Enzyme-Assisted Extraction of Proteins from Cauliflower and Broccoli Waste Leaves

This research presents a novel approach to protein extraction from cauliflower (CL) and broccoli (BL) waste leaves by using enzymatic pretreatment, demonstrating its effectiveness on protein yield. Enzymatic pretreatment (pH 4.5, 10 h, t = 35 °C), was performed using commercial enzyme preparations, Viscozyme® L and Vinozyme®, in three different enzyme-to-substrate ratios E/S (0.2%, 2.5%, and 4.8%) of each enzyme. Leaf proteins (LPs) were obtained with alkaline extraction at pH 10–11 and their isoelectric precipitation at pH 4, following the control sample (extraction without enzymes). Protein yield (%), which was used as a parameter to monitor enzymatic efficiency, demonstrated a direct correlation with the enzyme-to-substrate (E/S) ratio. The highest protein yields were obtained at an enzyme concentration of 4.8% for both cellulolytic and pectolytic enzyme preparations, yielding 14.90 ± 0.12% for CL and 29.88 ± 0.86% for BL. The obtained proteins were characterized by FTIR spectroscopy and SDS-PAGE electrophoresis, and these methods confirmed the enzymatic efficiency of protein isolation. Isolated LPs showed high protein content for CLP 4.8% (77.27 ± 0.14%) and BPL 4.8% (84.66 ± 0.51%), and an increase in total amino acids, while the content of essential amino acids was over 40%. Protein solubility was assessed, revealing significant improvements (p < 0.05) in LPs derived from CL and BL at the highest E/S ratio of 4.8%, compared to the control sample C0%. Specifically, the solubility of CLP reached 29.4 mg/mL at pH 11, while BLP achieved 36.4 mg/mL at pH 10. As a result, these leaf proteins not only meet nutritional demands but also open innovative avenues of research in food science and biotechnology.