Choosing the right cooking oil

Types of oils

Natural fats contain varying ratios of three types of fats: saturated, monounsaturated and polyunsaturated.

Saturated fats are hard at room temperature. They're stable, resist oxidation, and are found primarily in meat and dairy but also in palm and coconut oil.

Polyunsaturated fats are liquid at room temperature and the least stable. They oxidize easily and are found in seafood and corn, safflower, soybean and sunflower oils.

Monounsaturated fats are more stable generally than polyunsaturates. They're found in canola, nut and olive oils.

Pressed vs. chemically extracted

The oils at PCC may be less familiar than brands in mass-market grocery stores — for good reason. PCC buyers seek out natural oils that are mechanically pressed from the seed without using chemical solvents.

Olive, avocado and walnut oils, for example, are from soft fruit or nuts that need only expeller pressing and centrifuging; they may be labeled "cold-pressed."

Hard oilseeds such as soy or canola usually require some pre-treatment such as steam before pressing but still do not rely on chemical solvents.

In contrast, mass-market oils generally are extracted with toxic solvents such as hexane. These oils then undergo harsh treatment to remove the solvent. More chemicals, very high heat, and straining are used to deodorize and bleach the oils — rendering them inferior in taste, fragrance, appearance and especially nutritional quality.

Unrefined oils

Unrefined oils are filtered only lightly to remove large particles. Some, such as sesame or olive oil, may appear cloudy or have visible sediment after sitting. This does not compromise quality.

Unrefined oils are "whole" oils and their flavor, color and fragrance are more pronounced than in refined oils. Like unrefined whole grain flours, unrefined oils are more nutritious and have a shorter storage life than refined.

Unrefined oils are best used unheated in dressings or with low heat, sautéing or baking. Their natural resins and other beneficial particles burn easily and develop unpleasant flavors and unhealthful properties if overheated. If you choose to bake with unrefined oils, expect the flavor to be more pronounced.

Refined oils

Naturally refined oils are more thoroughly filtered and strained than unrefined, usually with some additional heat, but without harsh or damaging chemicals. Refining reduces the nutrient level and flavor. It also removes particles and resins and makes naturally refined oils more stable for longer storage, more resistant to smoking, and a good choice for high-heat cooking and frying.

Refined oils recommended for high-heat cooking and deep-frying are "high oleic" safflower, sunflower, and peanut oil. These are from plants bred to be high in monounsaturated fats instead of polyunsaturates, which oxidize easily and aren't suited for high heat. To check if it's "high oleic," read the nutrition panel on the bottle. It lists polyunsaturated and monounsaturated fats separately.

Storing oils

All oils, especially unrefined oils, should be refrigerated after opening to prevent oxidation and rancidity. Natural oils should smell and taste fresh and pleasant. Can't tell? If in doubt, throw it out. Studies indicate that rancid fats may promote cancer and heart disease.

We suggest keeping a small dispenser of your everyday oil in the pantry for what you'll use in a week or so and keep the larger bottle refrigerated. Oil that's firmed up in the refrigerator will liquefy at room temperature in a few minutes. Place the bottle in a container of warm — not hot — water for five minutes. The quality will not be harmed.

Frequently asked questions

Should I heat oil to the smoke point?

If oil or fat smokes in the pan the temperature is too high for that oil. It's safest to discard it, clean the pan and start over at a lower temperature. This may conflict with sources that advise to heat the oil to the smoke point. The point at which oil smokes signals that the oil has been damaged and potentially cancer-causing properties have formed.

Which oils are genetically engineered?

Soy, corn, canola and cotton are some of the most common genetically modified (GM) crops and all are cooking oil sources.

Some non-organic oils claim non-GMO (no genetically modified organisms) on their labels. Manufacturers may have lab tests and other documents to back up these claims. There's no federal regulation of such claims — except for USDA organic standards, which prohibit genetically engineered ingredients.

Are tropical fats good or bad for you?

Tropical fats are found in coconut, cocoa, palm fruit and palm kernel and are highly saturated. Contrary to earlier assumptions, studies show that coconut, cocoa and palm fruit oil may not elevate blood cholesterol and may have heart-healthy properties.

Coconut oil is high in beneficial lauric acid, may help stabilize blood sugar, and may lower the risk of heart disease and diabetes.