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OIL AND ERUCIC ACID CONTENTS OF FIVE BRASSICA SPECIES GROWN FOR FOUR SUCCESSIVE YEARS IN EGYPT

Mahmoud K. Tahoun, Abdel-Halim I. Ghazy and Amin E. Aly

The Biotechnology Research Group, Faculty of Agriculture,
Alexandria University, Alexandria, Egypt.

ABSTRACT

With regard to the oil content in seeds, the results indicated significant differences between accessions. Accessions No.13 and 14 of Brassica nigra gave the highest oil content (43 and 41%, respectively) during 1997 and 1998. On the other hand, Brassica napus accessions No. 16 and 18 revealed the lowest oil content (16 and 24%, respectively), in the first season. In the second season, accession No.25 of Brassica juncea gave the lowest oil content, being 26.13%. A negative relationship was observed between the concentration of oleic, linoleic, linolenic and erucic acids. The lowest linolenic acid content that affects oil quality and stability was detected in Brassica campestris accession No.10, being 8% and Brassica napus accession No. 17, being 10.3%. The majority of accessions investigated contained high erucic acid content that reached 50% in Brassica carinata accession No. 3, except Brassica napus accession No. 17 was the only one that showed zero percentage erucic acid. Erucic acid contents in all accessions studied revealed stability during the years investigated. This finding indicates that erucic acid concentration is controlled by genetic make-up rather than to be affected by environmental factors. The oil extracted from the above accessions revealed high physical and edible properties.

KEYWORDS: Brassica species and accessions, Oil content, Fatty acids composition, Erucic acid content, Oil quality.

INTRODUCTION

Oilseed rape cultivation has increased tremendously during the last decade and, by now, oilseed rape is the second largest contributor to the world supply of vegetable oil. This success must be attributed to continuous breeding efforts, particularly the development of double zero erucic acid oilseed rape cultivars. Biotechnologically modified rape cultivars is increasingly contributing over 13.2% of the world’s edible oil supply that now comes from the oilseed Brassicas, rapeseed and mustered. Indeed, production and usage of Brassica seed oils have grown faster in the period 1975-1985 than other crops, making it the third most important edible oil source after soybean and palms.

In Egypt, there was no registered acreage for rapeseed on farmer’s fields before 1988, as it was not included as an edible oilseed in Egyptian code because of the high content of the long-chain fatty acid, erucic acid (C22:1), of the conventional cultivars oil. However, this problem was solved in some leading producing countries by selecting new rapeseed cultivars low or free from erucic acid and low in glucosinolates. Accordingly, rapeseed oil was legally added to the Egyptian code in 1988, but to include only these cultivars which had below 2% erucic acid. The Brassica oilseed normally yields an extraction of over 40% oil on dry weight basis and a meal containing 38 to 44% high quality protein used as a high protein feed for livestock and poultry.

The oil content of Brassica was the subject of numerous discussions and investigations. In India, Ahuja et al.(1989) reported that the oil content of 64 genotypes varied from 38.9 to 44.6%. They indicated further that the oil content was found to be positively correlated with that of erucic acid content. In a subsequent report, Ahuja et al.(1990) identified the seed oil content and quality of 26 genotypes to select desirable genotypes for further crop improvement programs. They reported that the oil content ranged between 41.2 and 54.4%. The major fatty acids were oleic (11.5-20.4%), linoleic (11.9-16.0%), the linolenic plus eicosenoic (gadoleic) (15.0-21.4%) and erucic (40.3-46.0%) acids. The same range of oil content was described by Kumar (1990) for Brassica juncea that varied between 34.2 and 43.5%, while for Brassica campestris the oil content was 36.9-45.0%. For both above species, erucic acid concentration of the seed oil was 44.0-45.0%.

The quality of rapeseed oil for human consumption is measured by its erucic acid content, since erucic acid is believed to cause myocardial lesions in experimental male rats (Vles, 1975). However, it is poorly digested by man (Thompson, 1983). Therefore, the present study is concerned with investigating a selection program including 25 cultivars (accessions) belonging to 5 species of Brassica to select one that could be used as an oil crop of low erucic acid content for cultivation under Egyptian environmental conditions.

