If there’s something weird and it don’t look good…who you gonna call?


I got asked some questions by Carrie Poppy about decay, because as everyone knows, my name is a synonym for “to rot”. Sorta. By association only.

Oh, I wish I had a cool name.


  1. unclefrogy says

    can anyone explain the date codes or sell by dates or use by dates or what ever they are that are printed on stuff in supper markets. what do they mean if anything?
    I have the practice of reheating the soup stock (chicken mostly) I use in cooking every day or so to sterilize it and I hope reseting the “clock” on it. if I keep it up it does not seem to go bad if I wait too long though “wow!!” out it goes
    uncle frogy

  2. themadtapper says

    Well your name may not be “cool”, but on the bright side Carrie spelled it correctly, unlike creationists.

  3. wzrd1 says

    Uncle Frogy, there are two factors at work with a commercially prepared container. Part is the decay rate from microorganisms in the food. The other, the quality of seal and container components.
    When I redeployed home from a five year deployment, I went through dad’s basement cupboard shelves and found foods highly past the “use by” date – to the point where tomato based sauces and canned tomatoes had rusted through their cans and French Dressing was a solid brown. There were things on those shelves that I was tempted to put a biosafety level 3 suit on!
    Going into his deep freezer in 2010, I found stuffing from thanksgiving prepared by my mother. That might not be a biggie, save that she passed away in 2001.
    Needless to say, a *lot* went out into the garbage cans and smaller amounts restocked.

    So, “Sell by” is the last date a store should sell a product, these days, we largely have use by dates instead. After a use by date has passed, the container or food may begin to break down chemically or the seals may fail and microorganisms enter and spoil the food, or any colonies still dormant from processing/preservatives may no longer be kept in check by the processing/preservatives.
    We still cheat a bit on that date by a few months, we’re not wealthy.
    Six months to a year, it’s in the trash. That’s both due to the risk of fun things like botulism and the fact that I have essentially no sense of smell. I’ve had food poisoning many times, usually in the field, but occasionally when out dining or worse, in a military mess facility. I just can’t tell if the food is off until the taste is effected. Botulism, I’ve thankfully managed to avoid and intend to continue avoiding it – you can’t smell or taste that nasty.
    If the food is off color/texture/consistency, regardless of date, out into the bin. Food poisoning sucks. Badly.

    Does that help?

  4. brucej says

    And the Microbiologist in me goes ARRRRRRGGHHHH!!!

    You macrobiologist sorts who go on about enzymes and cell membranes and bacteria forget that food is typically COOKED!

    This changes all those calculations. Remember Pasteur!

    You know: germ theory, crook-necked flask and all that jazz? He made some chicken broth and left it at room temp for days and days with no rot? Ringing a bell?

  5. says

    can anyone explain the date codes or sell by dates or use by dates or what ever they are that are printed on stuff in supper markets. what do they mean if anything?

    It actually depends on the product. Do not mess with chicken meat whereas eggs and milk will more or less immediately know they’ve gone overboard. Vegetables tend to be pretty obvious. There is some “engineering overhead” – eating eggs that are a couple days past the ‘sell by’ is no problem unless they start to smell funny.

    Some foods are very very stable and are usually sold as “best used before…” date. I.e: jam, smoked salmon, salami, butter, cookies. Your Little Debbie snack cakes are made of stuff that is more or less eternal.

    Refrigeration dramatically slows/pauses bacteria and other stuff growing in your food. But they’re still there. After all, it’s food!

  6. says

    PS – another thing to look at is if the food is preserved somehow, and to know something about the preservation process. Pickling in brine or vinegar (or lye, if it’s lutefisk!) generally results in something that can last longer than you want to think about eating it. Brining or sugaring something can also make it last a very long time but if you have mechanical failures in the containment then you’ll have bacteria and fungi screaming “FOOOOOOD!”

    My ex-wife left behind a can of mandarin oranges in the closet, where it had fallen out of sight. When it finally exploded I heard it from upstairs but it took me a day or two of the bacteria feasting on the now widely-distributed juice before I could locate it and clean it up.

    If you have a food/bacteria/fungus explosion, wear latex gloves and wash your hands with dilute bleach afterward. Pseudomonas is unpleasant stuff.

  7. coragyps says

    I did buy a bottled water a while back with an expiration date in 2095. I guess I should have saved it for the great-grandkids.

  8. microraptor says

    As the old Calvin and Hobbes comic put it, never take chances with something that has a date you might expire.

  9. leftwingfox says

    I probably should not have read that after eating the same ham for the better part of the week.

  10. Nerd of Redhead, Dances OM Trolls says

    How long left/planned overs will last also depends upon the temperature in your fridge. Ours runs cold (about 35 ℉, lots of planned overs), and we can usually get two weeks from cooked meat/veggies.

  11. stripeycat says

    You’ve two seperate but related problems: has the food degraded to become unappetising; and will anything in it make you ill? If you’re lucky, the thing that is poisonous is also nasty (eg toxic moulds on badly stored nuts), but more often there’s no obvious sign. So, if there’s not often a direct link between the two, how to tell? The quick answer is that normally, you can’t. Most of the obvious spoilage isn’t harmful; for example, I cooked fridge-sweepings soup this evening: slimy parsnips that’d been left in their bag, sprouting onions, and limp celery, all well washed, trimmed of anything oxidised brown because that tastes unpleasant, then all cooked up into perfectly safe deliciousness. Similarly, oils (or oils in foods) may turn rancid, but if you’re hungry enough they’re still safe to eat. Even some things that are unpalatable (gone-off eggs, say, with the sulphur stink) are unlikely to make you seriously ill by themselves, but can be an indicator that a foodstuff has been around and growing its own microbiota much longer than is healthy. Moulds are a bit dodgier: some are safe (eg the white sort on cheese-rind), but others are very toxic, and some of the toxins survive cooking.

