Color of orange juices in relation to their carotenoid contents as assessed from different spectroscopic data

The color of orange juice influences consumers’ choice, hence much importance has been given to the assessment of this attribute for decades. The instrumental measurement of orange juice color can be harnessed for the rapid, quality-control oriented estimation of its carotenoids, which are health-promoting compounds. In this work we compared and analyzed different spectroscopic data that can be used for these purposes, like the reflectance spectra of orange juices and the absorption spectra of their carotenoid extracts. Additionally, we have revisited the Kubelka–Munk theory and have concluded that its parameters are suitable to assess the carotenoid content of the samples, but not as much as the CIELAB color coordinates. In this regard, we have observed that K/S is the Kubelka–Munk parameter best correlated with the carotenoid content of the orange juices surveyed (r = −0.84), although better correlations were observed when the CIELAB coordinate a* was considered (r = 0.86 and 0.88 for measurements with white and black background, respectively). However, in our opinion, this fact should not lead to dismissing the usefulness of the Kubelka–Munk theory to estimate carotenoid contents, since its application can lead to obtaining valuable information about the absorption and scattering properties of the samples.