Pepperoni contains a lot of fat. Fat oxidizes, and that may make it taste soapy. The fennel may make it taste soapy, I don't know. Oxidation shouldn't cause illness, but if you hate the taste that much, it's enough.

I don't mind cilantro in small amounts, camouflaged by other ingredients, but on its own, I dislike the taste strongly. I can't describe the taste as 'soapy'. It's more of a 'DAMN!-how'd-my-lawn-mower-clippings-get-in-my-mouth!?' sort of thing. Makes me want to chew my toenails or lick a cat's ass to get the taste out of my mouth. (I've never actually done either of these, but I think toenails and cat ass probably taste better than cilantro.)

Pepperoni, I LOVE. (And fennel)