Evaluation of cheese whey protein precipitation methods based on efficiency and fractional composition
Cheese whey is a large-scale by-product of milk processing, characterized by high biological value. However, its irrational use can lead to a serious environmental burden. One of the ways to solve this problem is the isolation of proteins and their fractionation, the efficiency of which significantly depends on the method used. In this work, a comparative assessment of four methods of processing reconstituted cheese whey (6.0 % dry matter mass fraction) was carried out, such as chitosan precipitation (pH 4.5; 20 °C; 1 % gel; 20 min), thermal acid coagulation (pH 4.65; 90 °C; 15 min) using lactic, citric, phosphoric and hydrochloric acids, cryo-acid precipitation (pH 4.5; –18 °C; 24 h) and ultrafiltration (spiral membranes with a cutoff threshold of 10 kDa). The study determined the proportion of precipitated protein, the fractional composition of soluble nitrogenous compounds using gel filtration, and specific operating costs. Ultrafiltration provided the highest efficiency of protein separation (65.92 ± 0.59 %), which also turned out to be an order of magnitude cheaper (≈112 rubles/m3) than all chemical methods. Among the thermal acid options, citric (57.83 ± 0.51 %) and hydrochloric (56.63 ± 0.55 %) acids proved to be the most effective. Chitosan and cryo-acid treatment showed low overall efficiency (26.51 ± 0.20 % and 25.30 ± 0.15 %, respectively). Analysis of the fractional composition of the supernatant showed that thermal acid coagulation and ultrafiltration completely removed β-lactoglobulin and BSA. Chitosan precipitation preserved the native profile of all major whey proteins, removing only ballast impurities. The cryoacid method demonstrated unique selectivity, virtually completely removing peptides while preserving native α-lactalbumin and β-lactoglobulin. A step-by-step fractionation strategy is proposed: treatment with chitosan to remove impurities, cryoacid separation of peptides, followed by isolation of native proteins by ultrafiltration or the thermal acid method.