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Effect of Household Coffee Processing on Pesticide Residues as a Means of Ensuring Consumers’ Safety


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HCoffee is the highly consumed and popular beverage all over the world. However, coffee beans used for the daily consumption may contain pesticide residues which may cause adverse health effects to consumers. In this monitoring study, the effect of household coffee processing on pesticide residues in coffee beans was investigated. Twelve pesticides including metabolites and isomers (endosulfan α, endosulfan β, cypermethrin, permethrin, deltamethrin, chlorpyrifos ethyl, heptachlor epoxide, hexachlorobenzene, p'p-DDE, p'p-DDD, o'p-DDT and p'p-DDT) were spiked in coffee beans collected from local market in southwestern Ethiopia. The subsequent household coffee processing (washing, roasting and brewing) conditions were established as close as possible with the traditional household coffee processing in Ethiopia. The percent reduction in washing process is in the range of 14.63- 57.69, while the roasting reached up to 99.8 percent. Chlorpyrifos ethyl, permethrin, cypermethrin, endosulfan α and β in roasting and all of the 12 pesticides in the coffee brewing processes were not detected. Kruskal-Wallis analysis indicated that, the reduction of pesticide residues by washing is significantly different from roasting and brewing (P<0.0001). However, there was no significant difference between coffee roasting and brewing (P>0.05). The processing factor (PF) was less than one (PF<1), which indicates reduction of pesticides under study during processing of the coffee beans. The cumulative effect of the three processing methods has a paramount importance in evaluating the risks associated with ingestion of pesticide residues, particularly in coffee beans.
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Eect of Household Coee Processing on Pesticide Residues as a
Means of Ensuring ConsumersSafety
Seblework Mekonen,*
Argaw Ambelu,
and Pieter Spanoghe
Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
Department of Environmental Health Sciences and Technology, College of Health Sciences, Jimma University, Jimma, Ethiopia
ABSTRACT: Coee is a highly consumed and popular beverage all over the world; however, coee beans used for daily
consumption may contain pesticide residues that may cause adverse health eects to consumers. In this monitoring study, the
eect of household coee processing on pesticide residues in coee beans was investigated. Twelve pesticides, including
metabolites and isomers (endosulfan α, endosulfan β, cypermethrin, permethrin, deltamethrin, chlorpyrifos ethyl, heptachlor
epoxide, hexachlorobenzene, pp-DDE, pp-DDD, op-DDT, and pp-DDT) were spiked in coee beans collected from a local
market in southwestern Ethiopia. The subsequent household coee processing conditions (washing, roasting, and brewing) were
established as closely as possible to the traditional household coee processing in Ethiopia. Washing of coee beans showed
14.6357.69 percent reduction, while the roasting process reduced up to 99.8 percent. Chlorpyrifos ethyl, permethrin,
cypermethrin, endosulfan αand βin roasting and all of the 12 pesticides in the coee brewing processes were not detected.
KruskalWallis analysis indicated that the reduction of pesticide residues by washing is signicantly dierent from roasting and
brewing (P< 0.0001). However, there was no signicant dierence between coee roasting and brewing (P> 0.05). The
processing factor (PF) was less than one (PF < 1), which indicates reduction of pesticides under study during processing of the
coee beans. The cumulative eect of the three processing methods has a paramount importance in evaluating the risks
associated with ingestion of pesticide residues, particularly in coee beans.
KEYWORDS: coee ceremony, processing factor, roasting, washing, coee brewing
In recent years, public health issues aecting the food chain
have triggered health authorities to increase their concern on
the presence of pesticide residues in staple food items.
Pesticides are widely used for the control of pests, disease of
crops, and vectors of human and animal diseases. Despite their
wide range of application, pesticides may have adverse health
eects for consumers because their residues remain on food
items. As a result, food safety is a growing concern worldwide
because of its direct relation to human health. It is important
for consumers to know the possibilitiy of intake of pesticides
along with their food. As reported in the literature, food
processing may reduce pesticide residues in food and the
concurrent scenario of unsafe food for consumers.
Pesticide residue can be detected in any food items, such as
vegetables and fruits, cereals, animal products, or tea and coee
as a result of the application of the pesticides in the eld and
during storage of crops for the control of pests. Usually,
pesticide residue analysis is undertaken for raw agricultural
commodities to meet the purpose of marketing to consumers,
import/export certication, regulatory monitoring, and others.
However, to estimate the level of exposure to pesticide residues
in food, it is desirable to investigate the level of exposure at the
point of consumption, mainly after food processing, which may
lead to a large reduction of pesticide residues.
Food processing
is the action of transforming the food to more edible form
before the food is consumed and the processing can inuence
the pesticide residue present after the raw agricultural
commodity is harvested.
Dierent household and industrial
food processing, such as washing with water or with various
chemicals, peeling for fruits and vegetables, frying, boiling,
cooking, and baking, have been able to reduce the pesticide
residue in food to below the risk level.
Coee is a highly consumed and popular beverage all over
the world. Coee is the second most important commodity
next to oil as a source of foreign exchange for most producing
countries. In addition, it is considered a primary food due to its
contents of compounds with an antioxidant eect and other
benecial biological properties. Its characteristic avor and
aroma make it a unique beverage, and thousands of volatile
compounds are found in roasted coee.
Currently, Ethiopia is
the fth largest world coee producer and the top producer and
exporter in Africa. The country is believed to be the origin of
Coee arabica. On the other hand, half of the coee produced in
Ethiopia is used for domestic consumption. This makes the
nation to be the leading African country in coee consumption
with a yearly per capita consumption of 2.4 kg. Additionally,
coee is the most signicant agricultural product to the
countrys economy.
Specically, the beautiful traditional coee ceremony makes
the country very unique in consumption of coee. The coee
ceremony and drinking coee is an important part of Ethiopian
cultures. Coee is oered during holidays, visiting friends, and
on a daily basis as a staple food item. The Ethiopian coee
ceremony starts with washing the coee beans with water and
Received: July 10, 2015
Revised: September 1, 2015
Accepted: September 7, 2015
Published: September 7, 2015
© 2015 American Chemical Society 8568 DOI: 10.1021/acs.jafc.5b03327
J. Agric. Food Chem. 2015, 63, 85688573
roasting until it turns to dark brown. After roasting, sometimes
the roasted coee beans are brought to the family members or
visitors to allow them to experience the aroma. Afterwards, it
will be ground to a ne powder using a traditional wooden
mortar and pestle. The powder is poured into boiled water in a
special local coee clay pot called a jebena.Coee will be
ready to serve when the steam with an attractive avor starts to
come out from the nozzle. After that, the jebena is placed on
ground for about 3 min to let the coee sludge settle to the
bottom. The brewed coee is then poured into small cups and
served (personal observation). In general, coee is an
important crop for domestic consumption as well as a source
of hard currency for the nation.