MATERIALS AND METHODS

Materials

Seeds of different accessions used for oil extraction were obtained by experimental cultivation of 25 Brassica accessions for two successive years 1997 and 1998 as reported by Ali et al.(1999).

Methods

Oil content (%): It was determined on the basis of dry weight, from a random sample drawn from a mixture of all plant seeds for each replicate. Soxhelet extraction method was used with hexane solvent for eight hours, as described by A.O.A.C. (1980).

Fatty acid composition: Hexane extract of seeds was concentrated by evaporation under a stream of nitrogen and residual lipids were prepared by direct esterification of lipid extracts, according to Tahoun and Ali (1981).

A one to five milligram sample of rapeseed oil, dissolved in light petroleum, was pipetted in a 1 ml vial. The solvent was vaporized under a stream of nitrogen and four parts by volume of the esterifying reagent was prepared by dissolving chopped sodium into an appropriate volume of absolute methanol to obtain 0.3 M sodium methoxide. The viales were caped and shaked instantly to ensure complete mixing after which 5 or 25 μl light petroleum were added quickly to wash down the vial inner wall. The reaction mixture was injected directly in the GLC.

Gas chromatographic analysis of the fatty acid methyl esters was performed by using a Shimadzu Gas Chromatograph Model GC 8A, equipped with a hydrogen flame ionization detector and 2.6 m by 0.4 mm diameter glass columns, containing 15% ethylene glycol succinate (EGS) on chromosorb W/AW/DMCS (80-100 mesh). Column temperature was maintained at 190C during analysis. Other conditions were 250C for injector and 200C for detector. Gas flow rates were carrier gas 35 ml/min N2 and 20 ml/min H2. A sensitivity, in the range of 102 and an attenuation of 32, were found to result in a stable base line.

Identification: Peak identification was performed by comparing the relative retention time of each peak with those of standard fatty acid methyl esters of C14:0, C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C20:0, C21:0, C22:0 and C22:1 fatty acids. In some cases, identification was done by addition of authentic methyl esters to the unknown-Peaks. Area for each fatty acid was determined and the relative percentage was calculated from the ratio of its peak area to the total areas for all acids.

All data were statistically analyzed by the usual methods of analysis of variance according to Steel and Torrie (1984).

RESULTS AND DISCUSSION

Seed yield per plant (grams)

The analysis of variance for seed yield/plant, obtained in 1997 and 1998 growing seasons, is given in Table 1. Table 2 shows the mean values for seed yield/plant as affected by Brassica accessions in both seasons. Data in Table 1 indicated that Brassica accessions had a highly significant effect on seed yield/plant in both seasons.

The data in Table 2 revealed that the overall mean values for seed yield/plant in 1997 season of accessions No.4 and 5 (Brassica carinata), 13 and 15 (Brassica nigra), 17 (Brassica napus) and 21 and 23 (Brassica juncea) were the highest and significant. Whereas, in 1998 season, accessions No.4 (Brassica carinata) and 23 (Brassica juncea), produced the highest significant mean seed yield/plant, being 33.0 and 35.32 g/plant, respectively. This superiority over the other species and accessions might be attributed, in some cases, to the larger number of seeds/silique, and in other cases, to the higher number of inflorescences or number of silique/inflorescence. On the other hand, Brassica carinata (accession No.1) and Brassica juncea (accessions No.22 and 25), in 1997, and Brassica carinata (accession No.5) produced the lowest significant seed yield/plant. Their values ranged from 14.82 to 18.97 g seeds/plant. Other accessions gave intermediate values of seed yield/plant, and ranged from about 20 to 29 g (in 1997) and from 20 to 32 g in 1998.

Above results were similar to those obtained by Ahn and Kown (1989), Ahn et al.(1989) and Kunelius and Sanderson (1990).

Oil content (%) in seeds

The analysis of variance for oil content in seeds, obtained in 1997 and 1998 seasons, is given in Table 3. Table 4 shows the mean values for oil content as affected by Brassica accessions in both seasons.

