Effect of the preparation method and storage time on the in vitro protein digestibility of maize tortillas

Maize tortillas are still an important source of energy and proteins for Mesoamerican population. While starch digestibility has been characterized at some detail, studies on protein digestibility are still scarce. This work considered maize tortillas prepared from masa made with industrial and traditional nixtamalized flours to characterize the effect of the preparation method and storage time (up to 4 days). Protein content was slightly higher (8.5%) for artisanal tortilla than for industrial tortilla (7.4%), an effect caused by stringent nixtamalization under industrial and semi-industrial conditions. Tortilla made with artisanal methods exhibited increased hardness (2.14 N) and reduced adhesiveness (0.44 mJ) compared with its counterpart made with industrial flour (0.9 N and 0.41 mJ). FTIR analysis of Amide I group revealed that protein of artisanal tortilla had a lower amount (11.7%) of β formations (sheets and turns) as compared to tortilla made with industrial flour (27.5%). Protein digestibility of fresh tortilla was higher for artisanal method (∼89.0%) than for industrial method (∼84.0%). Also, protein digestibility decreased linearly with storage time, with artisanal tortilla presenting the lowest decreasing rate (∼0.5%/day). These results suggest that maize-based staple foods with improved nutritional values can be produced using artisanal methods.