Starch retrogradation in cooked pasta and rice

Effect of cooking time on starch retrogradation and water distribution was studied in pasta (spaghetti) and rice (parboiled and arborio) using differe ntial scanning calorimetry (DSC) and thermogravimetric analysis (TGA) Optim um cooking times (OCT) were 8, 16, and 18.5 min for spaghetti, parboiled, a nd arborio rice, respectively. Swelling was observed by image analysis. OCT spaghetti and rice showed various starch retrogradation rates at various a ging times and temperatures. Based on the classical Avrami function, the re trogradation rate at 5 degrees C followed the order spaghetti > parboiled r ice > arborio rice, while extent was in the opposite order. At higher tempe rature (20 degrees C), the rates decreased by 20x in all cases. Thermogravi metric analysis (TGA) investigations were undertaken to check the distribut ion of water within these products and its relationship to starch retrograd ation. During heating, water was released in two distinguishable steps at a pproximate to 80 and 100 degrees C. Results supported the conclusion that t he more tightly bound water might not participate or facilitate starch retr ogradation. In this study, the overall water content did not change during storage, and water appeared to migrate from sites of stronger binding to si tes of weaker binding. The temperature dependence of the Avrami constant wa s described with the Vogel-Tamman-Fulcher empirical expression.