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Extraction of Essential Oils from Citrus By-Products Using Microwave Steam Distillation

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The main objectives of this research is to extract essential oil from: orange ( citrus sinensis), lemon( citrus limon) and mandarin( citrus reticulata) peels by two methods: steam distillation (SD) and microwave assisted steam distillation (MASD), study the effect of extraction conditions (weight of the sample, extraction time, and microwave power, citrus peel type) on oil yield and compare the results of the two methods, the resulting essential oil was analyzed by Gas Chromatography (GC). Essential oils are highly concentrated substances used for their flavor and therapeutic or odoriferous properties, in a wide selection of products such as foods, medicines and cosmetics. Extraction of essential oil is one of the most time and effort consuming process. Microwave-assisted extraction is a green technique for the extraction of natural products. (MASD) was better than (SD) in terms of rapidity, energy saving and yield. (MASD) gave higher yield than (SD) with shorter extraction time, yield of orange oil extracted by (MASD) was (1.150%) in (35min.) compared to (1.095%) in (45min.) by (SD) process, same results obtained for lemon and mandarin. The optimal microwave power was (135W) gave oil yield: (1.150%, 1.115%, 0.940%) for orange, lemon and mandarin respectively, (MASD) increased extraction temperature in short time and to a higher level compared to (SD). The optimal weight was (398.56gm) gave yield in (SD): (1.095%) and MASD (1.091%) for orange oil, same results obtained for lemon and mandarin. The best citrus peel type which gave the highest yield was orange followed by lemon then mandarin in both processes. Limonene is the most abundant component in citrus essential oil, (GC) analysis showed that (SD) was more convenient to give high amount of limonene because of the graduate temperature rise, while in microwave extraction exposure to low microwave
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Iraqi Journal of Chemical and Petroleum Engineering
Vol.16 No.3 (September 2015) 11- 22
ISSN: 1997-4884
Extraction of Essential Oils from Citrus By-Products Using
Microwave Steam Distillation
Ibtehal K. Shakir and Sarah J. Salih
Chemical Engineering Department College of Engineering University of Baghdad
Abstract
The main objectives of this research is to extract essential oil from: orange ( citrus
sinensis), lemon( citrus limon) and mandarin( citrus reticulata) peels by two methods:
steam distillation (SD) and microwave assisted steam distillation (MASD), study the
effect of extraction conditions (weight of the sample, extraction time, and microwave
power, citrus peel type) on oil yield and compare the results of the two methods, the
resulting essential oil was analyzed by Gas Chromatography (GC).
Essential oils are highly concentrated substances used for their flavor and
therapeutic or odoriferous properties, in a wide selection of products such as foods,
medicines and cosmetics. Extraction of essential oil is one of the most time and effort
consuming process. Microwave-assisted extraction is a green technique for the
extraction of natural products. (MASD) was better than (SD) in terms of rapidity,
energy saving and yield. (MASD) gave higher yield than (SD) with shorter extraction
time, yield of orange oil extracted by (MASD) was (1.150%) in (35min.) compared to
(1.095%) in (45min.) by (SD) process, same results obtained for lemon and mandarin.
The optimal microwave power was (135W) gave oil yield: (1.150%, 1.115%,
0.940%) for orange, lemon and mandarin respectively, (MASD) increased extraction
temperature in short time and to a higher level compared to (SD). The optimal weight
was (398.56gm) gave yield in (SD): (1.095%) and MASD (1.091%) for orange oil,
same results obtained for lemon and mandarin. The best citrus peel type which gave
the highest yield was orange followed by lemon then mandarin in both processes.
Limonene is the most abundant component in citrus essential oil, (GC) analysis
showed that (SD) was more convenient to give high amount of limonene because of
the graduate temperature rise, while in microwave extraction exposure to low
microwave
Key Words: Essential oil, extraction, steam distillation, microwave assisted steam
distillation, orange, lemon, mandarin, citrus peels, yield
Introduction
Essential oils are volatile natural,
complex mixtures comprising many
unique compounds [1]. Essential oils
extracted from several plant organs
including flowers, leaves, twigs, seeds,
fruits, roots, wood or bark are valuable
natural products [2]. Nowadays, people
worldwide are looking towards natural
base products since there are no side
effects when taken accordingly.
Furthermore, there is also an interest in
Iraqi Journal of Chemical and
Petroleum Engineering
University of Baghdad
College of Engineering
Extraction of Essential Oils from Citrus By-Products Using Microwave Steam Distillation
12 IJCPE Vol.16 No.3 (Sept. 2015) -Available online at: www.iasj.net
the production of functional, high
value, natural products without
chemical modification and residues of
solvents or additives [3] , for these
reasons essential oils are used as raw
materials for many products including
food flavorings, additives, flavoring
agents used in the cigarette industry
and in the compounding of cosmetics
and perfumes [2].They are used also in
air fresheners and deodorizers as well
as in all branches of medicine such as:
pharmacy, balneology, massage and
homeopathy [3].
