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

Food Chem. 2018 May 15:248:52-60. doi: 10.1016/j.foodchem.2017.12.034. Epub 2017 Dec 11.

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.

Keywords: Adulteration; Arabica; Authentication; Coffee; Low-field; NMR; Robusta; Species; Spectroscopy.

MeSH terms

  • Coffea / chemistry
  • Coffee / chemistry*
  • Diterpenes / analysis*
  • Food Analysis / methods*
  • Food Contamination / analysis
  • Limit of Detection
  • Magnetic Resonance Spectroscopy / methods*
  • Reproducibility of Results

Substances

  • 16-O-methylcafestol
  • Coffee
  • Diterpenes