The present invention provides a method for preparing a plant derived beverage product or process intermediate, the method including the steps of: providing a crushed or liquefied extract of a plant material, exposing the extract to a size exclusion purification means involving membrane filtration (such as nanofiltration, ultrafiltration, reverse osmosis or cross flow filtration) to provide a beverage product or a process intermediate thereof, wherein the purification means is capable of at least partially separating an undesirable component, from a desirable component. The purification methods may be applied to plant materials to selectively remove various components, while leaving others. This allows for the preparation of custom plant extract beverages.
