Origin of Red Color in Edible Bird’s Nests Directed by the Binding of Fe Ions to Acidic Mammalian Chitinase-like Protein

• Published in: Journal of agricultural and food chemistry Vol. 66; no. 22; pp. 5644 - 5653
• Main Authors: Wong, Zack C. F, Chan, Gallant K. L, Dong, Tina T. X, Tsim, Karl W. K
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 06-06-2018
• Subjects: iron; acidic mammalian chitinase-like; edible bird’s nest; nitrite; color
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/acs.jafc.8b01500

The red color of edible bird’s nests (EBNs) has remained a mystery for hundreds of years. Here, different analytical methods were employed to identify the color origin of EBNs. The treatment of white EBNs with NaNO2/HCl turned them red. In a simulated-gastric-fluid (SGF)-digested EBN, the HPLC chromatogram, NMR spectrum, circular-dichroism spectrum, and Raman spectrum of a NaNO2-treated white EBN closely resembled those of an authentic red EBN. From the HPLC chromatogram of the SGF-digested EBN, the peptides associated with red color were identified in a red EBN and NaNO2-treated white EBN. Several lines of evidence indicated that the color-containing peptide could be derived from the acidic mammalian chitinase-like (AMCase-like) protein of EBNs. Additionally, there was a noticeable increase in Fe–O-bonding intensity after the color change. On the basis of the findings, we proposed that the oxidation of Fe ions in AMCase-like proteins contributed significantly to the color change of EBNs.