16-O-methylcafestol is present in ground roast Arabica coffees: Implications for authenticity testing

Yvonne Gunning, Marianne Defernez, Andrew D. Watson, Niles Beadman, Ian J. Colquhoun, Gwenaelle Le Gall, Mark Philo, Hollie Garwood, David Williamson, Aaron P. Davis, E. Kate Kemsley

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Abstract

High-field and low-field proton NMR spectroscopy were used to analyse lipophilic extracts from ground roast coffees. Using a sample preparation method that produced concentrated extracts, a small marker peak at 3.16 ppm was observed in 30 Arabica coffees of assured origin. This signal has previously been believed absent from Arabicas, and has been used as a marker for detecting adulteration with robusta. Via 2D 600 MHz NMR and LC-MS, 16-O-methylcafestol and 16-O-methylkahweol were detected for the first time in Arabica roast coffee and shown to be responsible for the marker peak. Using low-field NMR, robusta in Arabica could be detected at levels of the order of 1-2% w/w. A surveillance study of retail purchased "100% Arabica" coffees found that 6 out of 60 samples displayed the 3.16 ppm marker signal to a degree commensurate with adulteration at levels of 3-30% w/w.

Original languageEnglish
Pages (from-to)52-60
Number of pages9
JournalFood Chemistry
Volume248
Early online date11 Dec 2017
DOIs
Publication statusPublished - 15 May 2018

Keywords

  • NMR
  • Spectroscopy
  • Low-field
  • Coffee
  • Adulteration
  • Species
  • Arabica
  • Robusta
  • Authentication
  • H-1-NMR SPECTROSCOPY
  • GENETIC DIVERSITY
  • DITERPENE ESTERS
  • CANEPHORA
  • ETHIOPIA
  • MARKERS
  • KAHWEOL
  • L.
  • QUANTIFICATION
  • IDENTIFICATION

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