“…In order to enhance extraction efficiency, additional energy is put into the system either directly by heat (e.g. 70 • C), or by other techniques such as pressurized liquid extraction (Benthin et al, 1999), supercritical fluid extraction (Castioni et al, 1995;Jarvis and Morgan, 1997;Blanch et al, 1999), sonication (Sargenti and Vichnewski, 2000), subcritical water extraction (Gámiz-Gracia and de Castro, 2000), microwave techniques (Namiesnik and Gorecki, 2000), or pervaporation (Starmans and Nijhuis, 1996). Rarely data are available that compare these techniques and, furthermore, few systematic studies have been carried out on the occurrence of possible metabolite breakdown reactions caused, for example, by oxidation (Peng and Jayallemand, 1991).…”