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The effects of different concentrations of calcium hydroxide [Ca(OH)2] and calcium lactate [C6H10O6Ca] on the functional and physical properties of extruded ( EF) and nixtamalised ( NF) blue maize flours were evaluated. Calcium source and concentration showed no significant effects on the EF expansion index. The water absorption index ( WAI) of EF decreased as the concentrations of both calcium sources increased, and NF with C6H10O6Ca had the lowest WAI. The thermal and pasting properties of NFs were higher than those of EF. NF with C6H10O6Ca showed the highest final viscosity (FinV), indicating less damage to the starch granules, and this was correlated with microscopic analysis. In contrast, the FinV of EFs was significantly affected by calcium source and concentration. Extrusion with 0.3% and nixtamalisation at 2.95% of C6H10O6Ca yielded high WAI value and the best rheological properties in maize flour, respectively. These results suggest the use of C6H10O6Ca in extrusion or nixtamalisation to produce blue maize flours for tortilla or snacks with antioxidants. [ABSTRACT FROM AUTHOR]

Effects of extrusion cooking process (ECP) with citric acid (CA) addition on the physicochemical changes and resistant starch (RS) formation in native corn starch (NCS) are evaluated. NCS at different feed moisture levels (18–32%) and CA concentrations (0–10.3%), are subject ECP under constant conditions of screw speed (233 rpm) and die temperature (127 °C). The obtained extrudates are stored at 4 °C for 120 h and then at room temperature. The water absorption index (WAI), water solubility index (WSI), RS content, peak temperature (Tp), ∆H, peak viscosity (PV), setback viscosity (SV), FT‐IR, X‐ray analysis and microstructural (SEM) properties are evaluated. RS content and WSI increased with decreasing moisture content (MC), WAI, PV and SV shows that increases in MC caused an increase, while ∆H and Tp decreases with decreasing MC. SEM shows that ECP with CA destroys the granular structure of NCS generated amorphous structures owing to gelatinization and dextrinization. FT‐IR analysis shows that extruded samples with CA cause starch hydrolysis, increasing the intensity of bands 994 and 1016 cm−1 in comparison to NCS. The highest RS yield (1.15 g/100 g) is obtained at 18% moisture content and 5.2% of CA: an increase of 71% with respect to NCS. [ABSTRACT FROM AUTHOR]