Enhancement of Bioactivities in Sorghum and Italian Millet Through Household Thermal Processing: Antioxidant Capacity and Lipid Accumulation Inhibition

The aim of this study was to investigate the effects of common household thermal processing methods, such as steaming, pressure rice cooking, and roasting, on the enhancement of bioactivities in sorghum and Italian millet, with a focus on nonalcoholic fatty liver disease (NAFLD)–related functionality. The total phenolic and flavonoid contents, antioxidant activities, lipase inhibitory activity, and lipid accumulation in HepG2 cells were evaluated. In sorghum, pressure rice cooking resulted in the highest total phenolic (110.90 mg GAE/g) and flavonoid (46.83 mg CE/g) contents, whereas both pressure rice cooking and steaming improved antioxidant activities across all assays. However, steaming was the most effective in NAFLD-related functionality, showing the most pronounced lipase inhibition (35.66%) and the greatest reduction in lipid accumulation in HepG2 cells (84.67%) under free fatty acid (FFA)–induced conditions. Although Italian millet showed lower baseline activity than sorghum, steaming consistently resulted in the highest phenolic content (ranging from 19.06 to 26.16 mg GAE/g), improved antioxidant activities, and enhanced lipase inhibition (from 8.00% to 9.70%) compared to all other treatments. Lipid accumulation inhibition was observed only in the steaming group, where lipid levels were reduced to 94.15% of those in the FFA-induced control. Thermal treatments led to functional improvements that were associated with increases in bioactive compounds, such as arginine, branched-chain amino acids, and sulfur-containing amino acids, which have been associated with the regulation of lipid metabolism and hepatic function. These findings highlight the effectiveness of simple steaming for enhancing the health-promoting properties of cereal grains, suggesting the potential of this method for application in the development of functional food ingredients aimed at NAFLD prevention.