Thermal modifications of starch during high-temperature drying of pasta

Changes in starch at the molecular level during high-temperature (HT) dryin g of pasta were studied with differential scanning calorimetry (DSC). Pasta was manufactured from durum wheat semolina into the shape of spaghetti on a pilot-plant installation. The HT phase (100 degrees C) was applied at rel atively high (27 g/100 g, wb), intermediate (20 g/100 g), and low (15 g/100 g) product moisture, respectively. Spaghetti dried at 55 degrees C served as reference samples. The changes in the thermal properties of starch durin g drying were dependent on the drying conditions. The gelatinization enthal py of pasta dried at 55 degrees C was reduced by 30% during drying, which i ndicates a partial melting of the starch crystallites. With the beginning o f the HT phase, the gelatinization enthalpy increased to final values that were close to or higher than those of freshly extruded pasta. In general, H T drying of pasta induced a broadening of the gelatinization range. Starch crystallinity remained unchanged during extrusion and drying at HT. Based o n a state diagram of starch and on DSC measurements of pasta during drying, it is hypothesized that HT drying favors molecular rearrangements of starc h polymers at the double helical level.