Kinetics of ochratoxin A destruction during coffee roasting

Abstract

In the present study, Coffea arabica was artificially contaminated with spores of toxigenic Aspergillus westerdijkiae. The contaminated coffee was roasted in a vertical spouted bed roaster at four different temperatures (180 °C, 200 °C, 220 °C and 240 °C) and three different time periods (5, 8 and 12 min), in order to obtain more accurate results for the development of the kinetic model for ochratoxin A (OTA). Chlorogenic acids (CGA) content during coffee roasting was also evaluated to investigate the effect of the heat employed to destroy OTA in these health promoting compounds. Coffee treated with spouted bed roasting significantly reduced the OTA level from 8% to 98%. The spouted bed roasting proved to be a very efficient procedure for OTA reduction in coffee, and its reduction depended directly on the degree of roasting. OTA degradation during coffee roasting followed first order reaction kinetics. Using the apparent activation energy of OTA degradation and the temperature-dependent reaction rate, there was a compliance with the Arrhenius equation. This model was capable of predicting the thermal induced degradation of OTA and may become an important predicting tool in the coffee industry. The present study was also able to propose roasting conditions appropriate to destroy OTA and maintain most of the CGA at the same time.

Full text

Kinetics of ochratoxin A destruction during coffee roasting
Mariano B.M. Ferraz
a
, Adriana Farah
b
, Beatriz T. Iamanaka
a
, Daniel Perrone
b
, Marina V. Copetti
a
,
Viviane X. Marques
b
, Alfredo A. Vitali
a
, Marta H. Taniwaki
a,*
a
Instituto de Tecnologia de Alimentos – ITAL, Av. Brasil, 2880, 13070-178 Campinas, SP, Brazil
b
Laboratório de Bioquímica Nutricional e de Alimentos, Universidade Federal do Rio de Janeiro, Instituto de Química, Departamento de Bioquímica,
Ilha do Fundão, CT bloco A, 21949-900 Rio de Janeiro, RJ, Brazil
article info
Article history:
Received 3 August 2009
Received in revised form 24 November 2009
Accepted 4 December 2009
Keywords:
Coffee
Ochratoxin A
Chlorogenic acids
Coffee roasting
Modeling
abstract
In the present study, Coffea arabica was artificially contaminated with spores of toxigenic Aspergillus west-
erdijkiae. The contaminated coffee was roasted in a vertical spouted bed roaster at four different temper-
atures (180 °C, 200 °C, 220 °C and 240 °C) and three different time periods (5, 8 and 12 min), in order to
obtain more accurate results for the development of the kinetic model for ochratoxin A (OTA). Chlorogen-
ic acids (CGA) content during coffee roasting was also evaluated to investigate the effect of the heat
employed to destroy OTA in these health promoting compounds. Coffee treated with spouted bed roast-
ing significantly reduced the OTA level from 8% to 98%. The spouted bed roasting proved to be a very effi-
cient procedure for OTA reduction in coffee, and its reduction depended directly on the degree of roasting.
OTA degradation during coffee roasting followed first order reaction kinetics. Using the apparent activa-
tion energy of OTA degradation and the temperature-dependent reaction rate, there was a compliance
with the Arrhenius equation. This model was capable of predicting the thermal induced degradation of
OTA and may become an important predicting tool in the coffee industry. The present study was also able
to propose roasting conditions appropriate to destroy OTA and maintain most of the CGA at the same
time.
Ó2009 Elsevier Ltd. All rights reserved.
1. Introduction
Coffee is one of the most popular and consumed food products
in the world. Recently, epidemiological and clinical studies have
been attributing beneficial health effects to this beverage, mainly
due to its high content of phenolic compounds, which make coffee
one of the highest contributors to antioxidant intake in western
diets (Farah, 2009). In addition to phenolic compounds, coffee
may also contain other potentially beneficial bioactive components
such as the vitamin niacin and trigonelline, among others (Farah,
2009; Farah & Donangelo, 2006; Perrone, Donangelo, & Farah,
2008). Because of these bioactive components, coffee has been con-
sidered to be a potential functional food product (Farah, 2009).