However, studies have indicated that coee beans have
dierent pesticide residues. Even though coee is the most
important agricultural product for human consumption as well
as for the economic growth of the producing countries, the
beans might have dierent pesticide residues that can expose
consumers to hazardous agrochemicals.
Because of the high
consumption of coee and its economic importance, people
from the producer, exporter, and consumer countries give more
attention to its safety.
Even though pesticide contamination in
green coee beans is limited during agricultural treatments,
there may be contamination during transportation and storage.
Dierent studies have stated that coee is contaminated by
dierent classes of pesticides applied in the eld. According to
the U.S. Food and Drug Administration, from a survey of 60
imported green coee bean samples, some of them contained
dierent pesticide residues, such as chlorpyrifos at a
concentration ranging from 0.01 to 0.04 mg/kg and pirimiphos
methyl at 0.01 mg/kg.
From a study done in Brazil, the
residues of dierent pesticides, such as endosulfan, chlorpyrifos,
cypermethrin, and captafol, have been detected in coee beans
from either registered or illegal use.
Additionally, from the
previous study done in Ethiopia, DDT, cypermethrin,
permethrin, deltamethrin, chlorpyrifos ethyl, and endosulfan
(αand β) were detected in coee beans at concentrations
ranging from 0.011 to 1.115 mg/kg7.
The pesticide residues, to a variable extent, left in the food
materials after harvesting, are beyond the control of consumers
and may have deleterious eects on human health. Because
Ethiopia is the largest producer, exporter, and consumer of
coee in Africa, a pragmatic solution should be developed to
tackle the problem of coee safety. Dierent studies have
revealed that food processing can be one important solution
that has a signicant role for the reduction of pesticide residues
in dierent food items.
Nowadays, there is an increasing
need for information on the eect of various food processes on
pesticide residues. Few studies have indicated the eect of
coee roasting on the reduction of pesticide residues.
However, no studies are available on the eect of household
coee processing (washing, roasting, and brewing) methods on
pesticide residues. Therefore, the main aim of the present study
is to evaluate the eect of household processing on pesticide
residues in coee and to determine the processing factor (PF)
for each of the processing steps.
2.1. Chemicals and Reagents. Analytical grade acetoni-
trile (99.9% purity) was supplied by VWZ-prolabo. High
performance liquid chromatography grade n-hexane (98%
purity) and acetone (98.9% purity) that were obtained from
ALLthec were used to extract the pesticide residues from the
raw coee beans and after dierent processing steps. Thermo
Fisher Scientic supplied MgSO4(98% purity), NaAc (99%
purity), the 50 mL centrifuge tube, the 15 mL dispersive solid
phase extraction cleanup tube packed with primary secondary
amine (PSA: 99% purity), magnesium sulfate (MgSO4, 98%
purity), and octadecyl (C18, 99% purity). The pesticides under
study (pp-DDE (99.9%), pp-DDD (99.3%), op-DDT
(100%), pp-DDT (99%), endosulfan α(98.5%), endosulfan
β(98%), Permethrin (98%), cypermethrin (98%), deltamethrin
(99%), Chlorpyrifos ethyl (99.5%), Heptachlor epoxide
(99.5%) and hexachlorobenzene (98%)) with their highest
analytical purity, were obtained from Supelco and delivered by
Sigma-Aldrich Logistic Analytical. The physicochemical proper-
ties of the pesticides studied in the present study are presented
in Table 1.
2.2. Sampling. A 3 kg portion of green coee beans was
bought from a local market in Jimma zone, southwestern
Ethiopia in August, 2014 and served as a blank and spiked
sample. Samples were packed in polyethylene plastic bags, after
which they were sealed and labeled properly. The samples were
transported to the laboratory and stored at 20 °C until
extraction was done.
2.3. Quality Control. 2.3.1. Linearity. The quantitative
determination of the pesticide residues in processed and
unprocessed coee beans was done on the basis of an external
standard method. The calibration curves were obtained by
injecting ve dierent concentrations of the pesticide standards
in the range of 0.0051 mg/L. The regression coecient (r2)
was >0.995 for all the pesticides under study. Identication and
quantication of the pesticides were done on the basis of the
retention time and peak area, respectively.
2.3.2. Recovery Study. To evaluate the performance of the
analytical procedures recovery (% recovery), studies were
undertaken for each pesticide. A 10 g sample of pesticide-free
coee beans was weighed on the analytical balance and spiked
with 40 μL of 100 mg/L of each pesticide in three replicates.
The extraction was performed in a similar way with the
samples. The percent recovery was derived from the equation:
(amount of pesticide observed)/(amount of pesticides spiked)
×100. The percent relative standard deviation (% RSD) was
obtained by dividing the standard deviations by the average
concentration and multiplying the result by 100.
Table 1. Physicochemical Properties of the Pesticides under
(mg/L) log
vapor pressure
(mmHg) mode of
pp-DDE 0.025 6.91 1.6 ×107contact
pp-DDD 0.120 6.51 1.4 ×106contact
op-DDT 0.090 6.02 6.0 ×106contact
pp-DDT 0.085 6.79 1.1 ×107contact
endosulfan α0.530 3.83 1 ×105contact
endosulfan β0.280 3.62 1 ×105contact
permethrin 0.006 6.10 2.15 ×108contact
cypermethrin 0.009 5.40 2.3 ×107contact
deltamethrin 0.002 6.10 1.5 ×108contact
heptachlor epoxide 0.350 5.40 3.0 ×104contact
hexachlorobenzene 0.006 5.73 1.09 ×105systemic
chlorpyrifos ethyl 1.400 4.70 1.9 ×105contact
log kow = logarithm of octanol-water partion coecient.
Journal of Agricultural and Food Chemistry Article
DOI: 10.1021/acs.jafc.5b03327
J. Agric. Food Chem. 2015, 63, 85688573
2.4. Treatment of Raw Coee Bean. A 10 g portion of
raw coee beans was weighed on an analytical balance and
spiked with 40 μL of a 100 mg/L solution of each pesticides
under study (DDT metabolites, cypermethrin, deltamethrin,
permethrin, endosulfan [α,β] and chlorpyrifos ethyl,
heptachlor epoxide, and hexachlorobenzene) in three replicates
to increase the reliability of the results. Spiking was done for
each household coee processing method (washing, roasting,
and brewing). The pesticides selected for this study were
detected in the previous study done on Ethiopian coee beans,
except for heptachlorepoxide and hexachlorobenzene, in which
the investigators expected them from previous application in
the environment. The spraying of the coee beans was done in
a Petri dish to get equal distribution of the pesticides for each
bean. After spraying, the Petri dishes were covered with
aluminum foil and placed in refrigerator at 4 °C for 24 h to
increase the contact time between the pesticides and the matrix.
