The behavior of plant-based milks is proving to be a remarkably complex area of study. Scientists are only now delving into its intricacies, with the ultimate goal of enhancing the quality of these popular beverages.
Research conducted by Vivek Sharma and his team at the University of Illinois Chicago has revealed that most plant milks exhibit flow and dripping characteristics far more intricate and peculiar than those of their animal-based counterparts.
The investigation involved an analysis of eight distinct milk varieties: cow, goat, pea, soy, oat, almond, coconut, and rice. The researchers focused on their viscosity, essentially measuring the resistance to flow each possessed.
A significant finding was that all plant-derived milks, with the exception of rice milk, demonstrated a phenomenon known as shear thinning. This means their viscosity diminishes under applied pressure.
This characteristic classifies these milks as non-Newtonian liquids. In practical terms, they behave more akin to substances like ketchup or shampoo, which become less viscous and flow more readily when squeezed. This contrasts with cow or goat milk, which maintain a constant viscosity irrespective of pressure.
Sharma attributes this non-Newtonian behavior to the presence of minute quantities, often below 0.1 percent, of gums. These gums, derived from legumes or bacteria, are incorporated to improve shelf stability and impart a richer, creamier texture to the mouthfeel.
The inherent non-Newtonian nature of these beverages also influences daily interactions with them, Sharma noted. For instance, spills of shear-thinning plant milk tend to spread further on surfaces compared to traditional milk. Similarly, when a cookie is dipped into such milk, it receives a noticeably thinner coating.
The research team posits that a deeper understanding of the physics governing milk properties and their constituent ingredients could pave the way for the creation of novel drinks with precisely engineered desirable qualities. While experienced food scientists often rely on intuition and empirical knowledge to refine milk formulations, Sharma suggested they seldom employ rigorous physical models or quantitative measurements in their practice.
Sharma presented the findings of this research on March 18th at the American Physical Society Global Physics Summit held in Denver, Colorado.