    However, most dangerous bacterial contamination of food is not obvious. You can’t tell if the chicken you’ve just bought is covered in Campylobacter or not, so you have to assume it is (ie cook thoroughly, and clean the heck out of anything it might have contaminated). Similarly, you can’t tell if the rice with your old takeaway is OK or doing a good impression of an agar plate. So, like cooking raw meat, you need to take precautions with storage and reheating that will most of the time not be necessary. Keeping things really cold helps (so chill quickly, and refrigerate in a reliable fridge). Reheating things really thoroughly kills most pathogens, but not all toxins are destroyed, so you may still get acute poisoning even after the bugs that produced them are dead: if something is a high risk for growing certain moulds or botulism, you’re probably better off only keeping it for a short time, then throwing it out, rather than risking reheating. Frogy’s trick with the stock-pot works because chilling with frequent reboilings kills off any bacterial growth before it can reach dangerous levels. Some foods are a more hospitable environment to potential pathogens than others, so have a much shorter shelf life – generally, wetter foods with a large surface area, or that have had a lot of handling, are worse than drier lumps.

    Then, risk-reward analysis comes into play: my immunocompromised mother would be much more seriously endangered by food poisoning than someone in good health, so she is a lot more cautious about kitchen hygiene than most people. The elderly, young infants and pregnant mothers are other high risk groups. And of course commercial kitchens (and amateurs catering events or large parties) should be properly paranoid because the extent of one outbreak can be large and the liability vast.

    The net outcome of all of this is that there are a lot of rules-of-thumb, which you apply with varying strictness depending on circumstances. It’s best not to let the situation arise in the first place: keep on top of the fridge management and inventory, so you don’t have edge cases to worry about. And when you screw that up, apply common sense and knowledge of biology to make a judgement call.

  12. says

    Nerd of Redhead, Dances OM Trolls #10:

    How long left/planned overs will last also depends upon the temperature in your fridge. Ours runs cold (about 35 ℉, lots of planned overs), and we can usually get two weeks from cooked meat/veggies.

    Anywhere below 5° C (41° F) is fine. 3 to 4° C is optimal. Below that, you’re getting into territory where you’re probably spending more money keeping the fridge extra-cold than you’re saving by using the left-overs.

  13. Azkyroth, B*Cos[F(u)]==Y says

    Two….to five…days….

    *quizzical head tilt*

    I’ve been pretty successful assuming at least a two week margin for, for instance, macaroni and cheese transferred straight from the pot to a tupperware… (that I might let go three, the ones that are transferred from a pot to a tupperware after getting back from a potluck I tend to toss in the freezer if not finished in two).

  14. Trickster Goddess says

    The other day as I was putting away the items I got from the local food bank, I noticed that the expiry date on a can of chicken noodle soup was August 2005! (Don’t you love these people who clean out their cupboards and the stuff they don’t feel comfortable eating they decide to give to poor people instead?)

    Anyway, I guess I’ll be conducting a science experiment this weekend.

  15. birgerjohansson says

    Going off on a tangent a bit, your name sounds a bit like the Swedish word “myr”.
    Meaning (peat) bog, you know, where you find all those preserved corpses from the early iron age that have been sacrificed.
    Also, you find other cool organic stuff preserved, like the world’s oldest ski (5000 years old, in our local museum).

    “My name sounds like the place where you find old human sacrifices” -a slogan for your next T-shirt?

  16. Meg Thornton says

    One other thing to throw into the mix: climatic conditions where you are. Hotter weather means shorter storage times absent refrigeration (and a higher chance of sweet things like jam or marmalade fermenting… nothing quite like opening the marmalade on a summer morning to that lovely smell which says you now have lime wine which is completely unsuitable for spreading on your toast. Thank gods Vegemite doesn’t go off). The colder the ambient temperature, the longer you can leave things out on the counter.

    (I’m Australian. For me, winter is the season where I can store the butter outside the fridge and thus have it malleable enough to spread on toast without requiring heavy machinery. Try that in summer, and you come back to a little yellow pool of rapidly-becoming-rancid grease. On the other hand, in summer I can pull the butter out of the fridge at the same time as I put the bread into the toaster, and have malleable butter, which isn’t really an option any other time of the year.)

  17. says

    Meg Thornton@#16:
    Thank gods Vegemite doesn’t go off

    Isn’t that because it is already “off” and there’s no more “off”er for it to go?

    in summer I can pull the butter out of the fridge at the same time as I put the bread into the toaster, and have malleable butter

    Have you looked into the possibility of using a butter bell? They’re clever demonstrations of physics as well as practical – search on amazon or someplace for them. I have an old one made of marble, which has lots of thermal mass and keeps the butter at the exact right level of gooey even on hot summer days. The only downside to a butter bell is that you’ll find it easy to consume lots more butter.

  18. wzrd1 says

    Heh, tell me about local conditions, Meg. In the Persian Gulf, I was letting a ball of dough for pasta rest for 20 minutes, at the end, it was already growing green mold.
    It also seemed that in that region, compared to my home region of SE Pennsylvania, mold and bacteria traded places in the decay cycle of produce.
    Quite a challenge to adapt to!

  19. ck, the Irate Lump says

    Marcus Ranum wrote:

    Have you looked into the possibility of using a butter bell?

    Personally, I just switched to blended butter (butter blended with canola oil). I can keep in the fridge and it’s easily spreadable even at that temperature. It’s a bit more expensive, but I’m still saving money because I’m not throwing out partial containers of butter anymore.