ABSTRACT
Changes in starch at the molecular level during high-temperature (HT) drying 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°C) was applied at relatively high (27 g/100 g, wb), intermediate (20 g/100 g), and low (15 g/100 g) product moisture, respectively. Spaghetti dried at 55°C served as reference samples. The changes in the thermal properties of starch during drying were dependent on the drying conditions. The gelatinization enthalpy of pasta dried at 55°C was reduced by 30% during drying, which indicates a partial melting of the starch crystallites. With the beginning of the HT phase, the gelatinization enthalpy increased to final values that were close to or higher than those of freshly extruded pasta. In general, HT drying of pasta induced a broadening of the gelatinization range. Starch crystallinity remained unchanged during extrusion and drying at HT. Based on a state diagram of starch and on DSC measurements of pasta during drying, it is hypothesized that HT drying favors molecular rearrangements of starch polymers at the double helical level.
