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ORIGINAL PAPER
Effect of commercial processing on pesticide residues
in orange products
Yuncheng Li •Bining Jiao •Qiyang Zhao •
Chengqiu Wang •Yong Gong •Yaohai Zhang •
Weijun Chen
Received: 7 November 2011 / Revised: 6 December 2011 / Accepted: 15 December 2011 / Published online: 31 December 2011
ÓSpringer-Verlag 2011
Abstract The effect of commercial processing of orange
juice on pesticide residues was investigated, and the pro-
cessing factors of all orange products and by-products were
also determined. The pesticide residues were strengthened
using field trials and detected using Ultra-performance
Liquid Chromatography-tandem Mass Spectrometry
(UPLC-MS/MS). The results showed that the pesticide
residues were mainly distributed in orange peels, the
reduction of residue levels ranged from 43.6 to 85.4%
during washing process. One percent to 4.5% of initial
residues contained in the squeezed juice, 7–94.7% of the
total relative residues were distributed in pomace. Filtrat-
ing could further reduce all the residue levels, ranging from
96.0–99.4% relative to unwashed whole fruits. After ster-
ilization, there was only 0.5–3.1% of the residues contained
in Not from Concentrate juice (NFC juice). 0.2–7.1% of the
total relative residues was contained in concentrated juice,
comparing with the filtrated juice; however, the concen-
tration of cypermethrin and prochloraz was decreased, but
the other 3 pesticides were increased. The residue levels of
imidacloprid and carbendazim in orange oil were reduced
but abamectin, prochloraz, and cypermethrin were con-
centrated, and the concentrated factor was 28.214, 5.232,
and 5.621, respectively.
Keywords Pesticide residues Orange products
Commercial processing
Introduction
Pesticides are widely applied in field and post-harvest to a
variety of fruits and vegetables to control weeds, insects,
and diseases [1–5]. Although the correct use of pesticides
does not cause public health and environmental concerns,
awareness of potential health risks for consumers resulting
from chronic dietary exposure is increasing [6]. Food
processing has an effect on the fate of pesticide residues.
Owing to the effects of processing, the level and nature of
pesticide residues in food is changed. Numerous studies
have reported that food processing, including washing,
peeling, boiling, and juicing, can largely reduce the level
of pesticide residues in food [7–12]. However, some pro-
cessing operations, like drying, will lead to a concentration
of pesticides because of the loss of water [11,13]. More-
over, some pesticide residues will be transformed into other
chemical forms during food processing due to the effects of
temperature and microorganisms activities [14–17].
Good knowledge of the effects of food processing on
pesticide residues can provide the basis for the optimization
of processing technology. More importantly, it is necessary
to properly assess human dietary exposure. Dietary exposure
assessment includes two aspects: (1) Raw Agricultural
Commodities (RACs) that are directly consumed by
humans, such as apples or oranges; (2) Processed Food
Commodities (PFCs), such as cookies or orange juice.
Y. Li B. Jiao (&)W. Chen
College of Food Science, Southwest University,
Chongqing 400715, People’s Republic of China
e-mail: bljiao@tom.com
Y. Li B. Jiao Q. Zhao C. Wang Y. Zhang W. Chen
Citrus Research Institute c/o Key Laboratory of Horticulture
Science for Southern Mountainous Regions of Ministry
of Education, Southwest University, Chongqing 400715,
People’s Republic of China
Y. Gong
Institute for Control of Agrochemicals, Ministry of Agriculture,
Beijing 100125, People’s Republic of China
123
Eur Food Res Technol (2012) 234:449–456
DOI 10.1007/s00217-011-1651-1
Dietary exposures are generally being assessed on the basis
of established Maximum Residue Limits (MRLs). However,
MRL’s proved to be inadequate as a guide to pesticide res-
idue consumption in health risk assessment studies and this
is mainly because a wide range of RACs are processed
before they are consumed [18]. The information about
dilution and concentration of residues and the estimation of
processing factors is used to conduct refined dietary expo-
sure assessments with primary processed products to assess
consumer safety, and also used to recommending MRLs for
processed commodities, which the level of pesticide resi-
dues in processed products is higher than the MRLs in RACs
[19]. Therefore, we need to understand whether or not the
effects of food processing can cause degradation, concen-
tration, or other reactions to pesticide residues. The pro-
cessing factors are generally used to indicate the effect of
food processing on pesticide residues and also used to assess
the dietary burden of livestock. It was calculated by Joint
Meeting of Pesticide Residues (JMPR) as follows:
pf ¼Residue level in processed commodity
Residue level in the RAC or commodity to be processed
Citrus is considered to be one of the major fruit crops
produced in the world. Citrus fruits are mainly used for
processing and eating directly, about a third of citrus fruit
goes for processing; more than 80% of this is for juice
production. However, Citrus trees have adapted to warm
temperate and subtropical climates where pests and dis-
eases are very serious problems, which result in a large
amount and variety of pesticides being used in citrus
orchards, but there is not sufficient information on the fate
of pesticide residues during commercial processing of cit-
rus. The objective of this study was to evaluate the effects
of commercial processing on the pesticide residues in
orange juice and its by-products.
