Microfluidization-assisted extraction enhances the functionality and in vitro bioactivity of a guar meal-derived protein isolate: a sustainable approach

Abstract

Guar meal, a protein-rich by-product of guar gum manufacturing, remains underutilized in human nutrition owing to its limited functionality and the presence of anti-nutritional factors. This study employed microfluidization-assisted alkaline extraction (MF-AE; 90, 120, 150, and 180 MPa; single pass) to enhance the yield, structural, functional, and nutritional quality of guar meal protein isolate (GMPI), and conventional alkaline extraction (AE) served as a control. MF-AE significantly (P < 0.05) increased the protein yield from 8.9 to 16.44% and solubility from 23.62 ± 0.03% to 48.28 ± 0.86%, emulsifying stability (from 37.74 ± 0.32 to 84.81 ± 4.16%), and foaming stability (from 125 ± 2.77 to 199.67 ± 4.04%), with optimal effects observed at 150 MPa. These enhancements were associated with pressure-induced unfolding and aggregate disruption, evidenced by reduced particle size (from 690 to 548.33 nm) and increased ζ-potential (from −29.6 to −50.8 mV), and were well supported by UV-Vis, fluorescence, FTIR, and SEM analyses. MF-AE also decreased tannins (24%), phytate (29%), and saponins (53%), while significantly enhancing in vitro protein digestibility (from 75.33 ± 0.9% to 87.99 ± 1.0%) and improving essential amino acid levels. Antioxidant capacity increased in both DPPH (from 16.16 to 19.11 mmol TEAC per g) and FRAP (from 34.64 to 47.82 mmol TEAC per g) assays. An in vitro cytotoxicity assay using the Caco-2 cell line indicated that the MF-AE-derived GMPI showed no detectable cytotoxicity up to 100 mg mL⁻¹, preliminarily suggesting no processing induced toxicity at the tested concentrations. By simultaneously addressing functional limitations and anti-nutritional constraints, MF-AE positions guar protein as a potential alternative protein source for the formulation of functional foods and beverages.