Polymorphic crystallization and transformation pathways of 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO) during a liquid–solid-liquid journey

Abstract

The polymorphic behavior of triacylglycerol (TAG) crystals formed during the manufacturing process of lipid-based food products relates directly to their textural and melting properties. In this work, we analyzed the polymorphic crystallization and transformation behavior of 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO), a widespread TAG in edible fats and oils, during the application dynamic thermal treatments of cooling and heating. By implementing calorimetric, X-ray diffraction, and microscopy techniques, we mapped the polymorphic occurrence and the polymorphic transformation pathways of PPO as a function of the rate of thermal treatments. The results obtained were later compared to that reported for diverse TAGs in previous studies. Despite the overall crystallization and transformation behavior of PPO following a similar trend to other TAGs close in fatty acid composition, we can highlight the much lower influence of varying cooling and heating conditions on the crystallization properties of this TAG. In more detail, crystalline forms of low stability were generally promoted during crystallization, whereas transformations occurred always through the melt independently of the heating conditions. One may expect this behavior to influence the industrial processing and final properties of food products based on edible fats containing PPO.