Laura Bayés-García

In situ synchrotron radiation X-ray diffraction study of crystallization kinetics of polymorphs of 1,3-dioleoyl-2-palmitoyl glycerol (OPO)

We examined the influence of kinetics on the polymorphic behavior of 1,3-dioleoyl-2-palmitoyl glycerol (OPO), a triacylglycerol (TAG) present in natural oils such as olive oil and human breast milk. Pure OPO was heated at 15 °C min−1 in all cases. The polymorphic crystallization of OPO was studied at different cooling rates (15, 2, 1, and 0.5 °C min−1), and the dynamic polymorphic transformations were characterized on heating by simultaneously using Differential Scanning Calorimetry (DSC) and Synchrotron Radiation X-Ray Diffraction (SR-XRD) with small-angle X-ray diffraction (SAXD) and wide-angle X-ray diffraction (WAXD). Thermo-Optical Microscopy (TOM) was also used in order to observe the polymorphic transitions. Polymorphic forms of OPO were identified and characterized. As the cooling rate decreased, more stable forms crystallized, not following the Ostwald step rule, although in most cases concurrent crystallization occurred and the whole process was highly complex.

In situ observation of transformation pathways of polymorphic forms of 1,3-dipalmitoyl-2-oleoyl glycerol (POP) examined with synchrotron radiation X-ray diffraction and DSC

POP (1,3-dipalmitoyl-2-oleoyl glycerol), a major triacylglycerol component of vegetable and animal fats found in chocolate, fat spread, and other edible fats, crystallizes in seven polymorphic forms: α, γ, δ, β′2, β′1, β2, and β1. The crystallization and transformation pathways of the polymorphs of POP are influenced by many factors. In the present work, we studied the influence of the rates of cooling and heating on the polymorphic crystallization and transformation of POP. The rate of cooling (heating) was changed from 15 to 2, 1, and 0.5 °C min−1 (15 to 2, 1, 0.5, and 0.1 °C min−1). The crystallization and transformation processes were examined with differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (SR-XRD). The results indicated that more stable forms were formed in a higher quantity when POP was slowly cooled and heated, whereas less stable forms occurred at higher rates of cooling and heating. Specifically, less stable α and γ forms were directly obtained at cooling rates of 15 to 0.5 °C min−1. The more stable forms of β′ or β did not occur even at a rate of cooling of 0.5 °C min−1, whereas α or γ transformed to β′ or β at heating rates of 0.5 and 0.1 °C min−1. The polymorphic transformations occurred either in solid-state or melt-mediation and were largely influenced by the heating rates. We discuss the present results by considering the differences in activation free energies for the transformations from α or γ to more stable forms, which may determine the heating-rate-dependent transformation pathways.

Heterogeneous microstructures of spherulites of lipid mixtures characterized with synchrotron radiation microbeam X-ray diffraction

We observed microstructures of spherulites made of two triacylglycerols (TAGs) (POP (1,3-dipalmitoyl-2-oleoyl-sn-glycerol) and OPO (1,3-dioleoyl-2-palmitoyl-sn-glycerol)), which exhibit the mixing behavior of a molecular compound (MC) formation at a ratio of POP : OPO = 50 : 50, using synchrotron radiation microbeam (beam area of 5 × 5 μm2) X-ray diffraction (SR-μ-XRD). The spherulites were grown from neat liquid, and from solution containing 50% n-dodecane and 50% POP + OPO. SR-μ-XRD analysis revealed heterogeneous distributions of MCPOP:OPO and component TAGs in every spherulite; TAG compositions in the inner and outer areas differed when the relative ratios of POP and OPO were changed. In the 75POP : 25OPO spherulites, MCPOP:OPO always occupied the inner areas and POP dominated the outer areas as a result of different rates of crystallization of MCPOP:OPO and POP in the spherulite. In contrast, in the 25POP : 75OPO spherulites, the entire area was homogeneously occupied either with almost all OPO or with coexisting MCPOP:OPO and OPO. The microstructures of the spherulites grown from n-dodecane solutions demonstrated basically the same characteristics as those grown from the neat liquid both for 75POP : 25OPO and 25POP : 75OPO. SR-μ-XRD also clarified that the lamellar planes of the crystals are directed parallel to the radial direction from the central to the outer regions of the spherulites.

Phase behavior of binary mixture systems of saturated-unsaturated mixed-acid triacylglycerols: effects of glycerol structures and chain-chain interactions.

We systematically examined the phase behavior of binary mixtures of mixed-acid triacylglycerols (TAGs) containing palmitic and oleic acid moieties 1,3-dioleoyl-2-palmitoyl-glycerol (OPO), 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (PPO), and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP), which are widely present in natural fats and are employed in the food, pharmaceutical, and cosmetic industries. Differential scanning calorimetry and X-ray diffraction methods were applied to observe the mixing behavior of PPO/OPO, OOP/OPO, and PPO/OOP under metastable and stable conditions. The results led to three conclusions: (1) Eutectic behavior was observed in PPO/OPO. (2) Molecular compound (MC) crystals were formed in the mixtures of OOP/OPO and PPO/OOP. (3) However, the MC crystals occurred only under metastable conditions and tended to separate into component TAGs to form eutectic mixture systems after 17 months of incubation. These results were contrary to those of previous studies on 1,3-dipalmitoyl-2-oleoyl glycerol (POP)/OPO and POP/PPO in which the MC crystals were thermodynamically stable. We determined that specific molecular interactions may cause this different phase behavior (stability of POP/OPO and POP/PPO MC crystals and metastability of OOP/OPO and PPO/OOP MC crystals). All results confirm the significant effects of molecular structures of glycerol groups, interactions of fatty acid chains, and polymorphism of the component TAGs on the mixing behavior of mixed-acid TAGs.

Classification of Unelaborated Culinary Products: Scientific and Culinary Approaches Meet Face to Face

Abstract The ongoing academization of gastronomic studies indicates the necessity for a commonly accepted classification system for cooks that does not contradict scientific approaches. This work discusses the fundamentals used by chefs and scientists to classify unelaborated food products; proposes taxonomic gastronomy as a new interdisciplinary framework that studies the taxonomy surrounding gastronomy; and presents a categorization of unelaborated food products that follows commonly accepted culinary criteria yet avoids contradiction by scientific knowledge. As little literature focuses on these issues, and similar experiences are scarce, it is concluded that further cross-disciplinary endeavors such as this will continue to be greatly fruitful.