Experimental Validation of Modeling Approaches Describing the Crystallization of Pure Triacylglycerides and Their Mixtures: A Review

Lipids are essential macronutrients, with the ability to solubilize and enhance the uptake of specific micronutrients (e.g., vitamins A, D, E, and K). Solid fats provide desirable texture and palatability to food products, making them a key ingredient for food and particularly bakery products, ice cream, or confectionery. Outside of the food industry, lipids are often used in pharmaceutical formulations to facilitate the delivery of poorly water-soluble active pharmaceutical ingredients. Natural fats, such as cocoa butter or tallow, consist of a complex mixture of several triglycerides (TAGs) with different chemical compositions. Such differences can lead to partial or full immiscibility in the solid phase, which results in complex phase diagrams with multiple possible types of solid phases. Additionally, TAGs can crystallize in many crystalline forms (polymorphs) with different thermodynamic stabilities, which further complicates TAG solid-state thermodynamic and kinetic behavior. Due to this complexity, developing experimentally validated models that describe the crystallization behavior of TAG mixtures is challenging. Nevertheless, reliable models are essential to speed up product and process development and increase manufacturing efficiency. This review paper illustrates and discusses existing models developed to describe different aspects of TAGs crystallization, with a focus on their experimental validation and the necessary analytical tools. For all approaches and experimental techniques, advantages and limitations are presented. Finally, based on the reviewed literature, possible future research trends and developments are presented.