Effect of extrusion conditions on the anthocyanin content, functionality, and pasting properties of obtained nixtamalized blue corn flour (Zea mays L.) and process optimization.

The aim of this study was to evaluate the effect of extrusion factors on the properties of extruded nixtamalized corn flours (ENCFs), determine the optimal conditions, and produce a tortilla with texture and nutraceutical characteristics acceptable for consumers. The processing factors used were feed moisture (FM, 15 to 30%), extruder temperature (T, 70 to 110 °C), and screw speed (SS, 50 to 145 rpm). The properties evaluated in the flours were total anthocyanins (TA), subjective water absorption capacity, and peak viscosity (PV). Response surface methodology and analysis of variance were used in the evaluation. The linear and quadratic terms of FM had a greater effect on all evaluated parameters. The optimization was performed using the numerical method of global desirability. The response variables that were optimized in the ENCF were TAs (maximize) and PV (maximize). The optimal region was the following: FM (18.17%), T (92.03 °C), and SS (76.61 rpm). The experimental value for the TA in the optimized ENCF was 226.07 mg/kg, and the PV was 1063.9 cP. The results of this study could help develop nixtamalized corn flours with desirable characteristics to make tortillas using the extrusion process. PRACTICAL APPLICATION: The results obtained would be useful for the tortilla industry, developing nixtamalized corn flours with desirable characteristics to make healthy tortillas using the extrusion process, with minimum losses in biologically active compounds such as anthocyanins (health promoters) without affect negatively the eating quality of the product (good texture).

Effect of Malting and Nixtamalization Processes on the Physicochemical Properties of Instant Extruded Corn Flour and Tortilla Quality.

This research aimed to prepare instant flour from malted and raw (un-malted) corn flours nixtamalized by the extrusion process and evaluate the effect on the physicochemical properties of tortillas prepared using these flours. White maize was malted for 24 h, dried at 50 ± 1 °C, and ground. Subsequently, 0.3 % lime and 25 or 30 % water were added to ground malted or un-malted corn, and the mixture was refrigerated (4 °C) for 12 h. These samples were nixtamalized by an extrusion process in a single screw extruder at two temperature profiles within four heating zones, TP1 (60, 60, 70, and 80 °C) and TP2 (60, 70, 80, and 90 °C), to obtain corn flour. Water was added to the extruded corn flours to make a dough, or masa, and the masa was then molded and baked to obtain tortillas. The corn flours were characterized according to their ability to absorb water and viscosity profile (RVA). The firmness and rollability after 2 and 24 h of storage were determined, and a sensory evaluation was conducted. The malted corn flour extruded with a 25 % moisture content and TP2 temperature profile yielded tortillas with the best firmness and rollability. In conclusion, the changes during the malting of corn grain and the nixtamalization by the extrusion process improved the water absorption capacity of flours and textural properties of the tortilla and produced a product with acceptable sensory properties.

Obtaining ready-to-eat blue corn expanded snacks with anthocyanins using an extrusion process and response surface methodology.

Extrusion is an alternative technology for the production of nixtamalized products. The aim of this study was to obtain an expanded nixtamalized snack with whole blue corn and using the extrusion process, to preserve the highest possible total anthocyanin content, intense blue/purple coloration (color b) and the highest expansion index. A central composite experimental design was used. The extrusion process factors were: feed moisture (FM, 15%-23%), calcium hydroxide concentration (CHC, 0%-0.25%) and final extruder temperature (T, 110-150 °C). The chemical and physical properties evaluated in the extrudates were moisture content (MC, %), total anthocyanins (TA, mg·kg(-1)), pH, color (L, a, b) and expansion index (EI). ANOVA and surface response methodology were applied to evaluate the effects of the extrusion factors. FM and T significantly affected the response variables. An optimization step was performed by overlaying three contour plots to predict the best combination region. The extrudates were obtained under the following optimum factors: FM (%) = 16.94, CHC (%) = 0.095 and T (°C) = 141.89. The predicted extrusion processing factors were highly accurate, yielding an expanded nixtamalized snack with 158.87 mg·kg(-1) TA (estimated: 160 mg·kg(-1)), an EI of 3.19 (estimated: 2.66), and color parameter b of -0.44 (estimated: 0.10).