I have seen, that many people use kitchen scraps for making broth (eg. onion root and scraps) or that they just crush garlic, but still keep it in its skin or that people even do not peel carrots.

I am using slow cooking, but when I would be using these 'leftovers', is not there a risk of bacteria (from garlic skin maybe)?

Is it recommended to bring it to boil every time for a while? And even if it is boiled, there can still be toxins, that do not breakdown by boiling.

So is there any advice concerning that? Is there a procedure, that should always be taken into consideration?

  • Are you planning on canning the vegetable stock, so it's sitting for a long time at room temperature, or refrigerating it quickly and using it up within a few days?
    – Joe
    Commented Jan 12, 2021 at 16:45

3 Answers 3


Simple washing (for carrots, or veg. you might peel) is fine, if you don't want to peel. There is no problem using root vegetables without peeling either. Stocks are typically brought to a simmer. So, you easily mitigate any bacterial concerns. Botulism toxins form in an anaerobic environment. So, you don't really have to worry about using fresh, even unpeeled, root vegetables. Of course, you need to adhere to general food safety, and have an awareness of "the danger zone." So your stock needs to at least cook above 140F (60C), and then be cooled below 40F (4C) with two hours of completion.

  • 1
    Thanks for detailed answer. But is garlic growth environment always considerable as aerobic? I have read, that it can be caused by garlic in oil and that ground usually contains at least some air, but is it then ok to use garlic scraps/skins? Commented Jan 10, 2021 at 19:20
  • 1
    Anaerobic environments lack access to free oxygen. That is why garlic stored in oil, or improperly canned food can be environments that support the development of botulism toxins. Fresh garlic, stored normally, typically is not a problem in this regard.
    – moscafj
    Commented Jan 10, 2021 at 20:16

The safety of what you call "leftovers" is exactly the same as the safety of the vegetables they came from (assuming you store them under equal conditions after the vegetable is cut up into leftovers and main part). If you can eat the one, you can eat the other.

The whole idea that the leftovers are inedible is also strictly untrue. I had to smirk at "people even do not peel carrots" - I don't peel my carrots in general, not for broth and not when eating them raw. People peel vegetables for a variety of reasons, but "the skin is full of bacteria and the inside is pure and untainted" is not one of them.

For the rest of your concerns and ideas, it would be probably good to read our general information on the topic how food safety works: https://cooking.stackexchange.com/tags/food-safety/info. There we have invested some effort to explain the basics of how food safety works (and how it doesn't) and it covers a lot of the information first-time askers don't yet know.

  • Not quite true ... most people don't eat the skins or roots of onions and garlic.
    – Joe
    Commented Jan 12, 2021 at 16:31
  • @Joe indeed they don't - and if they suddenly decide to eat them anyway, they won't keel over from a bacterial infection.
    – rumtscho
    Commented Jan 12, 2021 at 16:38
  • I peel my root vegetables in order to find bruises or rot that might otherwise be hidden by the peel.
    – csk
    Commented Jan 12, 2021 at 16:53
  • OK, I get that there are more reasons for peeling than I mentioned at first. As listing them all seems quite a bit of a tangent, I changed the sentence, hoping that now the connection to the rest of the answer is clearer.
    – rumtscho
    Commented Jan 12, 2021 at 17:04

I live in the UK and frequently don't peel a lot of my veg, just take off the outside of things like brussel sprouts and cabbages and cut any bad bits off root vegetables etc.

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