Spaghetti was prepared using dies made of different materials. The surface was observed using digital and optical microscopes, and was rougher for the spaghettis prepared using the Teflon, polypropylene, polycarbonate, aluminum, and bronze dies in this order. The extrusion velocity when passing through the die was faster, the bulk density was higher, and the rupture strength was greater for the spaghetti having the smoother surface. The die material did not affect the gelatinization temperature. The water sorption curves in boiling water containing 0.5% (w/v) sodium chloride were also observed. The curves were expressed by an equation of the hyperbolic type except for the early stage of sorption in order to estimate the equilibrium amount of water sorbed based on the bone-dry sample. The momentarily-sorbed amount of water, which is a hypothetical quantity to characterize the initial water intake, was estimated by fitting the experimental points within 60 s. The amount was higher for the spaghetti having the rougher surface.
The effects of the die material on the surface roughness and water sorption kinetics of spaghetti were investigated. The spaghetti prepared using Teflon, polypropylene, and polycarbonate dies had a smooth surface, high bulk density, and high rupture strength, while the spaghetti prepared using the aluminum and bronze dies could be cooked in the state of al dente in a shorter time. Thus, the die material affected the properties and water-sorption kinetics of the dried spaghetti.