Materials and methods
Field trials
The Beibei 447 sweet oranges were selected as the RAC
samples for this experiment. Imidacloprid, carbendazim,
abamectin, cypermethrin, and prochloraz were chosen as
the target pesticides, due to their common utilization in
conventional citrus orchards (imidacloprid, carbendazim,
abamectin, and cypermethrin) and in post-harvest preser-
vation (prochloraz). They had been mostly detected in
orange fruits during routine analysis in the Chinese moni-
toring program for fruits and vegetables. The physical
property details of the pesticides are listed in Table 1.
In order to ensure that each target pesticide in various by-
products could be quantified, the field trials for imidacloprid,
carbendazim, cypermethrin, and abamectin were carried out
to guarantee sufficient residue levels in RAC samples for
further processing studies. We selected citrus orchards during
the blossom season in May 2010, and managed the orchards
based on the rule of Good Agricultural Practices (GAP). The
trees were sprayed with fivefold the concentration of the
maximum recommended dosage solutions using a bucket
pump sprayer, for a total of three sprayings at an interval of
7 days. The fruits were picked 24 h after the third spraying
and were sent immediately to the workshop for processing.
Because prochloraz is mainly used for preservation of
oranges during the post-harvest storage period, we applied
fivefold the concentration of the maximum recommended
dosage solutions to soak the fruits, then drained the fruits
and stored them for 3 days before processing. The details
of the field trials for each pesticide are shown in Table 2.
Commercial processing
Organization for Economic Co-operation and Development
(OECD) reported that processing operations should simulate
commercial practices as closely as possible during the lab-
oratory experiment when the fate of pesticide residues in
food processing is studied, so that the processing factors for
various products can be determined more realistically [19].
This processing was implemented at the National Citrus
Engineering Research Center of China. Processing steps and
sampling points are shown in Fig. 1. All fruits sprayed with
each pesticide were divided into three batches; the process-
ing line was washed well after the processing of each batch.
Sample homogenization was performed by using a knife
or a hand blender during peeling and sample preparation
and all equipments were carefully rinsed with ultra-pure
Table 1 Physical property
details for each pesticide
a
n-octanol–water-partitioning
coefficient (K
ow
)
b
a mixture of avermectins
containing [80% avermectin
B1a and \20% avermectin B1b
Pesticide Category Water solubility
(mg L
-1
)
Melting
point (°C)
Log
K
owa
Vapor pressure
(mPa)
Imidacloprid Insecticide 510 (20 °C) 143.8 0.57 2 910
-4
(20 °C)
Carbendazim Fungicide 29 (24 °C) [300 1.51 0.09 (20 °C)
Abamectin
b
Insecticide 0.0078 (21 °C) 150 4.4 \2910
-4
(25 °C)
Cypermethrin Insecticide 0.01–0.2 (21 °C) 60–80 6.6 2.3 910
-4
(20 °C)
Prochloraz Fungicide 55 (25 °C) 46.5–49.3 4.06 0.15 (25 °C)
450 Eur Food Res Technol (2012) 234:449–456
123
water, detergent, and ethanol after each sample treatment.
The samples were packed in polypropylene bottles and
stored at -20 °C for further analysis.
Washing
The whole unprocessed oranges were immersed in water
and bubble washed for 5 min, then transported to a spurt
brush type fruit cleaning machine to spurt brush clean for
3 min. Samples were taken of the unwashed and washed
fruits at different times of the process randomly. Approx-
imately 10 kg of whole fruits were taken of each batch.
