USC
About this Article
Written by: Stephanie Ego
Written on: March 1st, 2017
Tags: health & medicine, food & drink, water, lifestyle, material science, chemical engineering
Thumbnail by:
About the Author
Stephanie Ego is a senior studying chemical engineering at the University of Southern California.
Stay Connected

Volume XVIII Issue I > Engineering Ice Cream
An additional ingredient that affects the texture and body of ice cream is stabilizers, which are made of large polysaccharide macromolecules. Common stabilizers used include cellulose gum, guam bean, and carrageenan. Hydrophilic (water-loving) polysaccharide stabilizers have the ability to bind with water molecules, which affects the ice cream in a variety of ways. For example: increased mix viscosity, reduced ice recrystallization, resistance to melting, increased product volume and uniformity, and a smooth texture eating experience. Stabilizers ultimately play a crucial role in the shelf life of ice cream, which is determined by ice recrystallization and melting [1]. Although stabilizers enhance multiple qualities of ice cream, an excess of polysaccharides can also result in a chewy texture and off flavor. Additionally, because the benefits of stabilizers are molecular based, different molecules change the way ice cream ingredients interact in a variety of ways. For example, cellulose gum has a high water-holding capacity that contributes to volume; guam bean dissolves readily in cold water and produces high viscosity mixes; and carrageenan interactions prevent phase separation and increase shelf life [1]. Therefore, food chemists must consider different polysaccharide stabilizers to achieve their desired product based on the qualities each stabilizer enhances.

Step 2: The mixture is pasteurized and heated at a high temperature for a short period of time

The process of pasteurization involves heating and mixing the ice cream mixture for a short period of time. Pasteurization is important because the high temperature destroys pathogenic microorganisms, making the ice cream bacteria-free and therefore safe for consumption. Additionally, high-temperature mixing ensures that the mixture is homogeneous (uniform throughout), decreases viscosity (thickness), and denaturizes (unfolds) proteins for increased water retention and volume. Ultimately, pasteurization and the manipulation of the mix components at high temperatures are invaluable for flavor retention, preventing spoilage, and achieving a higher quality product [1, 4]. Without pasteurization, the ice cream mix risks contamination and inconsistencies in the flavor and texture of the frozen product.

Step 3: The hot mixture is passed into the homogenizer under high pressure

The purpose of homogenization is to modify the fat globules in the ice cream mixture. Fat globules play an important role in the dryness, shape retention, melting resistance, and smoothness of the finished ice cream product [5]. During homogenization, larger fat globules in the ice cream mix are passed through an orifice (smaller opening) in a tube, causing the fat particles to accelerate and collide with a surface, such as the obstructer plate as seen in Fig. 3, and break up into smaller particles. These fat particles interact with each other, play a role in partial coalescence, and form networks that provide structure [5].
Controlling homogenization and the size of fat globules is important for determining the melting rate of and providing structure to the ice cream product. Research has found that there is a negative correlation between fat destabilization (fat globule networks) and melting rate: ice cream with larger fat globule networks had slower melting rates. Scholars such as Hartel, et al. attribute slower melting to an increased flow resistance as the ice crystals melted [6, 7]. Also, if fat globules are too large, excess churning may occur, forming an undesirable cream layer [1].