Characterization of Roasted Coffea arabica Species by the Relationship Between Caffeine and Diterpenes Contents

Abstract Commercial roasted and ground coffees are usually blends of Coffea arabica and Coffea canephora. Considering the differences in price and sensory characteristics between these two species, the identification of the presence of each species in commercial blends is of great interest. The aim of this study was to describe typical profiles of caffeine and diterpenes (kahweol and cafestol) contents and the ratios among these compounds to support the characterization of Coffea species in roasted coffees. 32 good cup quality Brazilian C. arabica coffees (from coffee quality contests) produced using different postharvest treatments were studied. All analysis were performed by HPLC. Higher ranges were observed in diterpene contents - kahweol varied from 1.75 to 10.68 g/kg (coefficient of variation of 510%) and cafestol from 1.76 to 9.66 g/kg (449%) - than caffeine, that varied from 5.1 to 16.2 g/kg (coefficient of variation of 218%). Wide ranges of the kahweol/cafestol ratio (0.63 to 2.77) and the caffeine/kahweol ratio (0.84 to 5.15) were also observed. Hence it was proposed the additional use of a new parameter, the ratio of caffeine/sum of diterpenes (kahweol + cafestol) that presents values from 0.54 to 2.39. The results indicated that the combined use of these parameters could be a potential tool for discriminating Coffea species in blends of roasted and ground coffee. It was proposed as potentially indicative of C. arabica: values of kahweol/cafestol ratio above 0.50, associated with caffeine/kahweol ratio lower than 5.50 and caffeine/sum of diterpenes ratio lower than 2.50.

Ochratoxigenic fungi associated with green coffee beans (Coffea arabica L.) in conventional and organic cultivation in Brazil

The genera Aspergillus comprises species that produce mycotoxins such as aflatoxins, ochratoxins and patulin. These are cosmopolitan species, natural contaminants of agricultural products. In coffee grains, the most important Aspergillus species in terms of the risk of presenting mycotoxins belong to the genera Aspergillus Section Circumdati and Section Nigri. The purpose of this study was to assess the occurrence of isolated ochratoxigenic fungi of coffee grains from organic and conventional cultivation from the South of Minas Gerais, Brazil, as well as to evaluate which farming system presents higher contamination risk by ochratoxin A (OTA) produced by fungi. Thirty samples of coffee grains (Coffea arabica L.) were analysed, being 20 of them of conventional coffee grains and 10 of them organic. The microbiological analysis was done with the Direct Plating Technique in a Dichloran Rose Bengal Chloramphenicol Agar (DRBC) media. The identification was done based on the macro and micro morphological characteristics and on the toxigenic potential with the Plug Agar technique. From the 30 samples analysed, 480 filamentous fungi of the genera Aspergillus of the Circumdati and Nigri Sections were isolated. The ochratoxigenic species identified were: Aspergillus auricoumus, A. ochraceus, A. ostianus, A. niger and A. niger Aggregate. The most frequent species which produces ochratoxin A among the isolated ones was A. ochraceus, corresponding to 89.55%. There was no significant difference regarding the presence of ochratoxigenic A. ochreceus between the conventional and organic cultivation systems, which suggests that the contamination risk is similar for both cultivation systems.