Pork spoiling.. but.. how.. far...? Food Science n00b alert
I'm working on iteration number 4 zillion in my effort to create really good Denver area Green Chile (see post http://chowhound.chow.com/topics/782583 ) ... the elusive orange-green wonderfulness that fills breakfast burritos with love and heat.
ANYWAY.. I found some pork sirloin chunks in the "manager clearance" section of my local groc shop. $2 something a pound and I can hack them into smaller bits for my sauce/stew.. and of course I grumble to myself that it's the treated "moist and tender" pork product and not natural pork which is getting damn hard to find in the big stores. ANYWAY
So I didn't get to the Green Chile project right away.. and several days past.. in fact.. 5 probably.. I uncover the shrink wrap this morning and yes.. it's got that sort-of-greenish glint that it's turning.. and you can smell some moderate sour.. nothing horrifying or vomit inducing.. but .. Captain.. she's listing.. and she's going down soon! All hands on deck!
Super cautious cook (eg: American) throws this out without a second thought. I've cooked "sort of questionable" meat before without incident.. so I'm inclined to roll the dice again. And this is just for me- I make my GC very very hot so there's no danger of family members (read: German wife) wanting a bite. It's my bed to lie in. And vomit in I suppose.
I've cooked it.. I've yet to taste the stew but it smells GREAT and it smelled like good pork when it was just pork browning in fat earlier. I'm not super worried.
That said- I've got an open mind and have much to learn... Since my pork was obviously turning.. what sort of bacteria / mold / etc.. was growing on it most likely? If that's not answerable... What's next? My limited knowledge tells me that the microbes will cause an off taste in my meat even when cooked.. and that if they lived there long enough they would create toxins that exist post cooking that will cause illness even if cooked at 200deg for eternity.
What ARE these toxins? Why doesn't cooking kill them? And before you ask- yes- I've done a little Google-research first and have yet to find anything that explains the results of bacteria feeding on meat and leaving behind a trail of poison. EVERYTHING I can find is some form of "cook everything thoroughly or you'll die".
My research stopped where yours ended also. Basically that bacteria start to produce toxins (endotoxins?) that aren't destroyed by cooking. And eventually the toxins will build up in quantities sufficient to harm you, even if the food is cooked thoroughly. Is there a scientist in the house?
I am glad to hear you are considerate enough not to serve your questionable meat to others. I will offer a little more of an answer than joonjoon, working in the food industry, I know enough to realize I am not an expert.
I am guessing the green slime type thing is from spoilage microbes. Pathogens are less likely to show themselves so visibly, and to your point most 'pathogenic bacteria,' as in those that require consuming live bacteria to infect, are usually destroyed by cooking. There are a few bacteria that I can think of offhand that produce toxins, which as you said are the vehicle that actually makes people sick.
This links talks about staph poisoning from the stapholococcus aureus toxin, an enterotoxin that is a heat-stable protein and affects your digestive tract. Staph bacteria themselves are fairly ubiquitous on human skin as well as in dirt. And the bacteria can thrive in salty places (like ham), where other bacterial growth is normally limited.
Another (famous, but much less common one) is botulism poisoning from the toxin in clostridium botulinum. This one is actually a neurotoxin- affecting your nervous system (hence paralyzation). And the reason this bugger is so scary is that it is common in soil in the spore stage- an inert little seed type of thing that will pass quickly if digested as is. But given the chance to grow in a can not fully cooked to kill the spore, it will 'sprout' and grow as it prefers anaerobic environments, producing its toxin- also a heat-stable protein.
So while you may kill any leftover bacteria with cooking- the toxin is unharmed by the heat, and can only take small amounts to make you feel the consequences. Hope this helps shed some light- and food microbiologists out there please add.
Thanks D in MN and also JJ for adding to a discussion that fascinates me to a degree. I probably wouldn't be so curious if I'd just sit my ass down for a few hours and research but.. I haven't done that yet. FWIW- I have had 4 servings of the green chile.. and whereas I'm sad to report that it's still not perfect (although much closer) it certainly didn't taste off or make me ill in the least. The meat was certainly dodgy at best but the finished product is health-neutral.
So Staph is certainly in the category of things that could potentially be a culprit in a spoiled -but -cooked food poisoning episode. I know it's hugely common in the ambient environment. C.B. doesn't scare me as much in *this* scenario as it's unlikely to be present in a package of pre-processed pork due to controls in place in meat packing industry. (but as noted- I'm the king of dangerous assumptions).
