DSC enthalpic transitions during starch gelatinization in excess water, dilute sodium chloride, and dilute sucrose solutions

Background: Starch phase transition characteristics were studied by pre-treating starch samples in excess water, dilute sodium chloride and dilute sucrose solutions and subjecting them to differential scanning calorimetry (DSC). Unmodified maize, wheat and potato starches were held at specific temperatures between 30 and 90 °C for 30 min and promptly cooled to 25 °C. Treated samples were then analyzed in situ by DSC. Results: It was found that the progression of the phase transition behavior differed among the three starches and was dependent on the solvent. It was also revealed that phase transition-related enthalpic changes started to occur at low temperatures and that this process involved a continuous sequence of structural changes, resulting in progressive differences in endothermic patterns from low to high temperatures. Conclusion: These findings are in agreement with recent evidence suggesting that starch gelatinization occurs over a wider temperature range rather than as a sudden order–disorder transition taking place within a narrow temperature range. The phase transition mechanism is determined by starch type and solvent combination.