DEAR DR. BLONZ: What is the propellant used in the nonstick cooking sprays, and how do the sprays work? Why are they more effective than merely spreading oil on the pan? I rely on these sprays when I stir-fry vegetables or when I roast a chicken. Is this practice as healthy as it's made out to be? -- S.T., New Orleans
DEAR S.T.: Nonstick cooking sprays contain a vegetable oil -- such as corn, soy, canola or olive oil -- plus lecithin, an ingredient from soybeans traditionally used to keep oil and water in solution together. Aerosol versions also contain a propellant gas. Although each uses oil, cooking sprays differ in their ability to form a thin, well-disbursed oil-lecithin film that stays between the cooking surface and the food. Some products also include very small amounts of a silicone compound and alcohol to prevent foaming and to facilitate the formation of the nonstick film.
Because the sprays use a minimum amount of oil, little fat is contributed to the meal. A one-second application -- an amount sufficient to cover a 10-inch skillet -- will contain less than one gram of fat. The Nutrition Facts label on many of these products have a "recommended serving" of a third of a second or less. Tough to pull off, but it does allow the manufacturer to claim the product supplies less than a half of a gram of fat per serving, which in turn allows the product to be labeled as "fat-free."
The ingredients should be clearly stated on the container so you can opt for a product that contains no more than the basic components. About the only safety issue would come from the fact that aerosol sprays require a compressed gas for a propellant. Some make use of hydrocarbons such as propane or isobutane, both of which can be highly flammable. Such sprays should only be used on cold surfaces and kept away from all flames. If a flammable hydrocarbon gas is used, there should be an appropriate warning label to this effect. You may be able to find a product that does not rely on flammable hydrocarbon gas propellants.
When using these sprays, shake well, as the ingredients need to be thoroughly mixed to work properly. An oft-ignored drawback from the use of these products is the waste contributed by the empty aerosol can. There are refillable pump sprays that limit this aspect, but the high pressure of the aerosol is what helps facilitate spray performance. If you go the homemade pump-spray route, you may have to experiment with oils, staying away from unfiltered oils with particulate matter that might clog the nozzle.
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to email@example.com. Due to the volume of mail, personal replies cannot be provided.