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Summary:
The main goal of the project was
to develop rapid and accurate procedures for assessing the oxidative
stability of selected oils with modified fatty acid composition using
small sample sizes suitable for the breeders. Samples of different
cultivars of canola seeds were obtained from different growing
locations. Oils extracted from the specific oilseed samples were
assessed for their composition and oxidative stability. The stored oils
were assessed in an accelerated storage test and changes in oxidation
status monitored by measuring peroxide value (PV), conjugated dienes
(CD) and aldehydes content, as well as the decomposition of tocopherols.
Based on these results a fast test was developed capable of ranking
samples by their oxidative stability using small samples of oils
extracted from breeding-size samples. New tests require only a few
milligrams of oil samples to assess both oxidative stability and
composition of tocopherols. When the analysis of fatty acids was
included, about 50 mg of oil proved sufficient for all assessments. In
this report the composition and storage stability of the different
canola and soybean samples are discussed. However, in the overall
project other types of oilseeds were also evaluated. The composition of
the main components and their degradation during accelerated storage
were typical for canola and soybean oils. Some effects of growing
locations on the composition and performance were observed but the
number of locations was insufficient to allow final and generalized
conclusions.
Procedure and Project Activities:
The study established the
oxidative stability of the analyzed canola oils under accelerated
conditions at 60°C. Fatty acids and minor components were analyzed to
assess their impact on oxidation as well as any variations due to
location and growing conditions.
Oilseed Samples
Samples were collected and
analyzed in groups appropriate to species, cultivar and growing
location. Results were therefore presented in groups as detailed below.
Canola Group 1 - Canola Group 1
contained one traditional and two modified cultivars grown at one
location in Arizona, one location in Mexico and one location in Idaho
during the same year.
Canola Group 2 - Canola Group 2
contained one traditional and one modified cultivar grown at one
location in Manitoba and one location in Alberta during the same year.
Soybean Group 1 - Soybean Group
1 contained one traditional and two modified soybean cultivars grown at
two locations in Ontario and one location in Manitoba during 1996.
Soybean Group 2 - Soybean Group
2 contained two modified soybean varieties grown at two locations in
Manitoba and one location in Ontario during 2000.
Soybean Group 3 - Soybean Group
3 contained three modified soybean varieties grown at the same location
in Ontario during two consecutive years, 1999 and 2000.
Flax and Solin Group 1 - Solin
Group 1 contained two traditional flax varieties and four modified solin
varieties grown at two locations in Saskatchewan during 1999.
Solin Group 2 - Solin Group 2
contained three modified solin varieties grown at one location in
Saskatchewan and two locations in Manitoba during 1999.
Extraction of Oils for
Storage and Testing
Oils were extracted from seeds
by grinding in hexane using a ball mill. After filtration, the hexane
was removed by evaporation in a rotary evaporator. Samples of oil were
then stored frozen until used.
Sample Preparation and
Storage
The oil samples (1mL) were
dispensed into 4mL glass vials which provide a surface to volume ratio
of one. Individual vials were prepared for each sampling period.
Samples were stored in the open vials at 60°C in the dark, with samples
removed for analysis after 0, 2, 4, 8 and 16 days of storage.
Composition of Oils
Fatty Acid Composition
Fatty acid composition was
analysed using acidic catalyst for methylation. Oil samples were
weighed (50 mg) and combined with 1mL isooctane containing internal
standard C17:1 (1 mg/mL, Nu-Chek Prep, Elysian). Then 12 mL of 2%
sulphuric acid in methanol was added. Samples were mixed and heated for
1 hour at 65-70°C. During heating samples were mixed every 3-5 minutes
for the first 20 minutes of this operation. Samples were cooled to room
temperature, 2 mL isooctane and 6 mL of distilled water were added and
samples were centrifuged at 2000 rpm for 5 minutes to assist separation
of layers. The upper organic layer (1µL) was analyzed on a Hewlett
Packard 5890 GC (Hewlett Packard, Avondale, PA) equipped with a flame
ionization detector. Separation was performed on SP-2560 column (100m x
0.25mm i.d. with 0.20µm film thickness; Supelco, Oakville, Ontario).
