@article{IslamKhalilMaenneretal.2017,
  author    = {Islam, Khan M. S. and Khalil, Mahmoud Abd Elhamid and Maenner, Klaus and Raila, Jens and Rawel, Harshadrai Manilal and Zentek, J{\"u}rgen and Schweigert, Florian J.},
  title     = {Lutein Specific Relationships among Some Spectrophotometric and Colorimetric Parameters of Chicken Egg Yolk},
  series = {The journal of poultry science},
  volume    = {54},
  journal   = {The journal of poultry science},
  publisher = {Japan Poultry Science Association},
  address   = {Tsukuba},
  issn      = {1346-7395},
  doi       = {10.2141/jpsa.0160065},
  pages     = {271 -- 277},
  year      = {2017},
  abstract  = {Lutein is an essential dietary carotenoid with health benefits and is inter alia responsible for the colouration of egg yolk. The relationship between lutein accumulation and egg yolk colouration was therefore studied in more detail. After feeding a low-luteine diet for 21 days, 14 birds (Lohmann brown hens aged 20 weeks) were fed a diet containing marigold (80 mg lutein/kg feed) and 14 other birds were fed a diet containing oleoresin (45 mg lutein/kg feed) for 21 days; for both groups of birds, this feeding period was followed by withdrawal for 21 days. The Roche Yolk Colour Fan (RYCF) score (0 to 15, where higher values denote greater colour intensity; R-2=0.87; P<0.01) and redness (R-2=0.89; P<0.01) increased with increasing lutein content of egg yolk. Total carotenoid content had a poor relationship with lightness (R-2=0.13; P>0.05) and yellowness (R-2=0.12; P>0.05) of the yolk. It may be concluded that increased lutein is potentially responsible for an increased RYCF score and redness (a*), but decreased yellowness (b*) and lightness (L*), of egg yolk.},
  language  = {en}
}
@article{KhalilRailaAlietal.2012,
  author    = {Khalil, Mahmoud and Raila, Jens and Ali, Mostafa and Islam, Khan M. S. and Schenk, Regina and Krause, Jens-Peter and Schweigert, Florian J. and Rawel, Harshadrai Manilal},
  title     = {Stability and bioavailability of lutein ester supplements from Tagetes flower prepared under food processing conditions},
  series = {Journal of functional food},
  volume    = {4},
  journal   = {Journal of functional food},
  number    = {3},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1756-4646},
  doi       = {10.1016/j.jff.2012.03.006},
  pages     = {602 -- 610},
  year      = {2012},
  abstract  = {Tagetes spp. belongs to the Asteraceae family. It is recognized as a major source of lutein ester (lutein esterified with fatty acids such as lauric, myristic and palmitic acids), a natural colorant belonging to the xanthophylls or oxygenated carotenoids. Four species of Tagetes flower (Tagetes tenuifolia, Tagetes erecta, Tagetes patula, and Tagetes lucida) were used to extract lutein and lutein esters with three different methods. The results showed that T. erecta, type "orangeprinz", is the richest source of lutein esters (14.4 +/- 0.234 mg/g) in comparison to other Tagetes spp. No significant differences between extractions of lutein esters with medium-chain triacylglycerols (MCT) oil, orange oil or solvent (hexane/isopropanol) could be observed. MCT oil also improved stability of lutein esters at 100 degrees C for 40 min. Emulsification of MCT oil improved the stability of lutein ester extract against UV light at 365 nm for 72 h. Finally, an emulsion was prepared under food processing conditions, spray dried and its bioavailability investigated in a preliminary human intervention study. The results show a lower resorption, but further data suggest improvements in implementation of such supplements. (c) 2012 Elsevier Ltd. All rights reserved.},
  language  = {en}
}