Controlling the cold-set gelation of Bovine Serum Albumin protein using alcohol and ionic surfactant

Abstract

Heating of globular protein solutions usually leads to protein denaturation and subsequent gelation at high temperatures. Under “cold gelation”, protein forms a gel at a much lower temperature than its original gelation temperature (T_G), which can be achieved by modifying various physicochemical conditions such as the pH of the solution, the presence of salts, etc. In this study, we investigated the cold gelation of Bovine Serum Albumin (BSA) protein induced by ethanol and controlled by ionic surfactant, using small-angle neutron scattering (SANS), dynamic light scattering (DLS), and rheology The results show that the T_G of the protein with ethanol is systematically decreased as compared to the that of pure BSA solutions (∼80 °C), reaching ∼60 °C at 10 wt% ethanol, ∼55 °C at 20 wt% and finally as low as ∼38 °C in presence of 30 wt% ethanol in the solution. Rheological measurements demonstrate a significant strengthening of the gel network, with the enhancement in storage modulus (G′) from ∼20 Pa at 0 wt% to ∼250 Pa at 30 wt% ethanol. Structural characterization reveals an increase in fractal dimension with rising ethanol content, indicating denser and more branched gel networks. Interestingly, the addition of the anionic surfactant sodium dodecyl sulfate (SDS) inhibits the alcohol-assisted cold gelation of BSA protein, depending upon the relative amount of ethanol and SDS in solution. The results are explained based on the interplay of interactions in the protein, manipulated by the presence of alcohol, elevated temperatures, and ionic surfactant. Our study highlights the tunability of gelation pathways and offers useful inputs for controlled protein gelation in biomaterial and food industry.