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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Environmental Microbial & Food Safety Laboratory » Research » Publications at this Location » Publication #327645
Title: Detection of metanil yellow contamination in turmeric using FT-Raman and FT-IR spectroscopy

Author
item DHAKAL, SAGAR - Forest Service (FS)
item Chao, Kuanglin - Kevin Chao
item Qin, Jianwei - Tony Qin
item Kim, Moon
item Schmidt, Walter
item Chan, Diane

Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2016
Publication Date: 5/15/2016
Citation: Dhakal, S., Chao, K., Qin, J., Kim, M.S., Schmidt, W.F., Chan, D.E. 2016. Detection of metanil yellow contamination in turmeric using FT-Raman and FT-IR spectroscopy. Proceedings of SPIE 9864, Sensing for Agriculture and Food Quality and Safety VII, 98640A.

Interpretive Summary: Turmeric is valued for medicinal properties arising from its natural content of curcumin, a yellow pigment with anti-inflammatory, anti-cancer, antioxidant, and wound healing attributes. However, economically driven adulteration of turmeric has occurred repeatedly, such as the addition of metanil yellow, a known carcinogen, to increase yellow color and product weight. This study utilized Fourier Transform Raman (FT-Raman) and Fourier Transform Infrared (FT-IR) spectroscopy techniques to analyze spectra of pure metanil yellow, pure turmeric powder, and mixtures of the two, for identification of turmeric powder adulterated by metanil yellow. Mixtures of metanil yellow in turmeric were prepared at concentrations of 30%, 25%, 20%, 15%, 10%, 5%, 1% and 0.01% by weight. Spectral analysis showed that the FT-Raman peak at 1406 cm-1 and the FT-IR peak at 1140 cm-1 can be utilized to detect metanil yellow in turmeric at concentrations as low as 1% by FT-Raman and 5% by FT-IR, respectively. The spectral peak intensities were highly correlated with actual concentration. These results show that FT-Raman and FT-IR techniques can be applied for rapid and non-destructive inspection of turmeric for metanil yellow adulteration. With the increasing popularity of turmeric as a health food additive, these techniques may be considered a potential tool for food safety inspection that could greatly benefit the food industry, safety regulators, and consumers worldwide.

Technical Abstract: Turmeric is well known for its medicinal value and is often used in Asian cuisine. Economically motivated contamination of turmeric by chemicals such as metanil yellow has been repeatedly reported. Although traditional technologies can detect such contaminants in food, high operational costs and operational complexities have limited their use to the laboratory. This study used Fourier Transform Raman Spectroscopy (FT-Raman) and Fourier Transform – Infrared Spectroscopy (FT-IR) to identify metanil yellow contamination in turmeric powder. Mixtures of metanil yellow in turmeric were prepared at concentrations of 30%, 25%, 20%, 15%, 10%, 5%, 1% and 0.01% (w/w). The FT-Raman and FT-IR spectral signal of pure turmeric powder, pure metanil yellow powder and the 8 sample mixtures were obtained and analyzed independently to identify metanil yellow contamination in turmeric. The results show that FT-Raman spectroscopy and FT-IR spectroscopy can detect metanil yellow mixed with turmeric at concentrations as low as 1% and 5%, respectively, and may be useful for non-destructive detection of adulterated turmeric powder.