Vacuum drying of peeled coffee cherry beans: Drying kinetics and physiological effects




The drying process is a very important step for a large part of the grains, because, in general, these products are harvested with high moisture contents, which favors rapid deterioration. Several physical, physiological and biochemical changes can occur in the grains during drying. Physiological analyzes have been used as indicators of this quality. Alternatives that allow reducing the drying time without changing the quality of the coffee are required. Considering that vacuum drying provides smaller exposure times, by reducing the vapor pressure, this study aimed at assessing the drying kinetics and the physiological effects caused in peeled coffee beans, when subjected to vacuum drying. The fruits were harvested at their maximum maturation potential and submitted to the removal of the peel by a mechanical process. The peeled fruits were dried in a vacuum oven under absolute pressures of 147, 447 and 747 mmHg (at
the local atmospheric pressure of 747 mmHg) at 40 °C, until reaching 11 kg of water/kg of material. After drying, the grains were stored under controlled conditions of refrigerated air (10 °C and 50% relative humidity) for 30 days, standardizing drying. Coffee grains were evaluated by scanning electron microscopy and drying kinetics. For the adjustment of the mathematical models, a non-linear regression analysis was performed using the Quasi-Newton method. It was concluded that the use of vacuum significantly reduced the drying time. The model that best fit was Page Modified. Drying under absolute pressure of 447 mmHg was an interesting alternative to the conventional one, as it did not damage the cellular structures of the grain, which was similar to that obtained at the local pressure of 747 mmHg. However, the lower pressure, 147 mmHg, led to significant changes in grain quality.

Key words: Absolute pressures; Mathematical models; Scanning Electron Microscopy (SEM).


AFONSO JUNIOR, P. C. et. al. Propriedades termofísicas dos frutos e sementes de café: Determinação e modelagem. Revista Brasileira de Armazenamento, 2(4):9-15, 2002.

ALVES, G. E. et al. Drying kinetics of natural coffee for different temperatures and low relative humidity. Coffee Science, 8(2):226-236, 2013.

BRASIL. Ministério da Agricultura, Pecuária e Abastecimento. Regras para análise de sementes. Brasília: MAPA/ACS, 300p. 2009.

BORÉM, F. M.; ANDRADE, E. T.; ISQUIERDO, E. P. Coffee drying. In: BORÉM, F. M. (Ed.). Handbook of coffee post-harvest technology. Georgia: Norcross:(1)94-118, 2014.

BORÉM, F. M. et al. Microscopia eletrônica de varredura de grãos de café submetidos a diferentes formas de processamento e secagem. Coffee Science, 8(2):227-237, 2013.

BORÉM, F. M.; REINATO, C. H. R.; ANDRADE, E. T. Secagem do café. In: BORÉM, F. M. (Ed.). Pós-colheita do café. Lavras: Editora UFLA, 7 (1): 203-240, 2008.

CALLAGHAN, J. R. O.; MENZIES, D. J.; BAILEY, P. H. Digital simulation of agricultural drier performance. Journal of Agricultural Engineering Research, 16(3):223-244, 1971.

DONG, W. et al. Effect of different drying techniques on bioactive components, fatty acid composition, and volatile profile of robusta coffee beans. Food Chemistry, 234:121-130, 2017.

DOYMAZ, I. The kinetics of forced convective air-drying of pumpkin slices. Journal of Food Engineering, 79(1):243-249, 2007.

ERTEKIN, C.; FIRAT, M. Z. A comprehensive review of thin layer drying models used in Agricultural products. Critical Reviews in Food Science and Nutrition, 57:701-717, 2017.

FERREIRA, L. F. D. et al. Modelagem matemática da secagem em camada delgada de bagaço de uva fermentado. Pesquisa Agropecuaria Brasileira, 47(6):855-862, 2012.

FIORENTIN, L. D. et al. Análise da secagem do bagaço de laranja em camada fina utilizando modelos semi-teóricos e empíricos. Engevista, 14(1):22-33, 2012.

HENDERSON, S. M.; PABIS, S. Temperature effect on drying coefficient. Journal of Agricultural Engineering Research, 6(3):169-174, 1961.