However, coffee may also contain undesirable compounds that
may be intrinsic to the beans or produced during primary or indus-
trial processing. One of the most relevant prejudicial compounds in
coffee is ochratoxin A (OTA).
OTA consists of a polyketide-derived dihydroisocoumarin moi-
ety linked through the 12-carboxy group to phenylalanine (Van
der Merwe, Steyn, & Fourie, 1965). Its toxicity has been reviewed
by the International Agency for Research on Cancer (IARC, 1993)
which has classified OTA as a possible human carcinogen (group
2B). The kidneys are considered to be the main target organ for
OTA effects, and nephrotoxic and carcinogenic properties have,
therefore, been the major focus of the safety evaluation performed
by scientific bodies (Krogh et al., 1988; Kuiper-Goodman, 1996).
In coffee, OTA is mainly produced by Aspergillus westerdijkiae,
Aspergillus steynii, Aspergillus ochraceus and related species, and
Aspergillus carbonarius, with a small number of isolates of Aspergil-
lus niger (Frisvad, Thrane, Samson, & Pitt, 2006; Pardo, Marin, Ra-
mos, & Sanchis, 2004; Taniwaki, Pitt, Teixeira, & Iamanaka, 2003;
Urbano, Leitão, Vicentini, & Taniwaki, 2001). The contamination
of coffee by fungi may take place when coffee fruits fall onto the
ground and if acquire higher moisture content during drying and
storage (Bucheli & Taniwaki, 2002; Pardo et al., 2004; Suárez-Quir-
oz et al., 2004; Taniwaki et al., 2003; Urbano et al., 2001). The pres-
ence of OTA in coffee was first reported by Levi, Trenk, and Mohr
(1974) and, since then, systematic investigations on OTA incidence
in green, roasted and instant coffee and brew have been exten-
sively reported (Burdaspal & Legarda, 1998; Lombaert et al.,
2002; Perez de Obanos, Gonzales-Penas, & Lopez de Cerain, 2005;
Studer-Rohr, Dietrich, Schlatter, & Schlatter, 1995; Taniwaki,
2006; Taniwaki et al., 2003).
OTA is generally stable to the level of heat utilized in ordinary
cooking. Boudra, Le Bars, and Le Bars (1995) showed that OTA is
0956-7135/$ - see front matter Ó2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.foodcont.2009.12.001
*Corresponding author. Tel.: +55 19 3743 1819; fax: +55 19 3743 1822.
E-mail address: marta@ital.sp.gov.br (M.H. Taniwaki).
Food Control 21 (2010) 872–877
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heat stable and only up to 20% of OTA in wheat was decomposed
by dry heat at 100 °C for 160 min or 150 °C for 32 min. On the other
hand, because of the high temperatures used for coffee roasting, a
higher percentage of destruction is observed. However, contradic-
tory results from different studies have been reported. Tsubouchi,
Yamamoto, Hisada, Sakabe, and Udagawa (1987) reported that
OTA in artificially contaminated green coffee beans was only
slightly reduced (0–12%) by heat treatment at 200 °C for 10–
20 min and that almost all the toxin was infused into the coffee
decoction when the roasted samples were ground and extracted
with boiling water. This is broadly in agreement with results of
Studer-Rohr et al. (1995) but in contradiction with those of Micco,
Grossi, Miraglia, and Brera (1989) and Blanc, Pittet, Munoz-Box,
and Viani (1998) which showed that up to 80% of the OTA was de-
stroyed during industrial roasting due to both thermal destruction
and coffee chaff removal.
