Nondestructive Measurement Technique of Fruit Sugar Content with Near-Infrared Lasers

Abstract

We have developed a nondestructive measurement technique of fruit sugar content with near-infrared lasers. The technique is based on spatially resolved reflectance spectroscopy and gives a new physical parameter γ, which is independent of the optical path length and exhibits a good linear correlativity with fruit sugar content. We performed theoretical analysis with a fruit model based on the diffusion approximation and an experimental test, which employed an electronically tuned Ti:sapphire laser in the wavelength range 900-1070 nm. Both clearly show high linear correlation of the parameter γ and fruit sugar content with an accuracy of 0.5 Brix% or less.

Three-Fibre-Based Diffuse Reflectance Spectroscopy for Estimation of Total Solid Content in Natural Rubber Latex

“…When r and r + D are longer than a specific length, this equation is independent of the distances of the receiving fibres r and r + D. Shimomura et al measured 50 apples, with a large variation in both scattering and sugar content, by the TFDRS method and showed that g(900 nm, 940 nm, 1060 nm) had a strong linear relationship with the sugar content. 16 They separated the contributions from absorption (by measuring the absorption coefficients of water and glucose) and scattering [by fitting equation (12) to the measured data with the assumption that µ¢ s is a function of wavelength as µ¢ s = P 1l -P 2 which is an approximation of the Mie theory] in the samples. P 1 and P 2 are constant values.…”

“…In order to investigate the effect of the scattering coefficient, we simulated −log(i ref ), −log(R) and g(970 nm, 909 nm, 849 nm) at TSC of 0.3 g g −1 and 0.4 g g −1 systematically changing µ¢ s . For this simulation, µ a was calculated as a function of TSC using equation (16). Parameter µ¢ s was systematically chosen from calculated values from particle size distribution using Mie theory.…”

“…Shimomura et al established three-fibre-based diffuse reflectance spectroscopy (TFDRS) based on spatially resolved spectroscopy for the estimation of sugar content in fruits or total haemoglobin concentration and tissue oxygen saturation in human tissues at wavelengths between 800 nm and 1100 nm. [10][11][12][13][14][15][16][17][18] A schematic of the TFDR spectrometer is presented in Figure 1. A continuous wave laser beam is emitted into the sample through an optical fibre at the centre of the sensing probe.…”