Transformation of water clusters in wet starch under changing environmental conditions

Resumo

Transformation of the water cluster distribution in wet potato starch (with a water content of 27 to 45%) at temperatures that ranged from–50 to +80°C was studied by differential scanning calorimetry. A significant difference was observed between the transformations in the temperature ranges below and above 0°C. Both cooling and heating at T < 0°C enabled a reorganization of the initial size distribution of water clusters characteristic for room temperature. These changes could lead to an increase of the average cluster size during both crystallization and melting. The transformation intensity depended on the water content and scanning rate and differed between the native and amorphous states of starch. In this case, the cluster-size distribution remained unimodal. However, heating of wet native starch to temperatures close to the point of transition into the amorphous state (75–80°C) induced a bimodal distribution due to the emergence of large water clusters; thus, the heterogeneity of the water distribution within the native granules increased.