Citrus is the largest fruit crop in the
world (100 million cubic tons per year)
and the orange account for 60% [4].
The remaining orange peel account for
approximately 45% of the total bulk
[5], represent a problem for
management, pollution, and
environmental issues, due to microbial
spoilage. Thus new aspects concerning
the use of these by-products for further
exploitation on the production of food
additives or supplements with high
nutritional value and economically
attractive have gained increasingly
interest [6].
The traditional method to extract
essential oils from the citrus peels is by
cold pressing. Distillation is also used
in some countries as an economical
way to recover the oils, with a better
yield of 0.21% vs. 0.05% for cold
pressing [7].
Nowadays, many novel techniques
for the extraction of essential oils that
could lead to more compact, safer,
more efficient, energy saving, and
sustainable extraction processes,
including ultrasound-assisted
extraction (UAE), microwave-assisted
extraction (MAE), supercritical fluid
extraction (SFE) and accelerated
solvent extraction (ASE) have become
relatively mature and widely accepted
by industries [8].
Microwave is intrinsically one
type of electromagnetic waves with
frequency ranging from 300MHZ to
300GHZ, which can penetrate
biomaterials and interact with polar
molecules such as water in the
biomaterials to create heat [9]. Due to
it's high selectivity, microwave heating
is capable of expanding and rupturing
of cell walls followed by the liberation
of chemicals into surrounding solvent
in short time [10].
Sahraoui et al. [11] extracted
essential oil from citrus by-products
(orange peels) with a new process,
microwave steam distillation (MSD).
Compared to the conventional steam
distillation (SD), the results obtained
confirm the effectiveness of this new
technique, which allows substantial
savings in term of extraction time and
energy. MSD highly accelerated the
extraction process, without causing
changes in the volatile oil composition.
MSD offered important advantages
like shorter extraction time, with MSD
6 min provides yields comparable to
those obtained after 2 h by SD, which
is the reference method in essential oil
isolation. The values of yield obtained
are respectively 5.43 ± 0.03% for MSD
and 5.45 ± 0.04% for SD. MSD offered
cleaner features and provided an
essential oil with better sensory
properties (better reproduction of
natural fresh fruit aroma of the citrus
essential oil) at optimized power
(500 W).
Cassel et al. [12] used rectification
extraction (RE) to isolate essential oils
from Chinese herbs, RE and steam
distillation (SD) techniques were
applied to isolate essential oils from
three typical Chinese herbs Bupleurum,
Pogostemon cablin (Blanco) Benth
(PCB), Pericarpium Citri Reticulatae
(PCR). The experiment shows that SD
technique cannot get volatile oils and
only aromatic water from Bupleurum
but RE can prepare both. RE technique
increases 10% oil yield of PCB and
20% of PCR compared with SD,
Ibtehal K. Shakir and Sarah J. Salih
-Available online at: www.iasj.net IJCPE Vol.16 No.3 (Sept. 2015) 13
respectively. Therefore, RE would be
more effective and suitable for
enriching volatile oils from plants or
herbs in which volatile oils are water-
soluble and with low-content.
Therefore, RE can significantly shorten
the operation time of extracting
volatile constituents of herbs such as
Chuanxiong and Bupleurum, and
reduce energy consumption relatively
during isolating process. The common
components in the oils prepared by SD
and RE, occupy more than 91% of the
volatile oil samples. Compared with
SD, RE technology not only increases
volatile oil yield, but also barely
changes the constituents and
compositions of volatile oils.
Farhat et al. [13] Microwave steam
diffusion (MSD) was developed as a
cleaner and new process design and
operation for isolation of essentials oils
from dry lavender flowers and was
compared to conventional steam
diffusion (SD). The essential oils
extracted by MSD for 3 min were
quantitatively (yield) and qualitatively
(aromatic profile) similar to those
obtained by conventional steam
diffusion for 20 min. In addition, an
optimal operating steam flow rate of
25 g min−1 and microwave power
200 W were found to ensure complete
extraction yield with reduced
extraction time. MSD was better than
SD in terms of energy saving,
cleanliness and reduced waste water.
Lucchesi etal. [14] used two
different extraction methods for a
comparative study of Algerian Myrtle
leaf essential oils: solvent-free-
microwave-extraction (SFME) and
conventional hydrodistillation (HD).
