| Abstract: | Starch properties of corn tortillas were characterized during storage. Tortillas were chopped into pieces, macerated with ethanol, centrifuged, extracted again with ethanol, centrifuged, dried, and ground into flour to dehydrate and stabilize starch. Water absorption and water solubility at 25°C, starch pasting properties, and amount and molecular weight of starch extracted at 95°C in water were quantified. Increased levels of soluble amylopectin and increased cold paste viscosity distinguished fresh (0, 0.5, and 1 h) from aged (120 h) tortillas. Water solubility at 25°C decreased continuously during storage; whereas, water absorption increased 0.5 h after baking and then decreased during storage. Rapid changes in starch properties were stabilized using the dehydration procedure and clearly distinguished by pasting viscosities and other methods. Measured starch properties were consistent with very rapid associations (retrogradation) of amylose and rapid associations of amylose and amylopectin yielding insoluble structures in corn tortillas. Retention of some starch crystal nuclei after baking facilitated starch associations that yielded rapid structural changes in corn tortillas. |
