@article{MunzkeSaundersOmranietal.2012,
  author    = {Munzke, Dorit and Saunders, John and Omrani, Hengameh and Reich, Oliver and Loock, Hans-Peter},
  title     = {Modeling of fiber-optic fluorescence probes for strongly absorbing samples},
  series = {Applied optics},
  volume    = {51},
  journal   = {Applied optics},
  number    = {26},
  publisher = {Optical Society of America},
  address   = {Washington},
  issn      = {1559-128X},
  doi       = {10.1364/AO.51.006343},
  pages     = {6343 -- 6351},
  year      = {2012},
  abstract  = {The dynamic range of fiber-optic fluorescent probes such as single fibers and fiber bundles is calculated for strongly absorbing samples, such as process liquids, foodstuffs, and lubricants. The model assumes an excitation beam profile based on a Lambertian light source and uses analytical forms of the collection efficiency, followed by an Abel transformation and numerical integration. It is found that the effect of primary absorption of the excitation light and secondary absorption of the fluorescence is profound. For fiber bundles and bifurcated fiber probes, the upper accessible concentration limit is roughly given by the absorption length of the primary and secondary absorption. Fluorescence detectors that are placed at right angles to the excitation beam axis or collinear to the beam axis are equally strongly affected by secondary absorption. A probe in which the same fiber is used for excitation and for collection of the fluorescence emerges as the fiber probe with the largest accessible concentration range.},
  language  = {en}
}
@article{RuizHassReich2012,
  author    = {Ruiz, Salome Vargas and Hass, Roland and Reich, Oliver},
  title     = {Optical monitoring of milk fat phase transition within homogenized fresh milk by Photon Density Wave spectroscopy},
  series = {International dairy journal},
  volume    = {26},
  journal   = {International dairy journal},
  number    = {2},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0958-6946},
  doi       = {10.1016/j.idairyj.2012.03.012},
  pages     = {120 -- 126},
  year      = {2012},
  abstract  = {Photon Density Wave (PDW) spectroscopy was applied for temperature dependent monitoring of melting and crystallization of milk fat within homogenized fresh milk. As an in-line process analytical technique, PDW spectroscopy quantifies continuously the optical properties of turbid material, providing an insight into its structural processes. Here, the measured absorption coefficients reflect temperature as well as fat content of milk and the reduced scattering coefficients probe physical changes of the light scattering fat droplets and casein micelles. Thermal processing reveals breakpoints within the temperature trend of the reduced scattering coefficient of fat containing milk. Found at 16 degrees C and 24 degrees C while cooling and heating, respectively, they are associated to the phase transitions of milk fat. Continuous isothermal measurement of the optical coefficients showed that the crystallization process requires several hours. The strongly changing reduced scattering coefficient implies that the thermal history of milk will have a major impact on any method based on light scattering as quantitative analytical technique.},
  language  = {en}
}