Abstract
The Maillard reaction (MR) is a chemical process that occurs in foods between reducing sugars and amino compounds during heating, producing a complex mixture of compounds responsible for the browning, flavour, and aroma, called Maillard reaction products (MRPs). The antioxidant properties of Maillard reaction products (MRPs) and their potential as natural food preservatives have been explored, with particular emphasis on utilizing food by-products, such as milk whey, as substrates. This approach addresses the dual objectives of improving food preservation while valorising industrial waste streams. The introductory section discusses the Maillard reaction, its role in the generation of antioxidants and the methods used to evaluate their activity. In addition, the potential for valorisation of food by-products and the increasing demand for natural food preservatives are explored. The first study investigated the kinetics of antioxidant formation in a glucose-glycine model system. Advanced analytical techniques, including high-performance liquid chromatography (HPLC) with coulometric array detection and high-resolution mass spectrometry (HRMS), were used to identify key antioxidant MRPs such as methylpyridin-3-ol (MP) and dihydro-dihydroxymethylpyrone (DDMP). A kinetic model was developed to describe the relationship between reaction progress and antioxidant activity. The second study focused on refining methods for the detection and identification of antioxidant MRPs. Optimised chromatographic conditions and the creation of a comprehensive signal library of MRPs enabled improved characterisation. Factors such as pH, reaction time and sugar-amino acid combinations were investigated and neutral to basic pH was found to be optimal for MRP production. These findings provide a basis for controlling and optimising the generation of antioxidants during the Maillard reaction. The third study investigated the use of dairy whey as a substrate to produce antioxidant MRPs. Experiments with cow's cheese whey, goat's cheese whey and cow's yoghurt whey showed that whey composition significantly affects MRP profiles. Key antioxidant compounds, including DDMP and 2- pyrrolecarboxaldehyde, were identified, highlighting the potential of whey-derived MRPs as sustainable food preservatives. This work demonstrates the feasibility of transforming whey into a valuable source of bioactive compounds, supporting waste reduction and sustainability. The results highlight the versatility of MRPs as natural antioxidants and their potential to enhance food preservation. By utilising food by-products and optimising reaction conditions, the Maillard reaction offers a sustainable pathway for the development of functional food ingredients. Future research should focus on detailed structural characterisation, application in real food systems and addressing safety and regulatory aspects to enable wider use in the food industry.