Even though coffee roasting may be an effective process for OTA
destruction, the practice of severe roasting should not be used in
an indiscriminate way, since other thermolabile compounds which
are beneficial to human health, such as chlorogenic acids (CGA)
may be destroyed. CGA are the main phenolic compounds in coffee
(4–12% of green coffee composition), formed by the esterification
of one or two molecules of certain trans cinnamic acids with (-)-
quinic acid (Farah, DePaulis, Trugo, & Martin, 2005). The major
classes of CGA in coffee, containing at least three important iso-
mers, are caffeoylquinic acids (CQA), dicaffeoylquinic acids (diCQA)
and feruloylquinic acids (FQA). During roasting, CGA are lost as a
consequence of the thermal breakage of carbon–carbon covalent
bonds, resulting in molecule changes and degradation (Farah &
Donangelo, 2006; Farah et al., 2005). Several beneficial health ef-
fects have been attributed to CGA and derivatives, mainly related
to their potent antioxidant capacity. Other reported activities are
hypoglycemic and antibacterial, among others (Almeida, Farah, Sil-
va, Nunan, & Glória, 2006; Antonio et al., in press; Farah, 2009;
Hemmerle et al., 1997; Herling et al., 1998; Shearer, Sellars, Farah,
Graham, & Wasserman, 2007; Shearer et al., 2003).
Although kinetic studies are useful for food technologists to de-
sign specific processes with greater efficiency and avoid energy
and product losses, few studies on the kinetics of OTA destruction
in coffee have been carried out. In the present study, twelve roast-
ing conditions were used to model OTA thermal degradation kinet-
ics in coffee. Since the analysis of OTA in naturally contaminated
green coffee beans is difficult due to the low contents found in
these samples, we used artificially contaminated green coffee
beans (inoculated with A. westerdijkiae), in order to obtain more
accurate results for the development of the kinetic model. CGA
content during coffee roasting was also evaluated to investigate
the effect of the heat employed to destroy OTA in these health pro-
moting compounds.
2. Material and methods
2.1. Coffee sample
Green Coffea arabica beans obtained by drying and de-husking
of coffee fruits, were harvested in São Paulo State, Brazil and ac-
quired directly from producers.
2.2. Selection and preparation of spore suspensions
A. westerdijkiae isolated from coffee grown in Brazil was inocu-
lated into malt extract agar (MEA) and incubated at 25 °C for
5 days. The growing culture was transferred into a test tube con-
taining 30 mL of 0.1% peptone water plus 0.1% tween 80, and the
suspension was agitated in a vortex for 1 min. A spore concentra-
tion of 10
7
CFU/mL was obtained by dilution technique.
2.3. Inoculation of Aspergillus westerdijkiae spores into coffee beans
Sixteen 2 L Polyethylene Terephthalate (PET) flasks were sur-
face decontaminated with 70% alcohol and dried under UV light
for 15 min. Following this, 1 kg of green coffee beans was placed
into each flask and 120 mL of the inoculum were added. Content
was homogenized by hand shaking for 2 min. Additionally,
120 mL of peptone water 0.1% without fungal inoculum were
added to one flask containing the same amount of green coffee
beans to achieve similar water activity conditions and be used as
a control. Flask tops were loosened and the flasks were incubated
at 25 °C for 30 days. Flasks were shaken daily and opened for aer-
ation inside an aseptic cabinet flow. After 30 days, all the A. west-
erdijkiae contaminated coffee and the non-inoculated control
were homogenized and analyzed for OTA and CGA.
2.4. Coffee roasting
Coffee samples (300 g) were roasted in duplicate in a vertical
spouted bed roaster (105 mm diam, 590 mm height, 20 mm screen,
45°angle) operating at 180, 200, 220 and 240 °C for 5, 8 and
12 min. The roaster was previously heated with hot air until the
roasting temperature was achieved. After roasting, samples were
immediately placed into a dry air cooler until reaching room tem-
perature. Roasted coffee samples were ground in a Probat mill
(Probat Emmerich Stawert Mühlenbau Typ K32/20, Germany)
and sieved (20 mesh).
2.5. Roasting degree classification
Colorimetric values were obtained using an Agtron Model E10-
CP spectrophotometer (Agtron, Reno, NV – USA) and compared
with the color disks from the ‘‘Roasting Color Classification Sys-
tem” (Agtron) for determination of roasting degrees.