Data in Table 3 indicated that Brassica accessions had a highly significant effect on oil content in seeds in the two growing seasons. While, data in Table 4 revealed that the overall mean values for oil content in seeds of the 25 different accessions significantly differed from each other. Data showed that Brassica carinata accession No.5, Brassica nigra accessions No.13 and 14, in both seasons, and accession No 22 (Brassica juncea), in 1997, gave the highest significant mean values of oil content in seeds. Such values were 43.8, 44.97, 42.82 and 42.15% (in 1997) and 40.1, 42.15 and 40.75 in 1998 season, respectively. On the other hand, Brassica napus accessions No.16 and 18 (in 1997 season) and Brassica juncea accession No.25 (in 1998 season) produced the lowest significant mean oil contents in seed, being 26.32 and 26.22%, in the first season and 26.13% in the second season. Meanwhile, the other accessions gave significant intermediate mean values of oil content in seeds and ranged between about 31 to 39% over both seasons. Meanwhile, the other accessions gave significant intermediate mean values of oil content in seeds and ranged between about 31 to 39% over both seasons.

Similar results were obtained by Ovsishcher and Bonderva (1983), Rule et al.(1991) and Liu (1990). Also, Jiao (1991) reported that the oil content of three Brassica oil species was in the range of 32.7-43.1%.

Oleic and erucic acids

Erucic acid, which is (Docos-13 (z)) enoic acid is the main component (40-50%) of rapeseed and mustard oils. Brassica oils differ from other vegetable oils in containing a significant proportion of the long-chain monoenoic fatty acids and eicosenoic and erucic acids. In the 1950’s and again in the early 1970’s, feeding experiments with laboratory animals indicated that the nutritional value of rapeseed oil would be substantially improved, if erucic acid content would be reduced to 5% of the total fatty acid content (Vles, 1974 and Kramer et al., 1983). Similarly, Franzke et al.(1990) stated about reduction in growth rate of farm animals on feeding high erucic acid rations. Therefore, it was the effort of several researchers to identify plants with essentially no erucic acid in their seed oils in Brassica napus (Stefansson et al., 1961) and Brassica campestris (Doweny, 1964) and accordingly, resulted in the world-wide development of nutritionally superior oil with low erucic acid. However, Franzke and his co-workers (1990) stated that it was not possible to detect any harmful effect in man on feeding meals containing high amounts of erucic acid.

The results obtained, with regard to the fatty acids spectrum of different species and accessions of Brassica, are shown in Tables 5 and 6, which indicate that the higher the erucic acid content , the lower the amount of oleic acid. This can be explained by the fact that the former is synthesized through the elongation of oleic acid by the addition of two molecules of active acetate without shift in the double-bond position of the starting synthetic material (oleic acid). The relationship between the synthesis of the two fatty acids is very strong and can be observed in Brassica napus accession No.17 that indicated 0.00% erucic acid and about 59.3% of oleic acid. While, in Brassica carinata accession No.3, the amount of erucic acid reached the maximum among all accessions investigated (49.2%), whereas, oleic acid recorded the lowest concentration (about 8.5%), compared to the other species and accessions studied.

Such findings agreed with those reported by several authors (McKillican, 1966; Zadernowski and Sosulski, 1979 and Vaisey-Genser and Eskin, 1982), as they reported about a negative relationship between oleic and erucic acids in rapeseed oil. Similar tendency was observed between erucic and linoleic acids, as well as erucic and linolenic acids, that denotes a negative relationship. This can be explained by the fact that all of these fatty acids have a common biosynthetic pathway, as proposed by Jonsson (1977).

Linolenic acid

Another oil quality objective, is to reduce linolenic acid content, while maintaining or increasing the level of linoleic acid (Downey and Robbelen, 1989), since the former lowers the oil stability during storage.

Tables 5 and 6 represent the linolenic acid contents of different Brassica accessions investigated. Brassica rapa (compestris) accession No.10, Brassica napus accession No.17 and Brassica nigra accession No.11 showed the lowest linolenic acid contents among all accessions studied. The values for linolenic acid in such accessions were about 8.0, 10.3 and 13.2%, respectively. However, Downey and Robbelen (1989) stated that the major objectives of Brassica breeding programs were directed towards the production of varieties with low linolenic acid contents from varieties containing 8-11% (in the available commercial varieties) to new ones containing less than 3%.

