Starch gelatinization under pressure studied by high pressure DSC

The gelatinization process of waxy corn starch under different pressures up to 10.0 MPa was investigated using a high pressure DSC. Compressed air and carbon dioxide were used as pressure resources. Effect of pressure and annealing under pressure on gelatinization of waxy corn starch was systematically studied, in particular on the gelatinization temperature and enthalpy. The results show that the peak temperature of gelatinization was increased slightly initially then remained stable with increasing pressure. The gelatinization enthalpy was decreased under pressure processing. Annealing the starch under pressure condition, just below its gelatinization temperature, increased gelatinization temperature but kept gelatinized enthalpy constant. Morphologies of starch granules treated under pressure were studied using an optical microscope and SEM. There is no discernable difference of starch granules treated with and without pressure, which indicates the pressures are not high enough to destroy crystalline structure. The intensity of the pressure acts as a key factor to influence the gelatinization of starch rather than the nature of the gas. Effect of pressure on the multi-endotherm detected by DSC for starch with intermediate water is used to study the mechanisms. The effect of pressure can be explained by the enhancement of water diffusion in the amorphous range.