed meat. But, given the conditions you described, it should be safe.
However, I cannot imagine that meat would be any good after marinating for 5 whole days. After 24 hours, the marinade will really start to ruin the texture of your meat.
Chicken =2 days...meats such as steaks, lamb, pork = 5 days. Here's the link to Food safety.gov, you can find the definite answers you seek on this page :) http://www.foodsafety.gov/blog/marinades.html