Enhancing antioxidant activity in barnyard millet fermentation through RSM optimization

Abstract

The objective of this research was to enhance the fermentation process of barnyard millet with the aim of improving its antioxidant properties and iron content. Utilizing Response Surface Methodology (RSM), the study sought to optimize the fermentation conditions to maximize the nutritional value of this lesser-known cereal. The fermentation of barnyard millet was conducted under varying conditions, including temperature (30–50 °C), time duration (4–30 h), and pH levels (3−7). The research investigated the influence of these fermentation treatments on parameters such as Total Phenolic Content (TPC), DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity, Ferric Reducing Antioxidant Power (FRAP), iron content, and tannin. Employing a central composite design, the study systematically assessed the effects of different conditions. The optimized combination for fermenting barnyard millet was identified as a temperature of 40 °C, a fermentation time of approximately 14.70 h, and a pH level of 5. Statistical analysis revealed that both time and temperature had a highly significant impact (p < 0.05) on all the measured variables. Under the optimized conditions, there were notable improvements, with DPPH% increasing by up to 13.13%, FRAP content by 13%, TPC content by 3.2%, and iron content by up to 8.7%, while tannin was reduced by 14.97%.