Modifications on physical, chemical, functional and nutraceutical properties in soft blue maize (Zea mays L.) after parboiling treatment and its impact on resistance to Prostephanus truncatus

Mexico is the center of origin and diversification of maize (Zea mays L.). However, in this country, efforts have been focused on obtaining white corn over other varieties, such as pigmented ones. Although, pigmented varieties have recently received increased attention due to their nutraceutical properties, they tend to present kernels with floury endosperm. Therefore, efforts have been made in order to improve their physical features, by increasing the ratio of the hard endosperm and kernel hardness, mainly by genetical breeding without satisfactory results. In this way, the application of a hydrothermal treatment, such as parboiling, could serve as an approach to improve the quality of these maize varieties. Thus, the objective of this work was to evaluate the modifications in soft blue maize due to parboiling treatments in its physical, functional, chemical and nutraceutical properties, as well as the resistance to Prostephanus truncatus. Therefore, 96 parboiling treatments were developed by testing different conditions for each parboiling phase: hydration, steaming and drying. Then, maize kernels were evaluated for physical properties (endosperm texture, recovery percentage, quality parameters), functional properties of starch (pasting profiles), macronutrient composition (proximal analyses of whole kernels and endosperm), nutraceutical modifications (total anthocyanin content, anthocyanin profile, antioxidant activity) and resistance to P. truncatus (susceptibility parameters and Dobie Index). Parboiling decrease the kernel integrity by induces changes in its physical appearance; however, it increases maize quality by increasing test weight, thousand kernel weight, decreasing flotation index and promoting the movement of pigments to the endosperm. It also modified the pasting properties, by decreasing the peak viscosity; promoted the enrichment of the endosperm by inducing the diffusion of lipids and minerals; and improved the nutraceutical properties by enhancing the antioxidant activity. Thus, the optimization and the proper implementation of this treatment could serve as an approach to improve the quality of other pigmented maize varieties in terms of their physical features, but also according to their nutritional and nutraceutical profile.