Postharvest biology and technology vol:18 issue:2 pages:121-132
Some issues related to the non-destructive measurement of apple quality attributes by means of NIR reflectance spectroscopy are addressed. A comparison was made between two optical configurations, which can be used to perform NIR-spectroscopic measurements: the bifurcated and the 0 degrees/45 degrees optical configuration. A relationship was established between the reflectance spectra (880-1650 nm) and the soluble solids content by means of the partial least squares technique. Depending on the data pre-processing method, correlation coefficients between 79 and 91% were obtained. The results obtained with the bifurcated fibre were only marginally better than those obtained with the 0 degrees/45 degrees configuration. The apple skin reflectance and skin transmission properties with regard to NIR radiation were also investigated. The intensity of the light source was high enough to penetrate through the apple skin and gather information about the apple parenchyma tissue. A method was developed to calculate the light penetration depth for each wavelength in the range from 500 to 1900 nm. This method was applied to measure the light penetration depth in 'Jonagold' apple fruit tissue. The penetration depth is wavelength dependent: up to 4 mm in the 700-900 nm range and between 2 and 3 mm in the 900-1900 nm range. (C) 2000 Elsevier Science B.V. All rights reserved.