Traditionally, medicinal plants have been air dried in the sun. Depending on the surroundings of the drying location, the plants may be subject to various contaminations (such as through birds or insects) and varying weather conditions. Usually, there is no standardized procedure, which means that the plants can be over- or under-dried, or exposed to mould if humidity is too high. Drying, however, is an important process, during which active compounds need to be maintained and at the same time water content reduced to defined levels to allow for safe prolonged storage of the dried material.
Zeller, therefore, takes special care during the drying process. Zeller has implemented standardized and controlled drying processes for each individual plant, which enables consistent, gentle and homogenous drying. For this, e.g. special belt dryers are utilized on which the fresh plant materials are quickly and evenly dried under warm air. The parameters for drying such as temperature and duration are specifically defined for each plant. For instance, the conditions for drying the roots of Valeriana officinalis are not the same as the drying-conditions for Hypericum perforatum.
All the drying steps at Zeller comply with GACP guidelines.