The effect of atmospheric media variation on liquid characteristics of torrefied coffee beans

Abstract

Pollution and carbon footprints are still issues in the coffee roasting industry. Therefore, torrefaction of coffee beans with volatile condensation and atmospheric media variations can be an alternative to the roasting process. This study aims to determine the effect of the atmospheric media variations on the liquid characteristics resulting from coffee bean torrefaction using Gayo arabica green beans. The test was conducted with a fixed bed torrefier at 235 ± 8 °C for 60 min with a variety of oxidative air atmospheric media and non-oxidative inert gas (N2 &Ar) at a rate of 1 l/min. The torrefied coffee beans were cooled and removed at 50 °C. The volatile gas flowed to the condenser and flash tank, separating the liquid and uncondensed gas. The liquid yield was calculated based on mass data and its characteristics measured in pH, density and viscosity. Furthermore, FTIR and GC-MS methods were used to detect functional groups and the content of the compounds. The results showed that atmospheric media variations caused differences in yield for samples of liquid and air atmospheric of 11 % > N2: 10 % > Ar: 7 %. Insignificant differences were found in the value of pH, density and viscosity. These were also shown in functional groups and the content of liquid compounds. The difference was between samples using oxidative and non-oxidative gases and in between inert gases. Meanwhile, the variations in atmospheric media, impact differences in the number, type and amount of compound content.