2.6. Ochratoxin A analysis
Ochratoxin A from green and roasted coffee was analyzed
according to Vargas, Santos, and Pittet (2005). A 25 g aliquot of cof-
fee samples was extracted with 200 mL of a mixture of methanol:
3% aqueous sodium bicarbonate (50:50). Extracts were filtered and
diluted with phosphate buffered saline and applied to an immuno-
affinity column (Vicam L.P., Watertown, MA) containing monoclo-
nal antibody specific for OTA. After washing with distilled water,
OTA was eluted with HPLC grade methanol and quantified by re-
verse-phase HPLC with fluorescence detection. A volume of 20
l
L
was injected through a SIL-10ADVP auto injector (Shimadzu Cor-
poration, Japan). The mobile phase was methanol:acetronitri-
le:water:acetic acid [35:35:29:10, (v/v/v/v)], with an isocratic
flow rate of 0.8 mL/min pumped by a SLC-10AVP (Shimadzu Corpo-
ration, Japan). The equipment used was a Shimadzu LC-10VP sys-
tem (Shimadzu Corporation, Japan) with a fluorescence detector
RF-10AXL (Shimadzu Corporation, Japan) set at 333 nm excitation
and 477 nm emission. Chromatographic separation was achieved
using a Supelcosil
TM
LC-18 column (5
l
m, 250 4.6 mm, Supelco,
Bellefonte, PA) equipped with an ODS Hypersil pre-column (5
l
m,
25 4.6 mm) placed into a CTO-10ADVP column oven (Shimadzu
Corporation, Japan) at 40 °C. The method to analyze OTA in green
coffee was already validated. To recover determination, coffee
samples were spiked with OTA standard (Sigma, USA) at three lev-
els (4.8, 8.0 and 80.0 ng/g). The obtained OTA recoveries were
86.5%, 78% and 81%, respectively. The detection and quantification
M.B.M. Ferraz et al. / Food Control 21 (2010) 872–877 873

limits of the method were 0.1 and 0.3 ng/g, respectively. OTA levels
were expressed as ng/g of coffee on a wet basis.
2.7. Chlorogenic acids analysis
Green and roasted coffee samples were ground to pass through
a 0.046 mm sieve and extracted in duplicate with boiling water,
according to a modification of the method of Trugo and Macrae
(1984), described in detail in Farah et al. (2005). Analyses by a
HPLC gradient system using 10 mM citric acid solution and meth-
anol as the mobile phase were performed as also described in Farah
et al. (2005) and Farah, de Paulis, Moreira, Trugo, and Martin
(2006). Chromatographic separation was achieved using a Rex-
chrom ODS-C18 column (5
l
m, 250 4.6 mm, Regis Technologies,
Morton Grove, IL) coupled with a guard column (Rexchrom, 5
l
m,
10 3 mm). Detection was performed by a UV detector (Model
SPD-10AVp Shimadzu, Japan), operating at 325 nm. The variation
coefficient of the analytical method was lower than 5%. The detec-
tion limit for 5-CQA, the main representative of CGA class in coffee,
was 1.7
l
g/mL. CGA levels were expressed as g/100 g of coffee on a
dry weight basis.
2.8. Water content
In order to express the amount of CGA per weight of dry matter,
the water content of the freshly ground beans was determined
according to AOAC (2000).
2.9. Kinetics of OTA degradation
The kinetic model used in this study was chosen because of the
balance between its simplicity and the good performance of exper-
imental data it provided. We assumed that the kinetic parameters
followed the Arrhenius law. The dependence of the degradation
rate constant on the temperature was quantified by the Arrhenius
equation (Nisha, Singhal, & Pandit, 2005; Tarade, Singhal, Jayram, &
Pandit, 2007; Özdemir & Devres, 2000).
3. Results and discussion
3.1. Production of ochratoxin A by A. westerdijkiae
The average content of ochratoxin A produced by A. westerdij-
kiae in the contaminated raw coffee sample after 30 days of incu-
bation was 247 ng/g which is about 100 times the average values
reported in the literature for naturally contaminated coffee beans
(MAFF, 1996; Studer-Rohr et al., 1995; Taniwaki, 2006).