Essential oils analyzed by GC and GC-
MS presented 51 components
constituting 97.71 and 97.39% of the
total oils, respectively. Solvent-Free-
Microwave-Extract Essential oils
SFME-EO were richer in oxygenated
compounds. Several advantages with
SFME were observed: faster kinetics
and higher efficiency with similar
yields: 0.32% dry basis, in 30 min as
against 180 min for HD.
Ginies et al. [15] used a total of
eight extraction techniques ranging
from conventional methods
(hydrodistillation (HD), steam
distillation (SD), turbohydrodistillation
(THD)), through innovative techniques
(ultrasound assisted extraction (US-
SD) and finishing with microwave
assisted extraction techniques such as
In situ microwave-generated
hydrodistillation (ISMH), microwave
steam distillation (MSD), microwave
hydrodiffusion and gravity (MHG),
and microwave steam diffusion
(MSDf)) to extract essential oil from
lavandin flowers and their results were
compared. The method which gave the
best results was the microwave
hydrodiffusion and gravity (MHG), it
gave the maximum yield (5.4%) in
only 15 min (120 min for SD) and
consumed 1.3 kWh (against 8.06 kWh
for SD). The essential oil obtained was
of excellent quality (low degradation)
and natural odor (similar smell to the
original lavender).
Vieira et al. [16] studied
Supercritical carbon dioxide extraction
of essential oil from Thymus vulgaris
leaves in the Florys S.p.A. laboratory
at 40 °C and 20 MPa for three different
particle sizes and three different flow
rates. A mathematical model, proposed
in the literature, based on the local
adsorption equilibrium of essential oil
on lipid in leaves was used to calculate
internal and external mass transfer
resistances. The adsorption equilibrium
constant was fitted to these
experimental data, and preliminary
results suggested that the extraction
process is controlled by mass transfer
resistance due to intraparticle
diffusion.
In this study, microwave steam
distillation (MSD) apparatus has been
Extraction of Essential Oils from Citrus By-Products Using Microwave Steam Distillation
14 IJCPE Vol.16 No.3 (Sept. 2015) -Available online at: www.iasj.net
used for extraction of essential oil from
three types of fresh citrus peels: orange
( citrus sinensis), lemon( citrus limon),
and mandarin (citrus reticulate).
Comparisons have been made to
conventional steam distillation (SD) in
terms of extraction time, yield, weight
of the sample, and composition of
essential oil. The essential oils were
analyzed by gas chromatography to
determine the concentration of
limonene in each produced sample for
qualitative study.
Experimental Work
Collection of Plant Material
Citrus fresh fruits: orange (citrus
sinensis), lemon (citrus limon),
mandarin (citrus reticulata) brought
from local markets. Each type of citrus
fruit was washed and peeled
separately. The fresh peels were grated
using an electrical grater that results
small particles of the peels. They were
divided into three groups having three
different weights: (398.56gm,
281.8gm, and 116.76gm )
Experimental Procedure
1- Extraction of Essential oil by
microwave assisted steam
distillation (MASD)
In Microwave Assisted steam
distillation (MASD) unit an Pyrex
flask which contained boiled distilled
water generating steam and a
condenser placed outside the
microwave oven are connected to a
cartridge containing grated citrus peels
via Pyrex connecting tubes. The
condenser is connected to a receiving
flask which is preferably a separating
funnel to enable the continuously
collection of condensate essential oil
and water. This system presents the
advantage that the cartridge containing
plant materials can be easily and
quickly replaced and cleaned after each
cycle of extraction as shown in Fig.1.
The cartridge containing the required
weight for each run ( 398.56gm for full
flask, 281.8gm for half full, and
116.76gm the quarter of flask ) of
citrus peels is subjected to microwave
heating and vapor which cross the
plant material. The probe of the sensor
was placed on the extraction vessel in
order to record temperature, as the
steam rises up to the grated peels
charged with the essential oil on it's
way to the condenser with the first
drop of condensate flows in the
separation funnel the microwave
irradiation power is switched on.
Fig.1, Schematic Diagram of the
Experimental Extraction Unit of
Microwave Assisted Steam Distillation
Microwave energy can interact
selectively with the free water
molecules contained in plant cells and
causes localized heating, the final
effect is a sudden non-uniform rise in
temperature and dramatic expansion in
volume with in plant cells. The cell
walls cannot stand with such a high
internal pressure leading to cell wall
distraction and allowing the substance
inside of plant cells to flow freely
Ibtehal K. Shakir and Sarah J. Salih
-Available online at: www.iasj.net IJCPE Vol.16 No.3 (Sept. 2015) 15
toward surrounding steam the resulting
distillate is collected in a separation
funnel. The extraction was continued
until no more essential oil was
obtained.
