Whipped Milk Products
Comments(0)Liquid milk products such as cream, evaporated milk, and reconstituted nonfat dried milk can be made into a foam by whipping air into the liquid. During whipping, the protein in these milk products is mechanically stretched into thin layers that trap air bubbles, fat particles, and liquid.
Whipped Cream
Cream expands two to three times its volume when whipped. The stability of milk foams, especially whipped cream, is dependent on several factors: the fat content, the temperature of the cream and the equipment used, the age of the cream, the sugar content, and the length of whipping time.
Fat Content. The higher the fat content, the more stable the whipped cream, because solid fat particles provide rigidity to the foam. Heavy whipping cream beats more easily than lower-fat whipping creams, but becomes lumpy and buttery with overbeating. An advantage of using heavy whipping cream (36 to 40 percent butterfat) in one particular baking application is that its lower moisture content will prevent pastry crust from becoming soggy when it is filled with cream fillings.
Most whipping creams are sold unhomogenized to allow for easier aggregation of the fat globules. When the cream is homogenized, much of its protein surrounds the now smaller and more numerous fat globules instead of being available to envelop the air bubbles that are essential for foam formation. Vegetable gums and gelatin are sometimes added to improve the foaming ability of the commercial creams.
Temperature. Cooling cream increases its viscosity or firmness and its tendency to clump. For best result, refrigerate the cream, bowl, and beaters at 45oF (7oC) or less for at least two hours before whipping. Cream allowed to warm to room temperature or even to about 50oF (10oC) has more widely dispersed fat globules, which reduces the cream’s ability to be whipped and creates a softer texture. Most cream is pasteurized, but the heating process denatures an enzyme that helps fat globules to cluster, so nonpasteurized creams whip more readily and have a smoother texture. Although ultrapasteurized whipping cream takes even longer to beat to a peak-holding consistency, other ingredients can be added to improve its whipping ability and dramatically extend its shelf life.
Age. The older the cream, the greater its viscosity and ability to foam. Whipping cream must be at least one day old in order to allow it to incorporate the air necessary for the optimum increase in volume.
Sugar. Sugar increases the stability of whipped cream, but it should be added gradually, toward the end of the whipping period. Added earlier, it increases the whipping time and reduces overall volume and rigidity by delaying the clumping of fat. Sugar has the benefit, however, of lessening the likelihood of overbeating the cream. For the best stability, powdered sugar instead of granulated sugar should be used, because it dissolves more readily in the cold cream, and the cornstarch in the powdered sugar acts as stabilizer.
Whipping Time. Physical agitation of the cream is necessary, because it disrupts the phospholipid membranes surrounding the fat globules, preventing them from aggregating. Overbeating, for even a few seconds over the peak point turns whipped cream into butter and whey. To make whipped cream with an electric beater, it is best to beat on medium high and then slow to a lower speed as soon as the cream starts to thicken. To check for sufficient whipping, the beating is stopped and the beaters are lifted to see if the cream is falling into glossy, large globs with soft peaks. The formation of stiff, yet moist, peaks signals the completion of the whipping process. The cream should be underbeaten slightly if ingredients such as sugar are to be whipped into the cream.
Whipped Evaporated Milk
The high concentration of milk solids in evaporated milk makes it possible to whip it to three times it volume, but the flavor, texture, and stability are less acceptable than for whipped cream. The flavor of evaporated milk has a tendency to overpower other flavors; thus it is best used with highly flavored foods. The stability of evaporated milk foams is much more tenuous than that for whipped cream partly because of the former’s lower viscosity and its lower fat content. This can be compensated for to some degree by chilling the can of evaporated milk in the refrigerator for 12 hours or in the freezer until ice crystals form. Adding 1.5 tablespoons of sugar per chilled cup can further stabilize the protein and resulting foam. The main advantage of whipped evaporated milk over whipped cream is its lower cost.
Nonfat Dry Milk (NFDM)
Prepared nonfat dried milk powder can actually be whipped into a foam. This whipped milk product is very unstable, but it is much less expensive and lower in both calories (kcal) and fat than whipped cream. It is prepared by dissolving equal parts of nonfat dried milk and cold water, chilling, and beating until the mixture stands in soft peaks. Stability is increased by adding 1 tablespoon of lemon juice or 2 to 4 tablespoons of sugar during beating, which continues until the peaks bend over slightly on top.
