Underutilized maize kernels (Zea mays L. var. amylacea and var. saccharata) subjected to pan and microwave toasting: A comparative structure study in the whole kernel

Abstract

Toasting in a pan is a household activity to make ready-to-eat maize using the whole kernels of underutilized maize types (Zea mays L. var. amylacea and var. saccharata) in the Andean region. Floury (a0 and a1) and sweet (a2) maize kernels with 14 g/100 g moisture content (T0) were subjected to a pan (T1) and microwave (T2) toasting. The comparative evaluation by maize types and kernel conditions (raw and toasted processes) revealed structural variations in starch granule size measured by scanning electron microscopy (SEM). In floury maize, blue value (BV), number average of molecular weight (M‾n) and intrinsic viscosity [η] evidenced consistent conformational variations. The FWHM ratio 865/941 allowed the differentiation between floury and sweet maize and between raw and toasted kernels. Floury maize displayed high ATR FTIR band intensities in the range of 994–1151 cm−1 and low from 1646 to 3298 cm−1 compared with sweet maize. Microwave toasting exhibited higher (1454–2924 cm−1) and lower (3298 cm−1) ATR FTIR band intensities than those for raw kernel and toasting in a pan. Microwave toasting had the same effect as toasted in a pan on carbohydrate structure and caused changes linked to the band intensity increases ascribed to protein and lipid structures.