Novel divalent salt-based extraction technology for extracting fava bean protein with improved performance

Protein ingredient production must increase to meet future demand. This poses sustainability concerns for the food industry that are not often discussed in the literature, pushing the need to develop alternative sources and extraction methods. Fava bean is an emerging protein source that can produce high-quality food products. This study uses Response Surface Methodology to optimize a novel divalent salt-based extraction method for fava bean protein isolates (FBPI). A Box-Behnken design was used to optimize input variables. The optimum conditions for salt-based extraction were observed at 10% MgCl2 (w/v) concentration, 1:9 solid-to-liquid ratio (w/v), and 25°C temperature. The protein purity, recovery rate, extraction yield, and structure-functional properties of salt-extracted FBPI (SALT-FBPI) were compared to alkaline-extracted FBPI (ALK-FBPI). SALT-FBPI had a higher protein purity, protein recovery rate, and extraction yield of 94.60 ± 0.13%, 72.88 ± 9.57%, and 21.12 ± 2.77%, respectively, compared to ALK-FBPI with 87.61 ± 0.04%, 60.65 ± 4.99%, and 17.58 ± 1.45%. Protein secondary structure analysis demonstrated a higher composition of α-helix and β-turns for ALK-FBPI, with minimal differences in types of β-sheets between the two FBPI. SALT-FBPI has lower moisture, fat, and ash content of 1.83 ± 0.12%, 6.12 ± 2.28%, and 1.76 ± 0.01%, respectively. SALT-FBPI exhibited higher solubility than ALK-FBPI at pH 3, 5, and 7, with the highest value at pH 3 (77.08 ± 0.61%), while ALK-FBPI exhibited higher solubility of 54.33 ± 4.52% at pH 9. Both FBPI demonstrated similar water-holding capacity; however, ALK-FBPI had a higher oil-holding capacity due to the higher albumin protein extracted. Both proteins had higher emulsification capacity at pH 9 and higher foaming capacity at pH 3, with comparable results at other pHs. In conclusion, SALT-FBPI has improved protein purity and recovery rate, with neither FBPI demonstrating superior functional properties.