Optimization using response surface methodology of amylolytic capacity of maize Atp-Y and coca-sr varieties: In vitro digestibility capacity, physico-chemical and functional properties of optimal sample

Abstract

The use of sprouted cereals for the development of flavor, improvement of biochemical, physicochemical and techno-functional properties in beer production, improvement of nutritional quality and viscosity of supplementary foods is widespread in Africa. The objective of the current work was to evaluate the effect of malting conditions and variety on the amylolytic capacity, protein structures, physicochemical and functional properties of maize (Atp-Y and Coca-sr varieties). The Response Surface Methodology (RSM) using the central composite design (CCD) was applied to 5 independent factors, namely soaking time (18–42 h), vegetable salt concentration (0.5–1.2%), soaking temperature (25–41 ◦C), germination time (80–195 h) and maturation time (17.5–42 h). The optimal flours obtained were then subjected to physicochemical, digestibility, functional and antioxidant analysis. The analysis of the mathematical regression model showed that the linear and quadratic effects of all independent variables showed significant effects (p<0.05) on the amylolytic activity of the Atp-Y variety. The optimal malting conditions were 25.12 h soaking in the presence of 0.52% vegetable salt at a temperature of 25.54 ◦C followed by 144.37 h germination and 37.65 h maturation for Atp-Y. Coca-sr, on the other hand, required 1.608 h soaking in the presence of 1.11% vegetable salt at a temperature of 36.63 ◦C followed by 144.37 h germination and 27.07 h maturation. The production of optimal samples using above optimal conditions reduced the anti-nutrients, pH, mass density, water holding capacity and swelling rate; improved the availability of minerals (Ca and Mg), bioactive compounds and the antioxidant properties. The FTIR spectra revealed similar peaks and different intensities for the beta-sheets as the major secondary structure of the proteins. Therefore, the application of these malting conditions would improve the enzymatic activity of these two maize varieties for their application in malting, beer production and digestibility of resistant starches.