Deciphering the role of phenolics and antioxidants in rancidity development of pearl millet flour during storage

Pearl millet flour undergoes rapid post-milling rancidity, yet the interplay between lipid deterioration and endogenous antioxidant depletion remains poorly characterized. This study assessed hydrolytic and oxidative rancidity, concurrent with phenolic and antioxidant dynamics, in genotypes Chadi Bajra and MPMH-17 during 60 days of ambient storage. Lipid content declined progressively in both genotypes, from 5.43% to 4.58% in Chadi Bajra and 6.67% to 5.21% in MPMH-17. Acid value increased sharply to 18.16 mg KOH/g and 24.73 mg KOH/g by 30 days, while peroxide value peaked at 43.39 and 70.24 meq/kg, confirming rapid hydrolysis and hydroperoxide formation. Total phenolics decreased substantially (Chadi Bajra: 19.70 to 8.67 mg/100 g; MPMH-17: 16.47 to 5.81 mg/100 g), accompanied by marked reductions in thiols and FRAP activity, indicating progressive antioxidant exhaustion. Correlation and PCA analysis showed that declining antioxidant capacity aligned strongly with rising rancidity markers, with MPMH-17 consistently clustering toward high-deterioration vectors. Collectively, the results demonstrate that rancidity progression is initiated early, driven by coordinated lipid hydrolysis and oxidation, and amplified by depletion of phenolic and thiol-based antioxidants. The pronounced susceptibility of MPMH-17 highlights genotype-dependent biochemical resilience and underscores the need to integrate antioxidant traits when evaluating flour shelf life.