Fat is Crucial to Good Cooking

As with salt, the word "fat" in cooking has almost become evil. But it is impossible to be a good cook without knowing how to use fats effectively in daily cooking. In culinary terms, fats includes both fats that are solid at room temperature, e.g. butter, margarine, and lard, as well as fats that are liquid at room temperature, usually called oils, (canola oil, olive oil, etc.).

Fats have a myriad of functions in the kitchen. They add flavor. They tenderize. They provide texture and richness. Fats act as  preservatives (think of tuna in oil), and are an essential ingredient in most marinades. Fats are used in almost all cooking techniques, including frying, baking, roasting, pastry making, and sauce making. This article will discuss fats in general; I also have a column which specifies which fats to choose for a particular cooking need.

When choosing which fat to use, it is useful to consider four different characteristics. The first element is flavor. In general, butter and unrefined oils provide the most flavor. Unrefined oils are oils extracted from nuts, seeds, etc. without the use of either heat or solvents. Extra virgin olive oil and the nut oils (walnut, hazelnut, etc.) are the best known examples. Refined oils are usually bland in taste and are chosen for one of the reasons listed below.

Next, consider the desired texture of the final food. Texture is especially important in baking, and it is the fat ingredient that determines whether the final product is fluffy or flaky or tender.

In baking, the fat acts as both a leavening agent (causing the product to rise) and as a tenderizer. In pastries such as cream puffs or puff pastry, the fat particles melt in the heat of the oven, producing steam that leavens. In pie pastry, the same melting action produces a flaky crust. In cakes, where both steam and often carbon dioxide (produced by baking soda and/or powder) act as joint leaveners, it is necessary to have well-creamed fat to create empty cell pockets. These hold the steam and CO2 that are responsible for making a cake rise.

Fats accomplish their tenderizing activity by dispersing to coat the flour's starch molecules. This coating prevents too much gluten from forming, keeping the pastry from getting tough, (gluten is a protein that provides structure).

In general, solid fats are almost always used for baking as oil will tend to collect in one place and not disperse throughout the batter, producing a grainy texture. Oils, also, can not be creamed. The only time oil is usually used is for quick breads or cakes. Here, you can prevent gluten from forming by minimum stirring, and denseness is often a desired quality.

The third fact to know about are heat points, of which the Smoke Point is the most important. Smoke point defines the temperature at which a fat begins to smoke and develops acrid odors and off flavors.

While smoke points are important to know for sautéing or frying, knowing the smoke point is especially crucial for deep fat frying, where a fat should have a smoke point above 385 degrees. Deep fat frying is performed most effectively at approximately 375 degrees. If you fry at a much lower temperature, the food does not develop an immediate crust upon immersion, and will absorb the fat and become greasy. If you fry at a much higher temperature, the outside will burn before the food is cooked through.

The smoke point of any oil decreases with use, so by using a higher smoke point fat, you can use the same oil 2-3 times. Other heat points for fats include flash and fire points at 600 and 700 degrees respectively. At the flash point, there are tiny wisps of flame; at the fire point a fire is blazing. Do not put out an oil fire with water; it will spread the fire. Rather, smother the fire with a tight-fitting lid, suffocate it with baking soda, or use a specially formulated fire extinguisher.

Finally, consider price. In general, unrefined oils used for flavoring are pricier than the bland oils used for cooking. You should buy unrefined oils in small bottles as: 1) a little amount adds a lot of flavor, 2) these oils go rancid more easily than processed oils, and 3) since unrefined oils have low smoke points, they are inappropriate for most cooking purposes. In general, use the more expensive, unrefined oils for flavor, and the less expensive refined oils for cooking.

Regarding storage, all fats will eventually go rancid; however unrefined oils and unsalted butter will go rancid earlier. To keep fats as long as possible, limit exposure to light, moisture, and heat; a refrigerator is a good place for storage. Do not worry if the oil gets cloudy or firms up; it will clear and liquefy once it comes to room temperature. For oil that has been used for deep-frying, strain and store the oil either in its original container or in a clean glass jar.