Cooking spray is a spray form of an oil as a lubricant, lecithin as an emulsifier, and a propellant such as food-grade alcohol, nitrous oxide, carbon dioxide or propane. Cooking spray is applied to frying pans and other cookware to prevent food from sticking. Traditionally, cooks used butter, shortening, or oils poured or rubbed on cookware. Most cooking sprays have less food energy per serving than an application of vegetable oil, because they are applied in a much thinner layer: US regulations allow many to be labelled “zero-calorie”; in the UK sprays claim to supply “less than 1 calorie per serving”. Popular US brands include Pam, Crisco, and Baker's Joy. Sprays are available with plain vegetable oil, butter and olive oil flavor. (source)