Tracking structural changes of protein residues by two-dimensional correlation surface-enhanced Raman spectroscopy

Area of Science:

• Analytical Chemistry
• Food Science
• Spectroscopy

Background:

• Edible bird's nest (EBN) is a valuable delicacy often subjected to artificial dyeing to mimic natural products.
• Distinguishing natural EBN from counterfeit products is crucial for consumer trust and market integrity.
• Existing detection methods may not fully capture the subtle structural alterations caused by artificial processing.

Purpose of the Study:

• To develop a direct, in-situ method for tracking structural changes in protein residues of EBN.
• To establish a reliable technique for differentiating natural EBN from artificially dyed (A-EBN) samples.
• To integrate multiple detection indicators into a logical circuit for automated EBN authentication.

Main Methods:

• Utilized two-dimensional correlation surface-enhanced Raman spectroscopy (2DC-SERS) to monitor in-situ structural modifications.
• Interpreted changes in SERS fingerprints as alterations in amino acid residue structures during artificial nitrification.
• Employed azo dye testing for nitrites/nitrosamines and a data-driven analog soft independent modeling (DD-SIMCA) for classification.

Main Results:

• 2DC-SERS successfully tracked structural changes in protein residues, correlating them with artificial processing.
• The method achieved reliable discrimination between natural EBN and A-EBN, with LODs of 40.6 ppb for nitrite and 88.1 ppb for NDMA.
• A conceptual OR gate logical circuit, using protein structure and nitrite indicators, enabled automatic EBN recognition with 98% specificity by DD-SIMCA.

Conclusions:

• 2DC-SERS provides a direct structural tracking approach for authenticating EBN.
• Combined structural and chemical indicators offer a robust strategy for identifying artificially dyed EBN.
• The developed system facilitates rapid and accurate discrimination of EBN samples, enhancing food safety and quality control.