Juicing
Whole fruit juice machine produced by Food Machinery
Corporation (USA) was applied in this experiment, and
samples were taken of the squeezed juice and pomace.
Filtrating
The squeezed juice was further extracted using a centrifuge
at a speed of 400 r/min, and juice samples were taken at
every 5 min basis. At the end of each batch processing, all
the samples were homogenized and packed.
Sterilizing
The filtrated juice was sterilized for 30 s at 100 °C after
degassing.
Concentrating
The Thermally Accelerated Short Time Evaporator
(TASTE) was used with the primary temperature setting at
107 °C, and the subsequent at 50 °C to reach the final Brix
of 65°for this study.
Oil collecting
The oil–water mixture was separated using a disk separator
at 7,400 r/min; then, the raw oil was separated again using
the separator at 6,300 r/min.
Detection of pesticide residues
Equipment and chemicals
The pesticides were analyzed by UPLC-MS/MS (Waters
Quattro-Premier XE, USA) equipped with an electrospray
ionization source and operated in the positive ion mode
(ESI ?), the column was a BEH C
18
(50 92.1 mm i.d.,
1.7 lm particle size). The Homogenizer (ULTRA-TUR-
RAX T18 basic) and Vortex mixer (Vortex Genius 3) are
manufactured by IKA (Germany). The Centrifuge was a
Laborzentrifugen 3K15 manufactured by SIGMA (Ger-
many); and the Ultra-pure water system was a Milli-Q
Advantage A10 manufactured by Millipore (USA).
Table 2 Details of field trials
Pesticide Operating
method
Dose recommended
a
(mg kg
-1
)
Dose applied
b
(mg kg
-1
)
Number of
applications
Intervals
c
/day
Imidacloprid Spraying 50–100 500 3 7
Carbendazim Spraying 750–1,000 5,000 3 7
Abamectin Spraying 9–12 60 3 7
Cypermethrin Spraying 50–100 500 3 7
Prochloraz Soaking 250–500 2,500 1 –
a
Dose recommended in oranges in China
b
Fivefold concentration of the maximum recommended dosage
c
Intervals between two sprays
Filtrating
Filtrated juice
Extracting
Oil-water mixture
Juicing
Wet pomace Squeezed juice
Orange oil
Concentrating
Concentrated juice
Degassing
Sterilizing
NFC juice
Washed whole fruits
Washing
Unprocessed whole fruits
—sampling points
Fig. 1 Processing steps and sampling points
Eur Food Res Technol (2012) 234:449–456 451
123
Pesticide standards of Imidacloprid (99% Purity),
Carbendazim (99% Purity), Abamectin (92% Purity),
Cypermethrin (94% Purity), and Prochloraz (98% Purity)
were purchased from Dr Ehrenstorfer GmbH (Germany);
Acetonitrile (HPLC grade), Methanol (HPLC grade), and
Primary Secondary Amine (PSA, 40–63 lm) were pur-
chased from CNW Technologies GmbH (Germany).
Sample preparation method
The method of pesticide extraction and cleanup from
oranges described by Lehotay et al. [20] was referenced,
but it was modified appropriately: 10 g samples (8 g
samples add 2 g water for orange oil) were weighed in a
50 mL plastic centrifuge tube, to which was added 20 mL
MeCN in each tube; the peel, pulp, pomace, and whole
fruit samples were homogenized 4 min using the homog-
enizer, and the juice and oil were shaken for 30 min in the
oscillator. Each of the tubes then received 2 g NaCl and
4 g anhydrous MgSO
4
. The tubes were capped and shaken
vigorously by hand to ensure that the solvent interacted
well with the entire sample and that crystalline agglomer-
ates were sufficiently broken up during the shaking. The
tubes were centrifuged at 8,000 r/min for 6 min. Two
milliliter of the upper layer extract was decanted into the
4 mL centrifuge tubes containing 100 mg PSA and 300 mg
anhydrous MgSO4. The tubes were capped and shaken in
the vortex mixer for 3 min, then centrifuged at 6,000 r/min
for 6 min. From the centrifuged solution, 1 mL of the
supernatant was pipetted into a vial using a filter mem-
brane, and then analyzed using the UPLC-MS/MS.
