Abstract
Dyeing vegetables with harmful compounds has become an alarming public health issue over the past few years. Excessive consumption of these dyed vegetables can cause severe health hazards, including cancer. Copper sulfate, malachite green, and Sudan red are some of the non-food-grade dyes widely used on vegetables by untrusted entities in the food supply chain to make them look fresh and vibrant. In this study, the presence and quantity of dye-based adulteration in vegetables are determined by applying 1H-nuclear magnetic resonance (NMR) relaxometry. The proposed technique was validated by treating some vegetables in-house with different dyes and then soaking them in various solvents. The resulting solutions were collected and analyzed using NMR relaxometry. Specifically, the effective transverse relaxation time constant, T2,eff, of each solution was estimated using a Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence. Finally, the estimated time constants (i.e., measured signatures) were compared with a library of existing T2,eff data to detect and quantify the presence of unwanted dyes. The latter consists of data-driven models of transverse decay times for various concentrations of each water-soluble dye. The time required to analyze each sample using the proposed approach is dye-dependent but typically no longer than a few minutes. The analysis results can be used to generate warning flags if the detected dye concentrations violate widely accepted standards for food dyes. The proposed low-cost detection approach can be used in various stages of a produce supply chain, including consumer household.
Highlights
Food adulteration has reportedly increased over the last few years because of the complex supply chain of food from producer to consumer
To the best of our knowledge, it is the first to show that nuclear magnetic resonance (NMR) relaxometry can be used for rapid and low-cost detection of multiple dyes present within common vegetables
While the experiments in the paper were focused on three common dyes, the proposed method can be extended to any dye that exhibits NMR relaxation contrast
Summary
Food adulteration has reportedly increased over the last few years because of the complex supply chain of food from producer to consumer. Spectroscopy meets many of these criteria and is promising for analysis, chemical composition of a food product is investigated by measuring its detectingthe adulteration. NMR spectroscopy has many applications in food analysis and adulterant detection. Azo dyes are water-soluble, organic compounds that contain a functional group of the form R−N = N−R’, where R and R’ are typically aromatic groups These dyes are widely used in some foods and in the textile industry; common examples include Sudan red, metanil yellow, and malachite green. To the best of our knowledge, it is the first to show that NMR relaxometry can be used for rapid and low-cost detection of multiple dyes (including malachite green and Sudan red) present within common vegetables. A simple and practical approach was developed for quantification of multiple food dyes by combining an external reference with nonlinear regression
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