2- Extraction of essential oil by
steam distillation (SD)
For a rigorous comparison, the same
glassware and same operating
conditions have been used for
conventional steam distillation. The
vapor produced by the boiled distilled
water crosses the plant, charged with
essential oil and then passes through
the condenser to a receiving flask [17].
3- Separation of Essential oil from
Water
In separation funnel the essential oil
will float on top of the hydrosol
(distilled water component) also called
floral water and may be separated off.
Due to immiscibility of the oil and
water at room temperature for essential
oil is lighter than water, citrus essential
oil has a density in the limits of
0.8085gm/cm3 while density of water
is 1gm/cm3.
Water layer was carefully run out
from the bottom of the funnel by
opening the tap leaving the oil, which
was dried over anhydrous sodium
sulphate and kept in a dark glass vial at
temperature of 4 °C for further
analysis.
The yield percent was calculated by
using the following relationship:
Yield=
 100%
Parameters studied for both
extraction methods (MASD and
SD)for three types of citrus peels;
orange (citrus sinensis), lemon (citrus
limon), mandarin (citrus reticulata):
Extraction time
Extraction yield
Microwave irradiation power:(
135W, 265W, 445W)
Weight of grated peels(398.56gm,
281.8gm, and 116.76gm )
Result and Discussion
1- Effect of Extraction Time
Essential oil was extracted from two
types of citrus peels orange (citrus
sinensis), and mandarin (citrus
reticulata) each having three weights :
( 398.56 gm, 281.8 gm, 116.76 gm), at
(SD) process and (MASD) process
exposing to (265W). Extraction time
was different for these three weights
and extraction yield was studied until
equilibrium was reached.
Fig. (2) & (3) show oil yield in (SD)
process: the weights(398.56gm,
281.8gm) had longer time than
(116.76gm); at these two weights the
yield of orange oil was: (1.095%,
0.860%) with extraction times:
(45min., 50min.) respectively, while
the weight(116.76gm) gave yield for
orange oil: (0.969%) with extraction
time(35min). Mandarin had longer
extraction time than orange with lower
yield since mandarin peel is so tender
not much oil sacks or glands contained
in peels, oil yield for
weight(398.56gm) after (75min.)
extraction time was (0.707%), for
weight(281.8gm) after (55min.)
extraction time the yield was (0.702%)
and for weight(116.76gm)
after(50min.) extraction time the yield
was(0.848%).
Extraction of Essential Oils from Citrus By-Products Using Microwave Steam Distillation
16 IJCPE Vol.16 No.3 (Sept. 2015) -Available online at: www.iasj.net
Fig. 2, Effect of Extraction Time on
Yield of Orange Oil Extracted By (SD)
for the Three Weights
Fig. 3, Effect of Extraction Time on
Yield of Mandarin Oil Extracted By
(SD) for the Three Weights
Fig. (4) & (5) show oil yield in
(MASD) process: the
weights(398.56gm, 281.8gm) both had
extraction time (35min.), for orange
the yield for these two weights was:
(1.058%, 0.588%), while for
(116.76gm) after (20min.) extraction
time the yield was: (0.516%). For
mandarin having weight (398.56gm)
after (35min.) extraction time the yield
was: (0.846%), for weight (281.8gm)
after (30min.) extraction time the yield
was: (0.558%), and for weight
(116.76gm) after (15min.) extraction
time the yield was: (0.385%).
By analyzing data in figures above
the essential oil extracted by (SD)
process had longer time and higher
yield than oil extracted by (MASD)
process after exposing to microwave
power (265W) which delivered heat
higher than (SD) process and that
affected oil yield, since citrus essential
oil is highly sensitive to heat applied
by microwave irradiation which is
higher than heat applied by (SD) [11].
It can be notes from these figures
that extraction of oil increased with
time for the two methods: (SD),
(MASD) but, the yield of oil extracted
by (MASD) reached equilibrium in
shorter time than that of (SD) with
differences in yields. The ability of
(MASD) method to accelerate
extraction of essential oil is by rapid
increase in temperature causing a
dramatic expansion in volume within
plant cells, the cell walls cannot with
stand such high internal pressure
resulting with rupture of the cells and
glands of plant material more rapidly
than conventional (SD) [10], these
results are in agreement with results
obtained by Sahraoui et al. (2011) [11].
Fig. 4, Effect of Extraction Time on
Yield of Orange Oil Extracted By
(MASD) For the Three Weights.
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60
% oil Yield
Time( min.)
281.8gm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 20 40 60 80
% oil yield
Time( min.)
398.56g
m
281.8g
m
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40
%oil yield
Time( min.)
398.56gm
281.8gm
116.76gm
Ibtehal K. Shakir and Sarah J. Salih
-Available online at: www.iasj.net IJCPE Vol.16 No.3 (Sept. 2015) 17
Fig.5 Effect of Extraction Time on
Yield of Mandarin Oil Extracted By
(MASD) For The Three Weights.
