Black hollyhock (Alcea rosea var. nigra) flower as a functional additive to enhance the quality characteristics of red velvet cake

Red velvet cake is commonly prepared using synthetic food colorants. Given concerns regarding the adverse effects of synthetic colors on human health, using natural colorants in this product could be valuable. In this study, the effect of black hollyhock flower (BHF) at 0.1%, 0.3%, and 0.5% as a natural additive on the quality characteristics of red velvet cake was evaluated and compared with the synthetic colorant carmoisine. The BHF caused no significant difference in physicochemical properties (except for ash), L* value, and mold and yeast counts ( p > 0.05). The total phenolic content (TPC), flavonoids, anthocyanins, antioxidant activity, and a* value increased, while the b* value, peroxide value (PV), and free fatty acids (FFA) decreased ( p < 0.05). The highest levels of bioactive compounds were observed in cakes containing 0.5% BHF, with TPC (18.40 mg GAE/100 g), TFC (12.67 mg QE/100 g), and TAC (1.61 mg/100 g), which were increased by 22.16, 23.90, and 23 times, respectively, compared with the control. In addition, the PV and FFA values were reduced by 4 and 3.34 times, respectively, at the end of storage. The sensory characteristics were also acceptable with no significant difference between treatments ( p > 0.05). Therefore, BHF has potential as a natural functional additive and colorant in red velvet cake, with 0.5% BHF providing the most favorable overall quality characteristics.