Guide to Cooking Oils Return to the Spices Main Menu for More Information What's In This Section Refined Cooking Oils Unrefined Cooking Oils Extraction Processes Storing and Keeping Oil Description/Uses of Refined Cooking Oils Description/Uses of Unrefined Cooking Oils Signs of Deteriorated Oil Composition Of Fats Oils for Frying What Is The Smoke Point Which Oil is the Most Healthy?   Storing and Keeping Oil Whether refined or not, all oils are sensitive to heat, light and exposure to oxygen. Rancid oil has an unpleasant aroma and acrid taste, and its nutrients are greatly diminished. Regardless of refinement, it's best to store all oils in the refrigerator. Oils may thicken, but if you let them stand at room temperature they'll soon return to liquid. To prevent negative effects of heat and light, take oils out of cold storage just long enough to use them. Refined oils high in monounsaturated fats keep up to a year in the refrigerator, while those high in polyunsaturated fats keep about six months.Extra-virgin and virgin olive oils keep about a year after opening. Olive and other monounsaturated oils keep well up to eight months; unrefined polyunsaturated oils only about half as long. If you keep bacon fat store it in the fridge and use it within a few days. For longer storage measure by tablespoons in a muffin tin and freeze. Pop out the frozen portions and store them in a ziploc freezer bag yo use when needed. Extraction Processes Refinement Level - Oils are generally grouped into two camps: unrefined and refined.  Oil flavor intensity is generally inversely proportional to processing. The first step in producing any oil is removing it from its fruit, nut, seed or grain source. All oil extraction processes involve heating the oil in some way. However, temperatures over 300°F destroy the proteins and natural vitamin E in oils. Lower temperatures (in the 120°F to 160°F range) do not damage the oil significantly, but do reduce the yield, making good oils a little more expensive. It is essential to retain vitamin E in an oil because it prevents the oil from oxidizing. Oils with little vitamin E tend to go rancid quickly unless treated with antioxidant chemicals. Expeller-Pressed: These oils are obtained by squeezing the seed, grain, or fruit at pressures up to 15 tons per square inch. The higher the pressure, the more heat is generated. At extremely high pressures, the temperature can exceed 300°F.Most oils are extracted by expeller pressing and don't qualify as cold-pressed because friction heats them above 120°F. Still, unrefined expeller-pressed oils retain most of their flavor, aroma, color and nutrients. Cold-Pressed: The term cold pressed theoretically means that an oil is expeller-pressed at low temperatures. However the term has no legal definition and is absolutely meaningless when used as an indication of quality. Olive oil, sesame oil, and peanut oil are really the only kinds that can be truly cold-pressed on any sort of large commercial scale. Olive oil is still extracted by the centuries-old process of stone-pressing, though these days it's usually done with hydraulic presses. Both techniques generate little heat, hence the term cold-pressed. They are the only substances that will easily yield their oil by simple, low-intensity pressure, which does not generate a great deal of heat. .True cold-pressed oils are prized. They contain minerals, phosphatides, and vitamin E and are high in trace nutrients. Extracted: Extracted oils are invariably subjected to some sort of applied heat during processing. Chemical or Solvent Extraction: The cheaper brands of oil (most regular commercial brands) generally use chemical solvents to extract the oil. A description of how the majority of oils are processed, or refined, is sobering. The oil is separated from its food source with hexane or other petroleum solvents and then boiled to drive off the toxic solvents. The oil is next refined, bleached, and deodorized, which involves heating it to over 400°F. The oil extracted this way still contains some undesirable solvent residues, while the amounts of many key nutrients (especially vitamin E) are significantly reduced. Antioxidants or preservatives such as BHA (butylated hydroxyanisole) or BHT (butylated hydroxytoluene) are then frequently added. The resulting product lacks flavor, aroma, pigments, and nutrients. All that can be said for such an oil is that it has an extended shelf life, a clear, uniform color, and an oily texture. Signs of Deteriorated Oil Oil used for deep frying darkens with each use because the oil and food molecules burn when subjected to high/prolonged heat. The more you use an oil, the more slowly it will pour. Its viscosity changes because of changes to the oil's molecular structure. Loose absorbent particles accumulate as sediment at the bottom of the storage container or are suspended in the oil. When smoke appears on the oils' surface before the temperature reaches 190 degrees C (375 degrees F), your oil will no longer deep-fry effectively. If the oil has a rancid or "off" smell or if it smells like the