The possible change in the fatty acid composition of the 25 accessions of Brassica during the years 1997 and 1998 was measured by determining the fatty acid composition across the two years. The data in Tables 5 and 6 revealed consistent results of the fatty acids composition across the two years studied, taking into consideration that the seeds were planted in 1995 and 1996 for multiplying the number of seeds for further studies on field scale experiments. Such stability in the fatty acid composition different varieties clearly indicated that the fatty acid composition was controlled by a genetic make-up rather than to be affected by environmental factors.

Of paramount interest is the oil quality extracted from Brassica napus accession No.17. The oil was found to be colourless and odourless, that nominated it as an edible oil of high technological and industrial properties.

CONCLUSION

Among all Brassica species and accessions investigated, Brassica nigra accessions 13 and 14 gave the highest oil extract 43 and 41%, respectively. Brassica napus accession 17 gave an oil that showed high nutritional and technological quality. The oil is colourless, odourless and revealed 0.00% of erucic acid.

REFERENCES

1. Ahn, G.S. and Kown, B.S. (1989). J. Korean Anim. Sci. 31: 192-199.

2. Ahn, G.S., Kown, B.S. and Lee, J.I. (1989). J. Korean Crop Sci. 34: 335-340.

3. Ahuja, K.L., Batta, S.K., Raheja, R.K., Labana, K.S. and Gupta, M.L. (1989). Plant foods for human nutrition 39: 155-160.

4. Ahuja, K.L., Raheja, R.K., Labana, K.S. and Gomber, T.S. (1990). J. Oilseeds Res. 7: 114-116.

5. Association of Official Agriculture Chemists (A. O. A. C.) (1980). 11th ed., Washington D.C., USA

6. Ali, A.E., Ghazy, A.I. and Tahoun, M.K. (1999). (under publication)

7. Downey, R.K. and Craige, B.M. (1964). J. A. O. C. S., 41: 475-478.

8. Downey, R.K. and Robbelen, G. (1989). Oil Crops of the World. Mc Graw-Hill Publishing Company, U.S.A. pp. 339-362.

9. Franzke, C. (1990). Lehrbuch der Lebensmittelchemie. Akademie – Verlag, Berlin pp. 175-200.

10. Jiao, C.H. (1991). Crop Genetics Resources No.1, 4-6.

11. Kramer, J.K.G., Sauer, F.D. and Pigden, W.J. (1983). In high and low erucic acid rapeseed oils. Academic Press Canada pp. 414-471.

12. Kumar, P.R. (1990). Research on rapeseed and mustard. Proceedings of an Indo-Swedish Symposium, 1989, Uppsala.

13. Kunelius, H.T. and Sanderson, J.B. (1990). Appl. Agric. Res. (USA), 5: 159-163.

14. Liu, X.Y. (1990). Crop Genetics Resources No.4, 21-22.

15. McKillican, M.E. (1966). J. A. O. C. S., 43: 461-465.

16. Ovsishcher, B. and Bonderva, N. (1983). Molochnoe-I-Myasnoe-Skotovodstvo. 7, 24-27.

17. Rule, D.C., Koch, D.W., Jones, R.R. and Kercher, C.J. (1991). J. Prod. Agric. 4: 29-33.

18. Steel, R.G. and Torrie, J.H. (1984). A Biometrical Approach. 4th ed. Mc Graw-Hill Book Co., U.S.A.

19. Stefansson, B.R., Hougen, F.W. and Downey, R.K. (1961). Can. J. Plant Sci., 41: 218-219.

20. Tahoun, M.K. and Ali, H. (1981). Milchwissenschaft 36: 419-422.

21. Thompson, K.F. (1983). Adv. Appl. Biol. 7: 1-104.

22. Vaisey-Genser, M. and Eskin, N.A.M. (1982). Canola Council of Canada, Publication No. 60.

23. Vles, R.O. (1975). Proc. 4th Int. Rapeseed Conf., Giessen 1974 Germany pp. 17-30.

24. Zadernowski, R. and Sosulski, F. (1979). J. A. O. C. S., 56: 1004-1007.

Table 1: Analysis of variance for seed yield/plant (g) of Brassica accessions in 1997 and 1998 seasons.