The column temperature was held at 70°C for 2 minutes, then programmed
to 155°C at 15°C/minute, held for 25 minutes, then programmed to 215°C
at 3°C/minute and final temperature held for 8 minutes. Injector and
detector temperatures were both set at 250°C. Hydrogen was applied as
carrier and makeup gases, with column head pressure of 250 kPa. Fatty
acids were identified by comparison of corrected retention times of the
standards.
Tocopherol Composition
Tocopherol content was analysed
using AOCS method Ce 8-89. Briefly, 200 mg of oil samples were weighed
in vials and hexane (HPLC grade) added to achieve a concentration of oil
in the 20-40 mg/mL range. Samples were analysed using a Shimadzu HPLC
system, equipped with an LC-10AD pump, SIL-10AD auto injector, SCL-10A
system controller, and RF-10AXL fluorescence detector. The excitation
wavelength was 290 nm and the emission wavelength was 335 nm. The
normal phase column was Prodigy (5µm silica; 250cm x 3.2 mm i.d.;
Phenomenex, Torrance, CA). The mobile phase was 5% tert-butyl
methyl ether in hexane, at the flow rate of 0.8 mL/min, the run time was
25 minutes and 10µL of sample injected.
Tocopherol degradation data are
expressed as half-life time, the amount of time required for tocopherol
contents to fall to 50% of the initial amount.
Chlorophyll Content
Chlorophylls were analysed as
the sum of all isomers using AOCS method Cc 13d-55. Briefly, a 10%
solution of oil was made up, 0.5 g of oil in 5 mL of isooctane/ethanol
(3:1, v/v). Solution was scanned from 400 nm to 710 nm. Specified
maxima of absorption were used for calculation of the amount of
chlorophylls using an equation provided in the method.
Assessment of Oxidation
To assess oxidative status of
oils, primary oxidation products (peroxide value and conjugated dienes)
and secondary oxidation products (aldehydes) were analyzed.
Peroxide and Aldehyde Value
Peroxide and aldehyde values
were analyzed using the Saftest system (Safety Associates, Tustin,
California). These tests use a set of colorimetric reagents to
determine the content of peroxides and aldehydes by colorimetry.
Briefly, oil samples in the solvent were filtered before application of
specific reagent. After reagents were added samples were held for 15
minutes to form pigments, then absorption measured on a
spectrophotometer at 550/690 nm for aldehydes and at 570/690 nm for
peroxides. In both cases specific filters were applied with the Saftest
colorimeter. Reagent types used for these tests are protected by Safety
Associates and composition is not available.
Conjugated Dienes
Oil samples were prepared in
isooctane to a concentration that produced a reading of absorbance
within the range of 0.2 to 0.8 units at 232 nm. Results were expressed
as absorbance of a 1% solution of sample measured in 10 mm path length
cuvette.
Statistical Analysis
Results of sample assessment
were analyzed using SAS statistical software. Differences between means
were identified using the Student-Newman-Keuls test.
Rapid Testing for Oxidative
Stability
Test for rapid testing of
oxidative stability of oils is based on combination of thin layer
chromatography with a flame ionization detector. However, due to
intellectual property protection, results and description of the
methodology of this assessment are not included in this report.
Results and Discussion:
Canola Oil Samples
Initial Fatty Acid Composition
Canola Group 1 - One traditional
cultivar and 2 modified cultivars were grown at one location in Arizona,
one location in Mexico and one location in Idaho. The traditional
cultivar contained 9.2% of C18:3, while the modified cultivars contained
2.7% and 3.1%, respectively (Table 1). The modified cultivar 2
contained a lower amount of C18:2 (11.2%) compared to the traditional
(19.8%) and modified cultivar 1 (23.3%). Effect of location was
observed only for the content of C18:0 (Table 2).
Canola Group 2 - One traditional
cultivar and one modified cultivar were grown at one location in Alberta
and one location in Manitoba. The initial fatty acid composition was
significantly different for both cultivars studied (Table 1).
The modified cultivar had a higher content of C18:2, 25.1% than the
traditional cultivar, 19.7%. However, the modified cultivar had a lower
amount of C18:3, 2.4%, compared to the traditional cultivar with 8.4%.