2- Effect of Grated Peels Weight
Fig.(2) & (3) show that for (SD)
process since the extraction vessel is
spherical shaped the action of steam
was affected by the content of grated
peels in the vessel. For the weight
(398.56gm) the vessel was fully loaded
and for weight (281.8gm) the vessel
was half loaded when the steam passes
from the bottom of vessel through the
grated peels toward the top few
amounts of peels at the side were far
from the action of steam and extraction
was at the upper and lower layers of
peels where the steam moved freely.
It can be notes that (116.76gm)
weight had the least space in extraction
vessel and it was totally exposed to
steam where it moved freely charged
with essential oil, for this reason the
weight (116.76gm) subjected to (SD)
process gave yield (0.969%), while for
mandarin with weight(116.76gm) after
(50min.) the yield was (0.848%).
In (MASD) process oil yield
increases with increasing the weight
exposed to microwave power as shown
in Fig. (4) & (5). For orange peels
having weight(116.76gm) exposed to
microwave power (265W) for (20min.)
the yield was (0.532%), while for
weight(281.8gm) exposed to same
power for (35min.) the yield was
(0.606%) and for weight (398.56gm)
under same conditions the yield was
(1.091%).
For the weight(398.56gm) the yield
obtained by (SD) and (MASD)
processes were close no striking
differences found but the weights
(281.8gm, 116.76gm) their yields
obtained by (SD) were higher than
(MASD) this means that microwave
irradiation is inefficient with low
weights, for orange having
weights(281.8gm, 116.76gm) the oil
yield extracted by (SD) was: (0.860%,
0.969%) while for (MASD) for these
weights the yield was: (0.606%,
0.532%).
(MASD) method need the presence of
water as "in situ" water in the plant
material tissue, it is already known that
only water in a liquid state absorbs
microwaves but steam or even ice do
not absorb microwaves because in the
gas state the molecules are too far each
other to have frictions, and in solid
state the molecules are not free to
move and rotate to heat [13] , for this
reason (MASD) process is more
efficient with high weights of peels for
their high water content in tissues and
the yield decreases with low weights
for their low water content in their
tissues. These results are in agreement
with results obtained by Margosan et
al. (2001) [18].
3- Effect of Microwave Power
According to previous research
reports, essential oil yield differs in
different microwave powers therefore;
the effect of microwave power was
studied. In principle, higher
electromagnetic energy absorption
could result in more power dissipated
inside the plant material and generating
more effective molecular movement
and heating, leading to an
improvement in the extraction
efficiency [10].
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 20 40
% oil yield
Time( min.)
398.56gm
281.8gm
116.76gm
Extraction of Essential Oils from Citrus By-Products Using Microwave Steam Distillation
18 IJCPE Vol.16 No.3 (Sept. 2015) -Available online at: www.iasj.net
As shown in Fig. (6) & (7) essential
oil was extracted from three types of
citrus peels each type having a weight(
398.56gm), exposed to microwave
powers:( 135W, 265W, 445W) with
exposure time to irradiation
power:(5min., 10min.). In this method
the yield of essential oil was affected
by the amount of heat applied by
microwave power.
At the beginning of extraction
process oil yield increased by
increasing microwave power from
(135W) to (265W) for orange the yield
was after (5min.) of exposure to these
powers: (0.194%, 0.526%)
respectively and after (10min.) of
exposure to these powers the yield
increased: (0.701%, 0.818%)
respectively, moreover increasing in
extraction time the yield increases
slightly by power (265W) in
comparison with power (135W), the
yield was increasing until the
extraction ended after (35min.) with
yield: (1.150%, 1.091%) for powers:
(135W, 265W) respectively; same
results was obtained for mandarin.
When the power was raised to
(445W) the yield was lower than yield
obtained by the powers (135W, 265W)
from the beginning to the end of
extraction process.
Citrus essential oils are highly
sensitive to the variation of processing
temperature result from high
microwave power (265W, 445W) ,
they can cause thermal degradation to
essential oil, this fact explain why oil
yield was lower for high microwave
powers (265W, 445W). So in order to
avoid that it would be better to use low
microwave power (135W) for
complete recovery of essential oil,
these results are in agreement with
results obtained by Chun-Hui et
al.(2012) [19].
Fig. 6, Effect of Microwave Power on
Yield of Orange Oil Extracted By
(MASD)
Fig. 7, Effect of Microwave Power on
Mandarin Oil Extracted By (MASD)
4- Effect of Citrus Peel Type
Essential oil is present in citrus peels
in oil sacks and glands which are
located at different depths in citrus
peel, the amount of this oil differ from
citrus type to another, also conditions
of extraction process play role in the
complete recovery of essential oil [20].
