Saturated, Unsaturated, Hydrogenated Oil
A little bit of chemistry can be helpful in understanding the differences in oils and hydrogenated oil. All oils are fats. All fats are made of fatty acids, long chains of carbon and hydrogen atoms with an acidic group at one end, attached to a chemical backbone called glycerol. Simple fats, or triglycerides, are formed when three fatty acids combine with one glycerol molecule.
When the carbon atoms are full of hydrogen, the fat is called “saturated.” When one or more of the carbon atoms has an extra bond to another carbon atom instead of a hydrogen atom, the fat is called “unsaturated.” A fat with one carbon double bond is mono-unsaturated; with more than one, poly-unsaturated.
The saturated fats have long, straight chains that are easy to pack and are usually solid at room temperature. Palm kernel oil and cocoa butter are examples of naturally occurring highly saturated fats. Saturated fats raise blood cholesterol levels, one of the risk factors for heart disease. Saturated fats promote high levels of low-density lipoproteins or LDLs. These compounds transport cholesterol to the arterial walls and body tissues. This is why LDLs are referred to as “bad” cholesterol.
Unsaturated fatty acids have bends in the carbon chains at the double bonds, which make them difficult to pack. These fats tend to be liquid at room temperature, so we call them oil. Unsaturated fats reduce the production of cholesterol and LDLs. Olive and canola oil are excellent sources of mono- and polyunsaturated fats.
Super-poly-unsaturated oils have the highest concentration of essential fatty acids. These oils are found refrigerated in opaque containers. They are very sensitive to heat and light and react with oxygen very quickly. Flaxseed, primrose, and borage oils are all excellent sources of EFAs.
While it is important to consume both Omega-3 and Omega-6 fatty acids, it is important that they be in the proper ratio. Primitive diets probably contained equal amounts of these essential fatty acids, but today we may consume ten times more Omega-6 than Omega-3. This is important since these compounds compete in the body. High levels of alpha-linolenic (Omega-3) acid are thought to reduce the risk of heart disease. However, a high level of linoleic acid (Omega-6) relative to alpha- linolenic acid has been associated with increased incidence of cancer.
Most vegetable shortenings and margarine contain oils that have been hydrogenated, that is, the carbon-carbon double bonds are broken and hydrogen atoms are added. Hydrogenation of oils reduces their polyunsaturated nature and produces trans–fatty acids. Trans–fatty acids raise LDL levels and reduce HDL levels, much as saturated fats do. It is generally thought that these isomers, normally found in insignificant quantities in oils, have damaging effects on cell membrane integrity and immune function.
However, there are some solid vegetable shortenings with no hydrogenated fats. These products usually contain palm or coconut oil. (see glossary following) To make matters more confusing, some shortenings claim to have 0 grams of trans fat yet still contain hydrogenated oil. The catch here is that the level of trans-fatty acids is low and the amount per serving is considered negligible so the manufacturer can legally claim that there is no trans fat per serving. This does not mean that they’re not there!
The best way to avoid trans–fatty acids is to eat a low-fat diet and minimally processed foods. Hydrogenated oils must be listed separately on the ingredients list of packaged foods. By law, ingredients are listed by weight, so the lower down the list of ingredients hydrogenated oil appears, the less the product contains. This will be of importance when you are shopping for margarine. Another good rule of thumb is that the harder the margarine, the more hydrogenated the oil.
Know Your Oils
Supermarket shelves are painted with a delicate palette of oils, from almost clear peanut oil to pale canola oil, straw-colored sunflower oil, sun-bright corn oil, and deep green olive oils. Fats and oils enrich and lubricate foods, make us feel full, and help control appetite.
Each oil has a distinct profile, but which oil you use and how are largely a matter of personal preference. The only exceptions are the oils meant for flavoring. Walnut, hazelnut, toasted sesame and extra virgin olive oils lose their fragrance and become slightly bitter when heated. Since these are significantly more expensive than oils meant for cooking, there should be little temptation to misuse them. Certain oils sold as dietary supplements, such as flaxseed oil, should never be heated. Try adding these to grain salads, salad dressings, and smoothies.
