Non-invasive assessment of pineapple and mango fruit quality using near infra-red spectroscopy.
Guthrie J., Walsh K.
Author Affiliation: Department of Primary Industries, Rockhampton, Qld 4702, Australia.
Australian Journal of Experimental Agriculture 37 : 253-263
Abstract : The potential of near infrared (NIR) spectroscopy for non-invasive measurement of fruit quality of pineapple (cv. Smooth Cayenne) and mango (cv. Kensington) fruits was assessed. A remote reflectance fibre optic probe, placed in contact with the fruit skin surface in a light-proof box, was used to deliver monochromatic light to the fruit and to collect NIR reflectance spectra (760-2500 nm). The probe illuminated and collected reflected radiation from an area of about 16 cmČ. The NIR spectral attributes were correlated with pineapple juice Brix and with mango flesh dry matter (DM) measured from fruit flesh directly underlying the scanned area. The highest correlations for both fruits were found using the second derivative of the spectra (dČ log 1/R) and an additive calibration equation. Multiple linear regression (MLR) on 85 pineapple fruit spectra gave a calibration equation using dČ log 1/R at wavelengths of 866, 760, 1232 and 832 nm with a multiple coefficient of determination (RČ) of 0.75, and a standard error of calibration (SEC) of 1.21°Brix. Modified partial least squares (MPLS) regression analysis yielded a calibration equation with RČ=0.91, SEC=0.69, and a standard error of cross validation (SECV) of 1.09°Brix. For mangoes, MLR gave a calibration equation using dČ log 1/R at 904, 872, 1660 and 1516 nm with RČ=0.90 and SEC=0.85% DM and a bias of 0.39. Using MPLS analysis, a calibration equation with RČ=0.98, SEC=0.54 and SECV=1.19 was obtained. It was concluded that NIR technology offers the potential to assess fruit sweetness in intact whole pineapples and DM in mango fruits to within 1°Brix and 1% DM, respectively, and could be used for fruit grading in packing sheds.