Differences between locations for these cultivars were observed, as for
the previous group, in the amount of C18:0 (Table 2).
Initial Tocopherol Content
Gamma tocopherol was the major
isomer present in canola oils, alpha isomer second in the amount.
Canola Group 1 - The tocopherol
composition of the traditional canola cultivar and modified cultivar 1
were not significantly different (Table 3). While the modified
cultivar 2 contained significantly lower total amount of tocopherols,
892 µg/g oil (Table 1), location did not affect the amount and
composition of tocopherols (Table 4).
Canola Group 2 - For this group
of cultivars no differences in the composition and the amount of
tocopherols were observed between the traditional and modified
cultivars. Also growing location did not have an effect in this
group of canola samples (Table 3 and
Table 4).
Initial Chlorophylls Content
Canola Group 1 - Oils extracted
from all samples of the traditional and some modified canola cultivars
had chlorophyll levels below 0.2 µg/g, this value is a detection limit
for the method applied (Table 5). However, oil from modified
canola cultivar 2 grown in location 2 and 3 had 4.0µg/g and 36.3µg/g of
chlorophylls, respectively (Table 5. Elevated content of
chlorophylls indicates seed immaturity.
Canola Group 2 - The chlorophyll
content in the oil extracted from traditional canola cultivar was below
0.2µg/g at location 1, but was 1.6µg/g at location 2 (Table 5).
In contrast, the chlorophyll content in the oils extracted from modified
canola cultivar grown at both locations has similar amounts of
chlorophyll (2.0µg/g and 1.8µg/g). This amount of chlorophylls can
affect storage stability of oils when they are exposed to light.
Oxidative Stability
Canola Group 1 - The traditional
cultivar was significantly less stable than the modified cultivars, as
indicated by all three measurements of oxidation (Figure
1,
Figure 2 and
Figure 3). Oxidation of oil from the traditional cultivar resulted
in 1.8% of conjugated dienes, peroxide value of 264 meq/kg and 7.7 mmol/L
of aldehydes (Figure
1,
Figure 2 and
Figure 3). The amounts in
the modified cultivars 1 and 2 were 1.0% and 1.6% for conjugated dienes,
108 meq/kg and 48 meq/kg for peroxide value and 3.4 mmol/L and 1.8 mmol/L
for aldehydes, respectively. Oxidative stability was not affected by
growing location.
Canola Group 2 - No significant
differences in oxidative stability were observed between the traditional
and modified canola cultivars in this group (Figure 4,
Figure 5
and Figure 6). Oil from traditional canola cultivar produced a higher
content of conjugated dienes, and peroxide and aldehyde values (1.3%,
131 meq/kg and 6.7 mmol/L) than the modified cultivar (0.8%, 85 meq/kg
and 2.4 mmol/L) at day 16 of the storage period. The traditional
cultivar had more C18:3 but less C18:2 than the modified cultivar but
both had similar amount of tocopherols. Similarly to the previous
canola group, the effect of growing location was not observed.
Degradation of Major Tocopherols
Canola Group 1 - Of the major
canola tocopherols, α-tocopherol was less stable than γ-tocopherol, this
indicates better activity of this isomer as antioxidant (Figure
7). Major tocopherols in the
traditional cultivar were less stable than those in the modified
cultivars. Total amount of tocopherol and α- and γ-tocopherols in
the traditional canola cultivar had a half-life of 141,
80 and 157 hours, respectively. Compared to corresponding values of
304, 197 and 346 hours for modified cultivar 1 and 301, 185 and 365
hours for modified cultivar 2. Assessment of degradation of tocopherols
during storage was not affected by the growing location.
Canola Group 2 - Results for
Canola Group 2 showed similar pattern of tocopherol isomers stability as
for the previous group, where α-tocopherol was less stable than γ-tocopherol.
The half-life time of the total amount of tocopherols was reflected by
change in the major isomer, γ-tocopherol (Figure 8). The major
tocopherols in the traditional cultivar, α-; γ- and total amount of
tocopherols had a shorter half-life time, 92, 158 and 143 hours,
respectively, than those in the modified cultivar, 219, 304 and 285
hours, respectively. The half-life time of tocopherols was not affected
by growing location.
