To make block formation due to moisture absorption hardly occur and make browning hardly occur by subjecting a water suspension liquid of a soluble starch having a DE(dextrose equivalent) of not more than a particular number and a viscosity of a particular value at a specified condition to drum drying.

A starch emulsion of a soluble starch, e.g. natural starch such as potato starch, corn starch and the like, amylose or amylopectin fraction or processed starch obtained by processing them by a means for etherification, esterification or the like is reacted with an inorganic acid such as chloric acid, sulfuric acid and the like or an oxidizing agent such as sodium hypochlorite and the like. After decomposition is carried out so as to obtain a viscosity of 20-200 cps at 50°C, 30 rpm and in an aqueous solution having a content of 25 wt.%, neutralization and rinse with water are effected. An emulsion obtained can be dehydrated and shaped as is into a cake, or can be used as a dried product by drying it by a flush drying, vacuum drying or other drying method. By employing such a method, a powdered base material which hardly experiences block formation due to moisture absorption and is hardly browned even under alkaline conditions is obtained.