I used to be even LESS cautious if you can believe it even though I have a sensitive nose and a fairly easily-triggered gag reflex. A few years ago I left some sausages in the freezer for nearly an entire winter.. and this freezer was a top compartment in a fridge that lives in the garage. We had a looong cold spell in Colorado that winter so the uninsulated garage probably stayed somewhere from 25 - 50 deg F for over a month. This of course made the compressor stay dormant (since the thermostat is in the fridge) but the freezer compartment was up in the "thaw" range frequently. I'm picturing the freezer going long periods at 30-39 deg or something. I pulled those wonderful Italian sausages out in Feb or something and they looked bad.. off color.. smelled off.. but I thought... "that's on the outside.. I'll just make sure I *really* cook 'em.... We Yanks need to be less fussy and respect the meat." One bite and I was emotionally scarred. I didn't get sick as I think my body knew not to swallow and I spit it out .. but it was foul with a huge capital F.
But.. back to the original post... why? What happened?? Was it Staph?
So the answer is...
Most bacteria and organisms that cause food to spoil would be killed by the long, high-termperature cooking process.
The danger would be if there happened to be a organism that produced sufficient quantities of a heat-stable toxin before you killed it. Considering that the meat was just beginning to turn, I think you're safe.
Personally, I would have salted and rinsed the surface of the meat before cooking - the combination of abrasion and a high-ionic strength rinse would tend to remove most of the 'gunk' on the surface (chemically speaking)
When proteins break down, they will produce amine-containing compounds that reek. (Remember, proteins are made up of amino acids.) See http://en.wikipedia.org/wiki/Stink_bomb for some specific examples. Your gag reflex is probably an evolutionary response, dating from a time when humans didn't generally cook their rotten meat for several hours before they ate it.
Remember also, that the reason spices were treasured prior to refrigeration was to cover up the taint of slightly rotten meat. :-D .
Go for it!!
ETA: from the FDA staph link posted above:
Infective dose--a toxin dose of less than 1.0 microgram in contaminated food will produce symptoms of staphylococcal intoxication. This toxin level is reached when S. aureus populations exceed one hundred thousand bacteria per gram (of food).
So, even if the bacteria on your pork happened to be a dangerous staph strain (which is a very small subset, just like there are only a few dangerous strains of e. coli) there has to be a sufficient quantity to have produced enough toxin to make you sick. The vast majority of food poisoning cases will not be from residual heat-stable toxins, rather living bacteria that are not killed by a cooking process.
The botulism toxin is not heat stable. Cooking denatures the toxin. The problem is that the C. botulinum spores are heat stable to 250F. So storage of your food in anaerobic conditions can cause the spores to grow creating more of the toxin.
This is the danger in infusing oil with garlic for example. After the infusion, the oil promotes an anaerobic environment -- if the oil has any spores in it and you use the oil cold in the future the toxin could have accumulated.
I could give you a pretty decent run down of the bacteria that are commonly responsible for food poisoning, but Daniellempls pretty much already did that, along with some of the risks and why heating doesn't always alleviate the risk.
But here's the thing about meat that is truly past its prime: eventually it will start growing colonies of less-often-mentioned bacteria, some mostly harmless (lactic acid producing bacteria for example), some potentially less so; it will also grow various molds, yeasts, fungus, and potentially even small unpleasant invertebrates. Basically, eventually that petri dish gets so crowded and complicated that at least I couldn't name most of the likely lifeforms or accurately predict the effect on your system or even speculate as to what toxins on the meat would be heat stable aside from the obvious ones - staph toxin regardless of preparation, botulism toxin if the meat wasn't boiled, pressure cooked, or braised (though really botulism is not particularly likely unless maybe someone already crammed some garlic cloves deep inside the meat or sauced the meat or something - c. botulinum is an obligate anaerobe not often found on refrigerated meat. It's worth noting as an outside possibility and because it is particularly deadly). At any rate, I know that some spoilage molds commonly cause nausea and vomiting not too long after ingestion. Other than that - we can just hope that someone who knows more about meat-specific long term spoilage comes along and can tell you more than I can.
Generally speaking, we wealthy civilized folk tend to err on the side of caution and throw out a lot of food that might not make us sick, or that other cultures might still prepare. But there's a reason for that - if you're not likely to starve, the risk of eating funky meat is probably not justified by the cost or principle. And there is definitely a risk.