@article{EngelhardLoehmannsroebenSchael2004,
  author    = {Engelhard, Sonja and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Schael, Frank},
  title     = {Quantifying ethanol content of beer using interpretive near-infrared spectroscopy},
  issn      = {0003-7028},
  year      = {2004},
  abstract  = {On the basis of absorption measurements in the near-infrared (NIR) spectral range, a new method for the quantification of the ethanol content of beer is presented. Instead of the multivariate calibration models most commonly employed in NIR spectroscopic works, we use interpretive difference spectroscopy: Two wavelengths are selected according to the assignment of the absorption bands of the main substances of content of beer in the NIR region, and the difference between the absorbances at these wavelengths is used for ethanol quantification. Absorption spectra of the dominating beer ingredients are discussed and the calibration procedure with ethanol/water mixtures is shown. Robustness against the carbohydrate content of beer samples was demonstrated by analyzing solutions of ethanol and maltose in water. Validation of the method was performed with various beer samples with an ethanol concentration range between 0.5 and 7.7 vol \%. The pertinent advantage of the procedure developed in this work is the indication that the results are independent from seasonal variations of the ingredients, which is of high interest for products with natural ingredients such as beer},
  language  = {en}
}
@phdthesis{Engelhard2003,
  author    = {Engelhard, Sonja},
  title     = {Optische Verfahren zur Qualit{\"a}tskontrolle von Bier und zur Zellzahlbestimung in S. cerevisiae Kultivierungen},
  pages     = {129 S.},
  year      = {2003},
  language  = {de}
}
@misc{EngelhardKumkeLoehmannsroeben2006,
  author    = {Engelhard, Sonja and Kumke, Michael Uwe and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {OPQS - optical process and quality sensing : exemplary applications in the beerbrewing and polyurethane foaming processes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12191},
  year      = {2006},
  abstract  = {Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near-infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant.},
  language  = {en}
}
@article{SchaelEngelhardReich2001,
  author    = {Schael, Frank and Engelhard, Sonja and Reich, Oliver},
  title     = {Optische Sensorik f{\"u}r die in-situ-Analytik von Brauprozessen},
  year      = {2001},
  language  = {de}
}
@article{EngelhardKumkeLoehmannsroeben2006,
  author    = {Engelhard, Sonja and Kumke, Michael Uwe and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Examples of the application of optical process and quality sensing (OPQS) to beer brewing and polyurethane foaming processes},
  issn      = {1618-2642},
  doi       = {10.1007/s00216-005-3364-4},
  year      = {2006},
  abstract  = {Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near- infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O-2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant},
  language  = {en}
}