3.2. Roasting of the beans
Table 1 shows the colorimetric values and respective roasting
degrees of coffee before and after being roasted in different roast-
ing conditions. Color development was directly related to roasting
time and temperature, and roasting degrees varied from very light
to very dark.
Table 1
Roasting conditions, colorimetric values and roasting degree of the coffee samples used in this study.
Roasting conditions Instrumental color
a
(Agtron scale) Disc color # Roasting degree
Temperature (°C) Time (min)
180 5 96.9 ± 0.0 95 Very light
8 96.9 ± 0.0 95 Very light
12 92.5 ± 0.1 95 Very light
200 5 96.9 ± 0.0 95 Very light
8 85.8 ± 1.3 95 Very light
12 66.3 ± 0.6 85 Light
220 5 88.6 ± 0.3 95 Very light
8 55.9 ± 0.6 75 Moderately light
12 44.7 ± 0.1 55 Medium
240 5 59.7 ± 0.4 75 Moderately light
8 27.4 ± 0.2 35 Dark
12 10.9 ± 0.7 25 Very dark
a
Results are the average ± SD of three measurements.
Table 2
Ochratoxin A content and percent loss in green and roasted coffee samples used to compute the degradation model.
Roasting conditions Ochratoxin A (ng/g)
a
Ochratoxin A loss (%) k(min
1
)
Temperature (°C) Time (min)
Green coffee 247 ± 20.1 – –
180 5 227 ± 20.0 8.2 0.10
8 143 ± 12.9 42.1
12 115 ± 5.6 53.6
200 5 173 ± 31.7 29.9 0.11
8 108 ± 9.1 56.1
12 80.6 ± 3.2 67.4
220 5 132 ± 8.0 46.7 0.20
8 58.9 ± 3.3 76.2
12 31.7 ± 8.0 87.2
240 5 57.5 ± 9.5 76.7 0.43
8 14.0 ± 2.9 94.3
12 2.8 ± 1.0 98.9
a
Results are the average ± SD of four replicates of analysis.
874 M.B.M. Ferraz et al. / Food Control 21 (2010) 872–877

3.3. Ochratoxin A destruction
After roasting, coffee samples were analyzed for OTA content.
Table 2 shows the contents of OTA in green and roasted coffee sam-
ples used to compute the degradation kinetic models. Percent
reduction in OTA content due to roasting is also shown. After
12 min roasting, OTA content reduction ranged from 53% to 99%
for samples roasted at 180 and 240 °C, respectively. Samples
roasted at intermediate roasting temperatures showed intermedi-
ate OTA losses, as expected. Our results are in agreement with
those obtained using naturally contaminated coffee beans (Blanc
et al., 1998). On the other hand, the results of Tsubouchi et al.
(1987) showed that OTA was slightly reduced (0–12%) by heat
treatment at 200 °C for 10–20 min. This discrepancy may be
mainly due to their using of a static oven in which the convection
heat exchange is very low and a considerable part of the roasting
time might have been used just for drying, with the beans remain-
ing at the wet bulb temperature (estimated to be around 80–90 °C)
for this experimental condition.
Evaluation of zero and first order equations, based on correla-
tion coefficient, showed that the best fit (R
2
> 0.88) was obtained
when OTA degradation reaction was considered to be of first order.
Using linear regression analysis, the degradation rate equation data
were analyzed as a function of temperature.
Fig. 1 shows the first order plots of OTA degradation in coffee
samples at the tested temperatures. The half-life (t
½
), time re-
quired for OTA to degrade to 50% of its original value, was calcu-
lated from the rate constant k, as ‘ln2/k’. The average rate
constants for OTA degradation increased from 0.0687 to
0.3775 min
1
at 180 and 240 °C, respectively. A corresponding de-
crease in half-life, from 10.09 to 1.84 min, respectively, was
observed.
