Covalent modification of food proteins by plant-based ingredients (polyphenols and organosulphur compounds): A commonplace reaction with novel utilization potential

Background: Many food ingredients such as polyphenols, phenolic acids (e.g. present in fruit and vegetables) and organosulphur compounds (e.g. present in mustard, garlic and chives) covalently interact with meat, egg, dairy and plant-based proteins. The results of those interactions are manifold and range from altered technological properties (in emulsions, foams, gels) to sensory changes (colour formation, altered taste and smell) and different biological activity (allergy, antimicrobial effects, hydrolysis). Scope and approach: The present review discusses both the positive and the negative side effects of such interactions and explores the potential to fine-tune protein functionality during processing not only in model solutions but also in more complex foods. Key findings and conclusions: Traditionally, studies have focused on the negative effects of interactions between protein and plant ingredients (e.g. discolouration and solubility changes), but more recent studies highlight positive effects (e.g. enhanced emulsifying capacity, reduced allergy and targeted production of protein pigments). By controlling food processing conditions (e.g. protein nativity) and the food matrix (e.g. presence of antioxidative compounds or thiol groups, pH value during storage), the observed effects can be prevented or induced. On the basis of the listed findings, future processes can be developed that take such interactions into account to enable targeted co-processing of plant compounds with proteins. A better understanding of these interactions opens up a wealth of novel utilization potential.