In situ crystallization and transformation kinetics of polymorphic forms of saturated-unsaturated-unsaturated triacylglycerols: 1-palmitoyl-2,3-dioleoyl glycerol, 1-stearoyl-2,3-dioleoyl glycerol, and 1-palmitoyl-2-oleoyl-3-linoleoyl glycerol

• Published in: Food research international Vol. 85; pp. 244 - 258
• Main Authors: Bayés-García, L., Calvet, T., Cuevas-Diarte, M.A., Ueno, S.
• Format: Journal Article
• Language: English
• Published: Canada Elsevier Ltd 01.07.2016
• Subjects: Food product; Lipid; Polymorphism; Synchrotron radiation; Thermal treatment; Triacylglycerol; Triacylglycerol; Lipid; Synchrotron radiation; Food product; Polymorphism; Thermal treatment
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/j.foodres.2016.05.011

We examined the influence of dynamic thermal treatment (variation of cooling/heating rates) on the polymorphic crystallization and transformation pathways of 1-palmitoyl-2,3-dioleoyl glycerol (POO), 1-stearoyl-2,3-dioleoyl glycerol (SOO), and 1-palmitoyl-2-oleoyl-3-linoleoyl glycerol (POL), which are major saturated-unsaturated-unsaturated (SUU) triacylglycerols (TAGs) of vegetable oils and animal fats (e.g., palm oil, olive oil, and Iberian ham fat). Using mainly a combination of differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (SR-XRD), we analyzed the polymorphic behavior of TAGs when high (15°Cmin−1), intermediate (2°Cmin−1), and low (0.5°Cmin−1) cooling and heating rates were applied. Multiple polymorphic forms were detected in POO, SOO, and POL (sub-α, α, β’2, and β’1). Transient disordered phases, defined as kinetic liquid crystal (KLC) phases, were determined in POO and SOO for the first time. The results demonstrated that more stable forms were directly obtained from the melt by decreasing the cooling rates, whereas less stable forms predominated at high cooling rates, as confirmed in our previous work. Regarding heating rate variation, we confirmed that the nature of the polymorphic transformations observed (solid-state, transformation through KLC phase, or melt-mediation) depended largely on the heating rate. These results were discussed considering the activation energies involved in each process and compared with previous studies on TAGs with different saturated-unsaturated structures (1,3-dioleoyl-2-palmitoylglycerol, 1,3-dipalmitoyl-2-oleoyl-glycerol, trioleoyl glycerol, and 1,2-dioleoyl-3-linoleoyl glycerol). The use of dynamic thermal treatments on the polymorphic crystallization and transformation of POO, POL and SOO is closely related to actual crystallization processes of edible fats, as the occurrence of designed polymorphic forms may be controlled by tailoring the most efficient temperature programs. [Display omitted] •Dynamic thermal treatments are related to crystallization processes of edible fats.•Complex polymorphic behavior of TAGs was monitored by varying kinetic conditions.•Polymorphic transformation pathways were discussed in terms of molecular structures.•Functional polymorphs may be formed by tailoring most efficient thermal treatments.