The linear nature of the obtained plot (R
2
> 0.90) indicates that
thermal destruction of total OTA conforms to the Arrhenius equa-
tion. Apparent activation energies E
a
(kJ mol
1
) were calculated as
a product of the gas constant R(8.3145 J mol
1
K
1
) and the slope
of the graph obtained by plotting ‘lnk’ vs. ‘1/T’. The apparent acti-
vation energy for OTA thermal degradation was found to be
49.2 kJ mol
1
. The frequency factor A
0
(min
1
) was calculated as
the exponential of the intercept of the Arrhenius plot at 1/T=0
and found to be 1.26 10
5
.
The degradation of OTA during coffee roasting was used imple-
menting the calculated rate constants for OTA degradation, k.A
strong correlation (R
2
= 0.96) between experimental and calculated
values was obtained (Fig. 2). An average relative error of 9.1% was
found between experimental and calculated values. This relative
error is in agreement with those reported by other modeling stud-
ies in the literature (Nisha et al., 2005; Tarade et al., 2007).
3.4. Chlorogenic acids destruction
Because CGA are biologically relevant thermolabile com-
pounds in coffee, their destruction during coffee roasting was
also evaluated. The contents of total CGA and of CQA, FQA and
diCQA classes, as well as CGA percent loss in the coffee samples
used in this study are presented in Table 3. CGA content in green
coffee was 5.98 g/100 g, which is in agreement with numerous
studies in the literature (Clifford, 1999; Farah & Donangelo,
2006; Farah et al., 2005; Perrone et al., 2008; Trugo & Macrae,
1984). As expected, CGA content reduced during roasting, with
the exception of the sample roasted at 180 °C for 5 min. After
12 min roasting, CGA loss ranged from 17% to 99% for samples
roasted at 180 and 240 °C, respectively. Fig. 3 presents the per-
cent loss of both OTA and CGA contents due to coffee roasting.
It is possible to observe that OTA percent loss was more pro-
nounced that CGA percent loss when coffee was roasted at 180,
200 and 220 °C. When the roasting temperature was set to
y = -0.4306x + 0.651
R2 = 0.99
y = -0.2008x + 0.301
R2 = 0.98
y = -0.0953x + 0.328
R2 = 0.92
y = -0.1074x + 0.129
R2 = 0.96
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
4 5 6 7 8 9 10 11 12 13
Time (min)
180 oC
200 oC
220 oC
240 oC
ln (OTA t/OTA t=0)
Fig. 1. First order plots of OTA degradation in coffee samples at 180, 200, 220 and 240 °C.
y = 0.9814x
R2= 0.98
0
50
100
150
200
250
0 50 100 150 200 250
Calculated OTA content (ng/g)
Experimental OTA content (ng/g)
Fig. 2. Comparison of experimental and calculated OTA content (ng/g) in roasted
coffee samples using a kinetic model based on a first order reaction rate and the
Arrhenius law.
M.B.M. Ferraz et al. / Food Control 21 (2010) 872–877 875

240 °C, however, the percent losses of both compounds are very
similar, especially after longer periods of roasting (8 and 12 min).
To better compare the roasting conditions in terms of efficiency
to destroy OTA and retain CGA, we calculated the ratio between
CGA and OTA percent losses. Some restrictions were made, since
only high efficiencies of OTA destruction (>75%) were used. Two
samples showed OTA percent losses nearly to 80%, namely those
roasted at 220 °C for 8 min and at 240 °C for 5 min. These sam-
ples were both classified in terms of roasting degree as moder-
ately light (disc #75) and their calculated ratios (CGA/OTA)
were 0.84 and 0.76, respectively. The samples roasted at 220 °C
for 12 min and 240 °C for 8 and 12 min. showed roasting degrees
as medium (disc #55), dark (disc #35) and very dark (disc #25),
and their calculated ratios (CGA/OTA) were 0.92, 1.00 and 1.00,
respectively. In this way, lower roasting temperatures for longer
periods of time would favor OTA destruction and CGA retention.
Nevertheless, it is clear from our results that in order to destroy
most of the OTA present in the coffee, CGA content was signifi-
cantly affected. It should be noted, however, that the nature of
the cell wall of coffee beans probably changed during incubation,
which could have facilitated the destruction of CGA and also, to a
lower extent, OTA.
