Zinc

Zinc was a substance used as food additive for cooking Smapp.

Behind the scenes
Zinc was mentioned in a one-page cooking recipe titled "Cooking a Smapp", written by Bob Carrau for the 1993 book Monsters and Aliens from George Lucas, a publication that collects concept designs and photographs from various George Lucas projects. Lucasfilm employee Leland Chee, who maintains the Holocron continuity database, has indicated that information contained in the book is non-canonical.