Time-Resolved Reflectance Spectroscopy Applied to the Nondestructive Monitoring of the Internal Optical Properties in Apples

Abstract

Time-resolved reflectance has been used for the nondestructive measurement of optical properties in apples. The technique is based on the detection of the temporal dispersión of a short láser pulse injected into the probed médium. The time distribution of re-emitted photons interpreted with a solution of the diffusion equation yields the mean valúes of the absorption and reduced scattering coefficients of the médium. The proposed technique proved useful for the measurement of the absorption and scattering spectra of different varieties of apples, revealing the spectral shape of chlorophyll. No major variations were observed in the experimental data when the fruit was peeled, showing that the optical properties measured were those of the pulp. With this technique the change in chlorophyll absorption during storage and ripening could be followed. Finally, a compact prototype working at few selected wavelengths was designed and constructed, demonstrating potentialities of the technique for industrial applications.

Innovative Hyperspectral Imaging-Based Techniques for Quality Evaluation of Fruits and Vegetables: A Review

“…Because absorption and scattering are interwoven during light transfer in turbid media, fast and accurate measurement of the absorption and scattering coefficients still remains a challenging task. Over the years, researchers in the field of biomedical optics have developed several techniques for measuring the optical properties of biological tissues, which, according to their measurement principles, can be categorized into: time-resolved [93,94], frequency domain [95,96], spatially-resolved [56,97], and spatial frequency domain [98,99]. While time-resolved and frequency domain techniques are able to interrogate the tissues at a greater depth, they generally require more expensive and sophisticated instrumentation and have fewer wavelength selection options.…”

Numerical Study of Light Transport in Apple Models Based on Monte Carlo Simulations

“…The skin thickness was estimated from the boundary where a fast growth of the cells Table 2. The data concerning the flesh have been reported by authors who worked with the hyperspectral imaging-based spatially-resolved method [48,49] or with the time-resolved method [1,2], in the wavelengths ranging from 633 nm to 850 nm. The listed data especially show the variation between retrieved optical properties due to considered apple varieties or to the optical technique which has been used for the measurements.…”

“…Incident photons that penetrate in turbid tissues often undergo multiple scattering events before being absorbed or exiting from the material. Light absorption is primarily due to chemical constituents (chromophores and pigments) of the material [1][2][3], whereas light scattering is more related to structural features (density, particle size, and cellular structures) [4][5][6]. These two fundamental optical events are characterized by the absorption coefficient µ a , the scattering coefficient µ s , the scattering anisotropy g, the reduced scattering coefficient µ' s (µ' s = µ s (1´g)), and the refractive index (n) [7,8].…”

“…All these methods allow us to extract the optical properties of turbid tissues, provided that an appropriate radiation transfer equation coupled with an inverse algorithm is used to fit the reflectance data [11][12][13]. Optical techniques devoted to the measurements of quality attributes of fruits, and food products mainly concern the hyperspectral imaging-based spatially-resolved method [14][15][16][17], and time-resolved method [1,2,18,19]. Studies carried out by means of these two systems were based on the major assumption that the interrogated samples are plane and homogeneous.…”

Investigation of absorption and scattering characteristics of kiwifruit tissue using a single integrating sphere system

“…In the past decade, investigations for measuring tissue absorption and scattering coefficients of agro-products became popular for the previously mentioned reasons. Much attention was paid to the optical properties of apples perhaps because of the universality of this crop (Cubeddu et al, 2001a;2001b;Zerbini et al, 2002;Qin and Lu, 2008;Vanoli et al, 2009;Lu et al, 2010;Rizzolo et al, 2010). Other fruits (peach (Cen et al, 2012), pear (Zerbini et al, 2002), plum (Qin and Lu, 2008), etc.)…”