Chemical Discrimination of Arabica and Robusta Coffees by Fourier Transform Raman Spectroscopy

Abstract

This article deals with the potential of Fourier transform (FT) Raman spectroscopy in discrimination of botanical species of green and roasted coffees. There are two species of commercial importance: Coffea arabica (arabica) and Coffea canephora (robusta). It is recognized that they differ in their lipid fraction, especially in the content of the diterpene kahweol, which is present at 0.1-0.3% dry matter basis in arabica beans and only in traces (<0.01%) in robusta. The visual examination of the Raman spectra of the lipid fraction extracted from arabica, robusta and liberica samples shows differences in the mid-wavenumbers region: arabica spectra have two characteristic scattering bands at 1567 and 1478 cm(-1). The spectrum of the pure kahweol shows the same bands. Principal component analysis is applied to the spectra and reveals clustering according to the coffee species. The first principal component (PC1) explains 93% of the spectral variation and corresponds to the kahweol concentration. Using the PC1 score plot, two groups of arabica can be distinguished as follows: one group with high kahweol content and another group with low kahweol content. The first group includes samples coming from Kenya and Jamaica; the second group includes samples from Australia. The main difference between these coffees is that those from Kenya and Jamaica are well-known for growing at a high altitude whereas those ones from Australia are grown at a low altitude. To our knowledge, the application of Raman spectroscopy has never been used in coffee analysis.

Teores de compostos bioativos em cafés torrados e moídos comerciais

“…Para o café arábica, são descritos teores de caveol e cafestol entre 0,10 e 0,87 g/100 g e entre 0,10 e 0,70 g/100 g de café torrado, respectivamente. 14,16,[40][41][42][43] Para o café conilon, que possui menor teor de lipídios, é reportada concentração de cafestol na faixa de 0,08 a 0,37 g/100 g de café torrado. 14,16,41,42 Existe, ainda, controvérsia quanto à presença de caveol em café conilon.…”

“…9 Os cafés arábica e conilon podem ser caracterizados pelos teores de cafeína, trigonelina, ácido nicotínico, ácidos clorogênicos e alcoóis diterpênicos (caveol e cafestol). 8,13,14 A influência desses compostos específicos na saúde tem sido relatada, destacando-se, além do valor nutricional (ácido nicotínico), sua correlação com a atividade antioxidante e a redução do risco de doenças crônicas degenerativas (cafeína, trigonelina e ácidos clorogênicos). Para diterpenos são descritos efeitos hepatoprotetor e anticarcinogênico, mas também a elevação da taxa de colesterol, atribuída ao cafestol.…”

Green and roasted arabica coffees differentiated by ripeness, process and cup quality via electrospray ionization mass spectrometry fingerprinting

“…To search for faster methods for coffee discrimination based on fingerprinting analysis, NIR and NMR studies were also applied. 9,10 A new and potential technique is direct infusion electrospray ionization mass spectrometry (ESI-MS). ESI-MS employs little sample preparation and gives immediate compositional information for ESI-ionizable compounds.…”

Stability across environments of the coffee variety near infrared spectral signature

“…For instance, this technique has been used to authenticate asparagus cultivars (Perez et al, 2001). The chemometric discrimination of the two coffee species C. arabica and Coffea canephora with NIRS approaches (Downey and Boussion, 1996;Esteban-Diez et al, 2007) or Raman spectroscopy (Rubayiza and Meurens, 2005), have been tested with success. On the basis of NIR spectra treatment, Bertrand et al, 2005 investigated ways of discriminating between modern introgressed varieties and traditional ones.…”