The Science Of Oils And Fats

Despite their bad press, oils and fats are essential to support life. Your body needs them. You cannot live without them. They do far more than clog our arteries.

It is impossible to escape them no matter what your diet. And it is almost impossible to cook well without them.

Oils and fats are all about flavor. They absorb flavors from the plant and animals they come from, they amp up the flavors of other ingredients in a dish, they conduct heat well so they aid in browning, and brown is flavor.

They are extracted from animals or plants and cooks call them animal fats or vegetable oils although the terms fats and oils are often used interchangeably. Loosely defined, fats are solid at room temperature and oils are liquid, but there are exceptions to the rule.

The exact composition of each fat is different giving them different flavors, cooking characteristics, and health implications. Some oils have little flavor, like corn oil and canola oil, while others are strong, like extra virgin olive oil, bacon fat, and toasted sesame oil.

Some oils smoke at low temperatures, like butter (about 300°F) and others can absorb much more heat before they start to smoke, like safflower oil (about 500°F). This temperature is called the smoke point and they matter if you are chosing an oil for frying.

Oils can also dissolve compounds from the food they cook and become tainted with them. Oil used to fry fish will taste like fish, and other foods fried in that oil, perhaps potatoes, will taste fishy. If an oil is overheated or re-used too often, it can begin to break down, “crack”, and change color and taste. In fact almost all oils age and oxidize and turn rancid eventually, losing their original flavor and possibly their health benefits.

Fats and oils are all hydrophobic, meaning they don’t mix with water although they can be forced to mix in a form called an emulsion, when the oil is broken down into tiny droplets by whisking or shaking and dispersed throughout the water. A vinaigrette is a classic example since vinegar is mostly water.

But eventually they separate again, with the oil rising to the top of the water. The emulsion can be made to last longer with the help of an emulsifier or a surfactant, a compound that alters the surface of the oil. Mustard and egg yolk are common surfactants. Whisk in some mustard and the salad dressing will hang together pretty well for a while.

Egg yolks are mixed with oil and vinegar and lemon juice to make mayonnaise, an emulsion that lasts a long time. Hollandaise sauce is a blend of butter and lemon juice also held together by egg yolk. Xantham gum is a common emulsifier in commercial food processing.

Below I have tried to condense some important information about common culinary fats and oils. Please understand that the estimates of saturated fat and smoke points can vary significantly from animal to animal, and producer to producer. Factors that influence them can include the animal’s diet, its age, and in the case of vegetable oils, the ripeness of the seeds at harvest, climate, etc.

This information was gathered from multiple reliable sources including USDA and Centers for Disease Control and Prevention. They are just included here as approximate guides.

Olive oil

Vegetable oils are extracted from plants, usually their seeds, and yes, in answer to a frequently asked question, olive oil is a vegetable oil. Vegetable oils have no cholesterol and are usually liquid at room temperature but may thicken in the refrigerator. They should be stored in cool dark places but do not need to be refrigerated. Not all vegetable oils are edible. For example, cashew oil, made from the husks around the nuts, are used for industrial lubrication and even in auto parts.

Olive oil or Pure olive oil. Some people don’t consider olive oil to be vegetable oil, but it is clearly not animal fat so we classify it as a vegetable oil. Olive oil is the most praised and beloved oil in the world. Olive oil production is, simplified: Pick ripe olives from the trees, crush them into a paste, separate the solids from the liquids, and then separate the water from the oil. Traditional methods use a press with a stone wheel, and modern production methods involve steel presses, centrifuges, filters, and oxygen free processing. What is left of the paste is fed to livestock.

The Mediterranean basin is the source of most of the world’s olive oil, but some is now made in California, Mexico, Australia, and other nations. Most countries, most notably the EU countries, have strict laws surrounding its production, labeling, and pricing. Harvest time, ripeness of fruit, climate, soil, pressing, and even the variety of the olives are among the quality factors, much like wine. Some producers have achieved enviable reputations and prices can vary significantly.

If the bottle says simply “olive oil” or “pure olive oil” then it has probably been made by hard pressing the olives and probably been refined, a process of treating the oil with chemicals to reduce the acidity and make the taste more neutral. Usually less than 1.5% acidity. It is simple, bland, and because of a high smoke point great for cooking and frying. Higher grades (below) are more flavorful and more expensive. Recommended for: Cooking, frying. Saturated fat: About 15%. Smoke point: About 440°F.

Virgin olive oil. If the label says virgin then it has been extracted from ripe olives by pressure only, without the aid of chemicals and it is usually less than 2% acidity. Some websites and books say virgin means it is free run, made without pressure. Not so. Virgin oil is usually yellowish to green and has more flavor and distinction than just plain olive oil, and it costs more. Recommended for: Cooking, frying, salad dressings. Saturated fat: About 15%. Smoke point: About 420°F.