Of the canola samples, each of
the modified cultivars had the content of Cl8:3 below 4%, compared to
the traditional cultivars with 8.4 and 9.2% of this fatty acid. Due to
the higher susceptibility of C18:3 to oxidation, it was shown that
vegetable oils which contained below 2% of C18:3 oxidized slower than
oils with the higher amounts of this acid. Indeed, among the canola
samples, the traditional cultivars, which contained higher amounts of
C18:3 than the modified cultivars, had the lowest oxidative stability.
Soybean Samples
Soybeans were analysed for fatty
acid composition prior to storage. Major fatty acids were compared
between cultivars (Table 6) and in a separate analysis, between
locations or growing years (Table 7).
Initial Fatty Acid Profile
Soybean Group 1 - One
traditional soybean cultivar and 2 modified cultivars were grown at two
locations in Ontario and one location in Manitoba. The fatty acid
compositions of the modified cultivars are shown in
Table 6. The
modified cultivar 1 contained the largest amount of C18:3, 11.6%,
followed by the traditional soybean cultivar with 9.0%, while the
modified cultivar 2 contained the lowest amount of C18:3, 6.8%. In
addition, the traditional soybean cultivar was significantly different
from the modified cultivars by lower content of C18:2, 53.8%, compared
to the modified cultivars with 61.2% and 61.7%. Only the amount of
Cl8:1 was affected by the growing location (Table 7). Samples
grown at location 2 had the highest content of oleic acid, 21.1%, while
those grown at location 3 had the lowest amount of 18.6%.
Soybean Group 2 - In this group,
two modified soybean cultivars were grown at one location in Ontario and
two locations in Manitoba. Significant differences were evident for
each of the fatty acids analysed (Table 6). The modified
cultivar 1 had the highest contribution of C18:2, 58.9%, compared to
modified cultivar 2 with 52.3%. However, the modified cultivar 2 had
also the highest content of C18:3, 6.0%, while the modified cultivar 1
had the lowest amounts of this acid at 2.8% (Table 6). Growing
locations did not affect fatty acid composition significantly in any of
the assessed cultivars (Table 7).
Soybean Group 3 - Three modified
cultivars from this group were grown at a single location in Ontario
over a two years period, 1999 and 2000. Significant differences were
observed for each of the fatty acids analysed in this crop (Table 6).
The modified cultivar 1 had the lowest contribution of C18:2, 37.3%,
compared to modified cultivars 2 and 3 with 59.6% and 59.7%,
respectively. The modified cultivar 1 also contained the highest
amounts of C18:3, 10.5%, while cultivar 3 contained slightly lower
amounts of this acid, 9.5%, and the cultivar 2 contained the lowest
amount of C18:3, 2.3%. No significant differences were observed in
fatty acid composition as affected by growing years (Table 7).
Initial Tocopherol Content
The initial tocopherol content
was assessed for each of the groups studied. As with fatty acid
profiles, tocopherols composition for each cultivar (Table 8) and
location/year (Table 9) were assessed. Each of tocopherol
isomers was compared to the cultivars and location/years within the
group. Soybean oils had the highest quantities of tocopherols among all
oils assessed in this study.
Soybean Group 1 - Among samples
in Soybean Group 1, the modified cultivar 2 had the highest amounts of
γ-tocopherol (1759µg/g), δ-tocopherol (888µg/g) and total amount of
tocopherols (2765µg/g) among oils within this group (Table 8).
By contrast, the traditional cultivar had the lowest content of γ-tocopherol
(1350µg/g), δ-tocopherol (506µg/g) and the total amount of tocopherols
(1982µg/g) in this group. Location only affected composition of the
minor tocopherols (Table 9). Also γ-tocopherol at location 2
(1684µg/g) and at location 3 (1369µg/g) showed the biggest differences (Table 9).
Soybean Group 2 - Two cultivars
in this group, modified cultivar 1 had the highest content of γ-tocopherol
(1796µg/g), δ-tocopherol (988µg/g) and the amounts of total tocopherols
(2948 µg/g) (Table 8). The growing location did not affect the
composition of tocopherols in this group of samples (Table 9).
