Jerky processing

Mold	Some jerky is packaged in jars or is not vacuumed seal.  When this is the case oxygen will remain present.  Mold will sometimes grow on jerky if oxygen is present.  Vacuum sealing will remove oxygen, preventing mold growth.
Salts or Sugars	The use of too much salt or sugar in the marinade.  When the marinade dries, the salts and sugars crystallize out of solution and appear as a white residue.
Tyrosine	The amino acid Tyrosine. Tyrosine also forms crystals.  This can also be seen on cheese and ham.
Sodium nitrite	A rare cause but sodium nitrite can precipitate into a white film on the surface of jerky.  This would be the case "hard" water was used during the jerky making process.
too dry	A white film also appear if the jerky is dried too long.