Effect of the mixture of oleaster (E. angustifolia L.) and black cumin (Nigella sativa) flours as functional compounds on the quality characteristics of toast bread

The present study was conducted to evaluate the addition of a mixture of oleaster (OL; E. angustifolia L.) and black cumin (BC; Nigella sativa) flours on the quality characteristics of toast bread. The concentration of OL and BC mixture (1:1 w/w ratio) was 0 (T1), 1.5% (T2), 2% (T3), and 2.5% (T4) of total flour content. The bread samples containing the mixture of OL and BC flours had more protein content (8.49%–9.65%) than the control (6.81%; p < .05). The highest phenolic compounds and DPPH free radical scavenging capacity were observed in T4 and T3 samples, respectively. The OL and BC flours decreased the brightness, yellowness, and chroma and increased the redness compared to the control. The mixed flour concentration influenced the bread's hardness and chewiness. Adding OL and BC flours increased the calcium content in the bread (467.65–600.41 ppm) compared to the control (363.9 ppm; p < .05). The OL and BC flour mixture created a more compact texture in the bread samples. In the sensory evaluation, there was not a significant difference between the overall acceptability of the bread containing the mixture of OL and BC flours and the control (p > .05). Finally, it is recommended to utilize a mixture of 2% of OL and BC flours in toast bread to improve its nutritional properties.