It can be notes from Fig. (8) & (9)
that for orange and lemon with weight
(398.56gm) the yields were close for
(SD) with extraction time (45min.):
(1.095%, 1.061%) respectively, and
they were higher than mandarin:
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 10 20 30 40
% oil yield
Time( min.)
135W
265W
445W
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 50 100
% oil yield
Time( min.)
135
W
265
W
Ibtehal K. Shakir and Sarah J. Salih
-Available online at: www.iasj.net IJCPE Vol.16 No.3 (Sept. 2015) 19
(0.707%) with extraction time (75min.)
while for (MASD) the yield of orange
and lemon after (35min.) extraction
time was: (1.150%, 1.115%) while for
mandarin after (60min.) the yield was
(0.940%).
For both methods the yield of orange
and lemon were close same and were
higher than that for mandarin, where
oil yield for mandarin had longer
extraction time and gave lower yield
than orange and lemon in both
methods, the reason for that is the
nature of mandarin peel tissue, it do
not have much oil glands contained in
peels to be ruptured by steam or
microwaves to release the oil [18],
these results are in agreement with
results obtained by Meklati et al.
(2007) [21].
Fig. 8, Effect of Citrus Type on Yield
of Essential Oil Extracted By (SD)
From Citrus Peel Weight (398.56gm)
Fig. 9, Effect of Citrus Type on Yield
of Essential Oil Extracted By (MASD)
From Citrus Peel Weight (398.56gm)
5- Extraction Kinetics
As shown in Fig. (10) & (11) the
(MASD) process can give essential oil
with higher yield and better quality in
shorter extraction time than (SD)
process when the power is low, the use
of longer exposure time would be
helpful for the complete recovery of
essential oil when microwave power is
not too high to avoid thermal
degradation of essential oil.
By analyzing these figures two
phases are observed in (MASD) yield
the first step is represented by a rapid
increase in the yield followed by a
second step corresponding to a slight
increase until reach the end of
extraction, the rapid increase in the
yield during the first step suggests that
the essential oil is easily accessible by
the steam due to action of microwaves
in rupturing oil glands while the steam
passes charged with essential oil. For
(SD) method three phases are observed
the first step is represented by an
increasing line which characterizes the
first quantities of extracted essential oil
this phase is followed by second
increasing line representing the
diffusion of essential oil from the
middle layers of citrus peels, the third
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80
% oil yield
Time( min.)
orange
lemon
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 20 40 60 80
% oil yield
Time( min.)
orange,
MASD
lemon, MASD
Extraction of Essential Oils from Citrus By-Products Using Microwave Steam Distillation
20 IJCPE Vol.16 No.3 (Sept. 2015) -Available online at: www.iasj.net
phase corresponds to a horizontal line
which marks end of extraction, these
results are in agreement with results
obtained by Farhat et al. (2009) [13].
Fig. 10, Yield of Orange Oil Extracted
By (SD) and (MASD) As Function Of
Extraction Time
Fig. 11, Yield of Mandarin Oil
Extracted By (SD) and (MASD) As
Function Of Extraction Time
6- Gas Chromatography (GC)
Chemical identification of essential
oil was investigated by Gas
Chromatography equipped with (FID)
detector (BACKARD, 438A, U.S.A).
Essential oil extracted from (orange,
lemon, mandarin) peels is mainly
composed of Limonene, Linalool,
Citronellal, Nerol, Geranial etc. among
many other components. The relative
amounts of these components varied
according to type of citrus peel and
conditions of extraction process.
From Table (1) for mandarin oil the
amount of limonene extracted by
(MASD) in low microwave power with
long extraction time was (84.3891% at
135W in 60min.), while for (SD) it was
(83.0271% in 75min.) and decreased
with increasing microwave power, for
orange oil it was (80.9661% at 265W
in 35min.) while for (SD) it was
(83.2189% in 45min.). For orange and
lemon when microwave power was
increased the amount of limonene
decreased and was lower than that
extracted by (SD).
So when using microwave power for
extraction the best condition is
exposure to low microwave power for
long time. The influence of microwave
energy on extraction is strictly thermal
and it highly accelerated extraction
process, phenomenon which was
already described by Chemat et al.
(2006) [22].
Table 1, Amount of Limonene
extracted from citrus peels by (SD),
(MASD) and conditions of extraction.
Citrus
peel
Limonene
content%
[23]
Amount
of
limonene
% for
(SD)
Amount
of
limonene
% for
(MASD)
Mandarin
94.62%
83.0271
84.3891
Orange
91.40%
83.2189
80.9661
Lemon
65.44%
65.2867
59.156
Conclusions
According to the results obtained
from this study, the following
conclusions are obtained:
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 20 40 60
% oil yield
Time( min.)
