Controlled peeling of the surfaces of starch granules by gelatinization in aqueous dimethyl sulfoxide at selected temperatures

Microscopic examination of starch granules in 90:10 (v/v) Me2SO–H2O indicated that the granules were slowly being gelatinized from their surfaces. The rate of gelatinization was dependent on two variables: (1) the amount of water in Me2SO and (2) the temperature. An increase of water in Me2SO and/or an increase in temperature increased the rate of gelatinization and vice versa. Specific ratios of Me2SO and H2O (85:15–95:5) and temperatures (0–15 °C) were found to give controlled sequential peeling/gelatinization of eight kinds of starch granules in 1–12 h, with amounts of 10–25% gelatinization per hour. It was observed that the percent of starch granule remaining versus time gave curves that were linear and others that had linear parts separated by one or more abrupt changes. No two starches had a similar gelatinization curve for the same two conditions of the amount of water and the temperature. It is hypothesized that these curves reflect different structural characteristics for the individual kinds of starch granules.

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