Canola oil is a light, pleasant tasting oil derived from rapeseed, a member of the mustard family. The tangy mustard flavor, from erucic acid, was selectively bred out of the rapeseed plant to obtain the canola plant.
Canola was bred specifically to produce a favorable fatty acid profile: 6 percent saturated fat, 62 percent monounsaturated fat, and 32 percent polyunsaturated fat. Of these, 10 percent is alpha-linolenic (Omega-3), 24 percent is linoleic (Omega-6), and 60 percent is oleic (Omega-9). Canola oil can be used at medium-high heat for sautéing, roasting, baking, and some stir-frying.
Coconut oil has a pleasant flavor and may be used for either cooking or baking. It is often used to give a rich mouth feel reminiscent of butter. While the fact that it is 87 percent saturated fat concerns some, others believe that the high lauric acid content and medium chain triglycerides have health benefits.
Corn oil is pressed from corn kernels and has medium weight, with 13 percent saturated, 24 percent monounsaturated, and 59 percent polyunsaturated fat, and a high concentration of Omega-6 fatty acid. Corn oil has a light taste and is excellent for frying.
Flaxseed oil has a high concentration of EFAs and a delicate nature. It is used as a dietary supplement. Find flaxseed oil in the grocery or health food store. Never heat flaxseed oil. Use it as a healthful addition to salad dressings, on popcorn, on cereal, in smoothies, or straight out of the bottle. This oil has a wheaty, slightly bitter flavor. Because it is highly polyunsaturated, it can become rancid and smell fishy. Use flaxseed oil within 2 months of opening.
Grapeseed oil is virtually tasteless, with 72 percent polyunsaturated fat and 68 percent linoleic acid (Omega-6). Its high vitamin E content protects it from oxidation and increases the shelf life. It’s bland background makes it perfect for infusion with truffles or herbs. Grapeseed oil can be used over medium-high heat or in cold cuisine. Some manufacturers claim a smoke point as high as 425°, but experience says 350°. Grapeseed oil is more expensive than most general cooking oils.
Hazelnut oil is an excellent source of vitamin E. It has a delicate flavor that is destroyed by heating. Use it as a flavoring in salad dressings or drizzle it on cooked vegetables, grains, beans, or stews just before serving. It is rich in monounsaturated oils, and 1 tablespoon contains half of the RDA of vitamin E.
Olive oil is pressed from the fruit of the olive tree, which was a gift from the goddess Athena to the people of Athens and has been cultivated for 5,000 years. I am tempted to believe that there would be no civilization without olive oil and garlic. Olive oil can mean a mixture of virgin oil and oil refined through steaming or chemically processing the olives.
This is an unreasonably biased view, but olive oil, high in monounsaturated, has been implicated in the good health of Mediterranean peoples.
Cold-pressed olive oil is produced without the benefit of steam or chemical solvents. As the name implies, simple physical force is used to press the oil from the olives.
Extra virgin olive oil is made from the first cold pressing of olives, which yields a deep green oil with a full, fruity flavor. Extra virgin olive oils should not be heated to high heat since the delicate fragrance will be diminished. Try weaning yourself from bread with butter by combining extra virgin olive oil, sliced garlic, salt, and pepper as a dip for bread. Extra virgin oil is used like a nut oil, drizzled over raw or cooked vegetables, grains, beans, or stews just before serving.
Many countries require olive oils to carry the acid content on their labels since this is the way olive oils are distinguished. Acidity contributes a bitter flavor and hastens rancidity. Extra virgin olive oil may be no more than 1 percent acid.
Virgin olive oil is 1 to 3 percent acid and also comes from the first pressing of the olives. Virgin olive oils include a wide variation in color and flavor, from deep green and fruity to light yellow and mild.
