Validation of multispectral imaging for the detection of selected adulterants in turmeric samples

Turmeric (Curcuma longa), is a popular spice in traditional cuisine and now is globally available. As in the case of many widespread spices, turmeric powder is often adulterated using various additives and colorants. Therefore, the identification of adulterated turmeric is of paramount importance. However, the existing methods are laborious, expensive and time-consuming. In this study, we propose a multispectral imaging system for detecting the percentage of the common adulterant; tartrazine colored rice flour found in turmeric powder. A multispectral imaging system was developed utilizing nine spectral bands with peak wavelengths from 405 nm to 950 nm. An algorithm was developed based on Principal Component Analysis (PCA) and Bhattacharyya Distance. The relationship between the Bhattacharyya Distance and the adulteration level was modeled as a second-order polynomial with an R2 = 0.9911 and the results were validated using an independent set of samples with an R2 = 0.9816. •A multi-stage signal processing algorithm to estimate adulteration of turmeric.•Cost-effective nine-band in-house built multispectral imaging system.•Functional relationship between Bhattacharyya distance and adulteration level.•Validated using a set of independent samples with known adulteration levels.•A field test to show commercial applicability of the proposed solution.