Melanoidins　are　brown　recalcitrant　polymers　originating　from　the　thermal　hydrolysis　pretreatment　(THP)　of　organic　solid　waste　(OSW).　Owing　to　their　various　formation　pathways　and　complex　structures,　there　is　currently　no　reliable　method　to　quantify　melanoidins.　In　this　study,　a　spectrophotometric　method　was　developed　to　determine　melanoidins　concentration　in　different　OSW.　Three　typical　model　Maillard　reaction　systems　(glucose-glycine,　glucose/fructose-20　amino　acids,　and　dextran-bovine　serum　albumin)　were　used　to　acquire　the　characteristic　peaks　and　establish　standard　curves.　The　results　showed　that　a　standard　curve　using　glucose/fructose-20　amino　acids　model　melanoidins　at　280　nm　was　the　optimal　quantification　method,　because　it　had　the　best　correlation　with　the　physicochemical　indicators　of　melanoidins　and　semi-quantification　results　calculated　by　excitation-emission　matrix　fluorescence.　In　addition,　the　applicability　of　the　proposed　method　was　evaluated　using　multiple　real　melanoidins　samples　extracted　from　thermally　pretreated　OSW　under　different　THP　conditions　and　food-derived　melanoidins　as　well,　demonstrating　its　validity　and　advantages.　This　study　is　the　first　to　provide　a　simple,　effective,　and　accurate　method　for　quantifying　THP-origin　melanoidins　from　different　sources.　Remarkably,　as　a　specific　and　important　application　scenario,　the　proposed　quantification　method　was　employed　to　investigate　the　concentration　dependence　of　melanoidins　antioxidation　in　thermally　pretreated　OSW.　©　2024　Elsevier　B.V.