Cream is a collection of fat droplets that float to the top of nonhomogenized whole milk. The heavier and thicker the cram, the higher the fat content. Cooling the cream firms its fat globules and makes it even thicker. Creams vary in their milk fat content, ranging from a low of 18 percent to a high of 36 percent. Cream manufacturers are not required to list on the carton the percentage of fat in the cream. The fat content of light or coffee cream is 18 to 30 percent, of light whipping cream is 30 to 36 percent, and of heavy cream or heavy whipping cream is not less than 36 percent. Combining cream with pasteurized or unltrapasteurized milk yields half-and-half, which is not true cream and contains only 10.5 to 18 percent fat.

Some whipping creams are marketed containing added sugars and stabilizers to improve their taste and texture. Whipping cream is also sold in pressurized canisters, which provide the taste and texture of whipped cream in a convenient-to-use form.

Cream Substitutes

Some of the whipped toppings in pressurized cans and tubs, as well as coffee creamers, dry mixes, imitation sour cream, and snack dips are made from nondairy ingredients. These products came into being as low-cost substitutes that would last longer on the shelf. Nondairy coffee creamers can last over a year at room temperature. They often contain saturated fats, but many lighter substitutes have half the calories (kcal) and one-third the fat of cream, and contain no cholesterol. One fat replacer, Super-creme, can substitute for up to 100 percent of the fat in reduced fat milk (2 percent), sweet cream, sour cream, and butter. This product is made from milk protein that has been transformed into small, spherical globules; it has natural cream flavor and can be used in muffins, dressings, and low-fat soup. The nondairy whipped toppings in pressurized cans are made from water, vegetable oil, corn syrup solids, sodium caseinate or soy protein, emulsifiers, vegetable gums, coffee whiteners, and artificial flavors and colors.

Cream can be soured by Streptococcus lactis bacteria or some other acidifying agent. Light cream or half-and-half is fermented at 72^oF (22^oC) until the acidity from lactic acid reaches 0.5 percent. A thicker sour cream is produced if milk solids-not-fat (MSNF), vegetable gums (carrageenan), or certain enzymes are added. To be labeled sour cream, a minimum of 18 percent milk fat is required, although when sweeteners are added, the minimum milk fat content can be lowered to 14.4 percent. Lower-fat sour creams with half the fat content of standard sour cream, and sour cream substitutes, are also available.

Acidophilus milk is a cultured milk created with the assistance of Lactobacillus acidophilus. These bacteria break down lactose to glucose and galactose, resulting in twice as many sugar molecules. The resultingly somewhat sweeter milk, usually packaged in cartons, is made by inoculating pasteurized milk with L. acidophilus culture and letting it incubate at 99^oF (37^oC) until a slight curd forms. A slightly acidic, sour taste also results, but this can be eliminated by mixing the bacteria directly into cold milk.

Kefir

Kefir is a fermented milk product that originated in Russia. It is sometimes referred to as “the champagne of milk” because of its bubbly, fizzling nature. Kefir is made by adding bacteria, Lactobacillus caucasius, and yeast, Saccharomyces kefir and Torula kefir, to milk. The milk is initially heated to 185^oF (85^oC) for half an hour and then cooled to 73^oF (23^oC), which allows the milk to ferment to a soft, foamy curd. The strong, tangy, sour taste comes from the formation of lactic acid. Kefir contains about 1 percent alcohol and a little carbon dioxide due to fermentation, and provides 250 calories (kcal) and 4.5 grams of fat per cup.

Buttermilk contains little or no butterfat. Sweet natural buttermilk originally was the liquid left over after fresh cream had been chilled and churned to produce butter. Natural buttermilk is often dried and used in baked products and ice cream, because the phospholipids obtained from the fat-droplet membranes, which are broken down during churning, makes it an excellent emulsifier. Now, most commercially available buttermilk is cultured by adding Streptococcus lactis bacteria to pasteurized nonfat, reduced fat (2 percent), or low fat (1 percent) milk.

