Non-destructive prediction of color and pigment contents in mango peel

• Peel color of eight mango cultivars was characterized by the hue angle distribution.
• Visible reflectance measurement was used to estimate pigment contents in mango peel.
• Peel colors and pigment contents of eight mango cultivars were compared.
• Peel colors and pigment contents varied significantly between mango cultivars.
• Relationships between peel color and its pigment contents were cultivar dependent.

The pigment content of mango peel is an important quality determinant due to its involvement in the nutritional value and coloration of the fruit. In addition, pigment content in the peel is related to the fruit maturity stage and has been suggested as a reliable harvest criterion. Measurements of pigment content by vis-spectrophotometry and chromatography methods are destructive, time-consuming and expensive. This study deals with the potential of reflectance measurements as a non-destructive method to assess pigment content and color in mango fruit peel. We also investigated the relationship between the pigment content of the peel and its color. Eight mango cultivars, i.e., Cogshall, Kent, Caro, Sensation, Tommy Atkins, Nam Doc Mai, Irwin and Heidi, were studied. Hue angle distribution was used to characterize and to compare cultivar colors. The peel contents in anthocyanin, carotenoids, chlorophyll a and chlorophyll b were predicted using Partial Least Square Regressions based on reflectance indexes and compared between cultivars. Our results showed that reflectance measurements can accurately (R2 ≥ 0.91, RMSE ≤ 5.74 μg gFW−1) predict the contents of the main pigment contained in the mango peel. Further studies are nevertheless required to increase PLSR robustness. Significant differences were found in the hue angle distribution and the predicted peel pigment content between the eight mango cultivars studied. All relationships between pigments and hue angle values were found to be cultivar-dependent. The highest correlations between hue angle values and pigment contents were found for anthocyanin content in red cultivars (0.76 ≥ R2 ≥ 0.58), and chlorophyll content in green cultivars (0.88 ≥ R2 ≥ 0.62). Results showed that reflectance measurements could be used to predict mango quality determinants such as the fruit maturity stage according to the peel chlorophyll content, the fruit coloration and the content of valuable components, i.e., anthocyanins and carotenoids.