What Do Fats/Oils Do in Cooking?

Let's begin with the most basic question: Why do we cook with oils? The answer to that simple question highlights the surprising complexities of cooking oils.

To begin with, oils lend flavor to food, with many different flavor compounds. They also add an elegant and rich mouthfeel to foods. Oils also prevent sticking during sautéing, while enabling heat transfer, allowing sugars and proteins in food to brown and caramelize (the Maillard reaction) without adhering to the pan. And oils play a role in softening foods during cooking, helping to break down the cellular structure of plants and meats.

From the healthy benefits perspective, oils carry fat-soluble vitamins such as A, D and E. Finally, and importantly, oils carry fat-soluble aromas from various herbs and spices. (Spicier aromas, however, are carried on alcohol, not on oils, which is why you will sometimes see a chili or similar recipe call for a tablespoon or two of bourbon or vodka.)

Basic Types/Classes of Oils

There are several ways to group oils by different characteristics:

• Source: Animal (butter, lard, tallow) or vegetable/fruit oils. The latter are divided into subcategories of:
  • Fruits: such as olive, coconut, palm and avocado
  • Seeds: a large sub-type of vegetable oils that includes sunflower, canola, soybean, corn and safflower
  • Nuts: such as walnut, sesame and peanut (botanically considered seeds but often grouped separately as cooking oils)
• Flavor: Neutral or "light" oils (canola, sunflower) vs. more intensely flavored oils (olive, coconut)
• Smoke point: Basically how hot the oil can get before it starts to break down
• Fat composition: All oils contain both saturated and unsaturated fats (further divided into polyunsaturated and monounsaturated) but in varying ratios
• Processing: Unrefined (includes "cold press" or "virgin press" and is generally considered to yield the most flavorful and healthful oils), refined (chemically altered to achieve a high smoke point or lower acidity), and hydrogenated (chemically altered to be more shelf stable)

Using Oils

• Add oil to your pan, then preheat the pan using medium to medium-high heat. This ensures uniform heating of the pan bottom and sides without hot spots that can warp the pan.
• Never heat a pan on the highest setting unless it has water or a brothy soup in it.
• As soon as the oil starts to shimmer, add the food. Don't wait until the oil is smoking. This will begin to break down the healthful polyphenols and affect the taste.
• When you add the food to the oil, stir thoroughly to evenly coat all the food in the hot oil. Periodically scrape down any food bits clinging to the sides of the pan, which may burn if left there.
• You may periodically see the term "finishing oil." This is a high quality oil, typically a fresh extra-virgin olive oil (EVOO), to drizzle on the entrée, soup, or salad. It's a wonderful way to embellish flavors and appearance, enhance the mouth feel, and consume more of a high quality, healthful fat.

Smoke Points

Smoke points are important to understand because that is when the oil starts to turn bitter, adding undesirable flavors to the food. It is also when many healthful compounds, such as polyphenols and other antioxidants, begin to degrade.

Generally the more refined/processed the oil, the higher the smoke point. This can vary widely from one brand to the next however. Look to see if the product lists the smoke point on the container.

Understanding Each Oil and When to Use

Olive Oil

Olive oil, specifically "extra virgin" olive oil, is widely considered to be the highest quality and least processed of the most commonly used oils. "Extra virgin" refers to minimal processing, using manual extraction with no heat or chemicals, yielding fresh and vibrant flavors (often described as "grassy") and greater nutrients.

Olive oil is very high in oleic acid, a mono-unsaturated fat, and has more polyphenols than most other oils. These compounds have antioxidant properties and are a major reason olive oil is so highly recommended.

Purchasing tips:

• Look for the harvest date on the bottle (not the 'best buy' date) being within the past year. The shelf life for olive oil is 18 months, which would give you 6+ months to use it up. Olives are harvested October through January in the Northern Hemisphere and in April-July in the Southern Hemisphere.
• If only the "best by" date is shown, most brands of olive oil allow two years from harvest to the end of useful shelf life, so ideally you would see a "best by" date that is within 12-18 months of purchase.
• Purchase olive oil that comes in dark glass bottles.
• Avoid unfiltered olive oils. While marketed as more natural, the residue and extra humidity found in these oils lead to much faster degradation.
• Look for a clear provenance of the oil. Can you tell where it was harvested and extracted? The more specific in terms of country region, the better.

Sunflower Oil

Sunflower oil has become quite popular, prized for its neutral flavor and high smoke point. It is also considered a healthful oil, containing both monounsaturated and polyunsaturated (both omega-3 and omega-6) fats, as well as high amounts of the essential fatty acid, linoleic acid.

Coconut Oil

There are more saturated fats in this oil than other vegetable oils (note its solid state at room temperature). It also has a unique flavor, which can be used to good effect. Coconut oil has a very low smoke point, and the oil degrades quickly when heated, so it must be used with care.

Avocado Oil

This is a good all-purpose oil, with lots of antioxidants, unsaturated fats, nice flavor, and a very high smoke point (520 degrees!). It is expensive but mostly because of good marketing, not because it is an exceptional oil to use, since its health benefits are comparable to olive oil and other seed oils.

Canola (Rapeseed) Oil

This is widely used for home cooking, either alone or as part of a vegetable oil blend, in part because of its neutral flavor, affordability, wide availability, and fairly high smoke point (440 degrees). It is mostly known in Europe and other parts of the world as rapeseed oil (the name of the plant). 'Canola' is actually an acronym for Canadian Oil Low Acid.

Sesame Oil

A common ingredient in many Asian cuisines, even a small amount adds a burst of nutty and fragrant aromas and flavors. Supermarket brands range from mild (lighter colored) to very robust (dark) intensities, so adjust your measurements accordingly — it can easily overpower more delicate flavors.

Oils and Health

• We need fat in our diet, and fats from vegetable sources, such as cooking oils, are generally lower in saturated fats than from animal sources. But all fats are a blend of both saturated and unsaturated fats, although the ratios vary. When purchasing, look for oils that are less than 4 grams of saturated fat per tablespoon and contain no trans or partially hydrogenated fats.
• One way to think about the health effects of a fat is to think in terms of whether the fat is intrinsic to the food, such as fat within an avocado or egg, or extrinsic, such as fat added before sautéing or in a baked cake.
• Seed oils are currently getting something of a bad rap from "health influencers" on YouTube and social media. But quality nutrition research is clear that seed oils are basically a healthy choice, almost as beneficial as extra virgin olive oil. Claims that they are overly processed and inflammatory are not borne out in careful analysis.

Shopping and Storing Tips

• Buy in small quantities. Oils do go rancid and will lose their protective polyphenols over time. The smoke points also decline as the oil ages.
• Store in dark, cool places (not over or next to the stove).
• The less refining used in production, such as with extra-virgin olive oil, the shorter the shelf life, ideally within 6 months. Refined oils such as Canola and soybean have longer shelf lives. But using up any oil within six months is good advice for optimal flavor and health benefits.