Ester gums — formed by esterifying rosin or resin acids with polyhydric alcohols such as glycerol or pentaerythritol — have their own dedicated subheading (380630). Other chemical derivatives of rosin that do not qualify as ester gums fall under the residual subheading 380690. The distinction turns on the specific reaction chemistry and the alcohol used.

Rosin esters used as food additives or indirect food-contact materials may be subject to FDA review under food additive regulations. Importers should verify that the specific ester gum grade and its intended use conform to applicable FDA food additive authorizations before entry.