After 1 day, the processing methods (washing, roasting,
brewing) and the extraction, clean up, and analysis were
followed as stated below.
2.5. Extraction and Cleanup of the Samples. To assess
the eect of washing, roasting, and brewing of coee on
pesticide residues, the extraction and cleanup of the raw and
processed coee beans were done using the modied Quick,
Easy, Cheap, Eective, Rugged and Safe (QuEChERS) method
combined with a dispersive solid phase extraction cleanup (d-
SPE) method. The analytical procedure was based on the
method AOAC 2007.01.
The subsequent processing steps of
the coee beans were done to correspond, as closely as
possible, to the actual traditional household coee processing in
Ethiopia. Blank coee bean (nonspiked) was also analyzed
together with the raw and processed coee beans. The
extraction and cleanup procedures for raw coee beans and
processed coee beans were as follows:
2.5.1. Raw coee beans. After holding the spiked samples
for 1 day, the treated raw coee bean was ground and
homogenized using a coee grinder with a knife in it. A 15 mL
portion of acetonitrile was added, and the sample was shaken
by hand for 30 s. Then 6 g of MgSO4/1.5 g of NaCl/1.5 g of
Na3citrate·2H2O/0.750 g of Na2Hcitrate was added, and the
mixture was again shaken for 5 min to prevent formation of
agglomerates between the water and MgSO4. Then the samples
were centrifuged at 5000 rpm for 5 min. The upper organic
layer was taken for cleanup using a 15 mL dispersive solid phase
extraction tube (d-SPE) containing 300 mg of PSA, 900 mg of
MgSO4, and 150 mg of C18 and then shaken for 30 s. The
cleaned extracts were centrifuged to get a clear solution. After
centrifugation, 5 mL of the upper layer was taken into a 100 mL
at bottom ask and evaporated to dryness using a rotary
evaporator (N18673 Rotavapor; Buchi) at a temperature of 40
°C. A 2 mL portion of n-hexane/acetone (9:1 V/V) was added
for solvent exchange to make the sample amenable for GC/
ECD analysis. The blank coee bean was also extracted in a
similar way, as were with the spiked samples. Then the extract
was placed into a vial for GC/ECD analysis.
2.5.2. Washed Coee Beans. The spiked coee beans were
washed thoroughly for 5 min under normal tap water (2530
°C), which resembles coee bean washing at the household
level. Then all other procedures for the unprocessed coee
beans were applied for the extraction, cleanup, and analysis for
the presence of pesticides.
2.5.3. Roasted Coee Beans. The spiked coee beans were
roasted on a stove at a temperature range of 230240 °C (light
to medium) roasting and an average time of 1214 min until
the characteristics aroma or avor of coee appears. The
roasting temperature and duration of roasting was based on a
study done by Moon and Shibamoto.
The roasting processes
were done in a way similar to the traditional Ethiopian
household coee roasting procedures. Then the other
procedures for extraction and cleanup used for raw coee
beans were applied.
2.5.4. Brewed Coee Beans. Some heat-resistant pesticides
may be detected in a cup of coee after the coee beans were
roasted. To determine the eect of brewing on the pesticides
under study, the brewing process was also undertaken. The
roasted coee beans were ground to a ne powder using a
coee grinder (type 4041, 220-230 V/150w). The ne coee
powder was added to a coee pot traditionally called a Jebena
containing 100 mL boiled water and brewed for 1012 min in
a way similar to that of the tradition Ethiopian coee brewing
processes (personal observation). After brewing, the coee pot
was picked up from the stove and put on the ground until the
infusion of the coee was cooled and the coee powder or
sludge had settled to the bottom of the coee pot. Then the
upper liquid layer was removed carefully to the cups, and then
extraction, cleanup and analysis of the brewed coee solution
was done in a way similar to that of the raw coee beans.
2.6. Determination of Processing Factor (PF). The
eect of household processing on the level of pesticides often
correlates with the physicochemical properties of the pesticides
under study, so it is important to adequately monitor the
processing factor. The processing factor (PF) for all trans-
formation steps was calculated as the ratio between the
pesticide concentrations in the processed commodity (mg/kg)
to the pesticide concentration in unprocessed (raw) commod-
ity (mg/kg). According to Bonnechere and his colleagues,
PF of <1 indicated that there is reduction of pesticides by the
processing method (PF < 1 = reduction factor), whereas >1
indicated no reduction in weight or volume, (PF > 1 = a
concentration factor). The processing factor is the proportional
amount by which residues change when food is processed. For
this study, it is calculated by the formula below:
processing factor (PF)
concentration of pesticides in processed coffee beans (mg/kg)
concentration of pesticides in raw coffee beans (mg/kg)
After obtaining the processing factor, the percent reduction (%
reduction) for each processing method was calculated as
follows: % reduction = (1 PF) ×100.
2.7. Wash Water and Coee Sludge Remaining at the
Bottom of Pot after Coee Brewing. Before the coee was
roasted, it was washed with water (which may remove some
residues on the surface of the coee beans). Additionally, after
the coee was brewed, there is sludge (powder or coee
residue) remaining in the bottom of the coee pot, which may
contain some pesticide residue that can evade the roasting
process. Traditionally, this wash water and coee sludge is often
disposed of in the environment, which may contaminate food
grown there. To check whether the wash water from the
samples and the sludge of the coee contain pesticide residues,
these two samples were analyzed. The procedure was as
follows: A 10 mL portion of the wash water (assuming 10 g of
water) and 68 g of coee sludge were weighed on an
analytical balance and placed into a 50 mL centrifuge tube.
Journal of Agricultural and Food Chemistry Article
DOI: 10.1021/acs.jafc.5b03327
J. Agric. Food Chem. 2015, 63, 85688573
Then the extraction, cleanup, and analysis were done in a way
similar to that of the raw coee bean.
