Encapsulation and release of menthol. Part 2: Direct monitoring of L-menthol release from spray-dried powders made with OSAn-substituted dextrins and gum acacia

The objective of this research was to use dynamic real-time analysis to determine how carrier material affects menthol release characteristics from various spray-dried powders. Dynamic menthol release profiles were obtained from spray-dried powders as a function of time (0-60 min) and 90% relative humidity (RH) by interfacing a dynamic vapour sorption device to a proton transfer reaction mass spectrometer. The menthol release profile varied greatly with carrier material. Increased octenyl succinic anhydride (OSAn) substitution (up to 3% treatment level) of the carrier material resulted in a significantly greater, but not earlier, burst of menthol release. For most samples, the characteristic burst of menthol was followed by a decrease in release, which was attributed to an observed matrix collapse. Moisture uptake rates of the powders were related to corresponding menthol release rates. As OSAn substitution increased for gum acacia (Acacia seyal), a trend of increased moisture uptake rate with menthol release rate was evident. However, for the dextrins, the moisture uptake rate had no influence on the rate of menthol release. Also, static headspace was used to determine how increased OSAn substitution affects menthol release from aqueous mixtures of dissolved carrier material and menthol. The increased hydrophobicity of the OSAn groups did not affect the volatility of menthol, therefore interactions between OSAn groups and menthol should not affect dynamic menthol release.