I don't know the chemistry. What I do know is that if you start searching for food-grade storage containers you'll mostly find plain white HDPE, and that other

I don't know the chemistry. What I do know is that if you start searching for food-grade storage containers you'll mostly find plain white HDPE, and that other colors of the same containers, from the same manufacturers, are not rated food-safe. I forget how I formed the impression that black was least likely to be food safe, except that black is what I otherwise would have wanted, and I could not for the life of me find food-safe black containers. But I think there was something else about that specific colorant as well. Sorry I can't find more specifics. I might be motivated to find a real expert now.