Menthol As The Flavour Quality Indicator For Tablets Containing Peppermint Oil
A procedure to assess the flavour quality of water-swellable and soluble tablets containing peppermint oil was developed. Menthol, the predominant ingredient in peppermint oil, was extracted and then analysed using gas chromatography (GC). Sample tablets containing peppermint oil were pulverised, dissolved in double distilled water and then extracted prior to GC analysis. Methyl tert-butyl ether (MTBE) was found to be the most effective amongst the four solvents evaluated for menthol extraction. With the GC column temperature initially held at 60°C for 5 min, a linear program from 60 to 200°C at 4°C/min followed by holding at 200°C for 9 min gave the highest signal-to-noise ratios (SNRs). A discrete peak of menthol was obtained at 19.92 min of retention time. An excellent representation of the total amount of peppermint oil in the tablets was achieved by using the amount of menthol detected by GC, as compared to the results from the Soxhlet method. The most dramatic loss of flavour happened during the first month, whereas only 0.01% reduction was observed afterwards. It is suggested that the proposed procedure could be used for routine quality control of peppermint flavour in water-swellable and soluble tablets.