Advancing sustainable food processing: molecular-scale understanding of incipient protein fouling in falling-film evaporators

Aligned with the green transition of the food industry, this study addresses the downstream processing of food protein ingredients from novel sources and enhanced production methods. As with current liquid foods (e.g., milk), reducing the water content to create concentrates or powders is necessary for longer shelf-life and ease of transport. A dominant unit operation for this purpose is the falling-film evaporator (FFE). This study focuses on the inevitable protein-fouling issue of FFEs that limits energy efficiency. To understand the incipient adsorption behavior (i.e., fouling behavior at the initial stages) of a model protein (namely, lysozyme) onto the chromium (III) oxide (Cr₂O₃) surface of the stainless-steel heat-transfer surface of FFEs, molecular dynamics simulations were performed. Six lysozyme orientations were initialized at four temperatures each. Results indicate adsorption is primarily governed by attractive electrostatic interactions by basic amino acid residues, whereas acidic amino acids tend to be repulsive due to the negative charges. Temperature effects are secondary to local interactions, with no clear correlation with adsorption tendencies, suggesting the onset of fouling is temperature independent. The adsorption tendencies of amino acid residues onto Cr₂O₃ revealed here are expected to be valuable for providing insights into FFE-fouling by emerging food protein formulations.