5 min 8 min 12 min
10
20
30
40
50
60
70
80
90
100
OTA
CGA
Component loss (%)
5 min 8 min 12 min
0
10
20
30
40
50
60
70
80
90
100
OTA
CGA
Component loss (%)
5 min 8 min 12 min
0
10
20
30
40
50
60
70
80
90
100 OTA
CGA
Component loss (%)
5 min 8 min 12 min
0
10
20
30
40
50
60
70
80
90
100
OTA
CGA
Component loss (%)
180ºC
220ºC 240ºC
200ºC
Fig. 3. Percent loss in OTA and CGA contents when green coffee was for roasted at 180, 200, 220 and 240 °C for 5, 8 and 12 min.
Table 3
Chlorogenic acids contents and percent loss in green and roasted coffee samples.
a
Roasting conditions Total CGA (g/100 g)
b
CQA (g/100 g)
b
FQA (g/100 g)
b
diCQA (g/100 g)
b
Total CGA loss (%)
Temperature (°C) Time (min)
Green 5.98 ± 0.03 4.84 ± 0.02 0.15 ± 0.00 0.90 ± 0.01 –
180 5 6.17 ± 0.05 5.13 ± 0.03 0.17 ± 0.00 0.85 ± 0.02 3.0
8 5.73 ± 0.29 4.87 ± 0.22 0.15 ± 0.01 0.70 ± 0.05 4.2
12 4.99 ± 0.13 4.25 ± 0.12 0.17 ± 0.01 0.56 ± 0.01 16.6
200 5 5.69 ± 0.58 4.78 ± 0.41 0.20 ± 0.11 0.71 ± 0.05 4.9
8 4.26 ± 0.42 3.67 ± 0.30 0.17 ± 0.05 0.42 ± 0.08 28.7
12 3.23 ± 0.08 2.80 ± 0.10 0.14 ± 0.03 0.28 ± 0.01 45.9
220 5 4.52 ± 0.41 3.87 ± 0.30 0.19 ± 0.07 0.46 ± 0.04 24.4
8 2.14 ± 0.12 1.90 ± 0.12 0.09 ± 0.01 0.15 ± 0.02 64.2
12 1.20 ± 0.17 1.06 ± 0.11 0.09 ± 0.04 0.06 ± 0.01 79.9
240 5 2.50 ± 0.16 2.21 ± 0.14 0.11 ± 0.01 0.18 ± 0.01 58.2
8 0.35 ± 0.02 0.29 ± 0.01 0.05 ± 0.01 0.01 ± 0.00 94.2
12 0.05 ± 0.01 0.04 ± 0.00 0.01 ± 0.00 0.00 ± 0.00 99.1
a
CGA = chlorogenic acids; CQA = caffeoylquinic acids; FQA = feruloylquinic acids; diCQA = dicaffeoyl-quinic acids.
b
Results are the average ± SD of two replicates of analysis.
876 M.B.M. Ferraz et al. / Food Control 21 (2010) 872–877

In conclusion, in the present study, we showed that spouted bed
roasting is a very efficient procedure for OTA reduction in coffee,
and its reduction depends directly on the degree of roasting. OTA
degradation during coffee roasting followed first order reaction
kinetics. Using the apparent activation energy of OTA degradation
and the temperature-dependent reaction rate, a compliance with
the Arrhenius equation was shown. This model was capable of pre-
dicting the thermal induced degradation of OTA. The proposed
model may become an important predicting tool in the coffee
industry. However, it should be kept in mind that using contami-
nated beans will greatly affect the quality of the beverage and that
severe roasting of coffee beans to destroy OTA will also directly af-
fect the levels of CGA, which are beneficial compounds to human
health. Therefore, even though roasting may destroy OTA, the use
of highly contaminated beans in coffee blends is not a recom-
mended practice.
Acknowledgements
This work was funded by the Consórcio Brasileiro de Pesquisa e
Desenvolvimento do Café – EMBRAPA. The Support from CNPq and
FAPERJ (Brazil) are gratefully acknowledged.
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