Analytical method
UPLC Conditions: Phase A was methanol, and phase B
was 1 mmol/L ammonium acetate in water. The following
gradient condition was used for the analyses: 0–3.5 min,
from 10 to 90% A; held at 90% A for 2.5 min; then
returning to the initial mobile phase composition immedi-
ately and held 1 min; Flow rate was controlled at 0.25 mL/
min. Column oven temperature was set at 35 °C, and auto-
sampler temperature was set at 5 °C. Injection volume was
5lL, and the total run time was 8 min.
MS/MS conditions The ion source was electrospray
ionization in the positive ion mode (ESI?), and multiple
reactions monitoring (MRM) was used for Scan mode (the
MRM information is shown in Table 3). Ion source tem-
perature was set at 110 °C; desolvation gas temperature
was 350 °C and the gas volume was 600 L/h; the collision
gas volume was set at 0.18 mL/min; capillary voltage was
3 kV. The parameters of MRM mode are shown in
Table 3.
Results and discussions
Method validation
The methods were validated for whole fruit, peel, pulp,
pomace, juice, and oil. Recovery and accuracy were
determined with spiked samples at three concentration
levels (0.01, 0.1, and 1 mg kg
-1
). The resulting coeffi-
cients of regression (R
2
values) were higher than 0.9955 in
all cases. Acceptable mean recoveries and Relative Stan-
dard Deviation (RSD) values (n=6) are ranging from
70.9–117% for all pesticide with RSD lower than 21%
(Table 4). The limits of detection (LODs) and the limits of
quantification (LOQs) were evaluated as the signal-to-noise
ratios of 3:1 and 10:1, respectively, and varied from 0.03 to
3lgkg
-1
and 0.07 to 10 lgkg
-1
, respectively.
Table 3 Parameters of MRM mode
Pesticide Formula Retention
time (min)
MM
a
Ionization Parent
ion
Daughter
ion
Cone
voltages (V)
Collision
energy (eV)
Dwell
time (s)
Imidacloprid C
9
H
10
ClN
5
O
2
2.27 255.1 [M?H]
?
256.1 175.1 34 20 0.05
209.1 34 15 0.05
Carbendazim C
9
H
9
N
3
O
2
2.71 191.1 [M?H]
?
192.1 160.1 33 18 0.05
132.1 33 28 0.05
Prochloraz C
15
H
16
Cl
3
N
3
O
2
4.31 375.0 [M?H]
?
376.0 70.1 16 34 0.05
307.1 16 16 0.05
Cypermethrin C
22
H
19
C
l2
NO
3
4.79 415.1 [M?NH
4
]
?
433.1 127 10 25 0.05
191 10 20 0.05
Abamectin (B1a) C
48
H
72
O
14
5.03 872.5 [M?Na]
?
895.5 751.3 90 41 0.05
449.2 90 47 0.05
a
Monoisotopic mass
452 Eur Food Res Technol (2012) 234:449–456
123
The distribution of pesticide residues in orange fruits
Table 5indicates that the pesticide residues were mainly
distributed in orange peels, about 7.5–17.9% of total rela-
tive pesticide residues were contained in the pulps of
unwashed oranges. However, prochloraz was an exception,
with 65.4% of the total residues present in the pulp of
unwashed oranges. The residues distributed in the face of
peels could be partially removed by washing during com-
mercial processing of orange juice, washing with tap water
gave the whole fruits 85.4, 73.0, 57.3, 47.8, and 43.6% loss
in carbendazim, abamectin, imidacloprid, prochloraz, and
cypermethrin, respectively. The washing processing factor
of imidacloprid, carbendazim, abamectin, cypermethrin,
and prochloraz was 0.427, 0.146, 0.270, 0.564, and 0.522,
respectively (Table 6). The factor of carbendazim is agrees
with the report of the Federal Institute for Risk Assessment
(BfR) compilation of processing factors for pesticide resi-
dues [21].
The habits of oranges eaten in mainland China are to
peel the fruit by hand or with a knife, or to cut the orange
into sections, and to eat the pulp directly from the section.
