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Efecto del superenfriamiento y la viscosidad en la formación de redes cristalinas en sistemas modelo a base de triacilgliceridos puros y aceites vegetales
| Content Provider | Semantic Scholar |
|---|---|
| Author | Alvarado, Elena Dibildox |
| Copyright Year | 2010 |
| Abstract | We have studied the pre-nucleation behavior of tripalmitin (TP) and tristearin (TS) blended in a 25:75 ratio with triolein (TO), high oleic safflower oil (HOSfO) and soybean oil (SBO) using fluorescence polarization spectroscopy (FPS), and molecular mechanics simulations (MM). We also determined the activation free energy to develop a stable nucleus (?Gc) using the Fisher-Turnbull equation. The crystallization temperatures used (i.e., 36°C-41°C in TP blends, and 46°C-51°C in TS blends) were selected to obtain similar supercooling conditions in both types of blends. The results were statistically analyzed using ANOVA and contrast among the treatment means. The FPS measurements showed that there is an increase in the anisotropy of TP:HOSfO and TP:SBO blends as opposed to TP:TO and all TS blends. This behavior is directly associated with an increase in the microviscosity of the liquid phase as a result of triacylglycerols (TAGS) structuring prior to the crystals' nucleation. We performed MM to understand the molecular interactions responsible for this behaviour. The results indicated that short range van der Waals interactions are responsible for the increase in microviscosity prior to TAGS crystallization. There seems to be a specific favourable interaction particularly when the oil contains TAGS with at least one palmitic acid in their composition, inducing a pre-nucleation structuring in the blends. In TS blends the molecular interaction occurred well before attaining supercooling conditions required for crystallization. As a result, ?Gc in TS:HOSfO and TS:SBO blends were lower than the ?Gc in the TS:TO blend. In contrast, in the TP blends TAGS structuring occurred as a function of time under isothermal conditions. We postulate that the molecular interactions occurring in the liquid phase between TP and TAGS with palmitic acid resulted in the development of mixed TAGS lamellar liquid structures. This resulted in higher ?Gc for TP nucleation as the concentration of TAGS containing palmitic acid increased in the blends. We need to understand the molecular interactions among TAGS in the liquid phase, since they relate to the TAGS crystallization process that in turn determines the macroscopic properties of lipid-based products. This study is included in this line of research. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://ri.uaq.mx/xmlui/bitstream/handle/123456789/6082/RI005176.pdf?isAllowed=y&sequence=1 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
