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ORIGINAL ARTICLE
Utilization of seeds from tomato processing wastes as raw materialfor oil production
Cristina Botinestean • Alexandra Teodora Gruia •
Ionel Jianu
Received: 19 April 2013 / Accepted: 9 January 2014
� Springer Japan 2014
Abstract The increase of waste quantities from tomato
processing industry is an important ecological and also
financial problem. Seeds are the major component of this
waste and one valuable alternative of transforming them
into raw materials is oil extraction. The isolated oil can be
used for nutritive or industrial purposes. In this research,
the influence of some extraction parameters (time, solvent
and granularity of tomato milled seeds) on the fatty acid
(FA) composition, water content and water reaction rate
has been evaluated. The FA composition of tomato seed
oil, determined by gas chromatography–mass spectrome-
try, has shown a high content of linoleic acid
(20.8–39.9 mg/mL), followed by palmitic acid
(6.3–19.3 mg/mL), oleic acid (2.5–14.2 mg/mL), linolenic
acid (0.7–4.9 mg/mL), stearic acid (0.1–0.8 mg/mL), pal-
mitoleic acid (0.03–0.5 mg/mL), arachidic acid
(0.08–0.4 mg/mL), myristic acid (0.05–0.2 mg/mL) and
margaric acid (0.02–0.11 mg/mL). The oil content of
tomato seeds was registered in the range of 13.3–19.3 %.
For evaluation of water content, a method using Karl
Fischer titration (KFT) has been established. Comparing
with the physical methods that do not distinguish the water
content from volatile matter, KFT is an important tech-
nique, very accurate, that determines water content by a
chemical reaction.
Keywords Waste � Tomato seeds � Fatty acids
Introduction
Industrial processing of tomatoes conducts to a very high
amount of waste, and seeds are the major by-product. Just a
small amount of these seeds are used as feeds or fertilizers,
and the rest of quantity represents an environmental pol-
lution problem. The processors were thinking on different
ways to capitalize tomato seeds resulting from the tomato
processing industry, to increase the profit from this industry
[1–3]. One application of using waste from tomato pro-
cessing industry is to obtain oil from tomato seeds by
extraction.
Fewer applications that imply the extraction and ana-
lysis of tomato oil extracted from tomato seeds are reported
in literature.
Regarding the fatty acid (FA) composition of tomato
seed oil, the major FA component was linoleic acid
(C18:2), with a concentration range of 37–57 %. The main
saturated FA identified was palmitic acid (C16:0), with a
concentration range from 7 to 24 %. Other important FA
identified in tomato seed oil were: oleic acid (C18:1)
18–30 %, stearic acid (C18:0) 4–13 %, and linolenic acid
(C18:3) 1–6 %. Small amounts of myristic acid (C14:0)
0.1–2.3 %, palmitoleic acid (C16:1) (0.3–7 %), margaric
acid (C17:0) 0.1–0.3 % and arachidic acid (C20:0)
(0.2–3 %) have been reported [4–11]. Behenic, lignoceric,
Authors declare that a small part of this paper has been presented as
an oral presentation entitled: ‘‘Water determination for tomato seed
oil extracts using Karl Fischer titration’’ at the scientific meeting: 3rd
International Conference on Food Chemistry, Engineering and
Technology (2012), Timisoara, Romania.
C. Botinestean (&) � I. Jianu
Food Technology Department, Banat’s University
of Agricultural Sciences and Veterinary Medicine of Timisoara,
Calea Aradului 119, 300645 Timisoara, Romania
e-mail: [email protected]
A. T. Gruia
Regional Center for Transplant Immunology,
Emergency Timis County Hospital, Bv. Iosif Bulbuca 10,
300736 Timisoara, Romania
123
J Mater Cycles Waste Manag
DOI 10.1007/s10163-014-0231-4
and gondoic acids were also identified in very small
amounts in tomato seed oils [4, 5].
