Cream is the thick part of milk that contains a rich concentration of butterfat. Before the advent of homogenization, milk naturally separated into two layers, cream at the top and milk on the bottom that was almost fat-free. Now, cream is separated out of milk by centrifugal force.

Cream has many uses, both savory and sweet, as well as some properties that give it distinct advantages over milk. Because the protein in cream is diluted by a large proportion of butterfat, cream is less likely than milk to form a skin on the surface when boiled. Also, cream is less likely than milk to curdle when mixed with acidic ingredients, such as lemon juice or tomatoes.

Different types of cream are based on their percentage of butterfat. Each has specific uses.

This cream is made from equal parts cream and milk. With 10-1/2 to 15 percent butterfat, it is used as a coffee whitener but also can be used in sauces and cream soups. In fact, it is often substituted for whipping cream in these foods because it has less fat.

Also called coffee cream, light cream contains about 20 percent fat, although the fat content can go as high as 30 percent. Even though it will not whip, light cream can replace whipping cream in many recipes, such as sauces, ice cream, soups and puddings. Light cream is not available everywhere. If it is not available in your area, substitute half-and-half for it.

Also called heavy cream, whipping cream has 35 to 40 percent butterfat or occasionally more. It is used in many preparations, including sauces, soups, ice creams and custards. It is the only cream suitable for whipping. Almost all whipping cream is now ultrapasteurized, a process of heating that considerably extends its shelf life by killing bacteria and enzymes. Cream that is not ultrapasteurized is preferred by some cooks who cite its superior taste and whipping qualities. It is available in some specialty markets and natural food stores.

Use a bowl that is deep enough to allow cream to double in volume. Cream whips better if it is well chilled. It also is helpful to chill the bowl and beaters. Begin with an electric mixer on low speed. After several seconds, increase to high speed and beat to the desired consistency. Softly whipped cream should hold soft peaks when the beater is lifted. To test for soft peaks, turn off mixer and lift beaters from whipped cream; it should have droopy but definite peaks.

In stiffly whipped cream, the beater will leave furrows through the cream and it will hold firm peaks when the beaters are lifted. Watch carefully because at this stage the cream is close to becoming butter. If the cream develops small curds and a yellow tint, it has been beaten too long.

If sugar and flavorings are to be added, add them to the cream just before it is fully whipped. Adding them earlier will prevent the cream from reaching full volume. Although it is best to use whipped cream immediately, it can be refrigerated for several hours. It can rewhipped briefly to stiffen it, but it will not have the volume it had initially.

Aerosol whipped cream is sold in pressurized cans in the dairy section of the supermarket. It is real cream, but it is not truly whipped. Instead, it is expanded by a gas, such as nitrous oxide. This product is sweetened and contains stabilizers and emulsifiers. Aerosol dessert toppings are also available, but these do not include cream and should not be confused with whipped cream.

Crème fraîche is a cultured, thickened French cream with a smooth texture and subtle nutty taste. It is used as a dessert topping and in cooked sauces and soups, where it has the advantage of not curdling when boiled. In France, crème fraîche is made from unpasteurized cream that thickens from the lactic acid contained in it. A version can be made at home by combining 2 tablespoons buttermilk and 1 cup whipping cream in a covered glass jar and letting it stand at room temperature for about 24 hours, until it thickens. It then can be refrigerated for about one week.