A method of producing a purification medium is provided comprising the steps of: (a) contacting plant fibres with a super heated fluid； and (b) processing the plant fibres into a particulate form. Preferably the plant fibres are grape pommace and/or buckwheat husks. The superheated fluid is preferably selected from superheated water and superheated alkanols, such as ethanol. Preferably step (a) involves multiple steps of contacting the plant fibres with superheated a superheated fluid. In particular step (a) comprises a step of contacting the plant fibres with superheated water and a step of contacting the plant fibres with a superheated alkanol. Preferably step (b) involves reducing the size of the plant fibres. A method of removing contaminant compounds from a liquid is provided, comprising the steps of (i) providing a purification medium comprising plant fibres that have been contacted with a super heated fluid； and (ii) contacting the liquid with a purification medium. Preferably the liquid is a beverage, in particular wine or beer, where the contaminant compounds removed from the liquid comprise toxins, such as the mycotoxin ochratoxin A (OTA).
