The other day, I learned some things I didn't know about toxins in food from the Healthy Food Guide (November 2008). (Yes, I'm that behind in my reading!) To avoid various common toxins, the following steps are recommended:
Fruit seeds and pips
Remove seeds and pips of apples and pears before juicing. I guess this could have implications at juice bars!
Soak for 4-5 hours before boiling in fresh water for at least 10 minutes. I knew this anyway, but I didn't know why.
Potato or Kumara
Avoid green or damaged areas of potatoes. Remove bruised or damaged parts of kumara before cooking. Don't eat if bitter-tasting when cooked. I applied this one when preparing my last lot of red (Maori) potatoes. I'll tell you what, it's hard to detect bad bits through such dark skin - it was only on peeling many bits that I found dry brown bits underneath!
Toxins from mould can permeate further into the food - including cheese. Hmm, there goes my (inhereted) "just cut it off, it's still good!" attitude...
Particularly home-grown courgettes can contain toxins. Never eat if bitter smelling or tasting. Well, if we ever grow any!
And last but not least:
Always remove the skin of parsnips. Don't use the cooking water from parsnips. This is the one that scares me the most because, especially recently, I've always left the skin on parsnips. I applied a mix of laziness and the assumption that, like potatoes, the skin would contain most of the nutrients, and therefore should be left on... I guess not.