Soybean Group 3 - The modified
cultivar 1 had the highest content of the major tocopherols, with
1674µg/g of γ-tocopherol, 858µg/g of δ-tocopherol and 2647µg/g of the
total amounts of tocopherols (Table 8). No differences were
observed between growing years and composition of tocopherols in the
group (Table 9).
Initial Chlorophylls Content
The chlorophyll content in oils
is an indication of seed maturity and is not crop dependent, however
only some oilseeds contain these pigments. The content of chlorophylls
in seed is mainly affected by growing and harvesting conditions. The
presence of chlorophyll can have a negative effect on the oxidative
stability of oils, particularly when they are exposed to light during
storage. Thus, the content of chlorophylls in oil can only be treated
as an additional factor in explaining oil oxidative stability, not as
endogenous component of oil.
Soybean Groups 1, 2 and 3 - Oil
extracted from all soybean seeds had chlorophyll content below detection
limit of 0.2µg/g for method used in this study. Hexane, the solvent
used for industrial extracting of oils, is non-polar and not an
efficient solvent in extracting chlorophylls. As the aim of this
project was to examine oxidative stability of oils extracted from
oilseeds, the content of chlorophylls in the extracted oils, rather than
in the seed, was considered most relevant.
Oxidative Stability
Soybean Group 1 - The
accumulation of conjugated dienes was slightly lower for the traditional
cultivar, 2.7% than for the modified cultivars, 3.1% and 3.0%,
respectively (Figure 9). Peroxide value (Figure 10) and
aldehyde value (Figure 11) at day 16 of storage showed similar
patterns. The traditional cultivar had an aldehyde value of 8.0 mmol/L,
while the modified cultivars 10.5 mmol/L and 9.1 mmol/L, respectively.
The peroxide value at the end of storage for the traditional cultivar
was 241 meq/kg, while for the modified cultivars were 327 meq/kg and 261
meq/kg, respectively. Growing location did not affect storage stability
of oils from this group.
Soybean Group 2 - As for Soybean
Group 1, conjugated diene contents were not significantly different in
Soybean Group 2 cultivars at the last day of storage, day 16 (Figure
12). However, modified cultivar 1 showed slightly better oxidative
stability, as measured by the lower amounts of conjugated diene, 2.5%,
compared to modified cultivar 2 with 2.9%. These results were confirmed
by similar pattern for hydroperoxide and aldehyde formation (Figure
13 and
Figure 14). Modified cultivar 1 had an aldehyde value of 6.3
mmol/L and a peroxide value of 180 meq/kg, while modified cultivar 2 had
the aldehyde value of 6.7 mmol/L and the peroxide value of 276 meq/kg
(Figure 13
and Figure 14). Growing location did not affect
oxidative stability of oils from this group.
Soybean Group 3 - In this group,
the modified cultivar 3 had a significantly lower oxidative stability
compared to the other cultivars, as indicated by the accumulation of
conjugated dienes (3%) at the end of storage time (Figure 15).
While modified cultivars 1 and 2 reached values of 2.2% and 2.3%,
respectively, peroxide values for these oils were not significantly
different (Figure 16); modified cultivars 1 and 2 had peroxide
values of 194 meq/kg and 238 meq/kg, respectively, while modified
cultivar 3 had higher peroxide value of 307 meq/kg. Aldehyde value, 9.1
mmol/L vs. 4.7 mmol/L indicated that modified cultivar 3 was less stable
than modified cultivar two, while modified cultivar 1 with aldehydes
value of 8.2 mmol/L was not significantly different from the less stable
cultivar (Figure 17). Growing years did not affect oxidative
stability for these samples.
Degradation of Major Tocopherols
During Storage
Disappearance of the major
tocopherols was expressed as half-life time, the time required for the
amount of each tocopherol to reach 50% of the original value.
Soybean Group 1 - The half-live
times for γ-, δ- and total tocopherol amount are shown in
Figure 18.
