Adsorption and desorption behaviors of flavor molecules into a microporous pillared clay mineral and the application to flavor capsule composites

Abstract

We have investigated adsorption and desorption behaviors of Hinokitiol, Vanillin and 3-Phenyl-2-propen-1-ol (POO) into microporous montmorillonite pillared with tetramethylammonium ions (TMA-Mnt) in order to examine the ability of TMA-Mnt to retain volatile flavor molecules, with a view to applying TMA-Mnt as a capsule for the preparation of flavor/polymer composites. The treatment of TMA-Mnt with Hinokitiol, Vanillin and POO in n-hexane at 313 K caused the adsorption of these molecules on the internal and external surfaces of TMA-Mnt. Their adsorption isotherms, having Langmuir adsorption form, revealed that these compounds occupy 62–131, 23–62 and 38–102% of these total capacities in TMA-Mnt. Differential thermal analysis and thermo gravimetric (DTA–TG) measurements of the resultant Hinokitiol/, Vanillin/ and POO/TMA-Mnt compounds showed that exothermic peaks and weight losses due to the decomposition or desorption of these molecules were observed above their sublimation temperatures. This indicates that their desorptions were suppressed above the sublimation temperatures owing to their immobilization in TMA-Mnt. Detailed analyses revealed that the adsorption of these compounds into the micropores decreases their volatility at higher temperatures, demonstrating the ability of TMA-Mnt to retain the volatile flavor compounds. Hinokitiol/TMA-Mnt compound was subsequently mixed with molten poly(ethylene terephthalate) (PET) to examine the desorption behavior of Hinokitiol molecules from the PET composite. A comparison of Hinokitiol/TMA-Mnt/PET and Hinokitiol/PET exposed to temperatures of 333, 373 and 413 K showed that the desorption of Hinokitiol molecules was suppressed in Hinokitiol/TMA-Mnt/PET due to their entrapment in the micropores of TMA-Mnt, while the molecules were easily desorbed from Hinokitiol/PET. Consequently, we have found that TMA-Mnt successfully encapsulates volatile flavor compounds in a polymer composite.