Why the difference in spoilage times?

November 4, 2010 11:40 PM

Why does meat go bad quicker than vegetables/fruit?

If you leave meat out on the counter for a day, you have to throw it out, at least according to the FDA. Fruit and veggies you can leave out for days at a time and they'll stay good, if not quite as fresh. Kept cold (not frozen), meat lasts a couple of days, fruit and vegetables close to a week, depending on the plant part in question.

What is it in the biological/chemical makeup of animal flesh that makes it more susceptible to decay than plant flesh?

posted by Hactar to science & nature (16 answers total)

I'm hardly a biologist, but it might have to do with the fact that a cut of meat is basically the innards of an animal, whereas a vegetable is a whole and intact part of a plant. There's a certain degree of structural integrity that probably prevents bacteria from completely invading the vegetable without first having to surpass various barriers.
posted by Sara C. at 11:42 PM on November 4, 2010

While I'm sure there are other reasons, the first that comes to mind is that what you think of as "meat" is not something that was designed to protect itself from decay. An apple, for example, is designed to hang around for a bit. If you cut it, however, it will quickly go bad. Your steak\ground meat\etc. are pieces of flesh cut from a once-living animal, and have had all of the protective bits removed.
posted by sanko at 11:45 PM on November 4, 2010 [1 favorite]

I wonder, how long does a whole (but dead) fish last? The skin is still protecting the fish. Or does this not count because the fish is dead and thus the protective mechanism have ceased?
posted by Hactar at 11:50 PM on November 4, 2010

Meat is basically muscle tissue without any integumentary barrier (like skin) between the component cell membranes and the environment. Microorganisms (and, for that matter, animals) just have to punch through a lipid bilayer studded with proteins and they're in.

Plant cells usually have cell walls made of a variety of tough polymers, and often fruit and veg are presented in their initial form with whatever additional organ-level integument they've got intact.

The reason an animal corpse rots faster than, say, a tree is that we have a big digestive tube stuffed full of bacteria that ordinarily can't punch through the gut wall - because it constantly secretes mucus to protect itself, and because it keeps moving the bacteria through, and because we keep our guts full of things that bacteria find tastier - but when we die all that activity comes to an immediate halt, the bacteria eat their way through the gut wall, and hey presto! They're already under our tough integument where the yummy stuff is.
posted by gingerest at 11:51 PM on November 4, 2010 [5 favorites]

Fruit is like eggs: it's sterile inside and it's sealed. For it to rot, fungi or yeast or bacteria have to penetrate the barrier that surrounds it.

Meat is not sealed, unless it's a whole carcass. Rotting can begin immediately.
posted by Chocolate Pickle at 11:52 PM on November 4, 2010

I think it's probably also to do with the type of bacteria that like to colonise each. And this in turn will be to do with things like the fat content (high in animals, low in fruit and veges - but also high in dairy products, oils, etc, which also go rancid quickly when exposed to air). Perhaps it also has to do with bacteria that are naturally occurring in animal products, which tend to be nastier for us than those that are naturally occurring in plant products. But I just made that last bit up.
posted by lollusc at 12:05 AM on November 5, 2010 [1 favorite]

Also, although this is anecdotal, I spent a few weeks last year on an island that has little power (a generator runs for a few hours a day), no refrigerators, and where people live a basic subistence life-style. From this I can tell you that meat and fish (and eggs, and pig's blood) left out at warm temperatures for two to three days is still edible - more so than you'd expect. I don't recommend trying this at home, but when you have no other option, it's amazing what you'll eat. (I'm not saying it tasted great, but it didn't make us sick.)
posted by lollusc at 12:07 AM on November 5, 2010

I am nowhere near a biologist, but my guess is that it might have something to do with how fruit/veg are not always technically dead when you buy them. Potatoes sprout if you leave them alone for too long, as do onions and garlic, and if you buy greens with roots attached you might be able to re-plant it. Meat and fish are all pretty dead by the time you get them.
posted by Xany at 12:08 AM on November 5, 2010 [4 favorites]

I wonder, how long does a whole (but dead) fish last?

