(17b) Recovery of Vapors and Organic Compounds during Industrial Coffee Roasting

Brazil is the largest coffee producer and exporter in the world, producing approximately 68 million sacks a year. To supply the required consumption, roasting is done industrially on a large scale. The time and degree of roasting are not only related to the temperature profile of the coffee, but also to higher extraction levels. During roasting, several factors are responsible for the formation of aromatic and volatile compounds. More than 1000 components have been identified, of which almost 850 are volatile aromatic compounds such as furans, pyranes, ketones, and phenols, among others. The volatile compounds are not only present in roasted coffee; during roasting several volatile compounds are lost. Within this context, the present work proposed to evaluate a procedure that allows the recovery, in a semi-industrial scale, of the volatile compounds released to the atmosphere through the stacks and to associate the degree of recovery with the coffee roasting levels through condensation. To execute this work, a partnership was made with a small coffee production company where the sizing of the flavor and vapor recovery system was based. Two gas capture systems were developed to be installed in the chimney with exhaustion capacity of approximately 40 m³/h. A total of eleven roastings were conducted, nine of arabica beans with 10 kg and two conilon beans with 5 kg. The collection time at the roaster ranged from 8 to 15 minutes. The volume of condensate recovered was approximately 9 to 16 mL/kg of green coffee. The results obtained for the total organic carbon concentration showed values between 0.15 and 0.35 g/kg of green coffee. The pH found in all samples presented acidity with a range of 2.4 to 7.0. Samples were selected for the identification of the components where it was possible to verify for the Arabica-type coffee an amount of approximately 30% of acetic acid, 26% of furfuryl alcohol, 20% of hydroxyacetone and 15% of caffeine. The compounds identified for the conilon-type coffee was approximately 71% acetic acid, 14% caffeine, 12% furfuryl alcohol and 2.5% ethanol.

Keywords: roasting; condensation; volatile aromatic compounds; recovery.