Various methods were used to determine the water
content of foodstuff. Even if thermal methods are prone to
error, they are frequently used because they are inexpen-
sive methods. Analytical methods are based on estimating
moisture by evaporation (‘‘loss of drying’’ or ‘‘oven-dry-
ing’’) and they have been compared with other more effi-
cient methods, one of them being Karl Fischer titration
(KFT) [12]. The disadvantage of thermal methods being
time-consuming can be reduced using Karl Fischer water
determination method [13].
Comparing with the physical methods that not distin-
guish the water content from volatile matter, KFT is an
important technique, very accurate, that determines the
water content by a chemical reaction of the amount of
water that is present in the sample (even in those containing
very low content of water such as oils). KFT technique
allows working with numerous samples in a short time and
automation; these improve reproducibility, repeatability
and accuracy of the experiments [14].
The aim of this study was to evaluate the influence of
some extraction parameters of tomato seed oil on the FA
composition, water content and water reaction rate from
KFT.
Materials and method
Materials
Tomato seeds were collected from tomatoes (Solanum
lycopersicum) cultivated in Timis County, Romania. The
seeds were separated and cleaned from the mixture of peel,
pulp, and seeds, with water, after that they were spread to
dry for 3 days and then kept at 10 �C until extraction. To
obtain different granularity of tomato seed powder that will
serve as raw material for oil extraction, two different lab-
oratory mills were used: electrical mill was used to obtain
tomato seed powder with a granularity \0.5 mm and
mechanical mill to obtain a granularity of tomato seed
powder in the range of 0.5–1.5 mm.
Petroleum ether, diethyl ether, ethanol 96 %, n-hexane
(analytical grade, Sigma-Aldrich), methanol�BF3 (reagent
grade, Fluka) and Standard 37 FAME mix (Supelco) were
used.
Methods
Isolation of oil from tomato seeds
Tomato seed oil was obtained using solid–liquid semi-
continuous Soxhlet extraction method. The percolation
(siphoning cycle), characteristic to Soxhlet extraction
method, represents the importance of extraction time on
tomato oil yield. To optimize the extraction process (by
reducing extraction time) the shortest period of time nec-
essary to obtain tomato oil with approximately maximum
yield (after how many siphoning cycles were not registered
significant differences on oil yield), has been determined.
For studying the influence of the surface contact (between
the tomato seed powder and solvent) on FA composition,
water content and water reaction rate, different granulari-
ties of tomato seed powder were used (as described in
‘‘Materials’’). Also, the influence of extraction solvent on
the FA composition, water content and water reaction
rate has been evaluated using petroleum ether and diethyl
ether.
The following codifications were used for the oil sam-
ples extracted from tomato seeds: DEE––tomato seed oil
extracted with diethyl ether using six percolations and a
granularity of the milled tomato seeds\0.5 mm; PE1/PE2/
PE4/PE6––tomato seed oil extracted with petroleum ether
using 1/2/4/6 percolations (significant differences after 6
percolation were not registered between the values of the
oil yield, therefore an increasing of time expressed in
number of percolation was not necessary) and a granularity
of the milled tomato seeds\0.5 mm, MMPE––tomato seed
oil extracted with petroleum ether using six percolations
and mechanically milled tomato seeds (granularity in the
range of 0.5–1.5 mm).
KFT water determination
Classical Karl Fischer water titration was carried out using
a Karl Fischer 701 Titrando apparatus from Metrohm, a
Metrohm 10 dosing and 703 Ti Stand mixing systems
(Metrohm).
KFT was performed using the two-component tech-
nique: component 1 was Titrant 5 apura and component 2
Solvent apura (both from Merck & Co., Inc.), which con-
tains imidazole, sulfur dioxide in methanolic solution. The
titer of the component 1 was determined using water
standard 1 %, standard for volumetric KFT (Merck).
The tomato seed oil sample amount was in the range of
0.6–1.1 g. The following KFT method parameters were
used: I (pol) of 50 lA, end point and dynamics at 250 mV,
maximum rate of 5 mL/min, drift was used as stop crite-
rion, with a stop drift of 20 lL/min. The titer of the iodine
solution, determined with the water standard solution, was
4.5924 mg/mL. The extraction time was 300 s.
