Abstract: Melanoidin was extracted from black soy sauce, and its spectral properties and bioactive functions were studied. The results showed that 22.8 g of crude melanoidin could be obtained from 100 mL black soy sauce by organic solvent precipitation. The crude melanoidin was purified by removing small molecular substances with Sephadex G-50 column. The molecular weight of the purified melanoidin was in the range of 3000 to 55000 u. The UV-Vis and infrared spectra revealed that the crude melanoidin was products of the Maillard reaction and enzymatic browning. The scavenging efficiency of the crude melanoidin on DPPH free radicals and on hydroxyl free radicals were 89.0% and 89.5%, respectively. The inhibitory action on the synthesis of nitrosamine was up to 80.0%. Conclusion: crude melanoidin from soy sauce can be developed as a functional solid soy sauce. Neat melanoidin has great potential to developed as a functional food coloring.

Key words: black soy sauce, melanoidin, DPPH free radical, hydroxyl free radical