2.8. Analytical equipment. Quantitative estimations and
chromatographic separation of each pesticide were done by gas
chromatography with an electron capture detector (GCECD,
Agilent Technologies 6890N) with an auto sampler. The coee
bean processing was undertaken to see their eect on the
pesticides previously detected in Ethiopian green coee beans,
so the chromatographic conditions for this study were the same
as the previous paper, as explained below. A HP-5 capillary
column of 30 m ×0.25 mm i.d. ×0.25 μmlm thickness
coated with 5% phenyl methyl siloxane (model no. Agilent
19091J-433) was used in combination with the following oven
temperature program: initial temperature, 80 °C; ramp at 30 °C
min1to 180 °C; ramp at 3 °C min1to 205 °C; held for 4
min; ramp at 20 °C min1to 290 °C; held for 8 min; ramp at
50 °Cmin
1to 325 °C. For deltamethrin, the oven
temperature was maintained initially at 130 °C, held for 1
min, ramped at 30 °C min1to 280 °C, held for 16 min,
ramped at 50 °C min1to 325 °C, and held for 3 min. The total
GC run time was 27.92 min. Helium (99.9999% purity) was
used as a carrier gas at a ow rate of 20 mL min1, and nitrogen
was the makeup gas at a ow rate of 60 mL min1. An aliquot of
1μL was injected in split mode at a split ratio of 50:1 and
injection temperature of 280 °C. The pesticide residues were
detected with an electron capture detector (μ-ECD) operated
at a temperature of 300 °C. For the reliability of the results,
each sample was analyzed in triplicate, and the mean
concentration was computed accordingly.
2.9. Statistical Analysis. All the treatments for the three
processing methods were done in three replicates, and values
are shown as mean ±SD. Statistical signicance was checked
using the KruskalWallis test to see if the processing methods
(washing, roasting, and brewing) are dierent in the percent
reduction of the pesticides under study. Dierences at P< 0.05
were considered as signicant.
3.1. Quality Control Studies. The mean percent recovery
for most of the pesticides was 80120% and the percent
relative standard deviation (% RSD) was below 10% for all the
pesticides under study, except for cypermethrin and deltameth-
rin. All pesticides were in the acceptable analytical range (70
120% recovery and RSD < 20%). The regression coecients
(r2) were >0.995 for all the pesticides. This method is accurate
and precise for the analysis of the pesticides under study and
fullled the requirement of European Document no. SANCO/
The results are indicated in Table 2.
3.2. Eect of Household Processing of Coee Beans
on Pesticide Residues. This study investigated the eect of
household processing of coee (washing, roasting, and
brewing) on the stability of 12 pesticides, including metabolites
and isomers. The concentration of the pesticides under study in
raw and processed coee beans are presented in Figure 1.
Among the household processes, washing decreased the
pesticide residues by 14.6357.69%. This eect may be due
to the fact that most of the pesticides have contact action and
are found on the surface of the coee beans. This washing
process may help for the removal of the pesticides with the
silverskin of the coee (very thin layer of a coee bean located
just above the main part of the coee beans), dust, or soil.
Reports indicated that surface residues are easily amenable to
removal by simple washing processes with water.
The majority
of the pesticides applied to agricultural crops are conned to
the surface and a much smaller amount undergoes penetration
to the plant system.
As a result, they can easily be acquiescent
to being washed, trimmed, or peeled from the surface of the
crop. The maximum reduction was observed for endosulfan α
and β, for which the residue decreased by 53.1357.69%,
respectively. A similar result was observed from a study done in
India: washing of the vegetable brinjal with tap water decreased
endosulfan residue up to 55%; however, a lesser removal of
heptachlor epoxide in cucumber was observed.
The rinsability of some pesticides by washing with water may
not always correlate with its water solubility.
As indicated in
Table 1, most of the pesticides under study have low water
solubility and high octanol-water partition coecient (log kow >
3). Washing was found comparatively less eective in reducing
the residues of pp-DDD (14.63%), hexachlorobenzene
(20.83%), heptachlor epoxide (23.40%), chlorpyrifos ethyl
(26.53%), op-DDT ((28%), and pp-DDT (28%).
In this study, roasting was found to be eective in aecting
the stability of pesticide residues in coee beans. By this
process, reductions of the residues of the pesticides were in the
range of 72.599.8%. The maximum reductions were observed
in hexachlorobenzene (99.8%), heptachlor epoxide (97.9%),
pp-DDE, pp-DDD (97.6%), and op-DDT (96%). Five of the
Table 2. Results of Regression Coecient, Percent Recovery
and Percent RSD
pesticides r2% recovery % RSD
endosulfan α0.998 80 6.3
endosulfan β0.997 130 3.8
chlorpyrfos ethyl 0.995 122.5 2.0
permethrin 0.998 112.5 8.9
cypermethrin 0.999 127.5 19.6
deltamethrin 0.999 100 15.0
pp-DDE 0.999 102.5 2.4
pp-DDD 0.999 102.5 4.9
op-DDT 0.998 125 4.0
pp-DDT 0.988 125 2.0
heptachlorepoxide 0.999 117.5 10.6
hexachlorobenzene 0.999 120 0.20
RSD = relative standard deviation.
Figure 1. Mean pesticide residues (mg/kg) at dierent coee
processing steps. The error bars indicate standard deviation. Pesticides
from brewed coee were not detected and are not shown in this graph.
Journal of Agricultural and Food Chemistry Article
DOI: 10.1021/acs.jafc.5b03327
J. Agric. Food Chem. 2015, 63, 85688573
spiked pesticides (chlorpyrifos ethyl, permethrin, cypermethrin,
and endosulfan αand β) were not detected after the roasting
process. This may be due to the instability of these pesticides to
the heat applied during the roasting process. Thermal
processing treatments such as cooking, backing, blanching,
steaming, and boiling have been found eective for the
breakdown of various pesticides, depending on the type of
Additionally, there may be a loss of the pesticides
during the application of heat depending on their phys-
icochemical properties, such as evaporation or thermal
From a study done in Japan on the behavior
of pesticides in coee beans, the pesticide residues decreased a
signicant amount after the coee beans were roasted.
After the coee brewing process, none of the pesticides
under study were detected. This process is found to be the
most eective for the breakdown of the pesticides under study.
As it has been explained by Abou-Arab and Abou Donia,
elimination of the pesticide residue from the boiled extract
(brewed coee) may be due to the decomposition of the
pesticide residue by the application of heat during brewing. The
pesticide residues were signicantly inuenced by the roasting
and brewing processes. In general, the three household coee
bean processing methods have a cumulative eect in the
reduction of pesticides and help in solving health problems that
can occur from exposure to pesticides in coee.
