Fourier transform infrared spectroscopy as a rapid method for the detection of adulteration in groundnut powder and paste retailed in Kampala

Abstract

Anecdotal evidence suggests that groundnut products in Uganda are frequently adulterated with maize, cassava, millet, bean, and jackfruit seed powders. Traditional detection methods currently in use such as HPLC, GC-MS, and MALDI-TOF, are costly and time-consuming, necessitating rapid, cost-effective, and non-destructive alternatives. This study aimed to evaluate the applicability of Fourier Transform Infrared (FTIR) spectroscopy as a fast and cost-effective method for detecting adulteration in groundnut products retailed in Kampala, Uganda. Methods: A cross-sectional study design involving 100 packaged and unpackaged retail samples purchased from 5 divisions of Kampala, alongside authentic groundnuts, 5 adulterants (maize flour, cassava flour, millet flour, bean seed powder, and jackfruit seed powder), and 50 deliberately adulterated groundnut samples. Spectral data (4000–400 cm⁻¹) were acquired using Shimadzu FTIR-8400S. PCA was done using SIMCA 18 to classify the adulterants in the samples. Authentic groundnuts showed distinct lipid peaks (2923, 2855, 1743 cm⁻¹), while adulterants exhibited carbohydrate (1000, 1149 cm⁻¹) and fiber (1418 cm⁻¹) markers. These spectral features helped differentiate authentic groundnut samples from those that were adulterated. PCA effectively separated clusters, with PC1 (65.4%) and PC2 (15.7%) accounting for 81.1% of the cumulative variance. Of the 100 market samples, 25 % were classified as authentic, 45 % were adulterated (cassava flour 13 %, millet flour 12 %, bean 9 %, jackfruit seed 7 %, maize 4 %), and 30 % remained unclassified (likely complex or unknown adulterant mixtures). Packaged samples showed very low adulteration (2 %), whereas unpackaged samples reached 43 %. Powder forms (40 %) were more adulterated than paste (5 %). Fourier Transform Infrared coupled with PCA, offers a nondestructive, rapid, and non-targeted method for groundnut adulteration detection in Kampala. Its integration into regulatory frameworks could enhance food safety monitoring, ensuring the authenticity and quality of groundnut products in local markets. Keywords: Food fraud, FTIR spectroscopy, Chemometrics, Principal Component Analysis, Groundnut adulteration, Kampala.