Is it safe to place plastic wrap directly on the surface of still-warm, fatty foods such as puddings or pastry creams?
For an answer, we consulted Daniel Schmidt, an associate professor in the Department of Plastics Engineering at the University of Massachusetts Lowell. He explained that in the past, plastic wraps were made with one of two types of plastic—polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC)—along with compounds known as “plasticizers” that enhanced their clinginess and stretchiness. However, health concerns associated with these plastics as well as many plasticizers have led most manufacturers to switch to polyethylene, which requires no plasticizers, at the expense of some clinginess. That said, if plasticizers or additives were present in a plastic wrap, they would indeed be more likely to migrate into warm, fatty foods. Not only are many plastic additives more soluble in fats and oils than in water, but small molecules in general migrate at much higher rates at elevated temperatures.
The bottom line: While there is no evidence to suggest that the newer, reformulated plastic wraps leach harmful compounds into food, keeping the wrap at least 1 inch from food surfaces will eliminate any potential risk. Another solution is to use parchment paper for direct surface contact, as we do in the test kitchen for puddings and custards.