Some polymers from some families are allowed to store food. For instance some PP and PETP grades may be allowed.
Then, because some poisons can be noxious in minute quantities, just telling "Polyester" or PBTP or PETP isn't accurate enough. The whole manufacturing process of these polymers AND the parts must guarantee maximum amounts for potential hazardous compounds. This includes unmoulding lubricants for instance, dyes and so on.
So from the same provider, you generally have within a polymer family some grades that are allowed for food contact and others that are not. Then the transformer, which makes a pot from the granules, must work adequately too.