Effect of extrusion factors and particle size on starch properties of nixtamalized whole blue corn snacks

The aim of this study, was to evaluate the effect of extrusion conditions and particle size index on the starch properties of expanded nixtamalized snacks elaborated with whole blue corn. Whole grains were ground to achieve two different particle size indexes (PSI), 83.9 and 94.1, and were extruded at three feed moistures (14, 16.5, and 20.5%). The data suggested that the severity of milling and the extrusion process resulted in higher starch degradation, specifically in the snacks obtained with a feed moisture of 20.5%, which showed the higher values of starch damage. Nixtamalization by extrusion produced minimum amounts of resistant starch, mainly as retrograded starch and amylose-lipid complex, as demonstrated by thermal and structural analyses. Snacks produced with feed moisture of 16.5–20.5% and a PSI of 94.1 showed the highest values of resistant starch. The rheological properties of snacks with PSI of 83.9 indicated lower starch degradation and presented lower amounts of resistant starch than snacks with higher PSI. The feed moisture affected all the parameters evaluated in the snacks more than the PSI.