Amylolysis of native and annealed potato starches following progressive gelatinisation

• Starch α-amylase hydrolysis is controlled primarily by the extent of gelatinisation.
• Composition, architecture and size moderate hydrolysis of native granules with α-amylase.
• The glycaemic index (GI) of starch will reflect the extent of gelatinisation.

The extent of α-amylase hydrolysis of normal potato starches, extracted from different varieties grown under the same conditions in the same season, is regulated more by gelatinisation than the composition or structure of the granules. This is evident for native and annealed starches gelatinised and then hydrolysed with α-amylase. With similar gelatinisation peak (Tp) temperatures (62.5–66.1 and 70.2–72.3 °C respectively) and enthalpies (15.1–17.8 and 15.8–19.5 Jg−1 respectively) for the native and annealed starches, increasing the temperature exposure in excess water (to cause progressive gelatinisation) by 10 °C increments creates progressively more hydrolysis reflecting the (similar) gelatinisation transition. Overall, therefore, processing has a greater potential impact on the glycaemic index (GI) of potato starches than any variety specific variations.

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