In all samples in this group, δ-tocopherol was more resistance to
changes than γ-tocopherol. As discussed previously, degradation of
total tocopherol amount reflects changes in the dominant tocopherol
isomer, in case of soybean 7-tocopherol. As with the oxidative
stability results, the half-live times for these components were not
significantly different. However half-live times for γ-, δ- and total
amount of tocopherols in modified cultivar 1 were 143, 272 and 171
hours, respectively. These values were longer for the traditional
soybean cultivar with 191, 295 and 208 hours, respectively and for
modified cultivar 2 with values 210, 322 and 236 hours, respectively.
Growing location did not affect degradation of tocopherols in this group
of samples.
Soybean Group 2 - As was found
in Soybean Group 1, γ-tocopherol degraded more quickly than δ-tocopherol,
and the degradation rate of the total amounts of tocopherol followed the
disappearance of the dominant γ-isomer (Figure 19). As discussed
previously, the modified cultivar 1 demonstrated the best oxidative
stability and lower degradation rate of tocopherols. Pattern of
degradation was similar in modified cultivar 1 and 2. The half-live
times of γ-, δ- and total tocopherols were 303, 489 and 335 hours,
respectively for modified cultivar 1, and those for modified cultivar 2
were shorter with corresponding values of 175, 267and 190 hours,
respectively. The degradation of tocopherols did not show relation with
growing location.
Soybean Group 3 - As reported
for the previous two soybean groups, the pattern of tocopherol
degradation was similar in the third group (Figure 20). The
major tocopherols of modified cultivar 1 had similar stability to those
of modified cultivar 3, with half-live times for γ-, δ- and total
tocopherols being 177, 285 and 193 hours, and 188, 307 and 218 hours,
respectively. The modified cultivar 2 showed better stability with
half-live time for discussed isomers of tocopherols at 343, 550 and 373
hours, respectively. As discussed with oxidative stability results,
there were no observed significant differences between the 1999 and 2000
growing seasons in degradation of tocopherols.
Flax and Solin Samples
As for the soybean and canola
samples, the initial fatty acid compositions were compared within the
same cultivar groups and locations.
Initial Fatty Acid Profile
Flax and Solin Group 1 - Two
traditional flaxseed varieties and 4 solin varieties were grown at two
locations in Saskatchewan. The defining difference between flax and
solin is the amount of C18:3, the contribution of this acid is reduced
to below 5% in solin. This difference is easily observed in the initial
fatty acid profiles of the samples studied, with the C18:3 content of
the flaxseed cultivars 1 and 2 at 58.7% and 57.3%, respectively, while
the content of Cl8:3 for the solin cultivars was below 5% (Table 10).
In addition, the content of C 18:2 in flaxseed cultivar 1 and 2 were
12.1% and 15.2%, respectively, whereas in solin cultivars contribution
of this acid was from 58.5% to 70.6%. Among the solin cultivars, solin
2 had a similar fatty acid profile to solin 4, while solin 1 was similar
to solin 3. Due to the large differences in the fatty acid composition
between flaxseed and solin, only solin samples were used in the
comparison of locations effect. Differences between growing locations
were observed for the content of C18:1, where crops grown in location 1
had higher amounts of C18:1 (16.6%) than location 2 (13.4%) (Table 11).
Solin Group 2 - Three solin
cultivars were grown at one location in Saskatchewan and two locations
in Manitoba. Solin cultivar 1 had higher amounts of C18:2 and C 18:3,
than solin cultivar 2 (Table 10). No differences were observed
in fatty acid composition as affected by growing locations (Table 11).
Initial Tocopherol Content
The main tocopherol isomer in
both flaxseed and solin was γ-tocopherol (Table
12 and
Table 13).
Total content of tocopherols in the Flax and Solin Group were typical
for flaxseed and solin samples.