Preparing of FA methyl esters (FAMEs)
Tomato seed oil samples were transmethylated using the
methanol�BF3 method (adapted after Hadaruga et al. [15])
J Mater Cycles Waste Manag
123
to identify and quantify the FAMEs by gas chromatogra-
phy–mass spectrometry (GC–MS) analysis.
About 25 mg of tomato seed oil was accurately weighed
into a screw cap tube, 5 mL methanol�BF3 solution was
added and refluxed for 2 min on a water bath. After cool-
ing, 5 mL of hexane was added, followed by 1 min of
refluxing and then the solution was treated with 15 mL
saturated NaCl solution under vigorous stirring. The mix-
ture was separated and the organic layer was removed,
dried over anhydrous CaCl2, and used for GC–MS analysis.
GC–MS analysis
A volume of 2 lL of derivatized sample was injected in a
HP 6890 Series Gas Chromatograph coupled with a Hew-
lett Packard 5973 Mass Selective Detector. The gas chro-
matograph was equipped with a split–splitless injector and
a Factor FourTM Capillary Column VF-35ms fused silica
column of 35 % phenyl-methylpolysiloxane, 30 m length,
0.25 mm internal diameter, and 0.25 lm film thickness.
GC conditions include a temperature range of 50–250 �C
with a heating rate of 6 �C/min and a solvent delay of
5 min. The inlet temperature was maintained at 250 �C,
helium was used as GC carrier gas at 1.0 mL/min and the
sample was injected in the splitless mode.
The following MS conditions were used: ionization
energy of 70 eV, quadrupole temperature of 280 �C, scan
rate of 1.6 scan/s and mass detection of 50–550 amu. The
mass spectra of the samples were compared with those
from the NIST/EPA/NIH Mass Spectral Library 2.0 to
identify the main compounds. All samples were monitored
on the scan mode.
Results and discussion
Extraction and physical–chemical analysis of tomato
seed oil
The yields obtained for oil extraction from tomato seeds
were in the range of 13.3–19.3 % (reported to dry weight
basis). The highest yield (19.3 %) was obtained using
petroleum ether for extraction.
Significant variations of classical physical–chemical
values were not registered. Thus, the main characteristics
determined for oil, which was isolated by solid–liquid
semi-continuous extraction from electrically milled tomato
seeds using standard methods [16], were: saponification
value (191 mg KOH/g), acid value (2 mg KOH/g), ester
value (189 mg KOH/g), density at 15 �C (0.9245 kg/m3),
refractive index at 25 �C (nD = 1.4733), and kinematic
viscosity at 40 �C (23 mm2/s).
More important was the FA composition of extracted
tomato seed oils, as well as the trace of water, which has a
negative influence on the oil stability.
FA composition of tomato seed oil
The effects of FA as components of triacylglycerols,
especially those essential (linoleic and linoleic) on the
quality of the final tomato seed oil are very important.
Vegetable oils are the main sources for the intake of
essential polyunsaturated FA and have an important role in
human diets. The FA with the highest concentration in
tomato seed oil is linoleic acid, a polyunsaturated x-6 FA
and contributes to increase the quality of the tomato seed
oil due to its chemical–nutritional–biological relevant
properties. Linoleic acid has an important role in a healthy
brain function, reproductive health, bone density, in the
maintenance of normal cholesterol level [17, 18].
The FA relative concentration of tomato seed oil
(Table 1), determined by GC–MS indicates that the most
concentrated is C18:2 (47–73 %), followed by C16:0 and
C18:1 (14–25 %, respectively, 8–21 %). Other important
identified FA: C18:3 (2–6 %) and C18:0 (0.5–1 %). Some
FA were detected in a lower relative concentrations: C14:0
(0.1–0.3 %), C16:1 (0.1–0.8 %), C17:0 (*0.1 %), and
C20:0 (0.3–0.6 %).
A slight variation of the relative concentration of
FA from derivatized samples of tomato seed oil was
noticed due to the influence of the conditions used for
extraction.
