Influence of high-temperature drying on structural and textural properties of durum wheat pasta

Starch and protein are the main polymeric ingredients of pasta and they determine the structural and textural properties of cooked pasta. The present investigation sought better understanding of the impact of high-temperature (HT) drying on the starch and the protein fraction, and their role in structure and texture of pasta. Durum wheat spaghetti was prepared in a pilot-plant installation. The drying conditions were selected for the HT phase at 80 or 100degreesC applied at high, intermediate, or low product moisture content. Spaghetti dried at 55degreesC served as a reference sample. The color of dry pasta was measured and the changes in the starch and protein fractions were determined by protein solubility, light microscopy, confocal scanning laser microscopy (CSLM), cooking tests, and texture measurements. HT drying at 100degreesC and low product moisture promoted browning of pasta. At the molecular level, HT drying promoted protein denaturation. At the microscopic level, HT drying contributed to a better preservation of the protein network and reduced swelling of starch and disintegration of granules. At the macroscopic level, HT drying enhanced the firmness of cooked pasta and reduced surface stickiness. In general, the changes were more pronounced by increasing the drying temperature from 80 to 100degreesC and by shifting the HT phase from an early to a late stage of the drying process. The drying conditions are determinant for the phase morphology of protein and starch in cooked pasta which, in turn, govern the textural properties of pasta.