Effect of Long-Term Storage on Water Status and Physicochemical Properties of Nutritionally Enhanced Tortillas

The effect of functional ingredients (carrot juice, whole soy flour, and whole kamut flour) and storage (180 days) on physicochemical properties (texture and amylopectin recrystallization) and water status (moisture content, water activity, ice melting peak thermal properties, and proton nuclear magnetic resonance (1H NMR) mobility) of tortillas has been studied. Different formulations significantly changed the parameters studied during storage resulting in larger changes than in the standard formulation (STD) that, therefore, may be considered the most stable product. The properties of whole kamut tortillas were very similar to those of standard sample while the formulation that contained carrot juice lead to an increased system rigidity observable both at macroscopic (textural properties), macromolecular (significantly reduced), and molecular (1H FID) levels. A decrease of moisture content, water activity, endothermic transition ~0 °C, and an increase of 1H NMR mobility (1H T2 pop A and C) were observed in soy-containing products [(soy enriched (SOY) and carrot, soy, and kamut (CSK)]. SOY and CSK had very low water activity, presented the highest 1H NMR molecular mobility and underwent the most marked changes during storage suggesting that water activity cannot be taken as a sole indicator of food stability as very important modifications occurred in tortillas at molecular level.