Reflectance spectral features and non-destructive estimation of chlorophyll, carotenoid and anthocyanin content in apple fruit
2003
Merzlyak, Mark N. | Solovchenko, Alexei E. | Gitelson, Anatoly A.
Fruit reflectance spectra of five apple (Malus domestica Borkh.) cultivars (Zhigulevskoe, Antonovka, Granny Smith, Golden Delicious and Renet Simirenko) with a wide range of peel pigment (chlorophylls a and b, carotenoids and anthocyanins) content have been studied to develop non-destructive techniques for pigment assessment. In addition to chlorophylls, positions of in vivo absorption maxima were established for carotenoids (480, 455 and a shoulder at 425 nm) and for anthocyanins (near 550 nm). In anthocyanin-free fruit, a close relationship between reflectance at 550 nm (R550) and 700 nm (R700) has been found (r2>0.95). In fruit with chlorophyll content more than 5 nmol/cm2, the reflectance near 678 nm was insensitive to a variation in chlorophylls, whereas, reflectance in the bands 550–650 nm and 690–705 nm remained sensitive to chlorophyll content in a wide range of its variation. The reflectance ratios, R800/R700 and R800/R640, were directly proportional to total chlorophyll content ranging from 0.4 to 11 nmol/cm2 (r2>0.93). The reflectance in the band 520–530 nm was found to be dependent mostly on carotenoids absorption. The index R800(1/R520−1/R700) was suggested for estimation of carotenoid content in the range 0.6–4.5 nmol/cm2. The index for assessment of a carotenoid/chlorophyll ratio was proposed in the form, (R480−R678)/R800. Reflectance in the green region of the spectrum proved to be sensitive to anthocyanin content. The index R800(1/R550−1/R700) was developed to estimate anthocyanin content in peel ranging from 2.5 to 50 nmol/cm2; the determination coefficient of the index with anthocyanin content was higher than 0.93.
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