These methods may cause pesticides in the peel to be
translocated into the pulp by hands or knives; Table 5
shows that the residues in the pulp of the unwashed whole
fruit were higher than the residues in the pulp of washed
whole fruits. Therefore, washing fruit before consumption
can decrease pesticide contamination to a certain degree.
Effects of juicing and filtrating on pesticide residues
Whole fruits were squeezed during the processing while
there were only 1–4.5% of the total residues contained
in squeezed juice. About 46.5, 46.0, 94.7, and 81.0% of
imidacloprid, abamectin, cypermethrin, and prochloraz
were distributed in pomace, respectively, while only 7.0%
of carbendazim could be observed in pomaces.
The effect of processing on 5 pesticide residues in fil-
trated juice is shown in Table 5, which indicates that fil-
trating during commercial processing of orange juice could
further reduce all the pesticide residues. About 1.4, 1.0, 2.0,
0.6, and 4.0% of imidacloprid, carbendazim, abamectin,
cypermethrin, and prochloraz were contained in filtrated
juice, respectively, and the residue levels were decreased
by 15.5, 18.2, 33.3, 38.9, 11.7%, respectively, comparing
with the filtrated juice samples.
Because of the partitioning properties of the pesticide
between the fruit skin/pulp and the juice, low residue levels
were observed in the squeezed juice [18,22]. Comparably
to the present study, the significant reductions of pesticide
residues during juice processing were also reported by
Buchat et al. [8], Holland et al. [22], Pappas et al. [23], and
Rasmussen et al. [24]. However, Buchat et al. [8] deter-
mined that the pesticides with the highest water solubility
were present in relatively lower amounts in pulps of juiced
carrots and tomatoes, but this conclusion could not be
confirmed in present experiment (the water solubility of
Table 4 Mean recoveries of the fortified control samples and observed relative standard deviation (RSD, n=6)
Samples Fortified level
(mg kg
-1
)
Imidacloprid Carbendazim Prochloraz Cypermethrin Abamectin
Recovery RSD Recovery RSD Recovery RSD Recovery RSD Recovery RSD
Peel 0.01 96 11 74.2 2 73.8 12 74.9 14 84 20
0.1 104.4 3 82.6 7 83.2 20 87.7 9 85.5 3
1 99.8 6 91.3 6 74.9 14 71.6 8 82.3 11
Pulp 0.01 88.3 9 73.3 9 105.2 17 89.6 18 83 14
0.1 98.2 7 101.1 4 89.4 18 96.7 5 109.8 7
1 71.6 11 76.1 10 94.5 10 90.6 14 100.9 7
Whole fruit 0.01 100.3 13 79.6 7 100.4 12 78 21 103.3 8
0.1 83.2 4 98.6 8 93.2 12 106.4 8 87.2 4
1 80.1 8 95.4 5 95.2 12 80.8 9 109.3 2
Pomace 0.01 73.3 8 75.3 8 88.2 13 92.8 17 81.2 10
0.1 90.1 8 80.7 7 81 14 82.9 13 78.9 3
1 92.3 6 79.8 7 92.4 4 78.2 5 79.1 1
Juice 0.01 73.3 7 91.3 9 97.6 21 94.4 19 117 8
0.1 80.9 3 92.6 9 90.5 19 102.2 5 79.5 4
1 74.7 6 115.7 5 77 8 84.7 5 75.8 2
Orange oil 0.01 81.3 13 82 13 84.9 14 70.9 20 81.3 6
0.1 83.6 7 91.2 4 92.3 13 83.8 18 102 6
1 106.7 5 84.7 8 89.4 16 104.2 20 79.2 1
Eur Food Res Technol (2012) 234:449–456 453
123
each pesticide is shown in Table 1). This result agrees with
the findings reported by Rasmussen et al. [24] who found
that there is no trend related to the n-octanol–water-parti-
tioning coefficient or to water solubility and pesticide
residue distribution between apple juice and pomace.
Orange pomace is an unconventional agro industrial
by-product contained 8.22% of crude protein, 4.97% ether
extract, 13.45% crude fiber, 64.20% nitrogen free extract,
and 9.31% total ash [25], which is usually applied to pro-
duce feeds, or extract functional components like crude
fiber and pectin. BfR reported that many of the pesticide
residues were concentrated in wet and dried pomace [21],
so the risk problem of pesticide residues should be con-
sidered during comprehensive utilization of orange pom-
ace. For example, microbial fermentation and heat
treatment during the feeds producing could reduce some
pesticide residues to a certain degree.