Source of variation

D.F.

Mean squares

1997

1998

Replications
Accessions
Error

3
24
72

8.24
116.16**
9.107

14.66
126.26**
3.72

C.V. %

 

11.33

7.75

** : Significant effects at 0.01 level.

C.V. : Coefficient of variability.

Table 2: Mean values for seed yield/plant (g) of twenty-five Brassica accessions in 1997 and 1998 seasons.

Species and accessions

Seed yield/plant (g)

1997

1998

Brassica carinata
1
2
3
4
5

Brassica rapa (campestris)

6
7
8
9
10

Brassica nigra

11
12
13
14
15

Brassica napus
16
17
18
19
20

Brassica juncea

21
22
23
24
25


17.60 jk
26.33 fgh
29.00 cdef
30.97 abcd
33.97 ab


29.75 bcde
27.77 defg
26.95 efgh
25.80 fgh
23.30 hi


25.85 fgh
20.15 ij
31.90 abcd
26.83 efgh
33.20 abc


25.81 fgh
34.92 a
20.60 ij
23.25 hi
24.40 ghi


32.03 abc
15.32 k
34.53 a
26.0 fgh
18.97 jk


19.92 mn
24.85 ghij
32.35 b
33.00 ab
28.80 p


31.17 bcd
27.17 efg
23.25 ijkl
21.75 klm
24.00 hijk


26.32 fgh
21.00 lm
31.62 bc
22.00 klm
29.47 cde


25.80 ghi
29.17 cde
17.82 no
22.65 jkl
24.77 ghij


28.60 def
14.85 p
35.32 a
23.70 hijkl
17.00 op

L.S.D. (0.05)

4.254

2.72

Means with the same letter(s) are not significantly different

at 0.05 level of probability.

Table 3. Analysis of variance for oil content (%) in seed and whole plant as affected by 25 Brassica accessions in 1997 and 1998 seasons.

Source of variation

D.F.

Mean squares
of oil content
in seed
(%)

Mean squares of
oil content in
whole plant
(%)

1997

1998

1997

1998

Replications
Accessions
Error

3
24
72

18.608
137.293**
4.657

10.286
83.35**
2.303

0.321
11.831**
0.224

0.809
12.982**
0.2048

C.V.

 

5.63

4.378

10.899

10.7

** : Significant effects at 0.01 level.

C.V. : Coefficient of variability.

Table 4. Mean values for oil content (%) in seed and whole plant as affected by 25 Brassica accessions in 1997 and 1998 seasons.

Species and accessions

Oil content in seed
(%)

1997

1998

Brassica carinata
1
2
3
4
5

Brassica rapa (campestris)

6
7
8
9
10

Brassica nigra

11
12
13
14
15

Brassica napus
16
17
18
19
20

Brassica juncea

21
22
23
24
25


35.30 hijk
37.37 fghi
40.40 def
39.17 efg
43.80 bc


39.17 efg
33.50 jk
43.80 bc
39.27 efg
37.60 fgh


42.85 bcd
36.02 hij
44.97 a
42.82 b
34.55 ijk


26.32 l
41.60 cde
26.22 l
41.90 cde
32.87 k


41.72 cde
42.15 bcde
37.30 ghi
33.20 jk
32.75 k


32.42 jkl
34.15 ghijk
37.70 de
37.22 def
40.10 abc


34.60 ghi
35.23 fgh
38.27 cde
33.80 hijk
32.15 kl


36.15 efg
32.60 ijkl
42.15 a
40.75 ab
32.10 kl


28.58 m
38.43 cd
23.03 o
37.92 de
30.53 lm


37.80 de
38.73 bcd
34.50 ghij
31.63 l
26.13 n

L.S.D. (0.05)

3.04

2.139

Means with the same letter(s) are not significantly different at 0.05 level of probability.