HENDERSON, S. M. Progress in developing the thin layer drying equation. Transactions of the ASAE, 17(6):1167-1168, 1974.

HORECKI, A. T. et al. Comparative drying of cornelian cherries: Kinetics modeling and physico-chemical properties. Journal of Food Processing and Preservation, 6(8):13, 2018.

ISQUIERDO, E. P. et al. Drying kinetics and quality of natural coffee. Transactions of the ASABE, 56(3):1003-1010, 2013.

KASSEM, A. S. Comparative studies on thin layer drying models for wheat. Int. Congress on Agricultural Mechanization and Enerdy, 6(2), 1998.

KAYACAN, S.; SAGDIC, O.; DOYMAZ, I. Effects of hot-air and vacuum drying on drying kinetics, bioactive compounds and color of bee pollen. Journal of Food Measurement and Characterization, 12:1274-1283, 2018.

LEE, J. H.; KIM, H. J. Vacuum drying kinetics of Asian white radish (Raphanus sativus L.) slices. LWT - Food Science and Technology, 42(1):180-186, 2009.

LIVRAMENTO, K. G. do. et al. Proteomic analysis of coffee grains exposed to different drying process. Food Chemistry, 221:1874-1882, 2017.

MARTINAZZO, A. P. et al. Modelagem matemática e parâmetros qualitativos da secagem de folhas de capim limão [Cymbopogon citratus]. Revista Brasileira de Plantas Medicinais, 12(4):488-498, 2010.

MCDONALD, M. B. Seed deterioration: Physiology, repair and assessment. Seed Science and Technology, Bassersdorf, 27(1):177-237, 1999.

MIDILLI, A.; KUCUK, H.; YAPAR, Z. A. New model for single-layer drying. Drying Technology, 20(5):1503-1513, 2002.

OLIVEIRA, P. D. et al. Aspectos fisiológicos de grãos de café, processados e secados de diferentes métodos, associados à qualidade sensorial. Coffee Science, 8(2):211-220, 2013.

ORIKASA, T. et al. Impacts of hot air and vacuum drying on the quality attributes of kiwifruit slices. Journal of Food Engineering,125:51-58, 2014.

ÖZDEMIR, M.; ONUR DEVRES, Y. Thin layer drying characteristics of hazelnuts during roasting. Journal of Food Engineering, 42(4):225-233, 1999.

PONTES, S. F. O. et al. Determinação das curvas de secagem em camada delgada de pimenta de cheiro (Capsicum chinese) a diferentes temperaturas. Revista Brasileira de Produtos Agroindustriais, 11( 2):143-148, 2009.

SAATH, R. et al. Microscopia eletrônica de varredura do endosperma de café ( Coffea arabica L.) durante o processo de secagem. Ciência e Agrotecnologia, 34(2):196-203, 2010.

SIQUEIRA, V. C. et al. Drying kinetics of processed natural coffee with. Coffee Science, 12(3):400-409, 2017.

STATSOFT. Statistica for Windows: software system for data-analysis. Version 8.0 Tulsa Statsoft, 2004.

TAVEIRA, J. H. S. da. et al. Perfis proteicos e desempenho fisiológico de sementes de café submetidas a diferentes métodos de processamento e secagem. Pesquisa Agropecuaria Brasileira, 47(10):1511-1517, 2012.

WANG, C. Y.; SINGH, R. P. A single layer drying equation for rough rice. ASAE, 78-3001, p. 33, 1978.

WAUGHON, T. G. M.; PENA, R. S. da. Modelagem da secagem em camada delgada da fibra residual do abacaxi. Boletim Centro de Pesquisa de Processamento de Alimentos, 27(2):257-270, 2009.

ZHANG, Z.; LIU, Y.; CHE, L. Effects of different drying methods on the extraction rate and qualities of oils from demucilaged flaxseed. Drying Technology, 5(3):1-11, 2018.




How to Cite

ROCHA, H. A.; CORREA, J. L. G. .; BORÉM, F. M. . Vacuum drying of peeled coffee cherry beans: Drying kinetics and physiological effects. Coffee Science - ISSN 1984-3909, [S. l.], v. 16, p. e161921, 2022. DOI: 10.25186/.v16i.1921. Disponível em: Acesso em: 30 sep. 2022.