Flavor may be enhanced by adding other bacteria, butterfat granules or flakes, natural sweeteners, citric acid (up to 0.15 percent), salt, and artificial flavors or colors. Fortification with vitamins A and D is optional. Cultured buttermilk must contain less than 0.5 percent milkfat, at least 8.25 percent milk solids-not-fat, and an acidic pH of about 4.6. It is not mandatory that this pH be created by lactic-acid-generating bacteria, but when these bacteria are not used, the milk should be labeled “acidified buttermilk”. A fat content between 0.5 and 2.0 percent changes the name to “cultured low fat milk” or “acidified low fat milk”. A milkfat content over 3.25 percent is denoted by “cultured milk” or “acidified milk”. Buttermilk has a longer shelf life than milk because the higher acid content inhibits the growth of spoilage-causing bacteria, and its lower fat content makes it less likely to go rancid. Salt may be added to further inhibit bacterial growth.

Many milk products can be dried, but by far the most common product is nonfat dried milk. Nonfat dried milk can be made from whole, reduced fat (2 percent), low fat (1 percent), or fat-free (nonfat) milks, as well as buttermilk, but nonfat is usually selected because it contains the least fat. Regardless of the milk chosen, the milk is dried by either spray, foam-spray, or roller drying processes. In spray drying, concentrated milk is sprayed into hot air, while foam-spray drying sends a jet of hot air into the concentrated milk. Roller drying consists of moving pasteurized fluid or condensed milk through two steam-heated rollers.

After the fat-free (nonfat) milk is dried, vitamins A and D may be added, although they are not required. Dried milks that originally contained some fat are required to be fortified with vitamin A and identified as “fortified with vitamins A and D”. Overall, nonfat dried milk is nutritionally similar to fat-free (nonfat) milk, except that the levels of vitamins may be reduced by 20 percent. The absence of fat also gives it a long shelf life; nonfat dried milk can keep for about 1 year in a cool, dry storage area. The calcium and protein content of meals or beverages can be increased easily by adding nonfat dried milk to puddings, shakes, soups, casseroles, milk, and many other food combinations. Although it is inferior in taste to fluid milks, reconstituted nonfat dried milk is ideal for making batters and doughs for baked goods.

“Instant Milk” is different from regular nonfat dried milk. It is manufactured by exposing nonfat dried milk to steam, after which it is redried. The double drying helps instant milk achieve the ability to agglomerate and instantly dissolve in cold water. Generally, about 1/3 cup of instant nonfat dried milk will reconstitute into 1 cup of fluid milk, but manufacturers’ instructions will vary. Allowing the reconstituted milk to refrigerate for several hours, and adding a teaspoon of vanilla to a half gallon of reconstituted chilled nonfat dried milk, make it taste more like regular milk. Also, more milk solids can be added by commercial food manufacturers to make it more flavorful and nutritious.

Unlike evaporated milk, sweetened condensed milk does not have to be sterilized, because its 40 to 45 percent by weight sugar concentration prevents microbial spoilage. The sugar content, either added or in the form of lactose, also contributes to the Maillard reaction. During heating the sugar combines with the protein in the milk to give it a light-brown color. This attribute makes sweetened condensed milk ideal for creating caramel-flavored or colored desserts such as pumpkin pie.

The evaporation process consists of initially exposing the milk for 10 to 20 minutes to a temperature of 203^oF (95^oC). This stabilizes the casein so that it will not coagulate during sterilization. In the next step of evaporation, the milk is heated to 121^o to 131^oF (50^o to 55^oC) at reduced atmospheric pressure, which allows the milk to boil at beneath the normal boiling temperature of 212.3^oF (100^oC). It is then homogenized, canned, and sterilized. The high temperatures of canning and the metal of the can may impart cooked and off-flavors to evaporated milk products.

Newer evaporation techniques produce evaporated milk by exposing it to ultrahigh temperatures for longer periods of time, placing it in sterilized cans, and aseptically sealing the cans. Compared to evaporated milk produced by the old method, UTH-evaporated milk is less viscous, less white, and has a different flavor.