Abstract
Curry powder is extensively used in Southeast Asian dishes. It has been subject to adulteration by azo dyes. This study used a newly developed 1064 nm dispersive point-scan Raman system for detection of metanil yellow and Sudan-I contamination in curry powder. Curry powder was mixed with metanil yellow and (separately) with Sudan-I, at concentration levels of 1%, 3%, 5%, 7%, and 10% (w/w). Each sample was packed into a nickel-plated sample container (25 mm × 25 mm × 1 mm). One Raman spectral image of each sample was acquired across the 25 mm × 25 mm surface area. Intensity threshold value was applied to the spectral images of Sudan-I mixtures (at 1593 cm−1) and metanil yellow mixtures (at 1147 cm−1) to obtain binary detection images. The results show that the number of detected adulterant pixels is linearly correlated with the sample concentration (R2 = 0.99). The Raman system was further used to obtain a Raman spectral image of a curry powder sample mixed together with Sudan-I and metanil yellow, with each contaminant at equal concentration of 5% (w/w). The multi-component spectra of the mixture sample were decomposed using self-modeling mixture analysis (SMA) to extract pure component spectra, which were then identified as matching those of Sudan-I and metanil yellow using spectral information divergence (SID) values. The results show that the 1064 nm dispersive Raman system is a potential tool for rapid and nondestructive detection of multiple chemical contaminants in the complex food matrix.
Highlights
Food spices are often used for food coloring and flavor
This study further demonstrates the use of the 1064 nm Raman system for simultaneous detection of multiple contaminants (Sudan-I and metanil yellow) in curry powder
The scattering Raman signal from the sample is directed to the volume phase grating (VPG) through a concave mirror in the spectrograph
Summary
Food spices are often used for food coloring and flavor. Curry powder is extensively used for food seasoning in Southeast Asian dishes. It is a blend of turmeric, coriander, cumin, cardamom, paprika, and other spices. These spices are free of economically motivated chemical contamination in their raw form, their powder form is often reported to be contaminated with chemicals for greater economic benefit. Instances of economically motivated adulteration of turmeric and paprika, the.
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