Microwave-ultrasound assisted extraction of red corn pigments and their effect on chemical composition and tecno-functional properties

Abstract

Currently, there is a growing interest in obtaining natural pigments, without presenting a risk to health, as well as to the matrix and food safety. The objective of this study was to characterize grains with different shades of red color (High pigmentation maize = RA, Medium pigmentation maize = RM, and Low pigmentation maize = RB, reddish maize with white segments = VO and white maize control = SC). The physical properties (kernel weight, length, width, thickness, and grain and flour color), chemical composition (moisture, fat, protein, fiber, starch, ash, and minerals), and techno-functional properties (capacity of absorption of organic molecules (OMAC), swelling (CH), oil retention (CAAC), and water absorption (WAS)) variables were measured. Afterward, RM was selected, and a pigment extraction (EAUM) was carried out using microwave-ultrasound equipment with different ratios of ethanol (0, 30, and 70%) and citric acid ratios (0 and 1%). The color and properties of the solid (starch, protein, fat, and their techno-functional properties) were determined in the aqueous phase and were compared with the properties prior to EAUM. The results indicated that the red grains have higher starch content (57.6%) and reddish colors, in addition, VO presented higher moisture (10.4%), fat (6.7%) and fiber (10.0%). The colors of the pigments obtained with EtOH (30 and 70%) show shades red and yellow. Finally, the EAUM decreased the fat content up to 57%, increased WAS and CAAC in the residual flour and generated changes in OMAC and CH, increasing in aqueous medium and reducing with EtOH.