SD, orange
MASD(135W),
orange
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80
% oil yield
Time (min.)
SD, mandarin
Ibtehal K. Shakir and Sarah J. Salih
-Available online at: www.iasj.net IJCPE Vol.16 No.3 (Sept. 2015) 21
1- The extraction yield of oil increased
with time for the two methods:
(SD), (MASD) but, the yield of oil
extracted by (MASD) reached
equilibrium in shorter time than that
of (SD).
2- The weight (116.76gm) subjected to
(SD) process: in orange and lemon
gave yield (0.969%, 0.939%)
higher than weight (281.8gm) which
gave yield (0.860%, 0.834%)
respectively, while for mandarin
this weight gave yield (0.848%)
higher than the other weights
(398.56gm, 281.8gm) which gave
yields (0.707%, 0.648%)
respectively.
3- It would be better to use low
microwave power (135W) for
complete recovery of essential oil
and higher microwave power
(265W) can be used but for short
exposure time to avoid thermal
degradation of essential oil.
4- Oil yield for mandarin had longer
extraction time and gave lower yield
than orange and lemon in both
methods.
5- The amount of limonene extracted
by (MASD) was higher than that
extracted by (SD) for mandarin.
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Several other organic micronutrients, such as carotenoids and polyphenols, impart health benefits. Carotenoids are mostly used as natural food colorants, but also some of them (β-carotene, apocarotenal) have a vitamin A activity as well as antioxidant activity in vitro and in vivo (Kiokias and Gordon 2004). Polyphenols also act as antioxidants; they scavenge free radicals which are responsible for serious diseases and for the oxidation of lipids, proteins, and DNA. Several studies have revealed their antimicrobial, antithrombotic, antimutagenic, and anticarcinogenic activities (Kandaswami and Middleton, 1997; Sahu and Green, 1997). In addition to health benefits, the supplementation of food products with antioxidants delays the formation of off-flavors and rancidity and extends the shelf life of the product. Carotenoids and polyphenols are extensively distributed in several plant by-products. Thus most fruit and vegetable by-products could serve as raw materials for their recovery. Moreover, these antioxidants or colorants would have a natural origin, which is in accordance with the demands of consumers for "all natural" because of the possible toxicity of synthetic additives. The role for food proteins in human nutrition is substantial, while according to modern nutrition recommendations the supply of proteins in human diet should rely mostly on vegetable proteins, i.e., cereals, legumes, oilseeds, etc., than on those from animal sources, i.e., meat. Because the amounts of proteins required to cover the nutritional needs of the world population are continuously increasing, the investigation and finding of new protein sources are of interest. In addition to their nutritional value, proteins offer great potential as functional food ingredients providing useful properties when incorporated into foods. In order to utilize a byproduct as a protein source it should both present high protein content and protein value (quality) based on well-balanced essential amino acids. An additional requirement to utilize a material for food purposes is the absence of allergic or toxic substances or the application of a proper pretreatment for their efficient removal. Several protein products (flours, concentrates, or isolates), depending on their protein content, can be introduced to food products in order to improve their nutritional value as well as their sensory and functional properties. Such protein products already have been used as meat extenders in processed meat products or as protein-enriching agents in nutritional beverages. Particularly, soy protein products are used for the production of several foods such as: imitation cheese, whipped toppings, soy milk, and baked products. Today consumers are highly aware of the close relationship between nutrition and health and they want to include health-promoting ingredients in their diets. Foods fortified with nutraceuticals, or functional foods in other terms, are expected to be the new food category with an expanding demand by future generations. Therefore, food scientists focus their effort on the development of new products with improved nutritional profiles. Natural ingredients recovered from agroindustrial by-products have specific dietary and functional properties and can be utilized effectively to develop this new food category.
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Microwave and conventional methods have been used to extract pectin from orange peels, with different extraction periods, different solvent pHs and different types of solvent systems. For microwave extraction, the greatest total amount of pectin yield was found to be 5.27% on a dry basis for 15 min of extraction, although the greatest amount of material per unit time (%/min) was obtained after 5 min, which was the same amount as that extracted using Soxhlet extraction for 3 h. The relative extraction rate between microwave and Soxhlet extraction was similar to that in previous work. Microwave treatment was further investigated at pHs of 1.5, 2.0, 5.5 and 10.0 for 15-min extraction periods, with the greatest amount of pectin being extracted at the most strongly acidic condition of pH 1.5. Fifteen-minute extraction periods and a pH of 1.5 were also studied with solvent systems containing ethanol and EDTA (ethylenediamine tetraacetic acid); giving approximately double the amount of pectin extracted using distilled water.
