Molecular dynamics simulation of high-pressure CO2 pasteurization reveals the interfacial denaturation of proteins at CO2/water interface

While mirobial and enzyme inactivation by CO2 is a promising non-thermal method for cold pasteurization of liquid foods, the poor understanding of the underlying molecular mechanism limits the development of this procedure. The complexity of the process along with the high-pressure conditions have disabled the experimental techniques to establish microstructural information for this phenomenon. In this work, molecular dynamics simulation method was used to find microscopic insights about this system. Myoglobin protein and lysozyme enzyme have applied as models in the simulations. It was found that CO2 and water make a distinct biphasic system in the experimental pressures of pasteurization process. Although many hypothesizes have attributed the enzyme inactivation to the solubilized CO2 molecules in the aqueous phase, we have shown that enzymes can be inactivated by an interfacial denaturation mechanism. Results show that the protein migrates from pure aqueous phase to the CO2/water interface and becomes denatured there. The molecular mechanism includes releasing the hydrophobic cores to the CO2 phase and escaping of the hydrophilic surface residues to the aqueous phase. These two phenomena denature the protein to a flat and extended conformation. Moreover, chemotrypsin inhibitor 2 protein was used to obtain the effect of distance from interface in the denaturation process. It was found that the distance from interface is critical in both performance and rate of the denaturation. Our simulations not only shed some lights on the molecular mechanism of CO2 pasteurization methods, but it can also be a basic computational model for further technological design and development.