Is "ash" a carcinogen?
Maybe you've seen some type of "ash" on menus. I've seen it in a few cookbooks, mostly from the types of places that do tasting menus, and the general preparation is: put a fruit/vegetable/plant in a hot oven for a long time until it's thoroughly blackened, grind it to a fine powder, and do whatever you want with it from there.
I tried this the other day with the pulp from juiced blood oranges and ended up with a fine, smoky powder with only mild bitterness and a fruity citrus thing in the background. It's pretty unique and I'd like to actually use it in something, but I also remember reading that blackening things isn't really healthy. Topics like "does x cause cancer???" are kind of risky ground on a forum but I am curious if there are any clear-cut health risks to eating this. If not I see no reason why you couldn't use it, say, as a more interesting substitute for squid ink.
I can see two ways of looking at this: 1) to be concerned that the ash contains heterocyclic amines and polycyclic aromatic hydrocarbons (which are carcinogenic), but I'm pretty sure that these compounds are mostly produced by charring animal protein, or 2) the charred plant powder is mostly composed of high surface area carbon, which adsorbs potentially toxic compounds in the gut and may actually be cleansing to some minor (very minor) degree. Similar to the activated charcoal that is administered in poisonings or drug overdoses.
For me, it comes down to whether or not the ashes are yummy. If yes, go with option 2. If no, go with option 1.
PS. Don't the ashes make the food unappealingly gritty? Just thinking about it makes my teeth hurt.
The carbon is not, but like chocoat said the heterocyclic amines and polycyclic aromatic hydrocarbons are carcinogen.
The way I see it is that it is fine to consume it once awhile, but try to avoid regular consumption.
Thanks to everyone for replying. This reinforced what I already thought: given that this isn't animal protein, there's no ironclad reason that this would be harmful, but at the same time given how weird a substance ash is eating it in large quantities isn't really advisable. That's fine - the pulp of a blood orange produces <1 tbsp of ash, and it's not like I do this often.
For a simultaneous answer to chococat and jill kibler: I'd heard of vegetable ash being used to coat cheeses, and I had goat cheese on hand and know that blood orange and goat cheese is a relatively well-accepted combination, so I mixed the ash into some of the goat cheese and thought it was great. This also prevents it from being unappealingly gritty.