Cafeina

ARTICLE IN PRESS

LWT 40 (2007) 1300–1303
www.elsevier.com/locate/lwt

Research Note

A comparative evaluation of methodologies for water content
determination in green coffee
Juliana C.F. Mendonc a, Adriana S. FrancaÃ, Leandro S. Oliveira
´cleo de Pesquisa e Desenvolvimento em Cafe Departamento de Engenharia Quımica/UFMG, R. Espırito Santo, 6 andar, 30160-030,
´,
´
´
Nu
BeloHorizonte, MG, Brazil
Received 7 April 2006; received in revised form 20 August 2006; accepted 28 August 2006

Abstract
The main objective of this study was to compare methods for mass loss evaluation in green coffee to water content determination by
Karl Fischer titration (KFT). The following methodologies were tested: (i) ISO 6673 (oven drying at 105 1C for 16 h); (ii) the reference
methodemployed by the Brazilian Agriculture Ministry (oven drying at 105 1C for 24 h)—BRAMw, employing whole beans and
BRAMg, employing ground beans; and (iii) infrared drying (IRD). Reference oven drying methodologies ISO 6673 and BRAMw
presented results statistically equivalent (p40:05) to those from KFT in the moisture content range that is of interest for green coffee
commercialization (8–13 g/100g), whereas IRD results were lower than those for KFT. ISO 6673 and BRAMw also presented the highest
values of correlation coefficients to KFT. Differences in moisture content determination became more significant for lower moisture
content values (4–7 g/100 g), probably due to loss of organic volatile substances during drying and occurrence of moisture loss during
sample grinding.
r 2006Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.
Keywords: Green coffee; Moisture content; Karl Fischer; Oven drying; Infrared drying

1. Introduction
Water content determination is the most frequent
analysis performed in food products and it is quite
significant in many aspects (Isengard, 2001). Nearly every
food product contains water and thisparameter affects
many others, both of physical and chemical nature.
Evaluation of most chemical parameters is based on dry
mass and therefore water content must be measured. Also,
water content affects microorganism growth and enzymatic
activity, affecting the stability and shelf-life of foodstuffs.
As different methods are available for water determination,
the question to which one is moreappropriate still remains.
The problem becomes more difficult due to the facts that
water in food is distributed in different bonding states and
that both the product itself (dry matrix) and its water
content affect method performance (Isengard, 2001;
Yazgan, Bernreuther, Ulberth, & Isengard, 2006).
ÃCorresponding author. Tel.: +55 31 32381777; fax: +55 31 32381789.

E-mail address:franca@deq.ufmg.br (A.S. Franca).

Water content determination is critical for evaluation of
green coffee quality. It affects mold growth, mycotoxin
production, fermentation, physical, chemical and sensory
parameters. As water is quite cheap compared to coffee, its
amount is also interesting from a commercial point of view.
Thus, a precise knowledge of water content in green coffee
isfundamental to ensure quality, as it should be in the
range of 8–13% to allow for safe transportation and
storage (Clarke, 1985; Reh, Gerber, Prodolliet, & Vuataz,
2006).
Reference methods for water content determination in
green coffee are based on oven drying. Such methods do
not measure water content itself, but the mass loss under
the heating conditions employed, which includes other
volatilesubstances. The term moisture content is usually
employed for this type of measurements, even though the
term mass loss should be most accurate (Isengard, 2001).
The major drawback associated to oven drying methods is
that they usually require long measuring times, which can
be overcome by using infrared dryers. However, depending
on heating conditions, some level of decomposition and...