Antioxidants, natural and commercial, are added to foods containing large amounts of unsaturated fats in order to prevent rancidity. The USDA’s Code of Federal Regulations defines antioxidants as substances used to preserve food by retarding deterioration, rancidity, or discoloration due to oxidation. Read more »

Preventing Rancidity

In the past, cereal manufacturers incorporated predominantly saturated fatty acids such as coconut and palm oils into their products to reduce the risk of rancidity. Public concern over saturated fat and its relationship to blood cholesterol levels has contributed to increasing use of unsaturated oils and new ways of deterring rancidity. Read more »

The different types of rancidity

There are two basic types of rancidity: hydrolytic rancidity, which occurs when water breaks larger compounds into smaller ones; and oxidative rancidity, in which the double bond of an unsaturated fatty acid reacts chemically with oxygen to result in two or more shorter molecules. Read more »

Storage of Fats

Although saturated fats resist rancidity better than unsaturated fats, it is best to protect both from this inevitable deterioration process. Fats such as butter and margarine are best stored in the refrigerator. Butter will keep for months in the freezer, but margarines do not freeze as well because their emulsions may separate. Read more »

Low-Fat Preparation Techniques

Reducing the consumption of dietary fat may be accomplished by following dietary guides recommending a meal pattern featuring the selection of foods that are lower in fat, especially the saturated type; relying on lower-fat or non-fat cooking methods; and reducing the fat in recipes. Read more »

The fats in a fryer go through stages that influence the quality of the fried product. At the “new” and “break-in” stages, foods absorb too little oil; just the right amount is absorbed at the “fresh” and “optimum” levels that follow; and then too much soaks in at the “degraded” and “runaway” phases. Many professional chefs claim that foods fry best in oil that has been used at least once. Read more »

Recommended equipment when deep-fat-frying

The quality of the fried food product is influenced by conditions other than temperature. It is important to use stainless-steel equipment. Iron, and especially copper or copper alloys such as brass, may increase rancidity. Hoods or exhaust systems above the fryer should be cleaned frequently so that accumulated particles do not drop back down into the fat. Read more »

Temperature Control

It is difficult to detect overheating visually, because fat does not boil, and heated oil is always hotter than it appears. Overheating contributes to the rapid deterioration of fat through polymerization. Any egg yolks used in the coating batter also contribute to the darkening effect on the fat. Read more »

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. Read more »

Deep Fat Frying Care

Not every fat is suited for the high temperatures of deep-fat frying. Vegetable oils, except for olive or sesame oil, and hydrogenated shortenings (without additives such as emulsifiers), all of which are 100 percent fat, are the ones most commonly used for this purpose. Read more »