Light olive oil has been filtered to produce an oil with a light fragrance.
Pomace oil is a low-grade oil produced by treating the seeds and pulp of olives after most of the oil has already been extracted, with steam or chemical solvents. It can have a slightly bitter, chemical taste.
Palm oil should not be confused with palm kernel oil. This is a pure white, neutral shortening with many uses. Palm oil is 50 percent saturated fat, 38 percent mono- unsaturated fat and 12 percent polyunsaturated, giving it a healthier profile than butter!
Palm kernel oil, sometimes used in the Caribbean for frying, rivals coconut oil in saturation. This strong-flavored fat has little to recommend it.
Peanut oil is versatile, with 17 percent saturated, 46 percent monounsaturated, and 32 percent polyunsaturated fats. It is excellent for high-heat frying or stir-frying. Its light flavor makes it adaptable for both cold and hot dishes. It is an excellent source of vitamin E.
Safflower oil would be the nutritional heavyweight, with its 75 percent polyunsaturated, but it lacks vitamin E. Safflower oil remains fluid when refrigerated, which makes it excellent for salad dressings. It can also take high heat without smoking, making it a good choice for frying.
Sesame oil, whether raw or toasted, is high in polyunsaturates. The raw oil is light in color, with a high smoke point, making it suitable for frying and most culinary applications. Nutty brown toasted sesame oil imparts a delightful flavor to Asian dishes, as well as dishes from other cuisines. Use it only for flavoring, adding it to hot dishes at the last minute. Never use toasted sesame oil for sautéing. It is also called “dark” or “Asian” sesame oil.
Sunflower oil is highly polyunsaturated and smokes at very low temperatures, making it suitable for low- to medium-temperature cooking and salad dressings. Sunflower oil is very high in vitamin E.
Vegetable oil, a term used on many labels, often means soy oil. Soy oil is high in polyunsaturates (38 percent), alpha-linolenic acid (Omega-3), and vitamin E. This is a good general cooking oil. It can stand the medium-high heat but also has a light enough flavor for salad dressing.
Walnut oil is one of the best plant sources of EFAs, especially alpha-linolenic acid (Omega-3). Walnut oil may be added to salad dressings or drizzled over vegetables, grains, beans, or stews just before serving.
Blended oil is the name given by oil packaging companies to oils that are a combination of varieties. Oils are blended to improve their nutritional and cooking profiles. I prefer a blend of 75 percent canola and 25 percent virgin olive oil as my general cooking oil. Manufacturers will normally explain the advantages of each blend on the bottles. There are even blends of supplemental oils, with flaxseed oil mixed with pumpkin seed oil and others to produce a favorable blend of essential fatty acids.
Cocoa butter is a fat extracted from cocoa beans during the processing of chocolate. It is particularly useful in vegan baking to simulate the texture of butter. Cocoa butter is highly saturated and not recommended for general consumption.
Margarine was developed in the late 1800s as a butter substitute. While there are some brands of both stick and tub margarine made entirely of naturally occurring fats, most margarine contain hydrogenated or partially hydrogenated oil. Generally, the harder the fat, the more hydrogenated it is. Many kinds of margarine are fortified with vitamins, particularly A and D. Milk solids and whey are often added to improve the flavor profile of margarine; check the label carefully if you want to avoid these. For all the applications in this book, a softer, stick margarine will work well. Find a brand with oil listed before hydrogenated oil and few additives. Try replacing the tub, whipped, and liquid margarine with olive oil, hummus, or white bean spread, or simply omit it from pancakes and waffles.
Shortening is fat which is solid at room temperature and can stand relatively high heats. Spectrum and Earth Balance both produce shortenings made entirely of naturally occurring fats. However, most shortening is made from highly hydrogenated oil. White and virtually flavorless, shortening does not have the water inherent in butter and added to margarine. When substituting, add 2 tablespoons of water along with 1 cup of shortening to replace 1 cup of margarine or butter.