Effects of juice sterilizing on pesticide residues
There was only 0.5–3.1% of the total relative pesticide
residues were contained in NFC juice. The processing
factor of NFC juice of imidacloprid, carbendazim, aba-
mectin, cypermethrin, and prochloraz was 0.017, 0.010,
0.020, 0.005, and 0.031, respectively. The residue level of
cypermethrin and prochloraz in NFC juice was decreased
by 7.6 and 20.8%, respectively, comparing with the fil-
trated juice samples. The residue level of abamectin was
unchanged. However, the concentration of imidacloprid
and carbendazim was increased 1.1 and 1.0 times,
respectively.
The effect of sterilizing on pesticide residues is probably
related to processing conditions and physical–chemical
properties of pesticides. Filtrated juice was sterilized for
30 s at 100 °C. Cypermethrin and prochloraz are thermally
unstable pesticides, during sterilization these two pesticides
might have got destroyed or degraded. The other three
pesticides are thermal stable and high water soluble pesti-
cide, so the concentration of these pesticides was increased
slightly or had no changes. The thermally decompositions
of these pesticides have not determined in present study,
but the registrants indicate that dangerous products are
unlikely to be formed during thermal degradation. The
above results seem to also indicate that the short time
sterilizing could not decrease the residues level sufficiently
during commercial process of orange juice.
Effects of juice concentrating on pesticide residues
The TASTE was used during concentration, with the pri-
mary temperature setting at 107 °C, and the subsequent at
50 °C to reach the final Brix of at 65°for this study.
Table 5 Residue levels during commercial processing expressed as lgkg
-1
(mean ±SD/n=6)
Processing Imidacloprid Carbendazim Abamectin Cypermethrin Prochloraz
Whole fruits, unwashed 683.5 ±139.1 5,433.4 ±1,366.5 10.0 ±2.4 1,115.7 ±239.5 6,994.0 ±1,766.3
Whole fruits, washed 292.1 ±31.6 792.3 ±170.4 2.7 ±0.8 629.6 ±62.2 3,651.2 ±29.9
Peels, unwashed 1,621.6 ±284.4 3,720.8 ±938.4 26.1 ±1.9 4,955.8 ±1,013.6 8,117.3 ±1,303.5
Peels, washed 1,232.2 ±145.7 1,459.0 ±455.6 13.9 ±3.3 3,754.2 ±565.8 5,212.0 ±965.8
Pulps, unwashed 51.3 ±7.5 973.6 ±404.7 1.3 ±0.2 152.5 ±20.6 4,576.9 ±896.8
Pulps, washed 12.1 ±0.9 432.5 ±48.5 0.5 ±0.1 65.6 ±14.7 2,578.3 ±141.5
Squeezed juice 11.6 ±2.3 68.0 ±21.4 0.3 ±0.1 10.8 ±2.6 314.4 ±94.5
Wet pomace 317.8 ±50.6 381.4 ±93.8 4.6 ±1.1 1,056.7 ±271.6 5,661.9 ±1,981.1
Filtrated juice 9.8 ±2.7 55.6 ±8.2 0.2 ±0.0 6.6 ±1.3 277.6 ±46.1
NFC juice 11.3 ±4.1 55.8 ±17.6 0.2 ±0.1 6.1 ±1.1 219.9 ±56.8
Concentrated juice 48.4 ±7.1 60.0 ±12.9 0.4 ±0.1 2.4 ±0.1 231.1 ±36.7
Orange oil 11.1 ±3.6 204.4 ±53.6 281.6 ±12.5 6,270.9 ±678.7 36,590.1 ±6,039.9
Table 6 Processing factors
for orange products
and by-products
Products Processing factor
Imidacloprid Carbendazim Abamectin Cypermethrin Prochloraz
Washed whole fruits 0.427 0.146 0.270 0.564 0.522
NFC juice 0.017 0.010 0.020 0.005 0.031
Concentrated juice 0.071 0.011 0.040 0.002 0.033
Wet pomace 0.465 0.070 0.459 0.947 0.810
Orange oil 0.016 0.038 28.160 5.621 5.232
454 Eur Food Res Technol (2012) 234:449–456
123
Table 5shows that juice concentrating produced 92.9,
98.9, 96.7, 99.8, and 96.0% loss in imidacloprid, carben-
dazim, prochloraz, cypermethrin, and abamectin, respec-
tively, comparing with unprocessed whole fruits. Owing to
high moisture dissipation during juice concentration, pes-
ticides with high thermal stability may be increased, but
pesticides with thermal instability may be degraded [7,11,
13]. Cypermethrin and prochloraz are thermally unstable
pesticides, and their residue levels in concentrated juice
were reduced by 63.6 and 16.7%, respectively, relative to
filtrated juice; imidacloprid, carbendazim, and abamectin
are thermally stable pesticides, and the residue levels were
increased 4.9, 1.1, and 2.0 times, respectively (Table 6).