3.3. Determination of the Processing Factor. The
processing factor for each pesticide from each processing step
was determined. The PFs for coee samples after each
processing step was <1, which indicated that the processing
methods have an eect on pesticide residues. A study done by
Bonnechere et al
has also indicated that a PF of less than a
unit is an indication of pesticide residue reduction due to a
specic food processing step. The PFs for the detected
pesticides in the roasting process were the lowest, particularly
for hexachlorobenzene. Heptachlorepoxide, pp-DDE, pp-
DDD, and op-DDT ranged from 0.001 to 0.04. This indicated
that the roasting process played the most important role in
removing the pesticides from coee beans compared with the
washing process. The processing factor was not calculated for
the pesticides not detected after the processing (Table 3).
The KruskalWallis test showed that there is a strong
variation in the stability of pesticide residues in coee beans
among the processing methods (P= 0.00001). The reduction
of pesticide residues due to washing is signicantly lower than
roasting (p= 0.0001) and brewing processes (P= 0.00001);
however, there is no signicant dierence between coee
roasting and coee brewing (P> 0.05). According to Hasmukh
et al.,
the washing process may depend on dierent factors,
such as location, age of residue, water solubility, and
temperature; this may be the reason for the variation. From
the household processing methods, roasting and brewing are
the most eective in decreasing the pesticides in coee beans.
3.4. Pesticide Residue in Wash Water and Coee
Sludge. To determine the level of pesticide liquid waste (wash
water) and the coee sludge that settled to the bottom of the
coee pot after the coee was brewed, these two samples were
analyzed. The result of the analyses revealed that all DDT
metabolites (pp-DDE, pp-DDD, op-DDT, and pp-DDT) and
deltamethrin were detected in the wash water (Figure 2). This
may be due to the fact that these pesticides have contact action
(acting on surface) and may be removed with the coee
silverskin and found in the wash water. Most of the pesticides
disappeared from the coee beans during the roasting process.
In the meantime, pesticides were not detected in the coee
sludge after brewing, except for deltamethrin and pp-DDT.
This may be because the percent reductions of deltamethrin
(72.5%) and pp-DDT (88%) after roasting of the coee beans
were low compared with other pesticides under study (Figure
2). The results indicated that the coee sludge should not be
scored when pouring the brewed coee into a cup before
human consumption. After brewing, it is necessary to wait some
time until the sludge of the coee completely settles to the
bottom of the coee pot.
In Ethiopia, the wash water from coee beans and the residue
from the brewed coee are discarded to the open environment,
which may pose contamination, so care should be taken during
the disposal of both the liquid (wash water) and semi-solid
coee sludge) waste. In addition, during pouring of the coee
solution to drink or serve coee, only the upper layer (not
mixed with the sludge at the bottom of the pot) should be used
for the safety of the consumers.
Corresponding Author
*Phone: +32 (0)9264 60 12 Fax: +32 (0)9 264 62 49. E-mails:;seblework2001@yahoo.
The authors declare no competing nancial interest.
Table 3. Processing Factor for the Eect of Washing,
Roasting and Brewing Processes
Pesticide PF Washing PF Roasting PF Brewing
endosulfan α0.47 aa
endosulfan β0.42 aa
chlorpyrefos ethyl 0.73 aa
permethrin 0.53 aa
cypermethrin 0.53 aa
deltamethrin 0.55 0.28 a
pp-DDE 0.73 0.02 a
pp-DDD 0.85 0.02 a
op-DDT 0.72 0.04 a
pp-DDT 0.72 0.12 a
heptachlor epoxide 0.77 0.02 a
hexachlorobenzene 0.79 0.001 a
Not detected and the processing factor is not calculated.
Figure 2. Average concentrations of pesticides detected in wash water
and coee sludge (mg/kg).
Journal of Agricultural and Food Chemistry Article
DOI: 10.1021/acs.jafc.5b03327
J. Agric. Food Chem. 2015, 63, 85688573
The authors are very grateful for a special research fund (BOF)
of Ghent University for sponsoring this study and Jimma
University for supporting the study. The authors also would
like to acknowledge Lillian Goeteyn and Claudine Schollaert
for their assistant in the laboratory work.
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J. Agric. Food Chem. 2015, 63, 85688573

Supplementary resource (1)

... pyrethroid reduction (Parmar, Korat, Shah, & Singh, 2012). Heat treatment of home roasting completely reduced pyrethroid residues in contaminated coffee beans (Mekonen, Ambelu, & Spanoghe, 2015). Although the previous studies mentioned above have demonstrated the effects of postharvest processing on the fate of pyrethroid residues in crops, the impact of commercial and household processing on these chemical hazards in the intricate matrix of fish remains unknown. ...
... This may be due to the heat generated from the cooking pan accelerating volatilization and thermal degradation of pyrethroid residues (Albaseer, 2019). The effectiveness of direct heat treatment from the cooking pan was also demonstrated by Mekonen et al. (2015) who found that home roasting process completely reduced residues of cypermethrin and permethrin in contaminated coffee beans. Thermal treatments have been found effective in the destruction of various pesticides, depending on their types and chemical structures (Bajwa & Sandhu, 2014). ...
... Moreover, available literature has indicated the potential degradation effects of thermal conditions (Lin et al., 2005;Mekonen et al., 2015;Takahashi, Mikami, Yamada, & Miyamoto, 1985). The researchers demonstrated that enhancing the cooking temperature accelerated the thermal degradation of pyrethroids in food samples. ...
Pyrethroid contamination in fish can contribute to the dietary uptake of pesticides. To mitigate this risk, the effects of frozen storage, thermal treatments (boiling and grilling), and non-thermal treatments (pickling and curing) on the reduction of bifenthrin, cypermethrin, deltamethrin, and permethrin in mackerel fillets were investigated. The curing process was the most effective method that significantly depleted 74.82–79.45% of pyrethroid residues from fish fillets, followed by the synergistic effect of eight weeks’ frozen storage and grilling method (69.19–78.31%). Moreover, pyrethroid degradation pathways in processed fish were proposed into three major mechanisms of C1-C3 bond cleavage in cyclopropyl, dehalogenation, and double bond cleavage. These identical pathways incorporated with additional four mechanisms of dimerization, ester hydrolysis, oxidation, and reduction. This study recommended simple and effective processing practices for consumers and/or manufacturers to enhance food safety from the potential risks of consuming pyrethroid-contaminated fish.
... The household, as well as industrial food processing, can influence the level of the pesticide present in the raw agricultural commodity after it is harvested [13]. Different kinds of literature revealed that food processing such as baking, cooking, roasting, and others may reduce pesticide residue from raw food crops [14,15]. In most of the cases, pesticide residue analyses are undertaken on raw agricultural crops such as cereals, vegetables, and fruits, animal products [8,16,17,18,19,20]. ...
