Influence of physical parameters on the germ-reducing effect of microwave irradiation on medicinal plants.

Plant material is to a different extent contaminated by microorganisms. As DAB 10 demands limiting values for aerobic bacteria, for yeasts and moulds, a reduction of microorganisms of the crude herbal drug is necessary. An effective method is the application of microwave irradiation. The microorganisms isolated and identified on different herbal drugs (leaves, flowers, herbs) were mainly spore-forming aerobic bacteria, Micrococcus luteus, and moulds of the genera Aspergillus and Penicillium. Various parameters such as the use of different microwave powers and the influence of humidity on the total count of microorganisms were tested according to the method described in DAB 10. It can be concluded from the results that microwave treatment allows careful drying with a germ-reducing effect, provided testing takes place under optimized and accurately defined conditions.