Abstract: The invention describes a method of forming a granule coated with a preservative composition, a preservative composition and a method of protecting food material. Food products are protected in storage, such as fruit and vegetable tubers, against rot and fungus by coating with a salt of a carboxylic acid, such as citric acid, and an alkyl amine such as 2-amino butane. This coating may be granular. A granular core of diatomaceous earth may be sprayed with the preservative composition and dried. The dried granules may be mixed with the food in storage.