... Pesticide residues, which were present to a variable extent in the food commodities after harvesting is beyond the control of consumers. Hence, a pragmatic solution should be developed to tackle the problem of pesticide residues in teff where food processing could be one of the important solutions to reduce pesticide residues in different food items [13,15,24,25,26]. Therefore, the main purpose of the present study is to investigate the effect of household processing (doughing and baking) on the pesticide residues in teff as a means of risk reduction to consumers. ...
Full-text available
Teff (Eragrostis tef) is an ancient cereal that is indigenous from Ethiopia. Nowadays, teff grain is becoming popular to many parts of the world. Teff is gluten-free in nature, has high iron and fiber content, and many other health benefits make this crop interesting to many consumers. Since no insect pests are attacking the teff grains, farmers do not apply pesticides on it, unlike maize and other grains. Nevertheless, residues of organochlorine pesticides have been detected at an alarming level that could pose a consumer risk. Teff is often consumed as injera which is a fermented flat pancake. The main aim of the present study is, therefore, to investigate the effect of household food processing (doughing and baking) on the reduction of pesticide residues from teff. Pesticide residues previously detected in teff grain such as permethrin, cypermethrin, deltamethrin, chlorpyrifos ethyl, p,p’-DDE, p,p’-DDD, o,p’-DDT, and p,p’-DDT were spiked and extracted followed by the subsequent household processing which are generally doughing (dough making followed by fermentation) and baking. From the findings of this study, doughing decrease the pesticide residues in the range of 59.9–86.4% and baking in the range of 63.2–90.2%. Kruskal−Wallis analysis indicates that the reduction of pesticide residues by baking is significantly different from doughing (p-value < 0.0001). There is also a significant difference between non-fermented and fermented dough (p-value = 0.012). The processing factor for doughing and baking was less than one (PF < 1 = reduction factor) which indicates the reduction of pesticides due to teff processing. The cumulative effect of these processing methods is important to evaluate the risks associated with the ingestion of pesticides, particularly in teff grain.
... In the 48 RASSF notifications from 2000 to 2020, it was mainly the same pesticide residues that were detected. Several authors have reported that food processing causes a decrease in pesticide content [43][44][45][46]. Cooking was more effective than washing for the removal of chlorpyrifos residue from five types of vegetables (cabbage, garlic sprouts, tomato, cucumber, eggplant) [47]. ...
Full-text available
The QuEChERS method was applied to the determination of pesticide residues in vine (Vitis vinifera) leaves by LC-MSMS. The method was validated in-house for 33 pesticides representing 17 different chemical groups, that are most commonly used in grape production. Recoveries for the pesticides tested ranged from 75 to 104%, and repeatability and reproducibility relative standard deviations (RSDr% and RSDRw%) were less than 20%. The method was applied to the analysis of pesticide residues in 17 market brands of vine leaves processed according to three different preservation methods and sampled from the Lebanese market. Dried vine leaves were more contaminated with pesticide residues than those preserved in brine or stuffed vine leaves. The systemic fungicides were the most frequently detected among all the phytosanitary compounds usually applied to grape production. Brine-preserved and stuffed vine leaves contained lower concentrations of the residues but still contained a cocktail of different pesticides.
... Thus, the cytotoxicity shown by the samples depends not only on the degree of roasting but also on grain quality. It is important to point out that other compounds not monitored in this study may contribute to the observed effects, such as melanoidins, mycotoxins -particularly ochratoxin A (OTA) -and pesticides (Glosl, 2004;Mekonen, 2015;Taniwaki, 2019). ...
During the coffee beans roasting process, occurs the formation of polycyclic aromatic hydrocarbons, which are associated with the incidence of cancer in humans. This study aimed to evaluate the influence of coffee bean quality and roasting degree regarding mutagenicity, cytotoxicity and genotoxicity. Six samples of coffee drink made with roasted and ground Coffea arabica beans from different qualities and roast degrees were used after freeze-drying. Both commercial and special quality grains suffered light, medium and dark roasting. According to the Salmonella/microsome assay, the highest concentration of commercial grain sample (dark roast) significantly increased the number of revertants of the TA98 strain in the absence of metabolization. All the samples induced cytotoxicity to HepG2 cells. These effects can be ranked in the following order from most to least toxic: medium roast – special grain > light roast – special grain > dark roast - commercial grain > dark roast – special grain > light roast – commercial grain > medium roast – commercial grain. None of the samples induced genotoxicity in HepG2 cells. Our findings show that the harmful effects of coffee depend not only on the degree of roasting but also on the grain quality.
... 93% of farmers in rural Tanzania reported past lifetime pesticide poisoning (Lekei et al., 2014). Several reports have demonstrated acute pesticide poisoning to be associated with behaviors including lack of protective clothing, poor pesticide handling, not washing vegetables before eating, nozzle sucking, etc. (Magauzi et al., 2011;Oesterlund et al., 2014;Mekonen et al., 2015;da Silva et al., 2016;Sankoh et al., 2016;Manyilizu et al., 2017). One study from Sierra Leone reported most farmers having no knowledge about the safe handling of pesticides as 71% of them have never received any form of safety training (Sankoh et al., 2016). ...
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The World Health Organization in 2016 estimated that over 20% of the global disease burden and deaths were attributed to modifiable environmental factors. However, data clearly characterizing the impact of environmental exposures and health endpoints in African populations is limited. To describe recent progress and identify important research gaps, we reviewed literature on environmental health research in African populations over the last decade, as well as research incorporating both genomic and environmental factors. We queried PubMed for peer-reviewed research articles, reviews, or books examining environmental exposures and health outcomes in human populations in Africa. Searches utilized medical subheading (MeSH) terms for environmental exposure categories listed in the March 2018 US National Report on Human Exposure to Environmental Chemicals, which includes chemicals with worldwide distributions. Our search strategy retrieved 540 relevant publications, with studies evaluating health impacts of ambient air pollution (n=105), indoor air pollution (n = 166), heavy metals (n = 130), pesticides (n = 95), dietary mold (n = 61), indoor mold (n = 9), per- and polyfluoroalkyl substances (PFASs, n = 0), electronic waste (n = 9), environmental phenols (n = 4), flame retardants (n = 8), and phthalates (n = 3), where publications could belong to more than one exposure category. Only 23 publications characterized both environmental and genomic risk factors. Cardiovascular and respiratory health endpoints impacted by air pollution were comparable to observations in other countries. Air pollution exposures unique to Africa and some other resource limited settings were dust and specific occupational exposures. Literature describing harmful health effects of metals, pesticides, and dietary mold represented a context unique to Africa. Studies of exposures to phthalates, PFASs, phenols, and flame retardants were very limited. These results underscore the need for further focus on current and emerging environmental and chemical health risks as well as better integration of genomic and environmental factors in African research studies. Environmental exposures with distinct routes of exposure, unique co-exposures and co-morbidities, combined with the extensive genomic diversity in Africa may lead to the identification of novel mechanisms underlying complex disease and promising potential for translation to global public health.
