Thermal stability of the linoleic acid/α- and β-cyclodextrin complexes

This paper presents a thermal stability study of the linoleic acid/alpha- and beta-cyclodextrin (alpha- and beta CD) complexes. Bionanoparticles were obtained by a solution method and were characterized by differential scanning calorimetry and transmission electron microscopy. The pure linoleic acid, the corresponding thermally (50-150 degrees C) degraded raw linoleic acid samples or those recovered from the complexes were analyzed by gas chromatography-mass spectrometry, after conversion to the methyl esters. Nanoparticles were obtained with good yields of 88% and 74% for alpha- and beta CD complexes, respectively. The main degradation products (for the thermally degraded raw samples) were aldehydes, epoxy, dihydroxy derivatives, homologues, and isomers of linoleic acid. A good thermal stability of nanoparticles can be observed, especially for the linoleic acid/alpha CD complex, which contains a relative concentration above 98% fatty acid in the case of temperature degradations of 50 and 100 degrees C. A lower concentration of 92% can be observed in the case of the linoleic acid/beta CD complex but, for the temperature degradation of 150 degrees C, the linoleic acid was partially converted to more stable geometrical isomers. (c) 2005 Elsevier Ltd. All rights reserved.