Thermal processing effects on the microbiological, physicochemical, mineral, and nutraceutical properties of a roasted purple maize beverage

Abstract

Thermal processing treatment of a roasted purple maize beverage was shown to be effective for reducing the microbiological growth since, after thermal treatment, microbial development was not detected. Physicochemical parameters, soluble solids, pH, and titratable acidity were not affected by the treatment, while L*, a*, b*, C*, and h chromatic parameters showed statistical differences. However, the visual aspects were not affected by the different thermal processing treatments. In terms of mineral content, the main effects were observed on Na, Mn, Cu and Zn concentrations. The thermal processing treatments resulted in higher contents of total phenols, total flavonoids, and total anthocyanins, while condensed tannins were not detected following any of the treatments. HPLC analysis detected ferulic acid in all treatments. On the other hand, chlorogenic acid was detected only in the control, while caffeic acid was detected in all thermal treatments, which means that caffeic acid is released from chlorogenic acid by thermal processing. The DPPH and FRAP antioxidant capacity levels were higher following thermal processing treatment, while the ABTS assay showed a contrasting behaviour.