Colorimetry in food analysis using digital imaging system

Abstract

A non-destructive, user-friendly, portable colour measurement system was developed using the MATLAB interface that gives acceptable results with any imaging sensor. Digital images captured by the imaging sensor were used to obtain quantitative colour information in three formats, namely, RGB, XYZ and CIELAB. The zoom-in feature is useful for obtaining detailed colour features of the image, while cropping of the region of interest aids in reducing the image matrix and, ultimately, the computational power required. Quantitative information on the colour value of the product (both average and region to region) can be obtained in all three formats (i.e., RGB, XYZ and CIELAB). It also gives the three closest Royal Horticultural Society (RHS) values of the product. The accuracy of the measurement system was first validated against a standard colour chart then it was tested using three image sensors of different configurations. Coefficient of determination (R2) and root mean square error values of 0.983 and 3.391 for L*, 0.994 and 1.851 for a* and 0.996 and 2.042 for b*, respectively, were obtained during performance evaluation. Similarly, when different imaging sensors were used for colour determination, the colour values showed no significant variation for all tested samples (i.e., various fruits and vegetables of different chroma/hues).