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Optimization of Eucommia Ulmoides Leaves Vinegar Process to Improve the Antioxidant Activity

Chlorogenic acid (CA) has strong oxidative resistance. The content of CA is high in Eucommia ulmoides leaves which are easily available and low cost. Therefore, in this work, using Eucommia ulmoides leaves enzymatic hydrolysate (EEH) as the main material, the fermentation conditions of Eucommia ulmoides leaves vinegar (EV) were studied to increase the antioxidant activity of the vinegar. Box–Behnken design indicated the following optimal fermentation conditions: EEH 48 %, acetic acid bacteria solution 10 %, ethanol addition 6 %. Under above conditions, the acetic acid content and CA content of EV was 41.5±2.2 mg/mL and 1.1±0.17 mg/mL, respectively. EV exhibited the higher antioxidant activity, with IC50 values of 2.62 μg/ mL, 27.21 μg/mL and 1.72 mg/mL for DPPH, hydroxyl radical scavenging activity and reducing power, respectively. The addition of Eucommia ulmoides leaves increased the antioxidant activity of vinegar.