Low-field (1)H NMR spectroscopy for distinguishing between arabica and robusta ground roast coffees.
This work reports a new screening protocol for addressing issues of coffee authenticity using low-field (60MHz) bench-top (1)H NMR spectroscopy. Using a simple chloroform-based extraction, useful spectra were obtained from the lipophilic fraction of ground roast coffees. It was found that 16-O-methylcafestol (16-OMC, a recognized marker compound for robusta beans) gives rise to an isolated peak in the 60MHz spectrum, which can be used as an indicator of the presence of robusta beans in the sample. A total of 81 extracts from authenticated coffees and mixtures were analysed, from which the detection limit of robusta in arabica was estimated to be between 10% and 20% w/w. Using the established protocol, a surveillance exercise was conducted of 27 retail samples of ground roast coffees which were labelled as "100% arabica". None were found to contain undeclared robusta content above the estimated detection limit.
Analytical Sciences Unit, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Electronic address: marianne.defernez@ifr.ac.uk.
Marianne
M
Defernez
Analytical Sciences Unit, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Electronic address: ella.wren@ifr.ac.uk.
Ella
E
Wren
Analytical Sciences Unit, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Electronic address: andrew.watson@ifr.ac.uk.
Andrew D
AD
Watson
Analytical Sciences Unit, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Electronic address: yvonne.gunning@ifr.ac.uk.
Yvonne
Y
Gunning
Analytical Sciences Unit, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Electronic address: ian.colquhoun@ifr.ac.uk.
Ian J
IJ
Colquhoun
Analytical Sciences Unit, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Electronic address: gwenaelle.legall@ifr.ac.uk.
Gwénaëlle
G
Le Gall
Oxford Instruments, Tubney Woods, Abingdon, Oxford OX13 5QX, UK. Electronic address: David.Williamson@oxinst.com.
David
D
Williamson
Analytical Sciences Unit, Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK. Electronic address: kate.kemsley@ifr.ac.uk.
E Kate
EK
Kemsley
D003069:Coffee / Q000737:chemistry* / Q000145:classification; D004224:Diterpenes / Q000032:analysis*; D005504:Food Analysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D012639:Seeds / Q000737:chemistry* / Q000145:classification
C000600293:16-O-methylcafestol; D003069:Coffee; D004224:Diterpenes
Authenticity; Coffee; NMR; Spectroscopy