Raw material samples (30 g dry matter basis) were spread in a
thin layer on a Petri dish and irradiated in a microwave oven KOR-63X5 (Daewoo, China) for 2 min with 400 W microwave power output and 2450 MHz frequency. After the pretreatment samples
were cooled to room temperature in a desiccator. Further procedure was the same as in Section