Optimization of Extraction Process of Protein from Citrus Peel and Its Antioxidant Activity

In order to explore the process optimization and antioxidant activity in vitro of protein extraction from citrus peel byalkali-solution and acid-isolation. The single factor experiments and response surface methodology (Box-Behnken) were combined to optimize the extraction process of citrus peel protein. V_C was used as the positive control to investigate the scavenging effect of the citrus peel protein on DPPH·, H₂O₂, ·OH and \rmNO_2^- . The results showed that the optimum extraction conditions of citrus peel protein by alkali-solution and acid-isolation were as follows: pH12.1, extraction temperature 52.8 ℃, extraction time 2.6 h, solid-liquid ratio 1:42 (g/mL). Under these conditions, the protein extraction rate of citrus peel was 62.23%±0.22%, which was close to the predicted value of regression model (63.01%), showing the good fitting degree. The protein prepared by the optimized process also had good antioxidant activity in vitro, and the half inhibitory concentration (IC₅₀) for scavenging of DPPH·, H₂O₂, ·OH and \rmNO_2^- of citrus peel protein were 1.20312, 0.52516, 0.79207, 0.87216 mg/mL. In summary, the extraction of citrus peel protein by alkali-solution and acid-isolation could provide a way for the resource utilization of citrus peel, and the citrus peel protein had good antioxidant activity and utilization prospect.