posted on 2012-11-21, 00:00authored byMostafa Ali, Thomas Homann, Janka Kreisel, Mahmoud Khalil, Ralf Puhlmann, Hans-Peter Kruse, Harshadrai Rawel
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.