Extra virgin olive oil . Real EVOO is virgin olive oil that is less than 0.8% acidity and it has passed taste tests by panels of experts. It is often green and distinctive in aroma and flavor: Robust, fruity, peppery in the back of your throat, grassy, herbaceous, with a tickle in the throat. The best EVOO is made with great care. Pickers try to prevent spoiled fruit from getting in the baskets because a few can impact the flavor greatly. In the northern hemisphere it is pressed in the fall and its flavor is best when fresh, less than six months old. Its flavors are somewhat fragile and can deteriorate in four months or so after exposure to air, so it should be stored in cool places, like a wine cellar. It will solidify in the refrigerator. EVOO is the most expensive, and connoisseurs think the best come from Italy, Spain, and Greece, and I have tasted some very fine examples from California. Recommended for: Salad dressings, drizzling, raw. Saturated fat: About 15%. Smoke point: About 375°F.

Olive oil fraud. Because the difference in price between the top grades of EVOO and garden variety OO is so great, olive oil fraud is common and there is a good chance that many of the oils sold in the US are not accurately labeled. In 2007 Tom Mueller wrote an excellent exposé on the problem in the New Yorker charging that only 40% of the oil labeled as extra virgin really was. He really shook up the industry and as a result Italy and others have revised their laws and stepped up policing of production and labeling. One of the scams is the statement on a label that says “Bottled in Italy”. What it probably means is that it is cheap oil from Morocco shipped to Italy and bottled there.

Other vegetable oils

Canola oil. Growing in popularity for frying and all purpose cooking uses, there are unfounded accusations floating around the internet that it is toxic. Recommended for: Cooking, frying. Saturated fat: About 6%. Smoke point: About 400°F.

Soybean oil, safflower oil, sunflower oil, and corn oil. These are commonly found in groceries and they all tend to be inexpensive, mild in flavor so they let the flavor of the fried food show through, and they have relatively high smoke points so they don’t burn easily. They are also suitable for salad dressings. Canola oil is among the lowest in saturated fat, about 7%. Soy is very common, especially in restaurants, partially because it has the highest smokepoint of the common oils, about 460°F. Soy and corn are high in omega-6 fatty acids although a new hybrid soybean called Plenish is producing oil that is much lower in saturated fat and claims to have a longer shelf life and fryer life. There are many vegetable oil blends on the market. Recommended for: Cooking, frying. Saturated fat: About 10-15%. Smoke point: About 450-500°F.

Shortening. Technically a fat because it been hydrogenated so it can be solid at room temperature. Crisco is the most popular by far. It is especially popular in making pie crusts. Recommended for: Pie crusts, cooking, frying. Saturated fat: About 25%. Smoke point: About 330°F.

Margarine and imitation butters. Technically fats because they have been hydrogenated so they can be solid at room temperature for use as spreads. These oil and water emulsions are designed to be similar to butter. Many are about 80% fat, similar to butter, but some are lower in fat. The water is often skim milk. Recommended for: Spreading on bread as a condiment, low temperature cooking. Saturated fat: Varies significantly from brand to brand. Smoke point: Varies significantly from brand to brand.

Nut and seed oils

Toasted sesame oil. If it is clear and yellowish, it is pretty much an ordinary vegetable oil. But if it is brown, the seeds have been toasted first, and the flavor is more intense than any other oil, powerful and distinctive. One sniff and you will say “Chinese food” because a few drops of it find their way into so many Asian foods. And a few drops is all it takes. You really should have a bottle around the house. If you have trouble finding it in your grocery store, you can find sesame oil on Amazon. Recommended for: Flavoring raw. Saturated fat: About 15%. Smoke point: About 350°F.

Walnut oil, grapeseed oil, palm oil, avocado oil, mustard seed oil, rice bran oil, coconut oil, pumpkin seed oil. Each has its unique flavor and cooking characteristics and its fan club as well as internet rumors about its health advantages and disadvantages. Walnut oil has a distinctive walnut flavor and is a fine salad oil. Avocado oil’s smoke point is about 520°F, among the highest. Palm oil is more than 50% saturated.

Peanut oil. Known for a high smoke point, it is widely used for deep frying and to fry Asian foods. Be careful, people with peanut allergies may not be able to tolerate this oil. Recommended for: Cooking, frying. Saturated fat: About 18%. Smoke point: About 450°F.

Animal fats

Animal fats are hard and waxy. With the exception of butter, they surround the muscles and organs of animals. They are usually solid at room temperature and can oxidize and go rancid in a few months even in the refrigerator. They can be frozen. They are sources of cholesterol. They also contain high quantities of saturated fats. Animal fats often carry some of the flavor of the animal’s feed. For example, animals that have grazed on wild sage or rosemary can actually taste like sage and rosemary. Grass finished cattle taste different than corn finished cattle.

