Selective extraction of oxygenates from savory and peppermint using subcritical water

The yields of oxygenated and non-oxygenated flavour and fragrance compounds from savory (Satureja hortensis) and peppermint (Mentha piperita) were com pared using subcritical water extraction, supercritical carbon dioxide extr action (SFE) and hydrodistillation. Extraction rates with subcritical water increased with temperature (100-175 degreesC), but some desired organics ( linalool and gamma -terpinene) showed substantial degradation at temperatur es >150 degreesC. However, subcritical water did not expose extracted compo unds to atmospheric oxygen (as occurs in hydrodistillation) and thus may av oid the degradation of compounds like thymoquinone. Extraction of savory wi th subcritical water at 100 degreesC for 40 min gave ca. 100% recoveries (c ompared to hydrodistillation) for thymol and carvacrol, and >150% recoverie s of borneol and linalool. Recoveries with 60 min of SFE (pure CO2 at 400 b ar and 50 degreesC) were similar to hydrodistillation for borneol and linal ool, but only ca. 50% for thymol and carvacrol. For peppermint, 30 min (at 150 degreesC) or 12 min (at 175 degreesC) of subcritical water extraction a nd 1 h of SFE gave good quantitative agreement with 4 h of hydrodistillatio n for carvone, pulegone, piperitone, eucalyptol, menthone, neomenthol and m enthol, but the short subcritical water extractions only recovered ca. 40% of the less polar menthyl acetate. Subcritical water preferentially extract s more polar (oxygenated) flavour compounds, and ca. 80% extraction of oxyg enated flavour compounds could be achieved under conditions which only extr acted ca. 10-15% of the monoterpenes and <5% of the sesquiterpenes. In cont rast, SFE had the lowest degree of selectivity and SFE extracts included pl ant alkane waxes as well as the same flavour compounds recovered by hydrodi stillation. Copyright (C) 2001 John Wiley & Sons, Ltd.