Effect of mild roasting on Arabica and Robusta coffee beans contamination with polycyclic aromatic hydrocarbons

Abstract

The aim of this research was to establish the effect of mild roasting on coffee beans contamination level by polycyclic aromatic hydrocarbons (PAHs). The materials investigated were green Arabica and Robusta coffee beans imported from different countries, as well as those already roasted. The experiment was carried out in a coffee-roasting plant, with the use of an electric coffee roaster, at the temperature of 125–135 °C for 25–26 min. PAHs analysis was conducted by means of high-performance liquid chromatography with fluorescence and diode array detectors (HPLC-FLD/DAD). Results had been verified by means of gas chromatography with mass spectrometry. Contamination level for 19 PAHs, 15 of which were heavy PAHs included on the list of European Union Scientific Committee in Food, varied from 4.29 to 16.17 µg/kg in roasted coffee beans, whereas in green coffee beans varied from 8.66 to 76.63 µg/kg. The results of statistical analysis showed that the contamination level in roasted coffee beans was significantly lower than that in green beans. The applied parameters of roasting did not lead to the occurrence of conditions in which PAHs, especially heavy ones, would possibly be formed. On the contrary, the roasting process itself had significantly reduced the PAHs content in the final product. The reason for this phenomenon was relatively high volatility of light PAHs.

Polycyclic aromatic hydrocarbons in coffee samples: Enquiry into processes and analytical methods

“…As PAHs are ubiquitous pollutant compounds, their occurrence in green coffee beans is mainly due to environmental contamination, and the various studies that have been reviewed herein have indicated that, when present, PAHs content in such matrices is low. An overview of PAHs amount in coffee of different origins can be found in an interesting work by Ciecierska et al (2019), which demonstrated that Kenya and Tanzania (both Eastern Africa) for Arabica green samples, and the Ivory Coast (south coast of West Africa) and Cameroon (Central Africa) for Robusta samples, were the most contaminated.…”

“…4). Moreover, an electron Table 2 Effect of mild roasting conditions on samples from different countries: green vs roasted coffee beans PAHs contamination level, standard deviations are not reported (Ciecierska et al, 2019 spin resonance (ESR) experiment led to the hypothesis that free radicals may be engaged in this pathway; as shown in Fig. 4, the ESR signal intensity were increased in the coffee model system when amino acids were added and results were correlated to the outcomes on the formation of nitro-PAHs.…”

“…Roasting method, degree and the desired characteristics of the final product are thus strictly related to PAHs generation in coffee. Ciecierska et al (2019) have recently studied how mild roasting conditions can affect PAHs contamination in their studies on green Arabica and Robusta coffee beans from different countries. Samples have been roasted with an electric heating system for 25-26 min at temperatures between 125 and 135 • C and results (see Table 3 for analytical conditions) showed that the contamination levels of 19 PAHs (15 of which belonging to the SCF list) were mainly due to the lighter analogues (PHE, ANT, FL and Pyr), while the mutagenic and carcinogenic heavy PAHs are present in low percentages (2-24%).…”

“…Nevertheless, the authors do not explicate the influence of their roasting procedure, at lower temperatures, on the organoleptic properties of coffee brews. In Table 2 we reported data as indicated by Ciecierska et al (2019), who consider Pyr and FL as light PAHs even if their atom mass units is slightly higher than 202 and they are formed by four aromatic rings.…”

Polycyclic Aromatic Hydrocarbons in Foods: Biological Effects, Legislation, Occurrence, Analytical Methods, and Strategies to Reduce Their Formation

“…Tfouni et al [72] reported no statistically significant difference in PAHs levels of coffee brews produced from beans roasted at different temperatures. Ciecierska et al [73] described that roasted coffee beans had significantly lower levels of contamination than green coffee beans, indicating that the roasting process can significantly reduce the levels of PAHs in the final product. This is attributed to the high volatility of light PAHs.…”