Questions & Answers
from "On Ice Cream" featured in Dairy Foods magazine
and sourced from "On Ice Cream" technical short courses.

Effects of Pasteurization, Homogenization on Ice Cream Mix Functionality:

Question: What effects do pasteurization and homogenization have on ice cream mix functionality and performance?

Answer: Thermal processing of frozen dessert mix is required by law. Whether it is batch, HTST, HHST (high, high temperature, short time) or UHT pasteurization, thermal processing of ice cream mix exerts several positive effects. Besides rendering the mix pathogen-free, pasteurization also helps inactivate naturally occurring enzymes. Inactivation of microorganisms and enzymes reduces the development of undesirable fermentation and enzymatic byproducts and thus, extends mix shelflife and preserves a mild mix flavor. Heating also prepares the mix for homogenization. Thermal processing melts milkfat and other high-melting point lipids such as emulsifiers, which is critical to effective emulsification. It also hydrates other solids into colloidal suspension or true solution.

Depending on the exact nature of the mix and the specific thermal treatment, positive or negative flavors can result. Slight cooked flavors may be highly desirable by some, whereas more pronounced cooked flavors may not be desirable at all. The same may be true relative to mix color.
In addition, depending on the amount and type of ingredients used, more or less functionality could be created during thermal processing. Finally, thermal processing helps prepare a uniform mix.

Homogenization reduces fat droplet size and creates a stable emulsion. A secondary, yet very important effect includes changing the physical and chemical function of the milkfat globule membrane by increasing available surface area. This enables interactions with soluble or colloidally suspended proteins, stabilizers and emulsifiers during mix aging. Increasing mix whiteness and viscosity may occur.
Of course, homogenization efficiency and the impact of homogenization varies with factors such as applied pressures, location of the homogenizer in the process, the number of homogenization stages, mix composition, temperature of homogenization and the occurrence of any insoluble matter.

The various chemistries and structures created by pasteurization, homogenization and subsequent mix aging are critical to mix performance during freezing, whipping, hardening and distribution. These, in turn, impact finished product sensory attributes including flavor, appearance, body, texture and overall product acceptability.