Flax and Solin Group 1 - While
the fatty acid profiles of the flax and solin samples differed, the
amounts of tocopherol was similar in these crops (Table
12). In
fact, the tocopherol content in solin cultivars 2 and 4 were similar to
that of flaxseed. Only slightly different compositions were observed
for solin cultivars 1 and 3 (Table
12). Solin cultivars 1 and 3
had the highest content of plastochromanol-8, 412µg/g and 407µg/g,
respectively, γ-tocopherol, 1310µg/g and 1335µg/g, respectively and
total amounts of tocopherols, 1744µg/g and 1770µg/g, respectively. The
flaxseed and solin cultivars 2 and 4 were not significantly different
from each other, with the exception of flaxseed 2 which had the lowest
content of plastochromanol-8, 234µg/g (Table
12). Location
differences were evident in this group, with higher γ-; δ- and total
amount of tocopherols at location 1 (844µg/g, 12µg/g and 1209µg/g,
respectively) than at location 2 (1156µg/g, 16µg/g and 1499µg/g,
respectively). The remaining major tocopherol, plastochromanol-8,
showed no location effect. Plastochromanol-8 is a derivative of γ-tocotrienol
with longer side chain.
Solin Group 2 - The three solin
cultivars in this group differed only in the content of
plastochromanol-8, with solin 2 having the lowest amount of 272µg/g (Table
12). Location did not have effect on the content of tocopherols in
this group (Table
13).
Initial Chlorophylls Content
Flax and Solin Group 1 - Oil
obtained from samples grown at location 2 had content of chlorophylls
below detection limit of the method, 0.2µg/g (Table 14).
However, seeds from location 1 provided oil with chlorophylls contents
between 1.7µg/g and 3.9µg/g. The amount of chlorophylls decreases as
oilseeds mature, and the elevated amounts of chlorophylls at location 1
suggests that samples may have been prematurely harvested.
Solin Group 2 - Oil extracted
from all solin samples in this group had chlorophylls content below
detection limit of the applied method, 0.2µg/g.
Oxidative Stability
Flax and Solin Group 1 - As
predicted by the difference in the content of C18:3 between flax and
solin samples, the conjugated diene contents of samples in this group
indicated a much greater stability for solin cultivars than for flax
cultivars (Figure 21). Conjugated diene contents for the flax
cultivars were 2.5% and 4.4%, respectively, while the solin cultivars
produced 1.1 to 1.4%. Similarly, peroxide values for the flax cultivars
were 487 meq/kg and 439 meq/kg respectively, while for the solin
cultivars only 107-258 meq/kg (Figure 22). Peroxide value
differences for flaxseed and solin samples were not statistically
significant due to the large estimation error of the method applied in
this study. Results for aldehyde value showed significant differences
between flax and solin cultivars (Figure 22
and Figure 23).
Aldehyde value for flax cultivars 1 and 2 were 37.7 mmol/L and 38.7 mmol/L,
respectively, while aldehyde value for the solin cultivars were about
ten folds lower, 2.7-3.7 mmol/L. Growing location did not affect
oxidative stability of samples in this group.
Solin Group 2 - Solin cultivar 3
was less stable than the other cultivars in this group, as indicated by
2.4% of conjugated dienes when in solin cultivars 1 and 2 the amount
were 1.7 and 1.5%, respectively (Figure 24). Similar pattern was
observed in peroxides formation, where all samples showed no differences
in accumulation of hydroperoxides (Figure 25). Formation of
aldehydes confirmed similar pattern of oxidative stability as conjugated
dienes (Figure 24). Solin cultivar 3 had an aldehyde value of
8.1 mmol/L, while solin 1 and solin 2 cultivars had 5.7 mmol/L and 3.9
mmol/L, respectively (Figure 26). Growing location did not
affect oxidative stability of solin samples in the group.
Degradation of Major Tocopherols
During Storage
Flax and Solin Group 1 -
Plastochromanol-8 degraded more quickly than γ-tocopherol in flaxseed
and solin oils (Figure 27). Oxidative stability results showed
distinct difference between flaxseed and solin oils. The half-live
times for the flaxseed plastochromanol-8, γ- and the total amount of
tocopherols were 76-102, 79-108 and 80-106 hours, while those for solin
cultivars were 264-334, 280-350 and 275-345 hours, respectively (Figure 27). There were no significant differences among two flaxseed
cultivars or 4 solin cultivars. Similarly to oxidative stability,
growing location did not affect tocopherol degradation.
