Graduate Student University of Manitoba Winnipeg, Manitoba, Canada
Abstract: DES is an emerging green solvent alternative to conventional organic solvents for protein extraction, and we have developed a effective protein extraction using DES solvents for fava bean protein extraction. However, the viscosity of DES limits the mass transfer within the system, creating practical challenges for technology scaling. Therefore, changing the water content in the DES could considerably reduce the viscosity, but adding water may affect the physiochemical properties of the resulting DES-water mixture and, consequently, protein structure-function. Therefore, this study was designed to understand the impact of water content on protein extraction yield, purity and the structure-function activities of the fava bean protein. A choline chloride/glycerol (ChCl/G)-based DES system, was first optimized using the response surface methodology for five variables. Then the water content in the DES system was amnipulated from 0-50 % (w/w), as a single-factor experiment. Extracted proteins were evaluated using established methods for protein yield (PY), protein content (PC), functional properties, thermal stability, and changes in secondary structures and protein’s molecular weight distribution. The addition of water significantly impacted the PY, which increased from 31.14±3.07 % to 55.50±2.40 % with increasing water content from 0-50 % (w/w). However, optimum PC was reported at 40 % (92.12-96.00 %) water content. Protein isolates obtained at 50 % water had significantly higher solubility at both pH 7 (78.15±1.27%) and 9 (98.63±0.75 %). Forming properties were not impacted by changes in water content.. Nevertheless, a significantly higher emulsification activity index (52.38±0.95 m2/g) was found at 60% water addition. Thermodynamic data showed significantly higher thermal stability (29.12±4.07 J/g) at 50 % water level. The proportion of α-helix structure was prominent at all levels, decreasing with increasing water content. According to molecular structure, adding water above 20 % revealed slight disintegration of the polypeptide band at 63 kDa (convicilin) and legumin (acidic subunits) at 35 kDa. The addition of water significantly impacts the PY, structural, and functional properties of fava bean protein isolates. Therefore, optimizing water substitution for DES is imperative to maintain its physiochemical properties.
