Are there any health risks when making vegetable stock from kitchen leftovers? 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?
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 &quot;the danger zone.&quot;  So your stock needs to at least cook above 140F (60C), and then be cooled below 40F (4C) with two hours of completion.