Table 1 The relative concentration (%) of the FA from tomato seed oil extracts
Code C14:0 C16:1 C16:0 C17:0 C18:0 C18:1 C18:2 C18:3 C20:0
DEE 0.14 ± 0 0.05 ± 0.01 18.47 ± 0.01 0.12 ± 0.01 0.51 ± 0.01 20.89 ± 0.07 56.81 ± 0.13 2.59 ± 0.01 0.42 ± 0.04
PE1 0.19 ± 0.02 0.84 ± 0.16 14.24 ± 0.10 0.07 ± 0.01 0.46 ± 0.07 8.60 ± 0.22 72.69 ± 0.58 2.62 ± 0.05 0.28 ± 0.05
PE2 0.24 ± 0.01 0.69 ± 0.02 13.92 ± 0.47 0.08 ± 0.01 0.47 ± 0.01 9.40 ± 0.09 71.78 ± 0.87 3.11 ± 0.29 0.31 ± 0.03
PE4 0.21 ± 0.02 0.68 ± 0.03 14.52 ± 1.31 0.08 ± 0.01 0.55 ± 0.12 9.69 ± 0.50 70.80 ± 2.25 3.19 ± 0.39 0.27 ± 0.03
PE6 0.31 ± 0.02 0.68 ± 0.04 24.82 ± 0.99 0.14 ± 0.01 1.07 ± 0.05 18.23 ± 0.56 47.85 ± 1.91 6.34 ± 0.23 0.55 ± 0.01
MMPE 0.12 ± 0.02 0.05 ± 0 18.16 ± 0.29 0.11 ± 0 0.47 ± 0 20.68 ± 0.29 57.8 ± 0.62 2.28 ± 0.04 0.32 ± 0.03
Results are presented as average of duplicates
J Mater Cycles Waste Manag
123
The type of the solvent used for extraction does not
influence just the oil yield, but also small variations in the
relative concentration (%) of FA from derivatized tomato
seed oil samples were registered. An increasing tendency
of concentration of polyunsaturated FA (i.e. C18:2) was
remarked when a reduced extraction time (1–2 percola-
tions) with petroleum ether was used.
The exceptions were C18:1 with a decreasing tendency
from 20.9 % (when diethyl ether was used) to 18.2 %
(when petroleum ether was used) and C18:2 with a
decreasing tendency from 56.8 % (for extended time of
extraction with diethyl ether) to 47.8 % (for extended time
of extraction with petroleum ether).
By increasing the contact surface between milled tomato
seeds (with granularity from 1.5 to \0.5 mm) and the
solvent used for extraction, a slight decrease trend was
noticed for C18:1 and C18:2. An increasing trend was
remarked for all the other FA (expressed in FAMEs) from
derivatized tomato seed oil samples, the most significant
variation was for C18:0 (from 18.2 up to 24.8 %).
A slight increase of the concentration of unsaturated FA
composition (C18:1 and C18:2) was revealed using diethyl
ether for extraction of the tomato seed oil and high gran-
ularity of tomato seeds.
Very interesting results were obtained for the variation
of the absolute concentration (mg/mL) of FAMEs with the
extraction parameters.
When diethyl ether and petroleum ether were used for
extraction of tomato seed oil, a slight variation of FAMEs
concentration (mg/mL) was noticed (Table 2).
An increasing tendency for all analyzed FA was
remarked when petroleum ether was used for extraction,
in comparison with the samples obtained by diethyl ether
extraction. The extraction of C18:2 using diethyl ether as
solvent conducts to a lower absolute concentration of
35 mg/mL in comparison with the petroleum ether case.