... Permethrin and cypermethrin were not detected in roasted coffee during the brewing processes (Mekonen, Ambelu, & Spanoghe, 2015). Thermal degradation has been shown to take place in liquid state at a greater rate than in solid state (Elpiniki, 2011). ...
Full-text available
Control of residual levels of synthetic pyrethroids in fresh fruits and vegetables as well as in foodstuff made of fresh agricultural produces is of utmost importance. Apart from the need to more control on application of pesticides by farmers, simple and effective postharvest practices by consumers and/or manufacturers usually applied to produces before consumption may enhance food safety from potentially harmful pesticide residues. The present review discusses the underline factors that control the effectiveness of crops postharvest treatments and the possible mechanisms of loss of pesticides during food processing. It is shown that the effectiveness of postharvest processes is controlled by various factors and that understanding such factors is essential for more control of residual pesticides. Though postharvest processes may lead to substantial reduction of residual pesticides, metabolites of broken pesticides are of great concern.
This investigation shows the pesticide distribution and reduction using three common household cooking methods. Extraction was performed using QuEChERS and solid phase microextraction methodologies for rice and water, respectively. Gas chromatography-mass spectrometry was used. Both methods showed good linearity (r2 > 0.9996 and 0.9945), adequate recoveries (between 98.9 – 107.8 % and 90.5 – 104.2 %) and relative standard deviations lower than 8.1 % and 7.0 %, for rice and water, respectively. The initial concentration of deltamethrin, penconazole, kresoxim-methyl, cyproconazole, epoxiconazole and azoxystrobin, were 84.9, 242.2, 298.5, 230.7, 253.4 and 293.5 µg/kg, respectively. Washing and soaking water reduce pesticides only 0.40 to 4.28 %. The pesticide reduction during cooking were 20.73 to 57.72 %, 32.74 to 70.39 %, and 68.87 to 87.50 % for traditional, excess water, and pre-soaking rice methods, respectively. Pre-soaking rice with extra water before cooking proved to be the method that generates the greatest reduction.
The residue distribution and dissipation of pyrimethanil, fludioxonil, cyprodinil and kresoxim-methyl which were introduced during postharvest waxing treatments of apples were investigated. In addition, different residue removal methods were tested for the four fungicides in apples and the removal efficiencies were compared. A multi-residue analytical method was developed based on quick, easy, cheap, effective, rugged, and safe method (QuEChERS) method for the determination of the fungicide residues in apples. The dissipation study demonstrated that there was no significant change of fungicide residues during a 40-day storage process under ambient temperature. Waxing treatment has negative effects on the dissipation of fungicides. The results of residue distribution study demonstrated that waxing treatment may help to reduce the risk of pesticide when only the pulp was consumed. In the residue removal study, results suggested that higher temperature and the addition of acetic acid can improve the residue removal efficiency.
Full-text available
To quantify the effect of household and industrial processing on the pesticide residues, carrots (Daucus carota) were sprayed during cultivation with three fungicides (boscalid, difenoconazole and tebuconazole), two insecticides (chlorpyrifos and dimethoate) and one herbicide (linuron). The most concentrated formulations were applied pursuant to Good Agricultural Practices, to ensure sufficiently high levels of residues, The subsequent processing conditions were established to correspond as close as possible to the actual conditions that are normally used in industrial practice. The effects of household and industrial processing on the levels of the six pesticide residues and eight associated degradation products were quantified. The washing step allowed decreasing the concentration of residues for all pesticides up to ~ 90%. It was the most effective step to remove pesticide residues from carrots. The second process, peeling, results in a reduction comparable to washing. The blanching step, combining heat with a large quantity of water, enhanced the elimination of residues (maximum 50%). After cutting and washing, the residual concentrations were below 5 ppb. However it was observed that the level of pesticide residues was not reduced by microwave cooking. The pesticide residues remaining after previous processing, except difenoconazole, were decreased by sterilization. The cumulative processes allowed the elimination of minimum 90% of pesticide residues. Degradation products, investigated in this study, were not detected.
Full-text available
In a monitoring study, the effects of household processing on removal of organophosphate residues (malathion, fenitrothion, formothion, parathion, methyl parathion and chlorpyriphos) in tomato, bean, okra, eggplant, cauliflower and capsicum were studied. The processes included washing separately with (water, 0.9 % NaCl, 0.1 % NaHCO 3 , and 0.1 % acetic acid, 0.001 % KMnO 4 , 0.1 % ascorbic acid, 0.1 % malic acid and 0.1 % oxalic acid and 2 % aqueous solution of raw Spondias pinnata (SP)) and boiling. Organophosphorous (OP) residues were estimated (for real market samples and spiked samples) using multi residue analytical technique employing with capillary gas chromatograph with mass spectrometry detector (GCMSD). In all of the vegetables, washing with different household chemicals reduced the residues by 20-89 % and boiling reduced the residues by 52-100 %. Boiling of vegetables was found to be more effective than washing in dislodging the residues.
