Optimization of flavonoid extraction from mulberry leaves and development of functional noodle products

This study aimed to optimize the extraction of flavonoids from mulberry leaves and their application in functional noodles to enhance the valorization of mulberry leaf resources. The dry-up method was selected as the optimal pretreatment based on ultraviolet spectrophotometry. Ultrasonic-assisted extraction was optimized by single-factor experiments and response surface methodology (RSM). The extract was incorporated into noodles as powder, juice, or pulp at varying concentrations to assess quality attributes and antioxidant activities. The dry-up method has proved to be most effective for drying mulberry leaves. The optimal extraction conditions identified via RSM included a solid–liquid ratio of 1:40 g/mL, 56% ethanol, a temperature of 60°C, and a time of 30 min, yielding a total flavonoid content of 26.04%. Three noodle formulations were developed: mulberry leaf powder (1.0% powder, 0.5% baking soda, and 1.0% salt), mulberry leaf juice (16.0% juice, 0.3% baking soda, and 1.0% salt), and mulberry leaf pulp (20.0% pulp, 0.4% baking soda, and 1.1% salt). The flavonoid content was 1.317 ± 0.01 mg/g for mulberry leaf powder noodles, 1.603 ± 0.01 mg/g for mulberry leaf juice noodles, and 1.413 ± 0.02 mg/g for mulberry leaf pulp noodles. All noodles exhibited significant antioxidant activity, with the mulberry leaf pulp variant demonstrating the highest radical scavenging capacity against both radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) and 2,2-diphenyl-1-picrylhydrazyl (DPPH), outperforming the other two forms. The established extraction method is efficient and applicable for producing flavonoid-enriched noodles with improved antioxidant properties. This approach supports the development of functional grain foods and offers a practical route for the high-value utilization of mulberry leaves.