Antioxidant and immunomodulatory effects of the white bread supplemented with blueberry and apple peel

We hypothesized that phytochemicals contained in blueberries and apple peels possess antioxidant and immunomodulatory properties. To test this hypothesis, we developed white bread supplemented with blueberry and apple peel powders. The freeze-dried extracts of white bread containing 3% blueberry powder and either 3% or 5% apple peel powder were designated as BP3APP3 and BP3APP5, respectively. The freeze-dried extracts of the control bread, blueberry powder, and apple peel powder were designated as CON, BP, and APP, respectively. Antioxidant activity was evaluated by measuring total polyphenol and flavonoid contents, DPPH and ABTS radical scavenging activities, Fe²⁺ chelating activity, and reducing power. Both BP3APP3 and BP3APP5 exhibited significantly higher levels of polyphenols and flavonoids, as well as enhanced antioxidant activity, compared to the control (CON). These effects are presumed to result from the antioxidant properties of BP and APP. The higher antioxidant activity observed in BP3APP5 compared to BP3APP3 is due to the increased content of apple peel, which exhibited stronger antioxidant effects than blueberry. Furthermore, BP3APP3 and BP3APP5 demonstrated immunomodulatory effects by increasing nitric oxide (NO) production in RAW 264.7 macrophages under basal conditions and suppressing NO production in LPS-stimulated RAW 264.7 cells. These findings suggest that white bread supplemented with blueberry and apple peel powders has potential as a functional food with both antioxidant and immunomodulatory benefits.