Full-text available
Samples of maize, teff, red pepper and coffee (green bean and coffee bean with pulp) were collected from a local market in Jimma zone, Ethiopia. Samples were analyzed for the occurrence of cypermethrin, permethrin, deltamethrin, chlorpyrifos ethyl, DTT and its metabolites, and endosulfan (α, β). In the analytical procedure, the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) extraction methodology with dispersive solid phase extraction clean up (d-SPE) technique was applied. Validation of the QuEChERS method showed satisfactory performance. Percent recovery of most pesticides was in the range of 70-120% with good repeatability (% RSD < 20). The limit of detection and limit of quantification varied between 0.001 to 0.092µg/g and 0.002 to 0.307µg/g, respectively. DDT, Endosulfan, Cypermethrin and Permethrin were the major detected pesticides. All the pesticides analyzed were detected in red pepper and green coffee bean. Residues of DDT in coffee pulp significantly differed (p value <0.01) from other food items except for red pepper. The concentration of pesticides in the food items varied from 0.011 to 1.115 mg/kg. All food items contained one or more pesticides and two third of the samples had residues below corresponding maximum residue limits (MRLs), while one third were above. These results indicate that there is a need for a good pesticide monitoring program and to evaluate consumer risk assessment for people in Ethiopia. Environ Toxicol Chem © 2014 SETAC
Marketed vegetables and fruits contaminated by organophosphorus, organochlorine, or carba-mate pesticides were cut into several regions (fruit stalk, pericarp, fruit receptacle, tissue around the stalk cavity, etc.) and the concentration of the pesticide residues in each region was assayed. In fruits and fruit-type vegetables, the concentra-tion of the pesticide residue was higher in the fruit stalk and near the epidermis (exocarp and fruit receptacle) than in the sarcocarp or peri-carp. In leaf vegetables, the concentration of the pesticide residue was higher in the outer leaves than in the inner ones. There was no pesticide contamination of the inner leaves of Chinese cab-bages with a well-formed head. Dieldrin and heptachlor epoxide were detected in pumpkins and cucumbers, although their use in agriculture has been prohibited in Japan for about 20 years. The removal rates of pesticide residues by washing with water or 0.1% liquid detergent for kitchen use were from 8 to 52% and from 19 to 67%, respec-tively. Removal of the fruit stalk, exocarp, and tissue around stalk cavity of fruits and fruit-type vegetables and washing of leaves with water or dilute detergent solution for kitchen use were necessary to decrease the intake of pesticide resi-dues from vegetables and fruit.
Pesticides are one of the major inputs used for increasing agricultural productivity of crops. The pesticide residues, left to variable extent in the food materials after harvesting, are beyond the control of consumer and have deleterious effect on human health. The presence of pesticide residues is a major bottleneck in the international trade of food commodities. The localization of pesticides in foods varies with the nature of pesticide molecule, type and portion of food material and environmental factors. The food crops treated with pesticides invariably contain unpredictable amount of these chemicals, therefore, it becomes imperative to find out some alternatives for decontamination of foods. The washing with water or soaking in solutions of salt and some chemicals e.g. chlorine, chlorine dioxide, hydrogen peroxide, ozone, acetic acid, hydroxy peracetic acid, iprodione and detergents are reported to be highly effective in reducing the level of pesticides. Preparatory steps like peeling, trimming etc. remove the residues from outer portions. Various thermal processing treatments like pasteurization, blanching, boiling, cooking, steaming, canning, scrambling etc. have been found valuable in degradation of various pesticides depending upon the type of pesticide and length of treatment. Preservation techniques like drying or dehydration and concentration increase the pesticide content many folds due to concentration effect. Many other techniques like refining, fermentation and curing have been reported to affect the pesticide level in foods to varied extent. Milling, baking, wine making, malting and brewing resulted in lowering of pesticide residue level in the end products. Post harvest treatments and cold storage have also been found effective. Many of the decontamination techniques bring down the concentration of pesticides below MRL. However, the diminution effect depends upon the initial concentration at the time of harvest, substrate/food and type of pesticide. There is diversified information available in literature on the effect of preparation, processing and subsequent handling and storage of foods on pesticide residues which has been compiled in this article.
Summary An analysis method for determination of organochloro pesticides in green and roasted coffees was developed. 17Arabica and 2Robusta coffees originating from 11 countries were investigated. With the exception of two samples the amounts of pesticide residues found in the green coffees were considerably lower than the amounts permitted, according to the „Höchstmengenverordnung”. In 2 coffees no residues were detectable. The residues were reduced to insignificant amounts during the roasting process. The degradation rates ranged from 85% to 100%. Since the residues detected in all of the roasted coffees were insignificant, no further investigation of the corresponding beverages was necessary.
In the light of recent increased interest in obtaining data on fate of pesticide residues during processing of food commodities for the more realistic estimates of the dietary intake of the pesticides, the present study was carried out to investigate the dissipation of pesticides during bread-making and the effect of pesticide contamination in the substrate on yeast growth required to mediate the fermentation. The bread was prepared from wheat flour spiked at different concentrations (1, 2, 3 and 4 mg/kg) with six pesticides (endosulfan, hexaconazole, propiaconazole, malathion, chlorpyriphos and deltamethrin) belonging to different chemical families. A simple, rapid analytical procedure for the quantification of analytes of interest in the matrix was developed using gas chromatography with electron capture detector. During bread-making process, considerable loss of pesticides (47–89%) was observed. Pesticide degradation during the process showed negative correlation with concentration of pesticides in wheat flour. The presence of endosulfan, hexaconazole and propiaconazole in the matrix suppressed the growth of the yeast in the range 7.5–33.5%, 12.5–44.7% and 11–40%, respectively. Other pesticides (malathion, chlorpyriphos and deltamethrin) did not show any significant effect on yeast growth. This kind of study is among the critical supporting studies required for the more realistic estimates to be made of the dietary intake of the pesticides and would help formulating regulatory guidelines for management of residues on such products by fixing or re-evaluating MRLs for their quality assurance and control.
Different combinations of Peelzym (I, II, III and IV) concentration (0.1, 0.55, 1cm3 enzyme/100cm3 solution), temperature (20°C, 35°C, 50°C), pH (3.0, 4.5, 6.0) and time (20, 40, 60min) were used for enzymatic peeling of apricots, nectarines and peaches. The optimum conditions were determined by using response surface methodology. Peeling yield, absorption of enzyme solution and texture changes were measured after peeling. For peeling of apricots with Peelzym IV, the optimum temperature was 45°C; the optimum values of time were in the range of 57–60min and that of pH and enzyme concentration were in the ranges of 3–3.5 and 0.85–0.90cm3 enzyme/100cm3 solution, respectively. Optimum conditions of peeling for nectarines were determined to be temperature, 44–47°C; time, 53–58min; pH, 3.5–4.1; and enzyme concentration, 0.70–0.90cm3 enzyme/100cm3 solution by using Peelzym I. For peaches the ranges were 41–46°C for temperature, 44–54min for time, 3.6–4.5 for pH and 0.73–0.90cm3 enzyme/100cm3 solution by using Peelzym IV. By this method, peeling was successful at moderately high temperatures.
An extensive analysis of the headspace (HS) of coffee brew using proton-transfer-reaction mass-spectrometry (PTR-MS) is presented. In particular, we present a set of methods that link mass spectral peaks, as observed in PTR-MS, to chemical compounds in the HS of coffee. Combining all this information, a tentative assignment and rough quantification of liquid coffee HS is presented. Coffee was chosen because it contains a large number of chemically diverse volatile organic compounds (VOCs), representing a challenging system for on-line analysis by PTR-MS.