Hemp Protein in the Food Industry: Optimizing Alkaline Extraction and Isoelectric Precipitation

preparations are obtained from plant materials by alkaline extraction (pH 6.0–12.0) followed by isoelectric precipitation. This article describes the effect of extraction and isoelectric precipitation parameters on protein yield from hydrolyzed hemp cake. Calculating the theoretical and experimental isoelectric point made it possible to improve the procedure and increase the yield. The study featured hemp cake of the Vera variety. A three-factor Box–Behnken design (15 experimental points) optimized the extraction parameters of pH, temperature, and time. The resulting regression model adequately described the process (R2 = 0.983) with the optimal extraction conditions as pH 11.2; 52°C; 3 h. Sodium chloride reduced extraction efficiency by 6.8–13.5% compared to the alkaline method. The optimal protein purity (92.6–93.1%) was achieved with isoelectric precipitation in the pH range of 4.4–4.6, which did not correspond to the modeled isoelectric point (6.95–7.22). The protein profile analysis of the isolated fraction demonstrated the predominance of edestin (~ 38 kDa) and albumin (~ 21 kDa). The resulting hemp protein isolate contained 89.53 to 92.28% protein, according to the Barnstein and Kjeldahl methods, respectively, which indicated a high-quality product. The use of alkaline extraction followed by protein precipitation in isoelectric point provided efficient protein isolation with a yield reaching 80% relative to its content in the raw material, containing 34.32 ± 3.43% crude protein.