Melting Properties and Lintnerisation of Potato Starch with Different Degrees of Phosphorylation

Lintner dextrins were prepared from size fractionated potato starch granules from two potato varieties (90BKG22 and Lady Rosetta) that contain high or low natural content of esterified phosphate, respectively. The time course of hydrolysis showed the typical two‐phase kinetics, with a maximal degree of hydrolysis of between 74% and 81% after 30 days of hydrolysis, except for the fraction of smallest granules of the low phosphorylated variety (low P), which was hydrolysed to 98%. The relative amount of retained glucose‐6‐P in the Lintner dextrins was 18.6% for the low P variety and 46.6% for the high P variety. However, when calculating the relative distribution of phosphate in the granules, it was shown that approximately 80% (low P) and 35.5% (high P) was located in the amorphous region. Melting characteristics were followed by differential scanning calorimetry (DSC). The DSC endothermic peak became low and broad during the time course of hydrolysis, with rise in enthalpy change, indicating a strong dependency on the amorphous region of the granules. After annealing the same fractions showed the typical raise in gelatinisation temperature and narrowing of gelatinisation peak. The values of the melting temperatures (T_o, T_m and T_c) are positively correlated to the degree of phosphorylation of the starch dextrin fractions both before and after annealing.