Optimization of protein extraction from watermelon seeds by liquid-phase pulsed discharge based on energy input for scale-up application

Abstract The study is about the watermelon seeds protein extraction using the specific energy per pulse (EPP) (W/g) as the operation parameter for optimization by liquid-phase pulsed discharge (LPD) at various scales, in comparison with the extraction using discharge voltage (kV) as the operation parameter for optimization by LPD. The optimization based on the intrinsic parameters of EPP (W/g), liquid to solid (L/S) ratio (mL/g) and extraction time (min) were firstly implemented. The protein yield of 462.26 ± 1.214 mg/g was obtained under optimal conditions (0.042 W/g EPP, 3.8 min extraction time and 40 mL/g L/S ratio), which was in accordance with the yield of 462.03 ± 1.061 mg/g obtained by traditional optimization based on discharge voltage, extraction time and L/S ratio. Then, the two optimization methods were compared at larger scale of 100–280 mL solvent loading. The protein yields of the EPP optimization were 461.313 ± 0.990, 462.102 ± 1.034, 462.009 ± 0.872 and 460.319 ± 0.981, respectively, which had no significant difference. However, the protein yields of traditional optimization method decreased rapidly. Thus, the results showed that the EPP optimization method had the favorable effect on the reliability and feasibility of the scale-up LPD extraction. These indicated that the EPP accurately reflected the LPD extraction mechanism, and could replace the discharge voltage.