@article{FigueroaCamposGKTKruizengaSaguTchewonpietal.2022,
  author    = {Figueroa Campos, Gustavo Adolfo and G. K. T. Kruizenga, Johannes and Sagu Tchewonpi, Sorel and Schwarz, Steffen and Homann, Thomas and Taubert, Andreas and Rawel, Harshadrai Manilal},
  title     = {Effect of the post-harvest processing on protein modification in green coffee beans by phenolic compounds},
  series = {Foods : open access journal},
  volume    = {11},
  journal   = {Foods : open access journal},
  edition   = {2},
  publisher = {MDPI},
  address   = {Basel, Schweiz},
  issn      = {2304-8158},
  doi       = {10.3390/foods11020159},
  pages     = {19},
  year      = {2022},
  abstract  = {The protein fraction, important for coffee cup quality, is modified during post-harvest treatment prior to roasting. Proteins may interact with phenolic compounds, which constitute the major metabolites of coffee, where the processing affects these interactions. This allows the hypothesis that the proteins are denatured and modified via enzymatic and/or redox activation steps. The present study was initiated to encompass changes in the protein fraction. The investigations were limited to major storage protein of green coffee beans. Fourteen Coffea arabica samples from various processing methods and countries were used. Different extraction protocols were compared to maintain the status quo of the protein modification. The extracts contained about 4-8 µg of chlorogenic acid derivatives per mg of extracted protein. High-resolution chromatography with multiple reaction monitoring was used to detect lysine modifications in the coffee protein. Marker peptides were allocated for the storage protein of the coffee beans. Among these, the modified peptides K.FFLANGPQQGGK.E and R.LGGK.T of the α-chain and R.ITTVNSQK.I and K.VFDDEVK.Q of β-chain were detected. Results showed a significant increase (p < 0.05) of modified peptides from wet processed green beans as compared to the dry ones. The present study contributes to a better understanding of the influence of the different processing methods on protein quality and its role in the scope of coffee cup quality and aroma. View Full-Text},
  language  = {en}
}
@article{AliHomannKhaliletal.2013,
  author    = {Ali, Mostafa and Homann, Thomas and Khalil, Mahmoud and Kruse, Hans-Peter and Rawel, Harshadrai Manilal},
  title     = {Milk whey protein modification by coffee-specific phenolics effect on structural and functional properties},
  series = {Journal of agricultural and food chemistry : a publication of the American Chemical Society},
  volume    = {61},
  journal   = {Journal of agricultural and food chemistry : a publication of the American Chemical Society},
  number    = {28},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0021-8561},
  doi       = {10.1021/jf402221m},
  pages     = {6911 -- 6920},
  year      = {2013},
  abstract  = {A suitable vehicle for integration of bioactive plant constituents is proposed. It involves modification of proteins using phenolics and applying these for protection of labile constituents. It dissects the noncovalent and covalent interactions of beta-lactoglobulin with coffee-specific phenolics. Alkaline and polyphenol oxidase modulated covalent reactions were compared. Tryptic digestion combined with MALDI-TOF-MS provided tentative allocation of the modification type and site in the protein, and an in silico modeling of modified beta-lactoglobulin is proposed. The modification delivers proteins with enhanced antioxidative properties. Changed structural properties and differences in solubility, surface hydrophobicity, and emulsification were observed. The polyphenol oxidase modulated reaction provides a modified beta-lactoglobulin with a high antioxidative power, is thermally more stable, requires less energy to unfold, and, when emulsified with lutein esters, exhibits their higher stability against UV light. Thus, adaptation of this modification provides an innovative approach for functionalizing proteins and their uses in the food industry.},
  language  = {en}
}
@article{AliHomannKreiseletal.2012,
  author    = {Ali, Mostafa and Homann, Thomas and Kreisel, Janka and Khalil, Mahmoud and Puhlmann, Ralf and Kruse, Hans-Peter and Rawel, Harshadrai Manilal},
  title     = {Characterization and modeling of the interactions between coffee storage proteins and phenolic compounds},
  series = {Journal of agricultural and food chemistry : a publication of the American Chemical Society},
  volume    = {60},
  journal   = {Journal of agricultural and food chemistry : a publication of the American Chemical Society},
  number    = {46},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0021-8561},
  doi       = {10.1021/jf303372a},
  pages     = {11601 -- 11608},
  year      = {2012},
  abstract  = {This study addresses the interactions of coffee storage proteins with coffee-specific phenolic compounds. Protein profiles, of Coffea arabica and Coffea canephora (var robusta) were compared. Major Phenolic compounds were extracted and analyzed with appropriate methods. The polyphenol-protein interactions during protein extraction have been addressed by different analytical setups [reversed-phase high-performance liquid chromatography (RP-HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), and Trolox equivalent antioxidant capacity (TEAC) assays], with focus directed toward identification of covalent adduct formation. The results indicate that C. arabica proteins are more susceptible to these interactions and the polyphenol oxidase activity seems to be a crucial factor for the formation of these addition products. A tentative allocation of the modification type and site in the protein has been attempted. Thus, the first available in silico modeling of modified coffee proteins is reported. The extent of these modifications may contribute to the structure and function of "coffee melanoidins" and are discussed in the context of coffee flavor formation.},
  language  = {en}
}