Solin Group 2 -
Plastochromanol-8 degraded slightly faster than γ-tocopherol in this
group (Figure 28). Solin cultivar 3 had shorter half-live times
for plastochromanol-8, γ-tocopherol and the total amount of tocopherols,
with values of 172, 182 and 179 hours, respectively, compared to solin
cultivar 1 values of 249, 259 and 255 hours, respectively and solin
cultivar 2 values of 261, 279 and 271 hours, respectively. As for
previous group, growing location did not affect tocopherol degradation.
Appendices:
-
Table 1. Fatty acid profile for canola samples by
cultivar (% of total fatty acids).
-
Table 2. Fatty acid profile for canola samples by
location (% of total fatty acids).
-
Table 3. Tocopherol profile for canola samples by
cultivar (µg/g oil).
-
Table 4. Tocopherol profile for canola samples by
location or year (µg/g oil).
-
Table 5. Chlorophylls content of Canola Groups (µg/g
oil).
-
Table 6. Fatty acid composition of soybean cultivar
(% of total fatty acids).
-
Table 7. Fatty acid composition of soybean samples
by location or year (% of total fatty acids).
-
Table 8. Tocopherol profiles for soybean oils by
cultivar (µg/g oil).
-
Table 9. Tocopherol profiles for soybean oils by
location or year (µg/g oil).
-
Table 10. Fatty acid profile for flax and solin
samples by cultivar (% of total fatty acids).
-
Table 11. Fatty acid profile of flax and solin
samples by location (% of total fatty acids).
-
Table
12. Tocopherol profile for flax and solin
samples by cultivar (µg/g oil).
-
Table
13. Tocopherol profile for flax and solin by
location or year (µg/g oil).
-
Table 14. Chlorophylls content of the Flax and Solin
Group (µg/g oil).
-
Figure
1. Accumulation of conjugated dienes in
cultivars of Canola Group 1.
-
Figure 2. Accumulation of hydroperoxides in
cultivars of Canola Group 1.
-
Figure 3. Accumulation of aldehydes in cultivars of
Canola Group 1.
-
Figure 4. Accumulation of conjugated dienes in
cultivars of Canola Group 2.
-
Figure 5. Accumulation of hydroperoxides in
cultivars of Canola Group 2.
-
Figure 6. Accumulation of aldehydes in cultivars of
Canola Group 2.
-
Figure 7. Degradation of major tocopherols in
cultivars of Canola Group 1.
-
Figure 8. Degradation of major tocopherols in
cultivars of Canola Group 2.
-
Figure 9. Accumulation of conjugated dienes in
cultivars of Soybean Group 1.
-
Figure 10. Accumulation of hydroperoxides in
cultivars of Soybean Group 1.
-
Figure 11. Accumulation of aldehydes in cultivars of
Soybean Group 1.
-
Figure
12. Accumulation of conjugated dienes in
cultivars of Soybean Group 1.
-
Figure 13. Accumulation of hydroperoxides in
cultivars of Soybean Group 2.
-
Figure 14. Accumulation of aldehydes in cultivars of
Soybean Group 2.
-
Figure 15. Accumulation of conjugated dienes in
cultivars of Soybean Group 3.
-
Figure 16. Accumulation of hydroperoxides in
cultivars of Soybean Group 3.
-
Figure 17. Accumulation of aldehydes in cultivars of
Soybean Group 3.
-
Figure 18. Degradation of major tocopherols in
cultivars of Soybean Group 1.
-
Figure 19. Degradation of major tocopherols in
cultivars of Soybean Group 2.
-
Figure 20. Degradation of major tocopherols in
cultivars of Canola Group 3.
-
Figure 21. Accumulation of conjugated dienes in
cultivars of Flax and Solin Group 1.
-
Figure 22. Accumulation of hydroperoxides in
cultivars of Flax and Solin Group 1.
-
Figure 23. Accumulation of aldehydes in cultivars of
Flax and Solin Group 1.
-
Figure 24. Accumulation of conjugated dienes in
cultivars of Solin Group 2.
-
Figure 25. Accumulation of hydroperoxides in
cultivars of Solin Group 2.
-
Figure 26. Accumulation of aldehydes in cultivars of
Solin Group 2.
-
Figure 27. Degradation of major tocopherols in
cultivars of Flax and Solin Group 1.
-
Figure 28. Degradation of major tocopherols in
cultivars of Solin Group 2.
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