Impact of coffee species, post-harvesting treatments and roasting conditions on coffee quality and safety related compounds

The aim of this study was to investigate the effect of coffee species (Arabica and Robusta), post-harvesting methods (dry and wet process) and roasting conditions on concentrations of coffee safety-related compounds, such as acrylamide and furanic compounds, and volatile compounds related to coffee sensory quality, such as 3-methylbutanal and hexanal. Acrylamide content was determined through a HPLC-MS/MS, while as regards furanic compounds, 3-methylbutanal and hexanal, quantification was performed with a new HS-SPME-GC-MS method. Firstly, a content screening of these seven VOCs was performed in eight commercially available coffee samples to evaluate the concentration of these compounds in real coffee samples. The concentration of 3-methylbutanal in commercial samples was between 18.4 and 77.7 mg kg−1, for hexanal between 0.03 and 0.2 mg kg−1, for furanic compounds between 694.1 and 3633.3 mg kg−1. The quantitative analysis on experimental coffee samples showed that the concentration of acrylamide decreased with stronger roasting conditions (ranged between 0.184 and 0.420 mg kg−1), while the levels of 3-methylbutanal, hexanal and furanic compounds had an oscillatory trend when the roasting degree increased. The highest concentrations of acrylamide (0.420 mg kg−1), hexanal (0.21 mg kg−1) and furanic compounds (3164.2 mg kg−1) were found in dried Arabica coffee samples with respect to all other samples, while 3-methylbutanal was found in dried Robusta coffee samples (20.7 mg kg−1). Moreover, wet-processing resulted to reduce the concentration of all monitored compounds. In conclusion, this study provided information about how to choose the proper species, post-harvesting method and roasting degree in order to mitigate the formation of toxic compounds during coffee production, thus avoiding their high dietary intake, and to prevent high levels of off-flavours. •Acrylamide content decreased with stronger roasting conditions.•3-methylbutanal, hexanal and furanic compounds showed an oscillatory trend.•Wet-processed coffees had the lowest concentrations of all monitored compounds.•The new HS-SPME-GC-MS method showed a good linearity and repeatability.