Manufacture

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top 1000Frozen Desserts
Frozen Desserts

By Francisco Migoya

Published 2008

  • About
There are six major steps involved in the manufacture of dairy-based frozen desserts. These steps hold true regardless of the size of production. All of the items in this chapter will have to go through all of these steps in order to produce a quality product.
  1. Making the Base: The desired ingredients are scaled out based on formulation, and the base is made according to the appropriate method (see Production Techniques).
  2. Pasteurization: In this step, the liquid is heated to a certain temperature for a certain amount of time, which will destroy all pathogenic bacteria. The preferred method for small-batch production is known as HTST (high temperature, short time). The base is heated to 85°C / 185°F, taken off the heat, and then stirred for 2 minutes. This stirring accomplishes three things: it ensures that the base is evenly pasteurized, that the ingredients are homogenized and that certain ingredients, such as stabilizers and proteins, are hydrated. Another form of pasteurizing is performed in batch pasteurizers, which have the same purpose of killing bacteria, but the process is slower since the liquid doesn’t get as hot as with the HTST method. In vat pasteurization, the mixture maintains a 65°C / 149°F temperature for 30 minutes. This process is more convenient for industrial production, where larger amounts of liquid will take longer to bring down to safe temperatures and the base spends less time in the danger zone. It is also used for bases with ingredients that are sensitive to higher temperatures (see chapter 3, Pasteurizing).
  3. Homogenization: A fat emulsion is formed through constant agitation (or stirring) of the mix at pasteurization temperatures, because the fat globules break up more readily and do not tend to clump at that point. Clumps of fat will cause a thick base, and thinner bases incorporate air better and form smaller, more uniform air bubbles. This in turn will make for a smoother, more stable, and more heat-shock-resistant product.
  4. Ageing: After the product has been homogenized, strained, and cooled down over an ice bath to 4°C / 39°F, it needs time to “age.” During this time the proteins and stabilizers get fully hydrated and the fat cools down and crystallizes. Protein and emulsifier networks are developed during this time. Ageing or “maturing” will improve the whipping properties of the base, which in turn will make for a smooth frozen product with a high tolerance to heat shock. Ageing time ranges from 4 hours minimum to 24 hours maximum. If there is a flavor being steeped, this time will also allow it to infuse a stronger flavor into the base.
  5. Churning or Freezing: This is the process in which the base’s water is partially frozen and air is whipped into the mix. This particular process takes place in a batch freezer. With the Pacojet, the base is frozen solid, then shaved in the machine, where minuscule air bubbles are formed.
  6. Hardening: When, for example, an ice cream is extracted from a batch freezer, it is frozen, but not frozen enough to serve. The consistency is too soft to be scooped, since it is around –4°C / 25°F. It needs to reach –10°C / 14°F or a maximum of –12°C / 10.4°F to make it hard enough to scoop easily, but still have it retain a smooth texture. The time it takes for a frozen product to reach this ideal temperature depends on the freezer. A good compressor equals quick hardening. A blast freezer set to –30°C / –22°F will harden 2 liters (2 quarts approximately) of finished product in 5 minutes. A conventional freezer can take up to 2 hours. Do not set the blast freezer any lower than –30°C / –22°F, because no matter how well you made your base and no mater what sort of stabilizers and emulsifiers you have added to it, it will become too hard to scoop.