GB853828A - Methods for treating starch - Google Patents

Abstract

Starch is dextrinized by maintaining a bed of fluidizable starch powder in a fluidized condition in a vessel with an upward flow of fluidizing gas, preferably about 0.5 ft./sec., heating said bed to and maintaining it at dextrinizing temperature (e.g. 150-400 DEG F.) until the desired degree of dextrinization is obtained and introducing steam into the flow of gas during at least a portion of the dextrinizing cycle. Dilute hydrochloric acid vapour may be introduced as a catalyst, the conversion being arrested by introducing ammonia. At the beginning of the process, at least a portion of the air withdrawn from the vessel may be vented until the starch is dried and thereafter the gas withdrawn is recycled. The heating and cooling of the fluidizing starch may be effected by heat exchangers mounted within the fluidizing vessel. The moisture content of starch may also be adjusted to a desired value by a process in which starch is maintained in fluidized condition in a vessel by an upward flow of gas which is maintained until the moisture content reaches the desired value, the moisture content of the gas being such as to produce the said adjustment of moisture content. The fluidized bed may be heated to hasten drying, the gas being recirculated after removal of moisture therefrom. Wet starch powder may be rendered fluidizable by blending with dried starch powder. The moisture content of fluidized starch may be increased by increasing the moisture content of the fluidizing gas. The fluidizing gas may be air, flue gas, nitrogen or carbon dioxide. The addition of a very small percentage of tricalcium phosphate will restore the fluidizability to starch which has been rendered non-fluidizable by the presence of oil. The use of tricalcium phosphate also reduces the bulk density of fluidized starch and permits the use of less fluidizing gas for a given weight of starch.