NONINVASIVE ASSESSMENT OF PINEAPPLE AND MANGO FRUIT-QUALITY USING NEAR-INFRARED SPECTROSCOPY

The potential of near infra-red (NIR) spectroscopy for non-invasive me asurement of fruit quality of pineapple (Ananas comosus var. Smooth Ca yenne) and mango (Magnifera indica var. Kensington) fruit was assessed . A remote reflectance fibre optic probe, placed in contact with the f ruit skin surface in a light-proof box, was used to deliver monochroma tic light to the fruit, and to collect NIR reflectance spectra (760-25 00 nm). The probe illuminated and collected reflected radiation from a n area of about 16 cm(2). The NIR spectral attributes were correlated with pineapple juice Brix and with mango flesh dry matter (DM) measure d from fruit flesh directly underlying the scanned area. The highest c orrelations for both fruit were found using the second derivative of t he spectra (d(2) log 1/R) and an additive calibration equation. Multip le linear regression (MLR) on pineapple fruit spectra (n = 85) gave a calibration equation using d(2) log 1/R at wavelengths of 866, 760, 12 32 and 832 nm with a multiple coefficient of determination (R(2)) of 0 .7l5, and a standard error of calibration (SEC) of 1.21 (o)Brix. Modif ied partial least squares (MPLS) regression analysis yielded a calibra tion equation with R(2) = 0.91, SEC = 0.69, and a standard error of cr oss validation (SECV) of 1.09 (o)Brix. For mango, MLR gave a calibrati on equation using d(2) log 1/R at 904, 872, 1660 and 1516 nm with R(2) = 0.90, and SEC = 0.85% DM and a bias of 0.39. Using MPLS analysis, a calibration equation with R(2) = 0.98, SEC = 0.54 and SECV = 1.19 was obtained. We conclude that NIR technology offers the potential to ass ess fruit sweetness in intact whole pineapple and DM in mango fruit, r espectively, to within 1 degrees Brix and 1% DM, and could be used for the grading of fruit in fruit packing sheds.