Smoking Point of Fats

It is important to select a fat with a high smoke point, at least above 420^oF (216^oC). This temperature is above the average range of temperatures used for deep-fat frying. Selecting a fat with a smoke point at or below the frying temperature will cause it to over-heat and decompose into glycerol and its individual fatty acids. The glycerol is further broken down (hydrolyzed) to a steel-blue smoke called acrolein. Acrolein’s sharp, offensive odor warns people of its presence. This smoke is extremely irritating and even harmful to the mucus membranes of the mouth and nasal passages.

To select a fat that will not easily break down to acrolein, it is important to know the smoke points for frying fats. Smoke points are much higher than the boiling point of water, so foods can be heated much more rapidly in oils where frying temperatures range from 350^o to 450^oF (177^o to 232^oC). Selecting fats with smoke points above 420^oF (216^oC) for commercial frying automatically excludes olive oil, lard, and vegetable shortenings. Hydrogenated shortenings with added mono- and diglycerides are not recommended for frying, because the fatty acids are easily removed from the glycerol molecule, which is then free to form acrolein.

A more serious problem than smoking with overheating an oil is that at about 600^oF (316^oC), the fat will reach its flash point. At 700^oF (371^oC), the fat will be at its fire point. If this occurs, water should not be used to put out the fire. Fire extinguishers with a “C” designation should be kept on hand for that purpose. If an extinguisher is not available, it may be possible to smother the fire with a pan lid or large amounts of baking soda.