@article{AdebayoHashimHassetal.2017,
  author    = {Adebayo, Segun Emmanuel and Hashim, Norhashila and Hass, Roland and Reich, Oliver and Regen, Christian and M{\"u}nzberg, Marvin and Abdan, Khalina and Hanafi, Marsyita and Zude-Sasse, Manuela},
  title     = {Using absorption and reduced scattering coefficients for non-destructive analyses of fruit flesh firmness and soluble solids content in pear},
  series = {Postharvest Biology and Technology},
  volume    = {130},
  journal   = {Postharvest Biology and Technology},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0925-5214},
  doi       = {10.1016/j.postharvbio.2017.04.004},
  pages     = {56 -- 63},
  year      = {2017},
  abstract  = {Quality attributes of fruit determine its acceptability by the retailer and consumer. The objective of this work was to investigate the potential of absorption (μa) and reduced scattering (μs') coefficients of European pear to analyze its fruit flesh firmness and soluble solids content (SSC). The absolute reference values, μa* (cm-1) and μs'* (cm-1), of pear were invasively measured, employing multi-spectral photon density wave (PDW) spectroscopy at preselected wavelengths of 515, 690, and 940 nm considering two batches of unripe and overripe fruit. On eight measuring dates during fruit development, μa and μs' were analyzed non-destructively by means of laser light backscattering imaging (LLBI) at similar wavelengths of 532, 660, and 830 nm by means of fitting according to Farrell's diffusion theory, using fix reference values of either μa* or μs'*. Both, the μa* and the μa as well as μs'* and μs' showed similar trends. Considering the non-destructively measured data during fruit development, μa at 660 nm decreased 91 till 141 days after full bloom (dafb) from 1.49 cm-1 to 0.74 cm-1 due to chlorophyll degradation. At 830 nm, μa only slightly decreased from 0.41 cm-1 to 0.35 cm-1. The μs' at all wavelengths revealed a decreasing trend as the fruit developed. The difference measured at 532 nm was most pronounced decreasing from 24 cm-1 to 10 cm-1, while at 660 nm and 830 nm values decreased from 15 cm-1 to 13 cm-1 and from 10 cm-1 to 8 cm-1, respectively. When building calibration models with partial least-squares regression analysis on the optical properties for non-destructive analysis of the fruit SSC, μa at 532 nm and 830 nm resulted in a correlation coefficient of R = 0.66, however, showing high measuring uncertainty. The combination of all three wavelengths gave an enhanced, encouraging R = 0.89 for firmness analysis using μs' in the freshly picked fruit.},
  language  = {en}
}
@article{ZudeSasseHashimHassetal.2019,
  author    = {Zude-Sasse, Manuela and Hashim, Norhashila and Hass, Roland and Polley, Nabarun and Regen, Christian},
  title     = {Validation study for measuring absorption and reduced scattering coefficients by means of laser-induced backscattering imaging},
  series = {Postharvest Biology and Technology},
  volume    = {153},
  journal   = {Postharvest Biology and Technology},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0925-5214},
  doi       = {10.1016/j.postharvbio.2019.04.002},
  pages     = {161 -- 168},
  year      = {2019},
  abstract  = {Decoupling of optical properties appears challenging, but vital to get better insight of the relationship between light and fruit attributes. In this study, nine solid phantoms capturing the ranges of absorption (μa) and reduced scattering (μs') coefficients in fruit were analysed non-destructively using laser-induced backscattering imaging (LLBI) at 1060 nm. Data analysis of LLBI was carried out on the diffuse reflectance, attenuation profile obtained by means of Farrell's diffusion theory either calculating μa [cm-1] and μs' [cm-1] in one fitting step or fitting only one optical variable and providing the other one from a destructive analysis. The nondestructive approach was approved when calculating one unknown coefficient non-destructively, while no ability of the method was found to analysis both, μa and μs', non-destructively. Setting μs' according to destructive photon density wave (PDW) spectroscopy and fitting μa resulted in root mean square error (rmse) of 18.7\% in comparison to fitting μs' resulting in rmse of 2.6\%, pointing to decreased measuring uncertainty, when the highly variable μa was known. The approach was tested on European pear, utilizing destructive PDW spectroscopy for setting one variable, while LLBI was applied for calculating the remaining coefficient. Results indicated that the optical properties of pear obtained from PDW spectroscopy as well as LLBI changed concurrently in correspondence to water content mainly. A destructive batch-wise analysis of μs' and online analysis of μa may be considered in future developments for improved fruit sorting results, when considering fruit with high variability of μs'.},
  language  = {en}
}