Carotenoid content and pulp colour non-destructively measured by time-resolved reflectance spectroscopy in different cultivars of Brazilian mangoes

Carotenoid biosynthesis is one of the most important biochemical changes occurring during mango ripening. Carotenoids are responsible for the yellow-orange pulp colour, which is one of the best maturity indices for mangoes, notwithstanding it is a destructive method. Time-resolved reflectance spectroscopy (TRS) is a nondestructive technique which simultaneously quantifies the internal optical properties of fruit related to pigments (absorption coefficient, μa) and to structure (reduced scattering coefficient, μs') by probing the pulp to a depth of 1-2 cm with no or limited influence from the skin. In previous works, it was found that TRS is able to predict with good accuracy the pulp colour of mangoes and then to sort fruit with different maturity degrees. The aim of this research was to study the relationships among TRS optical properties, total carotenoids content and pulp colour parameters of two cultivars of Brazilian mangoes transported by plane to Italy. Fruit were measured by TRS in the 540-690 nm range for 'Palmer' cultivar and in the 540-780 nm range for 'Haden' and analyzed for pulp colour and total carotenoids content. Total carotenoids ranged from 5.2 to 32.7 mg kg-1 FW for 'Palmer' and from 5.9 to 56.2 mg kg-1 FW for 'Haden'. By using partial least squares regression, good correlations were obtained between TRS absorption spectra and total carotenoids content (R2cv=0.83 and 0.93 for 'Haden' and 'Palmer', respectively) and pulp colour parameters (R2cv=0.78-0.96).