Determining the role of starch in flour tortilla staling using α-amylase

Effects of alpha-amylase modification on dough and tortilla properties were determined to establish the role of starch in tortilla staling and elucidate the antistaling mechanism of this enzyme. Control and amylasetreated tortillas were prepared using a standard bake test procedure, stored at 22 degrees C, and evaluated over four weeks. Amylase improved shelf-stability of tortillas. The enzyme also produced a significant amount of dextrins and sugars, decreased loss of amylose solubility, and weakened starch granules. Amylopectin crystallinity increased with time, but was similar for the control and treated tortillas. Staling of tortillas appears to mainly involve the starch in the amorphous phase. As such, amylase activity does not significantly interfere with amylopectin crystallization. It is proposed that amylase partially hydrolyzed the dispersed starch (i.e., mostly amylose), starch bridging the crystalline region, and protruding amylopectin branches. Starch hydrolysis decreases the rigid structure and plasticized polymers during storage. The flexibility of tortillas results from the combined functionalities of the amylose gel and amylopectin solidifying the starch granules during storage. Protein functionality may also be involved in tortilla staling, but this needs further research.