THE CENTRIFUGAL FLUIDIZED BED.

— Drying food pieces in a centrifugal fluidized bed with relatively high air flows may be self-limiting, even when only partial drying is desired. Rate increases obtained in early stages of drying may be more than offset through rate-retarding effects of a skin-like layer of collapsed surface tissue which forms on the pieces. This skin layer becomes increasingly resistant to heat and moisture transfer. Rate data and piece temperature patterns for potato, apple and carrot confirm visual observations that skin barriers 0.2–1.0 mm thick form in the first 8–10 min of drying with high air velocities and moderate temperatures. When air temperatures were 250°F with velocities of 15 fps, 1.2-cm cubes of potato could be blanched in only 6 min, suggesting a procedure for blanching some types of food products without leaching.