Starch crystal solubility and starch granule gelatinisation

The solubility and dissolution behaviour of A- and B-type crystals of short chain amylose were measured both directly and using differential scanning calorimetry in the temperature range 30-110 degrees C. Dissolution in the calorimeter was affected by super-heating to the extent of 24-28 degrees C. Following trends previously found by calorimetry the B-type crystal polymorph was more soluble than the A-type. Analysis of the chain composition of the dissolved material revealed a preferential solubilisation of the short chains at the lower temperatures. The solubility of both crystal polymorphs and the magnitude of the preferential solubilisation effect was reduced in the presence of 30% w/w sucrose. A comparison of calorimetric measurements of crystal dissolution and the gelatinisation of native granular waxy maize and potato starches found some broad similarities, such as transition temperatures and their composition dependence, and some differences, such as the relatively narrow temperature range of granular gelatinisation, which reflects its cooperative nature.