Because the concentrated juice is mainly used for pro-
ducing commercial orange juice by reconstituting with
water, so the residue levels in commercial juice may be
further decreased during the reconstituting step.
Effects of orange oil collecting on pesticide residues
Lipid-soluble pesticides are often left on the fruit skin, or
penetrated through the skin into the peels, so they are
difficult to effectively remove by washing, and easily
concentrated in orange oil. Table 5shows that the residue
levels of imidacloprid and carbendazim in orange oil were
reduced by 98.4 and 96.2%, respectively, relative to
unprocessed fruits, but the other 3 pesticides were con-
centrated in orange oil, and the concentrated factor of
abamectin, prochloraz, and cypermethrin was 28.160,
5.232, and 5.621, respectively (Table 6).
These results may relate to the log-octanol–water-par-
titioning coefficients of pesticides (shown in Table 1).
Pesticides with the lowest log-octanol–water-partitioning
coefficients were present in relatively lower residues in the
orange oil. Imidacloprid has the lowest log-octanol–water-
partitioning coefficient value of the pesticides in present
study (log K
ow
is 0.57), so low residue level was observed
in orange oil, the processing factor is 0.016. The log-oct-
anol–water-partitioning coefficient of carbendazim is 1.51,
and the process factor is 0.038 (Table 6), which disagrees
with the factor reported by BfR, BfR reported that the
processing factor of carbendazim is 1.36 [21], but we used
different processing conditions. The log-octanol–water-
partitioning coefficient of prochloraz, abamectin, and
cypermethrin is 4.06, 4.4, and 6.6, respectively, and all
were concentrated in orange oil in different extents.
The orange oils are widely used throughout the food and
cosmetics industry in products ranging from drink and
confectionary to bath and body oils. However, most of the
pesticide residues were significantly concentrated in orange
oil. BfR reported that the residual levels of 18 target pes-
ticides were increased in all 20 during orange oil collec-
tion, and the cyhexatin, trifloxystrobin, and malathion
concentrations were increased even hundreds of times, the
processing factor was 102, 130, and 219, respectively [21].
Therefore, the risk problem must be considered during the
utilization of orange oil, some refined operations such as
distillation should be employed to remove the pesticide
residues.
Conclusion
Several conclusions can be drawn from this study
1. The pesticide residues were mainly distributed in
orange peels, the reduction of residue levels ranged
from 43.6 to 85.4% during washing. Peeling reduced
all pesticide residues significantly in the edible part of
the oranges.
2. Low residue levels were observed in squeezed juice,
ranged from 1 to 4.5%. Filtrating could further reduce
all the residue levels. After sterilization, there was only
0.5–3.1% of the total relative residues contained in
NFC juice, and 0.2–7.1% was contained in concen-
trated juice.
3. About 46.0–94.7% of imidacloprid, abamectin, cyper-
methrin, and prochloraz residues were distributed in
pomace, while only 7% of carbendazim could be
observed in pomace. The residue level of imidacloprid
and carbendazim in orange oil was reduced but the
other 3 pesticides were increased in the collection of
orange oil.
Acknowledgments This work was supported by the Construction
and Development of National System of Modern Agriculture (Citrus)
Industrial Technology and the Research Project in Integrated Sup-
porting Technologies to Pesticide Risk Evaluation (No. 200903054).
We thank the Institute for the Control Agrochemicals of Chongqing
for collaboration in field trials.
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