The fractionation of potato starch

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Abstract
Amylose and amylopectin were prepared from non-autoclaved potato starch paste by successive additions on alternate days of cyclohexanol and thymol, which, on the whole, gave the best results, and by the methods of Schoch and of Haworth, Peat and Sagrott. No great differences were noted among the products obtained by use of 3 precipitants. There is no advantage to be gained by heating the starch paste under pressure. If this is omitted a fairly wide range of pH may be tolerated at the time of precipitation, but the amylose produced under acid conditions showed the greater tendency to retrograde in neutral soln. Prepns. of amylose with 17 times the blue value, as measured on the Spekker absorptiometer, of the corresponding amylopectin were obtained. The blue value of amylose is greatly influenced by the method of recrystallization from butanol-saturated water, and by the period of heating when redissolving. Exposure of amylose to hot water brings about changes even in the portion which does not retrograde. The blue value falls and beta-amylase action is incomplete. Amylo-pectin was not so successfully purified, but fractional precipitation with ethanol freed it slightly from amylose which had escaped the first precipitation.

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