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 ApplicationThe 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).

The blue corn-based products are considered functional foods due to their high concentration of anthocyanins. The aim of this study was to estimate the kinetic and thermodynamic parameters of the thermal degradation of anthocyanins from extruded nixtamalized corn products. A comparative study of anthocyanins thermal stability in these matrices in a buffer solution (pH 2.5) was investigated at different temperatures (60, 75 or 90 °C). Results showed the mechanism of anthocyanins degradation followed first-order reaction kinetics. The values of the reaction rate constant (k) were found to be in a range of 0.027-0.037 h −1 at 60 °C, 0.107-0.113 h −1 at 75 °C and 0.340-0.354 h −1 at 90 °C. The higher the k value was, the shorter the half-life time and D-value. The activation energy (Ea) and z-values were in the range of 75.1-89.2 kJ/mol and 28.8-35.1 °C, respectively. The coefficient Q 10 indicated the reaction rate approximately doubles with every 10 °C temperature increase. ∆H, ∆S and ∆G indicated the degradation of anthocyanins was an endothermic and nonspontaneous reaction. Even the major susceptibility of the anthocyanins in extruded nixtamalized corn products at the time-temperature combination applied, there was not difference between flour and tortilla, this imply that most of the anthocyanins were degraded during the nixtamalization extrusion process and no significative further degradation occur in the cooking step. This study provides and advance in the knowledge on the effect of nixtamalization extrusion process and tortillas making on the stability of anthocyanins from blue corn. However, further studies are needed.

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The lime-cooking extrusion process depicts emerging technologies to making maize tortillas with the advantages of reducing energy, little water use, and not environmental deletions effluents. Multi-response optimization by response surface methodology (RSM) was a tool to optimize native pigmented maize lime-cooking extrusion process to obtain flours to develop tortillas with high lipophilic compounds. The effects of extrusion temperature (ET, 65–135 ºC) and screw speed (SS, 78–212 rpm) were investigated. The best extruded blue maize tortillas were selected over response variables: Linoleic acid (LA), Oleic acid (OA), Campesterol (CP), Stigmasterol (SP), and b-sitosterol (bSP), where the quadratic predictive developed models were adequate and reproducible inside the specified array of process factors. Appling desirability function, the optimum lime-cooking extrusion conditions to development extruded blue maize tortillas correspond to ET (119 °C), SS (78 rpm) and a global desirability value (D = 0.906). Values response variables obtained from the predictive models were compared from experimental tests, a close agreement between both values was observed. Hence, RSM is still convenient for optimization, particularly once used in mixture with other procedures.