Nondestructive quantification of chemical and physical properties of fruits by time-resolved reflectance spectroscopy in the wavelength range 650–1000 nm

Abstract

Time-resolved reflectance spectroscopy can be used to assess nondestructively the bulk (rather than the superficial) optical properties of highly diffusive media. A fully automated system for time-resolved reflectance spectroscopy was used to evaluate the absorption and the transport scattering spectra of fruits in the red and the near-infrared regions. In particular, data were collected in the range 650-1000 nm from three varieties of apples and from peaches, kiwifruits, and tomatoes. The absorption spectra were usually dominated by the water peak near 970 nm, whereas chlorophyll was detected at 675 nm. For ail species the scattering decreased progressively with increasing wavelength. A best fit to water and chlorophyll absorption line shapes and to Mie theory permitted the estimation of water and chlorophyll content and the average size of scattering centers in the bulls; of intact fruits.

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.)…”

“…Other fruits (peach (Cen et al, 2012), pear (Zerbini et al, 2002), plum (Qin and Lu, 2008), etc.) and vegetables (tomato (Cubeddu et al, 2001a), cucumber (Qin and Lu, 2008), onion (Wang and Li, 2013), etc.) were also studied but not as frequently.…”