Original Article Impact of ‘‘ecological’’ post-harvest processing on the volatile fraction of coffee beans: I. Green coffee Oscar Gonzalez-Rios a , Mirna L. Suarez-Quiroz a , Renaud Boulanger b , Michel Barel b , Bernard Guyot b , Joseph-Pierre Guiraud c , Sabine Schorr-Galindo c,Ã a Inst. Tecnol. de Veracruz, Miguel Angel de Quevedo 2779, Apdo. Postal 539, Veracruz, Mexico b CIRAD-CP TA80/16, 34398 Montpellier Cedex 5, France c UMR-IR2B cc023 Universite´Montpellier-II, Place Bataillon, 34095 Montpellier Cedex 5, France Received 16 January 2006; received in revised form 18 July 2006; accepted 19 July 2006 Abstract Green coffees produced by three variants of the wet process and a new ‘‘ecological’’ process were characterised for their aroma using combined headspace solid-phase microextraction/gas chromatography–mass spectroscopy (HS-SPME/GC–MS) and headspace solid- phase microextraction/gas chromatography–olfactometry (HS-SPME/GC–O). The effect of each post-harvest processing operation on the volatile fraction of the coffee produced was studied, particularly the effect of reducing the amount of water used in the process. The comparison of the green coffees from the different treatments revealed the importance of mucilage removal in distinguishing between the samples, and showed the merits of microbial mucilage removal in water to obtain coffees with a better aroma quality. These latter coffees were in fact characterised by pleasant and fruity aromatic notes, whereas those obtained after mechanical mucilage removal used in the ecological process were characterised by volatile compounds with an unpleasant note. Keywords: Green coffee; Post-harvest process; Aroma; Solid-phase microextraction (SPME); Gas chromatography–olfactometry (GC–O); Food safety 1. Introduction The method chosen to prepare green coffee in producing countries depends on the species grown, and on the conditions and resources in each production region; the way a green coffee is obtained therefore differs. The dry method, generally used for Robusta, is technologically simpler than the wet method, which is generally used for Arabica coffee beans. Coffee preparation by the latter method consists in removing the pulp and skin from the cherries (or beans) while still fresh. This method comprises several stages. The first stage involves machine-pulping of the drupes; at this stage, the beans are still covered with remnants of pulp. They have to be washed in a series of concrete tanks or in appropriate machines. ‘‘Controlled’’ fermentation is then carried out, which eliminates any mucilage still stuck to the beans and helps to ‘‘improve beverage flavour’’ with the production of microbial volatile compounds and microbial metabolites which are precursor of volatile formed during roasting and also by limiting spontaneous fermentation due to incomplete mucilage removal (Finney, 1989; Barel and Jacquet, 1994; Mburu, 1999; Puerta-Quintero, 1999). In addition to the two main types of post-harvest process, dry or wet, different treatments exist for these two processes that are specific to each production region. As the wet process involves more stages than the dry process, it also has the largest number of variants. For example, in Mexico, conventional post-harvest coffee processing uses microbial mucilage removal under dry conditions (Bailly et al., 1992a), while in Kenya, fermentation is often carried out in water to prevent overfermentation of the mucilage (Vincent, 1971; Mburu, 1999). In fact, the wet process, as its name implies, consumes large amounts of water and is a major source of pollution in countries where it is used (Bailly et al., 1992b). To solve this problem, producers using the wet method are increasingly using post-harvest processes that use less ARTICLE IN PRESS Ã Corresponding author. Tel.: +33 4 6714 4603; fax: +33 4 6714 4292. E-mail address: galindo@univ-montp2.fr (S. Schorr-Galindo).