Frozen yogurt is a refreshing, tangy dessert that combines the flavors and textures of ice cream and sherbet. Frozen yogurt is a relative new-comer in the dessert market. The history of frozen desserts dates back thousands of years to Asia where water ices were first made. Although Roman literature describes how the Emperor Nero was treated to exotic fruit juices and wines chilled with mountain snow, it was not until the 13th century that Marco Polo introduced Asian water ices to Italy. The popularity of these frozen desserts spread throughout Europe and within a few centuries, European colonists introduced ice cream in the U.S.
Technological improvements throughout the 1800s simplified the process of making frozen desserts. The first hand-freezer was patented in 1848. Shortly thereafter the first wholesale ice cream manufacturing company in the U.S. was created by Jacob Fussell of Baltimore.
During the 1980s the frozen yogurt market reached sales of $25 million in 1986 with triple-digit growth rates. Major ice cream manufacturers quickly jumped on the band-wagon and started producing their own brands of frozen yogurt, recognizing that the low-calorie dessert was here to stay. By the early 1990s, frozen yogurt captured about 10% of the total frozen dessert market with sales of $330 million on 135 million gallons.
The Manufacturing Process
Processing the mix
- 1 The ingredients are selected for freshness and quality. They are measured in precise quantities according to the particular recipe. Liquid and dry ingredients are combined separately.
- 2 The liquids are poured into a vat, mixed together, and heated. Next, the dry ingredients are added to the liquids in a particular order. Meanwhile the batch is stiffed and the temperature gradually increased. Most ingredients must be incorporated before the mix is heated to 120°F (49°C) so that the mix does not become lumpy. The mixture must be heated to dissolve and blend the ingredients.
Pasteurizing the mix
- 3 Pasteurizing the batch is necessary to destroy pathogenic bacteria and to help preserve the finished product. It is also required by law in most regions. Pasteurization is a simple process that involves quickly bringing the mix to a high temperature for a specified time and then quickly reducing the temperature to less than 40°F (4°C). The trend in the industry has been toward increasing the pasteurization temperature to about 175°F (79°C) for about 25-40 seconds. For greater results, batches can be pasteurized at temperatures as high as 210°F (99°C) to 220°F (104°C). These high temperatures also improve the flavor and help blend the ingredients more effectively.
Homogenizing the mix
- 4 Homogenizing the batch makes it smoother, primarily by decreasing the size of fat globules to less than two micrometers.
Without homogenization fat could rise to the top of the mixture and create a layer of cream. Homogenization consists of pumping the batch through a small valve and against an impact ring. Three forces are at work. As the mix passes at a high velocity of about 30,000 fpm (feet per minute) through the valve, shear forces begin to break up the fat particles. The impact ring ruptures the fat further. Completing the process is cavitation, in which vapor bubbles are created by a sudden discharge of pressure. Within the bubbles the fat droplets crash against the vapor walls and disintegrate; thus, the more fat, the more homogenization required.
Inoculating with yogurt culture
- 5 While the temperature of the mix is 90°F (32°C), it is inoculated with 1% yogurt culture. The mix remains at this temperature until it sets and is ready for cooling.
Cooling and aging
- 6 After homogenization, the mixture must be cooled. If it is cooled slowly from about 90°F (32°C) to about 40°F (4°C), the mix will become more viscous. Once the temperature falls between 32°F (0°C) and 40°F (4°C), the batch is stored in aging tanks inside coolers. The mix is aged for up to four hours.
Flavoring, coloring, and freezing
- 7 The final ingredients are mixed together in a flavor vat. These include sweeteners, flavorings, and coloring. This mixture is then pumped into the freezer with the rest of the mixture which is about 20°F (-6°C) to 28°F (-2°C).
- 8 While the mix is hardening, it is agitated to incorporate air and create over-run, or excess volume. The addition of air also smoothes the consistency and creates a more palatable product. In about three minutes the mix begins to freeze and within a few more minutes, the desired overrun, about 50%, is achieved. About one- to two-thirds of the water freezes during this stage.