Incorporation of grapefruit albedo and flavedo into millet-based muffins: Effects on antioxidant activity and quality...

Industrial processing of grapefruit generates peel as a major by-product comprising flavedo and albedo tissues of technological and nutritional relevance. This study evaluated the effect of grapefruit flavedo powder (GFP) and grapefruit albedo powder (GAP) at incorporation levels of 3%, 6%, 9%, and 12% on the quality attributes of finger millet muffins. GFP and GAP incorporation enhanced the water and oil absorption capacities of the composite flours. Pasting profile parameters, including peak, final, and setback viscosities, were evaluated and exhibited a decreasing trend with increasing levels of GFP and GAP. Increasing GFP and GAP incorporation up to 12% reduced bake loss to 5.40% and 3.98%, respectively. Results revealed a significant (P < .05) increase in DPPH radical scavenging activity from 27.25% in the control to 43.08% and 40.88% at 12% incorporation of GFP and GAP, respectively. Similarly, ferric reducing antioxidant power, total phenolic content, and total flavonoid content also followed the increasing trend. FTIR spectra indicated the presence of functional groups associated with phenolic compounds in the fortified muffins. Scanning electron microscopy analysis revealed a heterogeneous crumb structure with smaller and irregularly distributed pores and embedded fibrous particles, suggesting disruption of the starch-protein matrix in fiber-enriched muffins. Such structural modifications are consistent with the texture profile analysis results, which showed increased hardness and reduced springiness. Color evaluation showed that increasing GFP from 3% to 12% led to lower L* values for both the crust and crumb, in contrast to GAP incorporation, where the value increased. Likewise, the a* and b* values rose for both GFP and GAP in the crust and crumb.