This research showed how defence metabolites in plants and seaweed, which belong to the chemical class of phenolics, can contribute to modification of proteins. The phenolics and proteins can interact in several ways during cell rupture upon industrial processing, depending on the phenolics type and defence mechanism. In sugar beet leaves, the enzyme polyphenol oxidase creates highly reactive phenolics. These reactive phenolics bind covalently to proteins, and other compounds, resulting in irreversible modification of proteins. In seaweeds phlorotannins, with high molecular weight, bind non-covalently (reversible) to proteins which results in loss of water-solubility of the latter. The interaction is affected by the type of protein, type of tannins and pH of the solution.
The knowledge on interactions between several types of phenolics and proteins can contribute to the design of industrial processes to isolate proteins without significant alteration of protein nutritional value.