Changes in the content of chlorophylls and carotenoids in the rind of Fino 49 lemons during maturation and their relationship with parameters from the CIELAB color space

In the present work, the coordinates L*, a* and b* from the CIELAB color space, as well as the chlorophyll, total carotenoids and the content of the carotenoids Lutein and β-cryptoxanthin were measured in the skin of fruits from the Fino 49 lemon during its development, with the aim of understanding the relationship that exists between the color changes of the fruit's skin (color coordinates) and the pigment content. Also, the understanding of the relative importance of the contents of lutein and β-cryptoxanthin with respect to the total content of carotenoids was sought. The period of study lasted three years; from September 2015 to January 2016, from September 2016 to January 2017, and from September 2017 to January 2018, the periods that comprised the color changes of the lemon fruit until its harvest. The fruits were measured every two weeks in the experimental plot of the IMIDA (Murcian Institute of Agricultural and Food Research and Development) located at La Alberca (Murcia, Spain) and in the experimental orchards from the CEBAS-CSIC, located in Santomera (Murcia). During the experiment, the color and chlorophyll, Lutein and β-cryptoxanthin concentrations were measured. The results showed that there was a good correlation between the color coordinates and the pigments responsible for the lemon's skin color: all the color pigments were correlated with the a*, b* color coordinates and the Hue angle index. Throughout the fruit's maturation, a degradation of the chlorophylls was observed, as well as an increase of β-cryptoxanthin, which is responsible for the green and yellow color of the fruits, respectively. Lutein, which was found in high concentrations, decreased with time, but did not contribute to the fruit's color.