The physicochemical characterization and the bound phenolic profile of melanoidins from dark beer

Melanoidins are complex Maillard reaction products synthesized during dark beer production. In this study, the molecular weight of melanoidins from dark beer was about 4.8 kDa. Carbohydrates were the main chemical composition with 61.07 ± 2.36 % w/w. Total phenol and flavonoid contents of melanoidins from dark beer were 2.31 ± 0.36 % w/w and 0.86 ± 0.26 % w/w. It exhibited broad spectrum UV absorption from melanoidins skeleton, proteins, and phenolic acids. Additionally, acid hydrolysis released the most phenolics (2.461 ± 0.089 mg/mL) by cleaving glycosidic bonds. The bound phenolics were clearly distinguished by PCA analysis. Phloroglucinol was an important phenol mainly linked with melanoidins by ester, which contributed antioxidant capacity and unique flavor of beer. Elemental analysis indicated the disrupted hydrogen bonds, peptide bonds, and glycosidic bonds after different treatments. Collectively, these findings suggest melanoidins from dark beer as a reservoir of phenolic compounds have potential health benefit.