Optimization of an Extrusion Cooking Process to Increase Formation of Resistant Starch from Corn Starch with Addition of Citric Acid

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimEffects 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.