From experience working shallow water fishing nets as a teenager, less than 6 hours in hot weather, even for whole fish. If we didn't pull nets shortly after sunrise on hot days, dead fish would be rotting in the net.
posted by Ahab at 12:13 AM on November 5, 2010 [1 favorite]

Alas, (poultry) eggs aren't sterile inside. It's been shown that laying hens' oviducts can be persistently colonized with (amongst other things) Salmonella enterica serovars, resulting in contamination of eggs before they even make it into the shell. II, A, 4, around p.56827 if you want an open online reference but it is huge and you will probably need to search for "transovarian" to get to it.

Or there's these refs ganked from same, if you have access to the journals.
Keller, L. H., C. E. Benson, K. Krotec, and R. J. Eckroade. Salmonella enteritidis Colonization of the Reproductive Tract and Forming of Freshly Laid Eggs of Chickens. Infection and Immunity 7: 2443-2449, 1995.
Snoeyenbos, G. H., C. F. Smyser, and H. Van Roekel, Salmonella Infections of the Ovary and Peritoneum of Chickens. Avian Diseases 13: 668-670, 1969.
posted by gingerest at 12:16 AM on November 5, 2010 [2 favorites]

Skin is the principal barrier to bacteria; once it's compromised on fruit or animal, decay is imminent. Slice fruit into slabs and it will rot just as quickly. Let's not make this complicated.
posted by Muirwylde at 12:27 AM on November 5, 2010 [1 favorite]

The bit about fruit being alive is relevant - animals have systems that exist to prevent rot and bacterial infection, and when dead those systems shut down (even if not cut up).

I think more significantly, meat (particularly from factory farm environments) is more likely to start out slightly contaminated, and when it's left out & not preserved or refrigerated then the bacteria can multiply, penetrate the meat more deeply, etc. So then either quick cooking isn't enough or the bacteria have produced sufficient levels of toxins that are resistant to cooking.
posted by Lady Li at 12:46 AM on November 5, 2010

Fruits are acidic, which stave off growth of certain spoilage bacteria. But they are full of water and fungal spores will make quick work of them.
posted by Blazecock Pileon at 4:01 AM on November 5, 2010

Blazecock Pileon- does this also apply to veggies? (I'm thinking of brocoli here as my example, as it has been cut in at least one place so the skin has been broken.)
posted by Hactar at 4:11 AM on November 5, 2010

Rotten meat is full of bugs a human can catch, because you, too, are meat. Rotten fruit and veggies are full of different kinds of beasties that won't be so harmful to you unless you're, say, a carrot. A plate of meat and a plate of veggies might be equally seething with decay, but it's the rotten meat that will kill you because the meat has already cultured a nice heap of bugs ready to infest your system and devour you.
posted by pracowity at 5:09 AM on November 5, 2010 [1 favorite]

It's probably useful at this point to distinguish between "rotting" and "unsafe to eat."

Meat becomes unsafe to eat fairly quickly at room temperature. Because it's chock full of pathogens, with no way to defeat them.

The living animal relies on its immune system for that. Once the immune system shuts off, the remaining flesh has no defense against microbes. Many of which, like e. coli, can make us very sick.

However, if you'll notice, a steak doesn't actually start to rot. It goes bad in an invisible fashion long before it starts smelling nasty or liquefying.

When I buy fresh berries in summer (strawberries, blackberries, raspberries, and tayberries are all grown in my area) they will have been picked that morning. But if I don't refrigerate them (like I would with meat) they will start breaking down by that evening. Within a few days, they degrade into a disgusting sticky moldy mush within a few days.

Which brings me to my final point: a lot of fruits and vegetables that you buy at the store have been specifically developed to "ship well." They have had all the flavor and nutrients bred out of them, in favor of tough skins and a low moisture content.
posted by ErikaB at 9:06 AM on November 5, 2010 [1 favorite]