GB570364A - Improvements in or relating to the manufacture of starch and the improved starch product resulting therefrom - Google Patents

Abstract

Thin boiling starch having a low solubles content is prepared by reacting a suspension of native starch in an aqueous solution of mineral acid containing a hexavalent chromium compound, such as chromium trioxide or a chromate, dichromate or chlorochromate, at a temperature below the swelling temperature of the starch granules. The reaction may be continued until substantially all the chromium compound has been reduced. For a given length of time of treatment, the addition of increasing amounts of chromium compound causes an increase in alkaline fluidity and, on the average, a decrease in solubles formed. With increasing time of treatment, the alkali fluidity rises rapidly up to a certain point and then changes relatively slowly. One half the weight of hydrochloric acid gives the same effect on alkali fluidity as sulphuric acid, but about 20 per cent more solubles are formed. Preferably, a suspension of 380 parts by weight of starch in 450-1000 parts of water, i.e. 22.5 DEG -13.5 DEG B<\>ae, is reacted with .1-9 parts of mineral acid and .15-10 parts of chromium trioxide between 35 DEG C. and 65 DEG C. from 10 mins. to 6 hours. The acid present may then be neutralized or partly neutralized and the starch recovered by filtering, washing and drying. The product will give very viscous gels when gelatinized at a pH less than about 6.5. By adjusting the pH of the suspension to between 7 and 9 after reaction with the chromium compound and immediately thereafter acidifying, preferably to a pH of 5 to 7, before filtering and drying the product is rendered capable of rapid gelatinization in hot water to give a low viscosity paste, less than about 1 per cent of the starch being rendered soluble.