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Traditional hydrodistillation (HD), cold pressing (CP) and innovative microwave ‘dry’ distillation or microwave-accelerated distillation (MAD) methods have been compared and evaluated for their effectiveness in the isolation of essential oil from fresh Citrus peels. The microwave method offers important advantages over traditional alternatives, viz. shorter extraction times (30 min vs. 3 h for hydrodistillation and 1 h for cold pressing); better yields (0.24% vs. 0.21% for HD and 0.05% for CP); environmental impact (energy cost is appreciably higher for performing HD and for mechanical motors (CP) than that required for rapid MAD extraction); cleaner features (as no residue generation and no water or solvent used); increases antimicrobial activities; and provides a more valuable essential oil (with high amounts of oxygenated compounds). It also offers the possibility for better reproduction of the natural aroma of the essential oil from Citrus fruit compared with CP, but more than the HD essential oil. Further, the microwave procedure yields essential oils that can be analysed or used directly without any clean-up, solvent exchange or centrifugation steps. Scanning electron microscopy provides more evidence of the cleanness of microwave extraction, in contrast to the huge perforations on the external surface of the Citrus fruit peel in the case of conventional hydrodistillation. Finally, a mechanism of microwave ‘dry’ distillation is proposed and discussed. Copyright © 2007 John Wiley & Sons, Ltd.
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This paper reports the state of the art of the microwave super-heated boiling phenomenon. When a liquid is heated by microwaves, the temperature increases rapidly to reach a steady temperature while refluxing. It happens that this steady state temperature can be up to 40 K higher than the boiling point of the liquid. With the same reactor, overheating is not observed under conventional heating. The bulk temperature of a microwaved solvent under boiling depends on many factors: physical properties of the solvent, reactor geometry, mass flow, heat flow, and electric field distribution. The influence of these factors is studied and discussed. The kinetics of homogeneous organic reactions shows an extension of Arrhenius behaviour into the superheated temperature region. Reaction rate enhancement of order 10-100 can thus be achieved, which is normally only possible under pressure. Finally, we present a model predicting reaction kinetics and yields under classical and microwave heating, based on predicted temperature profiles in agreement with experimental data.
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Supercritical CO2 extraction of essential oil from Thymus vulgaris leaves was studied using experimental data recently obtained in the Florys S.p.A. laboratory. Mass transfer coefficients in the supercritical and solid phases from extraction curves at 40°C and 20 MPa were evaluated using a mathematical model based on the local adsorption equilibrium of essential oil on lipid in leaves. The adsorption equilibrium constant was fitted to these experimental data, and internal and external mass transfer resistances were calculated, allowing identification of the mechanism controlling the extraction process.
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Microwave Clevenger or microwave accelerated distillation (MAD) is a combination of microwave heating and distillation, performed at atmospheric pressure without added any solvent or water. Isolation and concentration of volatile compounds are performed by a single stage. MAD extraction of orange essential oil was studied using fresh orange peel from Valencia late cultivar oranges as the raw material. MAD has been compared with a conventional technique, which used a Clevenger apparatus with hydro-distillation (HD). MAD and HD were compared in term of extraction time, yields, chemical composition and quality of the essential oil, efficiency and costs of the process. Extraction of essential oils from orange peels with MAD was better in terms of energy saving, extraction time (30 min versus 3 h), oxygenated fraction (11.7% versus 7.9%), product yield (0.42% versus 0.39%) and product quality. Orange peels treated by MAD and HD were observed by scanning electronic microscopy (SEM). Micrographs provide evidence of more rapid opening of essential oil glands treated by MAD, in contrast to conventional hydro-distillation.
Optimization of conditions of solvent-free microwave extraction and study on antioxidant capacity of essential oil from Schisandra Chinensis Baill
  • D A Margosan
  • L H Aung
  • W P Wergin
  • E F Erbe
IJCPE Vol.16 No.3 (Sept. 2015)-Available online at: www.iasj.net 18-D. A. Margosan, L. H. Aung, W. P. Wergin, E. F. Erbe, (2001), "The nature of oil gland and it's associated tissues in the pericarp of citrus limon (L.) Burn. F. by confocal microscopy ", PhytonInternational Journal of Experimental Botany, vol.(15), pp.107-119. 19-Chun-Hui, Lei Yang, YuanGangzu, Ting-ting Liu, (2012), "Optimization of conditions of solvent-free microwave extraction and study on antioxidant capacity of essential oil from Schisandra Chinensis Baill", Food Chemistry Journal, vol.(134), pp.2532-2539. 20-Napaporn Thavanapong, (2006), "The Essential oil from peel and flower of citrus maxima", M.Sc. thesis, Pharmacy of Silpakorn University.