Effect of combined bioprocessing on antioxidant activity, chemical, functional, and microstructural properties of malted and fermented pearl millet ( Pennisetum glaucum ) and sorghum flour ( Sorghum bicolour)

The study investigated the impact of malting and fermentation durations on the antioxidant activity, chemical, functional, and microstructural attributes of pearl millet cultivars (Agrigreen and Babala) and sorghum flour. Employing response surface methodology with a central composite design, 24, 48, and 72 intervals were tested. Results revealed significant (p < 0.05) alterations in total phenolic content (TPC), total flavonoid content (TFC), ferrous reducing antioxidant power (FRAP), 2,2-diphenyl-1-picryhydrazyl (DPPH), and other properties. Babala flour displayed the highest TPC (34.02–36.62 mg GAE/100 g), while Agrigreen had the highest TFC (9.76–18.22 mg Que/100 g), FRAP (0.268–1.168), and DPPH (57.68–70.04%) content. Various phenolic compounds were identified, including quercetin-3-O-glucoside, hesperetin, and petunidin. Babala flour exhibited higher pH (4.78) compared to Agrigreen (5.50) and sorghum (4.92), while Agrigreen showed higher total titratable acidity (TTA) (0.159%) than sorghum and Babala. Babala flour also demonstrated a higher water absorption capacity (WAC) at 2.37 ml g−1, while sorghum exhibited the lowest oil absorption capacity (OAC) at 1.67 ml g−1. Agrigreen's malted and fermented flour had the lowest bulk density (0.53 g ml−1), while sorghum flour had the highest dispersibility (56.34%). Morphological changes included varied shapes from isolated to smoother surfaces. Optimal processing times significantly impacted antioxidant activity and other properties, with potential applications for food processing companies seeking to enhance pearl millet and sorghum products.