Animal fats come in three types: Subcutaneous fats are the thick hard layers beneath the skin. Intermuscular fats are layers between muscle groups. Intramuscular fats woven amongst the muscle fibers add moisture, texture, and flavor to cooked meat. These threads of fat are called marbling because they have a striated look similar to marble. Subcutaneous and intermuscular fat can be ground for use in sausages and burgers, rendered for surface treatment, or rendered and solidified for use in pie crusts. Contrary to popular opinion, they do not melt and penetrate meat when cooked. Click here to read more about them and fat caps.

Lard. Lard is pork fat that has been melted and then allowed to solidify. The best lard comes from the “leaf lard” in the intestinal cavity, especially the fat surrounding the kidneys. Lard is prized by bakers because it makes especially flavorful and flaky pie crusts.

Lardo is cured pork fat, like the whispy melt in your mouth fat on prosciutto hame, and a version of it can be made spreadable. In the picture here you can see a spreadable lardo made by the famous Italian butcher Dario Cecchini in his shop in Tuscany. It is simply amazing once you overcome the mental blocks of eating pork fat. Recommended for: Pie crusts, cooking, frying. Saturated fat: About 40%. Smoke point: About 325°F.

Bacon fat. Bacon fat is the fat rendered when cooking bacon. If you are careful not to burn it you can pour it into a jar and store it in the fridge. Recommended for: Pie crusts, cooking, sauténg broccoli and other vegetables. Saturated fat: About 40%. Smoke point: About 325°F.

Chicken, duck, and goose fat. Chicken fat, called schmaltz in Yiddish, was used as the cooking oil, butter, and mayonnaise of the European peasantry until all the Jewish kids grew up and became cardiologists. It is tasty and creamy. Duck fat and goose fat are more flavorful, and if you’ve never had French fries cooked in duck fat, get up and go find a restaurant that makes them right now. That’s why the expression “He fell into a schmaltz bucket” means he fell into good fortune. Recommended for: Pie crusts, cooking, and frying (often blended with vegetable oils). Saturated fat: About 33% Smoke point: About 325°F.

Beef fat. Suet is fat trimmed from the meat. If it is melted and then allowed to solidify it is called tallow. Ground suet mixed in with ground meat can add flavor to burgers and sausages, and tallow painted on steaks just before serving amps it up to 11. It has also been used for making soap. Recommended for: Pie crusts, cooking, frying. Saturated fat: About 45%. Smoke point: About 400°F.

Butter. Butter is made by the long vigorous whisking of the cream skimmed from the top of milk that has not been homogenized, a process called churning. It is usually made from cow’s milk, but it can be made from the milk of sheep, goats, buffalo, and other mammals. It is made of approximately 5% milk proteins, 15% water, and 80% fat. The amounts vary from producer to producer. Some butter also has salt added and is usually labeled salted or unsalted. It can be used to gently cook foods like eggs or as a condiment, especially for spreading on toast. From a taste standpoint, I prefer salted, but from a cooking standpoint, many chefs prefer unsalted because you can always add salt later but you can’t take it away. On the other hand, the amount of salt in butter is small so it is not likely to ruin any dishes. For spreading on bread, I prefer salted, so I always have it on hand and that is what I call for in most of my recipes. You can use unsalted if you wish, just make sure to taste the dish and be prepared to add salt if needed.

Butter melts at a low temperature, then it starts to foam, then the milk solids brown, and then they burn. This makes cooking with butter tricky, and often it is best blending the butter with a vegetable oil. A typical stick of butter is 4 ounces, 1/4 pound, or 1/2 cup, and the wrapper is marked in eight tablespoon quantities. Recommended for: Pie crusts, baking, cooking, sauces, as a spread or condiment, and gentle frying. Saturated fat: About 66%. Smoke point: About 300°F.

Clarified butter and ghee. Clarifying butter is butter that is melted and the milk solids are removed. This helps prevent burning and raises the smoke temp, and makes it much better for frying. Ghee is a form of clarified butter that has had the water evaporated but it is cooked a bit longer with the milk solids so they caramelize and develop a nutty flavor. Sometimes it is even flavored with spices. Ghee easily found in Indian groceries. Click here to learn how to make clarified butter easily at home. Recommended for: Cooking, frying. Saturated fat: About 60%. Smoke point: About 450°F.

Flavored oils

Many specialty stores sell flavored oils such as tarragon oil or garlic oil. They can be very tasty, but I prefer to simply add my own tarragon or garlic to the oil when I need it rather than inventory yet another condiment. But a word of caution: Fresh herbs and garlic are exposed to the botulism microbe that lives in soil. It loves anaerobic environments, that is, it loves to grow in a jar of oil without air. And it is hard to kill but it can kill you. So it is not a good idea to keep bottles of homemade garlic oil around. If you need it, make it fresh. And if the Italian restaurant you’re in sets a bottle on the table, ask for just plain oil. A good olive oil doesn’t need garlic and you don’t need botulism.

