SERS Detection of Metanil Yellow in Turmeric

Significance of the Topic

The presence of illicit colorants in food products poses serious health risks and undermines consumer trust. Metanil Yellow (MY), an azo dye banned as a food additive, is still illicitly used to enhance the appearance of turmeric and other spices. A rapid, sensitive, and portable detection method is essential for ensuring product safety across the supply chain.

Objectives and Study Overview

This study demonstrates the application of Surface-Enhanced Raman Spectroscopy (SERS) using the Metrohm Instant SERS Analyzer (MISA) for detecting MY in turmeric. Key goals include establishing a reference SERS spectrum for MY, optimizing an extraction protocol, and assessing detection limits in simulated field conditions.

Methodology and Used Instrumentation

A conservative extraction procedure involved treating spiked turmeric samples with 0.5 M HCl, followed by mixing the extract with gold nanoparticle (Au NP) colloid and salt. SERS measurements were performed using MISA Advanced (firmware 0.9.33, MISA Cal V1.0.15) equipped with the Vial Attachment and Au NP ID Kit. Acquisition parameters included 5% laser power, 10 s integration time, 10 averages, and ORS raster scanning.

Main Results and Discussion

Detection of Metanil Yellow was achieved down to 0.1 mg/g in spiked turmeric samples. Characteristic Raman peaks at 504, 1176, 1383, and 1588 cm-1 provided reliable identification. Baseline-corrected spectra showed high signal-to-noise ratios, confirming the method's sensitivity and selectivity.

Benefits and Practical Applications

• High sensitivity allows trace-level detection of banned dyes.
• Portable analyzer enables on-site quality control at processing and distribution centers.
• Minimal sample preparation and user training streamline field testing.
• Cost-effective solution for routine monitoring of food authenticity.

Future Trends and Potential Applications

• Extension of the SERS library to other illicit additives and contaminants.
• Integration with mobile data analytics and digital reporting platforms.
• Adaptation of the protocol for diverse matrices including legumes and dietary supplements.
• Development of automated workflows for high-throughput screening.

Conclusion

The MISA-based SERS assay provides a rapid, reliable, and user-friendly approach for detecting Metanil Yellow in turmeric. Its portability and minimal resource requirements make it an attractive tool for enhancing food safety compliance and protecting consumers from harmful adulterants.

References

• No references provided in the source material.