foods you've cooked in it, it should be discarded. For all baking grease baking sheets and pans with refined oils because the pans become hotter than their contents. Which Oil is the Most Healthy? Safflower or corn oil? Sunflower vs. peanut? The bottom line is, the fat content differences between the poly- and monounsaturated oils probably are not sufficient to have any significant effect on your health in the long run. So your best bet is to use a variety of oils judiciously. When considering your options, keep in mind that Canola oil is lowest in the saturated fat that clogs our arteries, while olive oil is highest in monounsaturates.. One fact remains a constant. All cooking oils are 100 percent fat--plain and simple. And most of us need to curb the total amount of fat in our diet. So with cooking oil, remember, less is more. More important than splitting hairs over the fat composition of vying vegetable oils is limiting total fat intake to no more than 25 to 30 percent of calories. No matter how favorable the profile, all cooking oils are 100 percent fat, with a whopping 120 calories per tablespoon. And research consistently shows that people who regularly consume high-fat, high-calorie diets are more prone to diseases such as heart disease, some kinds of cancer, diabetes in adults, and obesity. The answer seems to lie not only in scrutinizing the fine print on labels at your supermarket and then choosing among the cooking oils that offer health benefits, but in using them sparingly All vegetable oils we cook with contain a combination of saturated, monounsaturated, and polyunsaturated fats in varying proportions. In other words, there is no such thing as a saturated-fat-free oil or one containing only polyunsaturated or monounsaturated fat. The dietary difference in cooking oils lies in the proportions each contains of the three basic types of fat. Be aware of some product advertisements boasting that an oil contains no cholesterol. It's true. But it's not due to any new "miracle process"- Vegetable oils contain no cholesterol because only foods from animals have cholesterol, not foods from plants.   Oils to Use for Frying There are several expeller-extracted oils that can handle high-heat cooking like sizzling stir-frying and deep-frying. Though refined, they're preferable to solvent-extracted oils. Refined peanut and high-oleic safflower and sunflower oils are other good alternatives. Never fry at high heats with corn oil, it's notorious for foaming and smoking. Some experts claim that the finest extra-virgin olive oils with exceedingly low acidity surpass other vegetable oils in heat resistance.   Some oils can tolerate high heat without causing carcinogenic compounds. Avocado 520° F Almond 495° F Coconut 450° F Composition Of Fats Like fats, oils differ from one another in their molecular structure and are categorized by their degree of "saturation." Without getting into too much chemistry, this refers to the arrangement of their carbon atoms and links with hydrogen and oxygen. We've all been told about the heart health risks of saturated fats, which generally come from animal sources. Three plant-based exceptions to this rule are the tropical oils - coconut, palm and palm kernel oils, and should avoid using them. Monounsaturated oils are liquid at room temperature but cloud and thicken when chilled. Olive, canola, peanut and hazelnut oils are monounsaturated fats, as are high-oleic safflower and sunflower oils. Consuming monounsaturated oils seems to reduce total blood cholesterol and the "bad" (low density lipoproteins [LDL]) cholesterol levels without affecting the "good" (high density lipoproteins [HDL]) cholesterol levels. Olive oil and canola oil have been recommended as the safest sources of fat in a heart-healthy diet. Polyunsaturated oils, such as regular safflower and sunflower, walnut, corn and soybean oils, remain liquid whether in or out of the refrigerator. Sesame oil contains approximately half monounsaturated and half polyunsaturated fatty acids. Polyunsaturated oils used to be the healthful heroes because they too reduce total cholesterol and LDL, but we now know they also decrease HDL's positive effects. Furthermore, polyunsaturated oils are chemically unstable, especially when exposed to heat, and are highly susceptible to attack by "free radicals," unbonded oxygen molecules that contribute to cancer and other chronic diseases. Still, some polyunsaturated oil is necessary to obtain essential fatty acids. Vegetable oils high in polyunsaturated fat include safflower, corn, soybean, and sunflower oils. Monounsaturated fats: Like Polyunsaturated oil, this lower blood cholesterol, especially when used to replace saturated fat. Monounsaturated fats boast an added bonus--they maintain HDL (high density lipoprotein), the "good" cholesterol that helps prevent heart disease. But even though polyunsaturated and monounsaturated fats are considered more desirable choices, they, too, should be limited to no more than 10 percent of total calories.. Olive, peanut, and canola oils are highest in monounsaturated fats.