EVALUATION OF FLUIDIZED VERSUS SPOUTED BED DRYING OF BAKERS-YEAST

Drying of baker's yeast (Saccharomyces cerevisiae) was examined experi mentally in laboratory scale fluidized bed and spouted bed dryers. Pre ssed yeast samples (70% moisture content, wb) were prepared in granula r form (0.8-1 mm diameter) and dried first in a fluidized bed to chara cterize their fluidization and drying properties. It was observed that high moisture yeast particles (up to 35%, wb) belong to group C and D of Geldart's classification, especially for higher (>200 mm) bed heig hts making their fluidization very difficult. On the other hand, fluid ization of pre-dried yeast particles with moisture content under 35%, wb (group B) was very easy. This characterization suggests a new conce pt for drying of baker's yeast i.e. spouted bed drying in the first st age and fluidized bed in the second stage or spouted bed drying for th e entire process. The quality parameter examined during the drying pro cess was viability of yeast cells at a standard moisture content (6-8% , wb).