抄録
A variety of powdered food products, including instant soup, instant beverages as well as seasonings, are frequently manufactured into granule form, since fine powder has poor flowability and dispersibility, which causes difficulties in measuring and packaging of powder and causes clumping when it is dissolved in water or other media. Among the several granulation methods, fluidized bed granulation is a major process for producing the instant soup and beverages because of the excellent solubility of the granule products. In the fluidized bed granulation process, an aqueous solution of polysaccharide is usually sprayed as a binder to the powder to bridge the particles, however, an increase in the moisture content of granules often spoils the product quality and elongates successive the drying period.
This article summarizes a new fluidized bed granulation method that was developed to improve the performance of the process by using Steam-Water Two-Phase (SWTP) binder. The steam has been traditionally known as an efficient binder for granulation since it rapidly bridges the particles by condensing and wetting the surface of particles. However, controlling the granule size is difficult and coarse agglomerates are produced in the fluidized bed granules with steam binder. It is presumably because the larger granules are grown more rapidly than smaller ones by the steam binder. The larger granules have a higher probability of contacting with other particles, which leads to faster granule growth by the steam binder while the granule growth rate is limited by the presence of droplets when a liquid binder is used in fluidized bed granulation. In SWTP binder granulation, the water droplets nucleate growth by bridging the fine particles, steam consequently condenses on these nuclei and efficiently grow them. In SWTP binder granulation, the amount of water sprayed on the powder decreased to 40~84% to produce granules having an equivalent size to that obtained by conventional fluidized bed granulation using a liquid binder.
