Isolation of high molecular weight amylose by dimethylsulfoxide dispersion

The problem of the isolation of the amylose component of starch under conditions of minimal degradation has been re‐examined. It is confirmed that aqueous leaching of granules under anaerobic conditions as advocated by Gilbert and co‐workers leads to amylose of high intrinsic viscosity and very high molecular weight (M̄w > 1 × 106), and of high degree of digestion by crystalline β‐amylase (∼95%). However, yields are poor under practical conditions. An alternative procedure is described based on the fact that fresh undried potato starch can be quantitatively dispersed in dimethylsulfoxide by prolonged contact at room temperature. Addition of butanol to this solution results in precipitation of both amylose and amylopectin components. This precipitate can, however, be redissolved in water and the amylose component separated in the customary manner by butanol complexing (following a brief heating of the aqueous solution to 70°C). After one recrystallization a product has been attained which possesses an iodine binding capacity of 18.9 mg./100 mg., and intrinsic viscosity and M̄w even higher than in case of the material leached by water under anaerobic conditions. Further, the high degree of digestibility by crystalline β‐amylase (>95%) indicates negligible chemical alteration of the normal linkages under the preparative conditions.