By increasing the contact surface between the milled
tomato seeds (with granularity from 0.5–1.5 mm to
\0.5 mm) and the solvent used for extraction, an
Ta
ble
2T
he
abso
lute
con
cen
trat
ion
(mg
/mL
)o
fth
eF
Afr
om
tom
ato
seed
oil
extr
acts
Co
de
C1
4:0
C1
6:1
C1
6:0
C1
7:0
C1
8:0
C1
8:1
C1
8:2
C1
8:3
C2
0:0
DE
E0
.08
±0
0.0
3±
0.0
11
1.2
8±
0.5
80
.08
±0
.01
0.3
1±
0.0
21
2.7
6±
0.7
13
4.7
±1
.72
1.5
8±
0.0
90
.26
±0
.04
PE
10
.05
±0
.01
0.2
4±
0.0
64
.08
±0
.23
0.0
2±
00
.13
±0
.03
2.4
7±
0.1
82
0.8
3±
0.8
60
.75
±0
.05
0.0
8±
0.0
1
PE
20
.10
±0
.02
0.3
1±
0.0
46
.29
±1
.27
0.0
4±
00
.21
±0
.04
4.2
4±
0.7
53
2.3
3±
5.0
71
.41
±0
.36
0.1
4±
0.0
4
PE
40
.12
±0
.04
0.3
8±
0.1
58
.39
±4
.23
0.0
5±
0.0
20
.33
±0
.20
5.5
5±
2.6
13
9.8
6±
15
.73
1.8
5±
0.9
90
.15
±0
.05
PE
60
.24
±0
.01
0.5
3±
0.0
31
9.2
9±
0.6
60
.11
±0
.01
0.8
3±
0.0
41
4.1
7±
0.3
53
7.2
±1
.71
4.9
2±
0.1
50
.43
±0
.01
MM
PE
0.0
7±
0.0
20
.03
±0
9.4
5±
1.2
60
.06
±0
.01
0.2
4±
0.0
31
0.7
6±
1.4
13
0.0
4±
3.2
1.1
9±
0.1
60
.16
±0
Res
ult
sar
ep
rese
nte
das
aver
age
of
du
pli
cate
s
Table 3 Karl Fischer water titration results for tomato seed oil
extracts
Code v1 (lM/s) v2 (lM/s) V/m (mL/g) W (%)a
DEE 10.01 0.46 ± 0.12 0.08 ± 0.01 0.08
PE1 7.97 ± 0.64 0.54 ± 0.03 0.06 ± 0.01 0.06
PE2 6.12 ± 1.67 0.48 ± 0.13 0.07 ± 0.01 0.06
PE4 5.37 ± 0.32 0.41 ± 0.08 0.05 ± 0.01 0.05
PE6 8.90 0.29 ± 0.16 0.07 ± 0.01 0.06
MMPE 2.78 ± 0.56 0.42 ± 0.08 0.04 ± 0.00 0.04
Results are presented as average of triplicatesa Standard deviation \0.01 for all the analyzed samples
J Mater Cycles Waste Manag
123
increasing trend of all the analyzed FA concentration was
measured. The concentration of the main FA (C18:2,
30 mg/mL) from tomato seed oils was reduced using
mechanically milled tomato seeds with granularity in the
range of 0.5–1.5 mm.
By increasing the number of percolations used for
extraction of tomato seed oil, an increasing tendency of the
FA absolute concentration from the derivatized tomato seed
oil samples was registered. Thus, the absolute concentration
of C18:2 increases with the increasing percolations,
from 20.8 mg/mL, in the case of one percolation, to
38–40 mg/mL, for 4–6 percolations. Using petroleum ether
for extraction of tomato seed oil, a high granularity of milled
tomato seeds (obtained using electric mill,\0.5 mm) and a
high number of percolations led to obtain a high absolute
concentration of FA in the final derivatized extracts of
tomato seed oils.
KFT for determining the water traces from tomato seed
oil
The water content of oily samples is an important
parameter for the quality and stability of these products.
Different methods can be used for water analysis, but
KFT method seems to be more appropriate for this type
of samples due to the possibility to determine only
water (not other volatile substances) in very low
concentration.
As shown in Table 3, the water content of tomato seed
oil samples was in the range of 0.04–0.08 %, the highest
concentration was obtained for tomato seed oil extracted
with diethyl ether (0.08 %), and the lowest concentration
was for the sample obtained from mechanically milled
tomato seeds (0.04 %). All other samples had a water
concentration of 0.05–0.06 %, without significant variation
with the number of percolations.
