Physical and hydration properties of specialty floury and sweet maize kernels subjected to pan and microwave toasting

Abstract The three main underutilized maize types from the Andean region have specialty floury and sweet kernels to make entire ready-to-eat maize by toasting in a pan until a golden brown surface color. The study aims to characterize these maize kernels before and after pan and microwave toasting. The initial moisture content for the raw kernel condition was the same (14.06 ± 0.13 g/100 g) to ensure data reliability by maize types and toasting conditions. The toasting conditions generated kernel expansions studied through the geometric, gravimetric, surface color, instrumental texture, milling average particle size, and hydration properties. Innate to maize types, the color properties (L*, a*, b*, C*, h*, and ΔE*) demonstrated that the toasted kernels developed a comparable range of surface color by the effect of pan and microwave toasting conditions (P ≥ 0.05). Large kernel sizes, low kernel hardness, and small average particle size ascribed to the endosperm softness were the main properties that characterize floury maize. High color differences, high water-soluble index, low density, high kernel hardness, and large average particle size confirmed the sugary-vitreous fraction in sweet maize. Microwave toasting produced lower remaining moisture content and kernel density, larger kernel size associated with the internal porosity created during toasting, higher water absorption capacity, and swelling power than pan toasting.