Trace Detection of Toxic Dye in Saffron

Importance of the Topic

Saffron is the world’s most valuable spice by weight and is renowned for its distinctive color, aroma, and flavor. Its labor-intensive harvesting process makes it susceptible to economic adulteration, often with toxic dyes like Sudan 1. Rapid, on-site detection of such adulterants is essential to protect consumer safety and maintain quality standards in the spice trade.

Study Objectives and Overview

This study demonstrates how a portable SERS (Surface-Enhanced Raman Scattering) system, the Metrohm Instant SERS Analyzer (MISA), can detect trace levels of the banned carcinogenic dye Sudan 1 in saffron. The goals include:

• Comparing the SERS signals of pure saffron crocin extracts and Sudan 1 dye.
• Assessing the system’s ability to differentiate authentic and adulterated saffron mixtures.
• Determining the detection limit for Sudan 1 with MISA.

Methodology and Instrumentation

Sample Preparation and Extraction:

• Pure saffron: 100 mg of stigmas extracted with methanol, mixed with NaCl and gold nanoparticles.
• Adulterated saffron: 1:1 (w/w) mix of authentic saffron and flower parts dyed in 1 mg/mL Sudan 1.

Instrumentation:

• MISA Basic and Advanced systems featuring Orbital-Raster-Scan (ORS) spectrography.
• Vial attachment for glass vials; P-SERS strip attachment for advanced package.
• Operating software: MISA Cal, connectivity via Bluetooth or USB.

Main Results and Discussion

Direct Raman analysis of saffron yields strong fluorescence, masking characteristic crocin peaks and limiting specificity. In contrast, SERS spectra provide clear, distinct fingerprints:

• Pure saffron SERS spectrum shows signature crocin peaks after baseline correction.
• Sudan 1 SERS spectrum at 0.01 mg/mL displays unique marker bands.
• Overlay of pure, adulterant, and mixed samples confirms the ability to distinguish both components in a counterfeit saffron blend.
• Serial dilutions of Sudan 1 demonstrate a detection limit down to 500 ng/mL.

Benefits and Practical Applications

The portable MISA system enables:

• Rapid, on-site authentication of saffron without complex laboratory infrastructure.
• Trace-level detection of banned dyes to enforce food safety regulations.
• Extension to other spice adulterants and colorants, enhancing frontline quality control.

Future Trends and Opportunities

Advancements in portable SERS technology will likely include:

• Expanded spectral libraries and chemometric algorithms for automated adulterant identification.
• Integration with mobile devices for real-time data reporting and cloud-based monitoring.
• Broader applications across food matrices, pharmaceuticals, and environmental screening.

Conclusion

This application note illustrates the efficacy of MISA’s SERS-based approach for authenticating saffron and detecting Sudan 1 adulteration. The high sensitivity and portability of the system make it a valuable tool for safeguarding food integrity at the point of need.

Reference

Metrohm AG. AN-RS-036 Trace Detection of Toxic Dye in Saffron: Protecting Consumer Safety with MISA. 2023.