2014 Volume 15 Issue 1 Pages 25-35
In the fluidized bed granulation process of powdered food, aqueous solution is usually sprayed as a binder to the powder to grow the granules, however, increase in the moisture content of granules often spoils the product quality and elongates successive drying period. In this study, Steam-Water Tow-Phase (SWTP) binder has been applied for fluidized bed granulation to reduce the amount of water added to the powder. In the SWTP binder granulation, superheated steam and water (127°C, 138 kPaG) were sprayed at 18.8 g/min and 0～40 g/min respectively through a signle-fluid nozzle to the mixed powder of maize starch (800 g) and dextrin (200 g). In the SWTP binder granulation, the amount of water sprayed to the powder decreased to 40～84％ to produce the granules having equivalent size with that obtained by the conventional fluidized bed granulation using the liquid binder. At lower water spraying rates, the reduction effect of binder water increased, however, coarse particles were produced in these conditions. The steam effectively grew the granules by condensing on the nuclear generated by the water droplets, however, the lack of sufficient number of nuclear permitted the steam to increase the ununiformity in granule size.