Another popular one is “truffle” oil. Most of it is simply cheap olive oil with a chemical perfume that smells like truffles added. It has never seen real truffles, a rare and very expensive exotic mushroom. Read the label. If it says “oil and truffles” it is the real thing. If it says oil and truffle aroma” it is artificial.

Cooking with oil in a pan

It is not true that if you start with a hot pan and cold oil, or visa versa, the food won’t stick, but I still prefer to add the oil to a cold pan, especially a non-stick since getting a non-stick pan too hot, over 450°F, can cause it to emit noxious fumes. The oil will help keep the temp down.

Don’t add your food until the oil is shimmering and perhaps until you see a whisp of smoke. Don’t let it smoke too much or it can crack, break down. Pat dry foods going into hot oil or they will spatter and burn you, and the steam will inhibit browning.

Fats, oils, and health

Anxiety created by fretting about fats may be more dangerous than the fats themselves.

Fats and their impact on our health have been the subject of numerous research studies. Our knowledge of the subject is growing rapidly and nutrition advice is a moving target. It appears that the only ones who are certain about the subject are the hucksters selling supplements, diets, and lifestyles. The internet is ripe with rumors about alleged health benefits and deficits of some fats.

One thing is for sure: Humans need to consume fat. There are some that are essential to our survival that the body does not produce.

The health impact of various fats can vary significantly depending on your health, genetics, age, exercise, metabolism, and other personal and environmental factors. In other words, some fats may be very bad for me and no problem for you. In addition, fats are unstable and oxidize and are changed by the cooking process. There are no single set of guidelines for us all to follow. That would be like prescribing the same glasses for everyone.

The problem in getting good data on fats is that you can’t easily run lab studies. It’s not like determining which lasts longer, alkaline or lithium batteries. We can’t take a group of people and make them consume only animal fats for a year, have another group consume only vegetable oils, and a third a mix of both. Instead we must rely on epidemiological or observational studies that are fraught with hazard.

Here are highlights of what we know. Today.

Some carbon atoms have double bonds to other carbon atoms (C=C) and they are called unsaturated fats. If hydrogen atoms are attached to all those carbons leaving them single bonded (C-C), the fat is called saturated because it is holding all the hydrogen it can handle. If some of the bonds are hydrogenated and one is not, the fat is called monounsaturated. If multiple carbon atoms retain their double bond, the hydrocarbon is called polyunsaturated. All three are made by both nature and man.

The more saturated the fat is, the thicker it gets, the faster it is to oxidize and turn rancid, while the melting point and smoke point increase. It is believed that saturated fats are less healthy than mono or polyunsaturated fats.

The location of the bonds is also thought to be crucial. If a double bond is in the sixth position it is called an omega-6 fatty acid, if it is in the third position, it is an omega-3, etc. Omega-3 fatty acids are considered healthy, and since they are not manufactured by our bodies, they are called Essential Fatty Acids (EFAs) meaning that we need them and we can only get them from eating them. They are common in fish oils.

The shapes of the carbon bonds are also important to how fats function. In unsaturated fats, some of the bonds go across groups of atoms and are thus called trans fats. Trans fats are believed to raise levels of bad low-density lipoprotein (LDL) cholesterol and lower good high-density lipoprotein (HDL) cholesterol and therefore be unhealthy, especially for the heart. The United States plans to ban trans fats.

Cooking with fats changes their chemistry and can thus alter their health impact as well as taste.

So the bottom line, until research proves otherwise, current wisdom is that saturated fats and trans fats are more or less bad, while unsaturated fats are more or less good, especially omega-3 fatty acids. But how bad or how good depends on a lot of things such as your health, age, gender, genetics, etc.

In addition, it is important to know that all oils are high in calories, all of them about 110 to 120 calories per tablespoon or about nine calories per gram.

My olive mistake

I love olives and olive oil. So my first trip to Italy, I rented a car in Tuscany and zoomed off to visit wineries and olive oil producers. In October the hills are magnificent and riotously colorful.

Before long I saw a stand of trees with sage colored leaves and as the orchard came closer to the road I could see the black and green orbs. Olives start out green and turn black as they ripen.

I immediately pulled over and galloped into the stand, snatched a deep black bauble, and popped it into my mouth. Pthew, pitt, sputter spit bleah. It was incredibly bitter and completely inedible.

It seems that olives must be cured in salt water or salt before they are palatable. My guess is that some ancient Italian found some olives floating in the ocean, dropped there by a tree overhanging a cliff, and had the guts to try them, and that is how this remarkable fruit came to our tables and martinis.