Key Points
- Researchers developed a rapid, non-destructive analytical framework using FT-IR, Raman spectroscopy, UV–visible spectroscopy, cyclic voltammetry, SEM, and advanced chemometric models to detect ferric oxide red adulteration in chili powder.
- The method successfully identified characteristic spectral and microscopic differences between pure and adulterated samples, offering a more accurate, faster, and cost-effective alternative to traditional food adulteration detection methods.
- While focused on ferric oxide in chili powder, the multi-modal approach can be adapted to detect various other food adulterants, supporting broader efforts to ensure food quality and protect public health.
Food adulteration is a concern in food safety applications. Ensuring that high-quality food products enter the food market is important to consumers, who want to know they are buying food products that have not been tampered with. A recent study published in Microchemical Journal explores this important topic, investigating the ingredient chili powder for adulteration with ferric oxide red (1). Because ferric oxide red poses significant health risks, the research team, which D. Selvakumar led from the PSG Institute of Technology and Applied Research in Coimbatore, India, developed and tested a new analytical framework for the rapid detection of this adulterant (1).
What is ferric oxide red?
Known as iron (III) oxide, ferric oxide red is a chemical compound commonly used in industrial applications like paints and pigments (1,2). It is sometimes illegally added to chili powder to boost its reddish hue and visual appeal (1). This adulteration may enhance toxic substances into the food chain. Because the contaminant closely resembles authentic chili powder in appearance, it is nearly impossible to detect through visual inspection alone (1).
As a result, the researchers explored how to fix this problem by developing a new, analytical framework that could accurately detect, classify, and quantify ferric oxide adulteration using advanced spectroscopic techniques and chemometric modeling. In their study, the researchers employed several spectroscopic techniques to analyze the chili powder samples, including Fourier transform infrared (FT-IR), Raman spectroscopy, ultraviolet–visible spectroscopy, and cyclic voltammetry. These were adulterated with ferric oxide red at concentrations of 5%, 10%, 15%, and 20% by weight (1).
What were the spectral results?
The spectroscopy techniques used in the study revealed the characteristic peaks of chili powder and ferric oxide red. For example, FT-IR spectra showed characteristic peaks of pure chili powder at 1385 cm⁻¹, 1600 cm⁻¹, and 2935 cm⁻¹, whereas ferric oxide red produced distinct peaks at 460 cm⁻¹ and 540 cm⁻¹ (1). Similarly, Raman spectroscopy identified peaks at 260 cm⁻¹, 615 cm⁻¹, and 1315 cm⁻¹ for unadulterated samples and 225 cm⁻¹, 306 cm⁻¹, and 670 cm⁻¹ for adulterated ones (1).
Additionally, scanning electron microscopy (SEM) and elemental mapping enabled visual differentiation between adulterated and pure samples by revealing the distribution of ferric oxide particles throughout the powdered matrix (1). This multi-modal approach provided layers of corroborative evidence to ensure detection accuracy.
Advanced statistical tools were also used to great effect in this study. Principal component analysis (PCA) and soft independent modelling of class analogy (SIMCA) to process spectral data and distinguish between adulterated and pure samples (1). They also utilized DD-SIMCA, a data-driven variant of SIMCA, to validate their classification models across independent data sets.
What are the key takeaways of the study?
There are several key takeaways from this study. First, the study’s findings show that this method improves upon traditional methods by overcoming three main challenges. Traditional methods are slow, invasive, and costly. This newly proposed method is rapid, non-destructive, and highly scalable (1). The potential for real-time, on-site testing makes it suitable for application across the supply chain, starting from farm-level monitoring to customs inspections and supermarket shelves (1).
The second takeaway from this study is that the effectiveness of the method will result in a push to automate the process and integrate it into portable, user-friendly devices (1). Moreover, the study serves as a springboard for broader applications. Although the study focuses on ferric oxide adulteration in chili powder, the techniques and models developed could be adapted to detect other common food adulterants, such as synthetic dyes, starch fillers, and even pesticide residues (1).
Previous studies have typically relied on a single method to detect adulteration, limiting accuracy and sensitivity. This research stands out by integrating multiple advanced techniques and statistical models to create a more robust and reliable detection system.
By enhancing the precision, sensitivity, and applicability of adulteration detection, the study offers a crucial tool in the fight for food safety and public health.
References
- Vignesh, T.; Selvakumar, D.; Jayavel, R. Detecting Ferric Oxide Adulteration in Chilli Powder: A Multimodal Analytical Approach for Enhanced Food Safety. Microchem. J. 2025, 208, 112332. DOI: 10.1016/j.microc.2024.112332
- Drugs.com, Ferric Oxide Red. Drugs.com. Available at: https://www.drugs.com/inactive/ferric-oxide-red-382.html (accessed 2025-08-04).
