Exploratory and discriminative studies of commercial processed Brazilian coffees with different degrees of roasting and decaffeinated

Juliano Souza Ribeiro,Reinaldo Francisco Teófilo,Terezinha De Jesus Garcia Salva,Fabio Augusto,Marcia Miguel Castro Ferreira

doi:10.1590/s1981-67232013005000025

Abstract

The fingerprints of the volatile compounds of 21 commercial Brazilian coffee samples submitted to different industrial processing i.e. decaffeinated or different roasting degrees (traditional and dark) were studied. The volatiles were collected by headspace solid phase microextraction (HS-SPME) and analyzed by GC-FID and GC-MS. The chromatographic data matrices (fingerprints) obtained were explored by the principal component analysis (PCA) and partial least squares - discriminative analysis (PLS-DA). Initially the chromatographic profiles were aligned by the algorithm correlation optimized warping (COW). The PCA showed the discrimination of the decaffeinated coffees from the others with both the SPME fibres used. This separation probably occurred due to the loss of some volatile precursors during the decaffeination process, such as sucrose. For both the fibres tested, PDMS/DVB and CX / PDMS SPME, the PLS-DA models correctly classified 100% of the samples according to their roasting degree: (medium and dark), the main differences being the concentrations of some of the volatile compounds such as 2-methyl furan, 2-methylbutanal, 2,3-pentanedione, pyrazine, 2-carboxyaldehyde pyrrole, furfural and 2-furanmethanol.

Highlights

Nowadays, world coffee consumers are looking for specific coffee tastes, and the food industries have had to invest into and create a greater variety of processed products from the same raw material
The volatile compounds obtained from the roasted coffee headspaces, extracted with the two Solid Phase Microextraction (SPME) fibres, were detected by GC-MS analysis and identified by comparing their fragmentations with the NIST data bank and some recently published papers (RIBEIRO et al, 2009, 2010)
The principal component analysis (PCA) was applied to the pre-treated data set in order to get an insight into which peaks could be responsible for the discrimination of the decaffeinated samples from the others

Summary

Introduction

World coffee consumers are looking for specific coffee tastes, and the food industries have had to invest into and create a greater variety of processed products from the same raw material. Amongst these processed coffee products originating from different coffee species (Coffea arabica and Coffea canephora), coffees with differentiated roasting degrees, decaffeination and freeze-drying, amongst others, are already present on the market. Trigonelline, for example, forms pyridine and pyrrole derivatives by degradation. The pyrazines are formed by degradation of carbohydrates and chlorogenic acids are responsible for the formation of phenolic derivatives. Furan derivatives are formed by glycides and sucrose and the lipids are the main class forming aldehydes, ketones, aliphatic alcohols and aromatic compounds

Objectives

Methods

Results

Conclusion