Pasteurization is one of the most delicate phases in the artisanal gelato-making process. Its purpose is to reduce the number of bacteria naturally present in the mixture. All foods naturally contain some level of microbial flora, including pathogens, which multiply rapidly at temperatures between 15°C and 20°C (59°F–68°F) and between 55°C and 60°C (131°F–140°F). Below or above these ranges, bacterial growth significantly slows down.
Thus, pasteurization is a heat treatment used to destroy spoilage agents, providing biological and enzymatic stability to the food, specifically the gelato mixture. A fundamental requirement is that this process does not excessively damage the organoleptic properties of the ingredients, such as sugars, compound ingredients, and other flavorings. During pasteurization, the gelato mixture is heated to a temperature between 65°C and 85°C (149°F–185°F) and then rapidly cooled down to 4–5°C (39°F–41°F).
Optimal pasteurization ensures a complete and hygienically safe production process for artisanal gelato. Modern pasteurizers—machines designed for this function—handle the entire cycle, from mixing ingredients and dissolving solids to heating, rapid cooling, maturation, and storing the mixture until freezing, all within a single closed tank. Proper pasteurization improves the product quality by optimizing the extraction of aromatic substances and semi-finished products, dissolving sugars, hydrating thickeners and proteins, liquefying and evenly dispersing fats, and ultimately achieving a stable emulsion.
In parallel with pasteurization, homogenization takes place. As the name implies, this phase aims to make the gelato mixture uniform, harmonious, and homogeneous. While dispersing substances like sugars or proteins in water is relatively easy due to their solubility, mixing water and fats presents more challenges.
During pasteurization, when the mixture temperature is between 60°C and 75°C (140°F–167°F), the fats present are broken down and blended to be homogenized. To maintain stability in a homogenized mixture, emulsifiers can be added. These substances reduce surface tension to create a stable emulsion, resulting in a smoother and creamier texture.
The entire pasteurization and homogenization cycle takes about 2 to 3 hours.