To Pasteurize Ice cream it is usually heated to 65°C for 30 minutes, which achieves “low” [temperature] pasteurization and is cool enough to avoid giving the mix a “cooked” flavor. The mix is then “aged,” chilled to 4°C. for an hour or more to age it. This makes the mix blend better and it is noticeably creamier. Thus the ice cream pasteurizer has both a heating function and also refrigeration. In many shops the mix is pasteurized late in the day and left in overnight at 4C, so it is ready for use in the morning.
Pasteurizer manufacturers like to tell you that the high-speed agitator that churns the mix “homogenizes” but it does not homogenize butterfat. So, you can’t use raw milk and think it has been homogenized. Heating and high speed mixing allows the ingredients to bind: sugar dissolves, proteins hydrate, stabilisers swell, fats blend and the emulsifier allows all ingredients to form a smooth mixture, creating the perfect ice cream mix The beating process also drives air into the product, which makes the ice cream light and fluffy.
In order to save space, some ice cream machines have single batch pasteuizers built on top of the batch freezer, so the mix can be pastrurized and then decanted into the machine. This does save space but the mix is a “hot batch,” and has not had the chance to age. It also takes a lot longer to chill the hot batch down in the batch freezer.
Since a typical pasteurizer cycle takes at least two hours, the gelato chef must stratigize, because the batch freezer can make ice cream a lot faster than the mix can be pasteurized. For this reason, a number of batches are often run late in the day and stored in a top-opening refrigerator, for use the next morning.
Another strategy is to purchase a pasteurizer equal to the outpiut of the machine.. If, for example, you have a 15L batch freezer, it will use 9L of mix every 12 minutes or in 2 hours, about 10 batches, totaling 90 L in two hours, so a 120L pasteurizer will keep up with the demand.