Fig. 1 The normalized KFT volume (V/m, mL/g) versus time (s) plot
for tomato seed oil obtained by diethyl ether extraction (triplicate
samples, DEE1, DEE2, DEE3)
Fig. 2 The normalized KFT volume (V/m, mL/g) versus time (s) plot
for tomato seed oil obtained by petroleum ether extraction (mechan-
ically milled seeds) (triplicate samples, MM1, MM2, MM3)
Fig. 3 The normalized KFT
volume (V/m, mL/g) versus time
(s) plot for tomato seed oil
obtained by petroleum ether
extraction (different
percolations)
J Mater Cycles Waste Manag
123
The highest concentration (0.08 %) of water content for
the samples extracted with diethyl ether (in comparison
with the sample extracted with petroleum ether) can be due
to the physical properties of the solvents: the water has a
very low solubility in petroleum ether in comparison with
the diethyl ether, where the water solubility is about 10 %
[19].
The water reaction rate can be an important indicator
for the type of water molecules from the liquid or solid
samples. In the case of tomato seed oil samples, only one
pseudo linear range (generally 10–40 s) in the KFT pro-
cess [titration volume weighted to the sample mass (V/m,
mL/g) versus time (s); see Table 3 for the final V/m
values] can be observed. A second range corresponding to
the normal KFT process (the drift range) can also be
observed.
The water molecules react with a rate of 3–10 lM/s
(which means micromoles/liter/second) in the KFT pro-
cess, with a highest rate of 10 lM/s for DEE samples
(pH 6.23, g = 22.7 mm2/s, standard deviation \0.01)
(Fig. 1).
The lowest reaction rate 3 lM/s (Fig. 2) was obtained
for oil samples isolated from mechanically milled tomato
seeds (MM), granularity in the range of 0.5–1.5 mm (pH
6.15, g = 23.4 mm2/s, standard deviation \0.01).
The number of percolations does not have a significant
influence on the reaction rate of water molecules. In Fig. 3
is presented the normalized KFT volume (V/m, mL/g)
versus time (s) plot for tomato seed oil obtained by
petroleum ether extraction with 1, 2, 4, and 6 percolations.
The water reaction rate values are in the range of
5.4–8.9 lM/s, but no variation with the extraction time was
observed.
Conclusions
Based on the presented results, the following conclusions
can be drawn: (1) tomato seeds from tomato processing
waste are valuable sources of edible nutritive oil that con-
tains a relatively high amount of x-6 essential FA (C18:2).
(2) FA composition of Romanian tomato seed oil is similar
with other results reported in literature. Regarding the type
of solvent used for extraction of the tomato seed oil, we can
conclude that small variations in the absolute concentration
of FA from derivatized tomato seed oil samples were reg-
istered. An increasing tendency of the FA absolute con-
centration in the derivatized tomato seed oil samples with
the number of percolation used for extraction was
remarked. An increasing trend of the concentration of all
FA was reported when the surface between tomato seeds
milled and solvent used for extraction has been increased.
(3) The water reaction rates in the KFT process significantly
depend on the solvent type (less hydrophobic solvent con-
ducts to a higher KFT water reaction rate) and the granu-
larity of the raw tomato seed powder used for extraction, but
no correlation with the FA composition of the tomato seed
oil was observed. Extraction time does not influence the
water content and has a very low influence on the water
reaction rate of all analyzed samples.
Acknowledgments This work was partially supported by the
‘‘Doctoral Studies for Training in Research (FOR-CE)’’ Program,
POSDRU/CPP107/DMI1.5/S/80127, co-financed by the Structural
Funds of the European Union, selected from the Sectoral Operational
Programme Human Resources Development 2007–2013. The authors
would like to thank Professor Heinz-Dieter Isengard from Hohenheim
University, Germany, for the help in the Karl Fischer water titration.
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