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Do all bacteria die out ?

  1. Nov 9, 2007 #1
    I like fresh mixed vegetable, they are sold cheaply so very very much more than the country I have been to, but the hygience seems more problematic
    If I leave the vegetable inside the fridge for hours till it gets frozen completely, will all the bacteria be get rid of by the low temperature ?
    I am just worried they will wake up after being brought back to normal temperature :smile:

  2. jcsd
  3. Nov 9, 2007 #2

    jim mcnamara

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    No. Cold temperatures do not kill bacteria - they simply stop bacterial growth.
    Yes, they will "wake up" when they get warm.

    Your best choice is washing. There are detergents meant to kill bacteria on food.
    Get all the dirt off the veggies, then soak them in a soltuion of the fetergent. Rinse really well.

    By bad hygiene - I assume you mean they use night soil - "human manure" on crops. If that is the case you really should cook your veggies at least a little bit. The chances of your getting some basty pathogen are pretty good.

    Boiling water, for example, kills most bacteria and other things like the amoeba that causes dysentery. It will kill things like that in about 60 seconds. This does not work on green leafy veggies meant to be eaten uncooked. There are other disinfectant kinds of veggie treatments you can use. They require soaking in a disinfectant soltuion.
  4. Nov 9, 2007 #3


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    If you really have no other options (not eating vegetables isn't a good option either), then aside from jim's suggestions of washing the vegetables thoroughly and cooking the ones you can cook, one thing he didn't suggest that can help if you suspect unsanitary handling is to eat the food the same day you buy it (after washing and/or cooking). If there are bacteria on the foods, they will continue to grow the longer the food sits, so what might not be enough to make you sick the first day it's picked may grow to be enough to make you sick within a few days.

    And remember that any bacteria on the foods you buy can be transferred to your work surfaces, so always clean your work area thoroughly after each food is prepared, or if you put unwashed food on it, before putting it back on it after it has been washed.

    Freezing will slow bacterial growth, so if it's not possible to buy fresh and you need to store it, then it's better to wash it first, then freeze it for storage. For most vegetables that can tolerate freezing, you can also blanch it before freezing, which means dropping them into boiling water for just a few minutes. Not long enough to fully cook them, but long enough to kill off surface bacteria before freezing. Finish cooking the food when you defrost it.
  5. Nov 12, 2007 #4
    Thank you, could that kill the parasites and parasites' eggs anyway ?
  6. Nov 12, 2007 #5

    jim mcnamara

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    Freezing would kill tropical parasites, probably. Refrigerator no - no guarantee of that happening.
  7. Nov 12, 2007 #6
    I thought the low temperature could destroy the eggs and most parasites' living system... Since they need air and some kind of food to grow.

    Plus, I completely agree with what you too said, I haven't there been yet any reports found thus far on this kind of parasite freeze anyaway...
  8. Nov 19, 2007 #7
    Even though you're original question has been answered, here's some more useful information about how bacteria can cause food poisoning:

    If food is left sitting at room temperature for sufficient time, it can give you food poisoning even if it is heated sufficiently to kill all the bacteria in it. This happens because some bacteria secrete toxins as they're growing. Even after their death, the toxins persist. If the toxin is heat stable, it can cause food poisoning.
  9. Nov 19, 2007 #8
    Unless it is performed in a very special way in a lab, freezing generally destroys eukaryotic cells. So freezing should kill what most people refer to as "parasites" such as the agent of malaria (a protozoa) or anything that lays an egg.
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