This article is from the Food Preserving FAQ, by Eric Decker email@example.com with numerous contributions by others.
From Denis DeFigueiredo :
I called Berlin and spoke to them, plus an outfit called Kirk Container (they
manufactured some 5 gallon paint buckets I saw in the local hardware store).
Both places said that buckets made from High Density Polyethylene are
approved for food. It has to do with the possibility of interaction between
any chemicals in the food and the plastic. As it turns out, Kirk
manufactures only *one* kind of bucket, and then markets it for paint,
hardware, food, etc. The price is right on the "paint buckets" - much cheaper
than the local restaurant supply house.
High density Polyethylene buckets will have HDPE stamped on them, or a
recycle symbol with a "2" in the middle. DISCLAIMER: I'm only passing on
information I received from the manufacturers. I am in no way professing
these things to be absolute fact!