Time-resolved reflectance spectroscopy for non-destructive assessment of food quality

Abstract

In the majority of most food and feed, visible, and near infrared light undergoes multiple scattering events and the overall light distribution is determined more by scattering rather than absorption due to the microscopic spatial changes in the refractive index. Conventional steady state reflectance spectroscopy can provide information on light attenuation, which depends both on light absorption and light scattering, but cannot separate these two effects. In contrast, time-resolved reflectance spectroscopy (TRS) allows more detailed optical characterization of diffusive media in terms of their absorption coefficient and reduced scattering coefficient. From the assessment of the absorption and reduced scattering coefficients, information can then be derived on the composition and internal structure of the medium. The main advantages of the technique are the absolute non-invasiveness, the potentiality for non-contact measurements and the capacity to probe internal properties with no influence from the skin. In this work we review the physical and technical issues related to the use of TRS for non-destructive quality assessment of fruit and vegetable. A laboratory system for broadband TRS, based on tunable mode-locked lasers and fast micro-channel plate photomultiplier and a portable set-up for TRS measurements, based on pulsed diode lasers and compact metal-channel photomultiplier, are described. Results on broadband optical characterization of fruits and applications of TRS to the detection of internal defects in pears and to maturity assessment in nectarines are presented.

Fast silicon photomultiplier improves signal harvesting and reduces complexity in time-domain diffuse optics

“…biological tissues -conveys information on the absorption and scattering properties of the medium explored by photons along their paths. Diffuse optics [5] is a powerful tool in many applications like functional brain imaging [6][7][8], oximetry [9], mammography [10], monitoring of neoadjuvant chemotherapy [11], quality assessment of food [12], wood [13], pharmaceuticals [14], investigations of photon migration in random media [15] and many others.…”

Relationship Between Texture Sensory Profiles and Optical Properties Measured by Time-Resolved Reflectance Spectroscopy During Post-Storage Shelf Life of ‘Braeburn’ Apples

“…Recently, non-destructive technologies based on fruit optical properties, such as VIS/NIR spectroscopy (Chen & Opara 2013;Mehinagic et al 2003 and2004), hyperspectral scattering images (Huang et al 2012) and time-resolved reflectance spectroscopy (TRS) have been proposed as tools for apple texture measurements. TRS provides a complete characterisation of diffusive media with the simultaneous measurement of the bulk optical properties, absorption coefficient (µa) and reduced scattering coefficient (µs') (Torricelli et al 2008), up to 1-2 cm depth (Cubeddu et al 2001) without being significantly affected by surface features (Saeys et al 2008). TRS has been used to assess fruit maturity and texture in intact fruit .…”

In-situ analysis of fruit anthocyanins by means of total internal reflectance, continuous wave and time-resolved spectroscopy

“…A system with optical geometry to measure transmittance was used for DTOF measurements, working at 670 nm, based on a pulsed laser diode (PDL800, PicoQuant GmbH, Germany) with 80 MHz repetition frequency, 100 ps duration, and 1 mW average power, with a compact photomultiplier (R5900U-L16, Hamamatsu Photonics, Japan) and an integrated PC board for time-correlated single photon counting (SPC130, Becker&Hickl GmbH, Germany). The width of the instrumental response function (IRF) was <160 ps [20]. TIRF measurements were performed using a confocal imaging system (Infinty 3, Visitron Systems, Germany) equipped with an additional TIRF port.…”