Table 5. Fatty acid composition of Brassica species and accessions during 1997.

Species and accessions

C16:0

C18:0

C18:1

C18:2

C18:3

C20:1

C22:1

Others

B. carinata
1
2
3
4
5

B. rapa (campestris)

6
7
8
9
10

B. nigra

11
12
13
14
15

B. napus

16
17
18
19
20

B. juncea

21
22
23
24
25


9.7
10.5
4.0
7.2
5.2


7.7
6.3
2.7
7.2
9.5


2.0
7.0
3.7
5.2
6.3


13.0
7.3
4.0
6.7
5.3


4.0
5.9
10.5
2.8
3.9


2.2
1.1
2.0
2.0
0.0


1.0
1.1
2.4
3.0
6.4


1.5
1.0
-
1.3
1.7


2.0
1.6
1.2
6.2
1.6


1.0
3.4
1.0
-
3.0


23.0
13.1
8.2
11.0
9.0


24.2
8.8
12.8
13.0
11.2


26.7
12.0
11.3
13.9
10.7


10.7
58.7
24.0
13.8
32.3


15.5
22.2
25.4
22.0
24.8


21.8
16.8
15.3
19.0
13.0


15.4
11.7
20.0
22.2
24.5


22.0
15.5
15.0
23.4
17.9


10.5
21.8
20.0
20.9
20.0


16.8
17.5
14.3
23.4
21.8


17.6
20.7
18.0
27.0
20.0


16.0
24.4
16.0
30.2
9.0


11.2
26.8
26.0
20.7
23.0


15.8
9.2
19.7
13.2
20.6


19.8
13.3
20.7
12.7
23.5


2.1
1.9
0.9
-
-


-
-
2.0
1.9
-


-
-
-
-
2.0


-
-
-
-
-


2.5
2.0
-
-
1.0


21.6
35.0
50.0
33.8
47.9


34.5
47.6
43.3
21.0
39.4


33.3
34.9
45.0
30.9
36.8


47.3
0.0
29.0
39.0
17.0


40.0
33.0
25.9
35.2
21.9


2.0
0.8
1.6
-
1.9


1.2
0.1
2.6
1.5
-


3.3
2.8
2.0
1.6
1.6


0.7
1.4
2.1
0.2
2.2


0.4
2.7
2.2
3.9
0.4

Others; includes C14:0, C16:1 and C22:0

Table 6. Fatty acid composition of Brassica species and accessions during 1998.

Species and accessions

C16:0

C18:0

C18:1

C18:2

C18:3

C20:1

C22:1

Others

B. carinata
1
2
3
4
5

B. rapa (campestris)

6
7
8
9
10

B. nigra

11
12
13
14
15

B. napus

16
17
18
19
20

B. juncea

21
22
23
24
25


11.7
9.3
5.8
5.8
3.7


5.7
8.0
3.1
10.2
7.0


2.7
5.9
7.5
5.2
5.8


10.4
6.1
4.6
8.6
4.0


4.2
7.0
10.0
4.9
4.5


3.2
2.5
1.0
1.6
1.2


1.2
1.7
1.0
2.7
7.3


2.2
3.7
-
1.9
1.0


1.8
3.2
1.0
5.4
1.2


1.8
6.4
1.0
2.1
2.2


18.2
16.2
8.9
9.4
10.3


21.8
10.1
10.0
16.2
15.7


24.3
11.7
12.5
10.5
11.4


9.5
0.0
22.0
12.0
30.8


13.4
20.2
26.4
24.4
19.0


19.9
13.9
12.8
17.7
17.0


13.5
13.5
24.6
19.8
24.5


20.5
16.0
11.0
22.2
22.1


9.6
16.4
23.5
19.9
21.8


17.2
15.4
14.3
21.7
24.2


19.6
21.1
21.1
27.0
22.0


20.4
20.2
17.9
27.9
7.0


15.2
24.8
23.0
22.7
20.2


19.6
11.4
17.6
15.1
23.5


18.0
15.3
22.7
14.0
26.8


3.0
2.1
1.9
-
-


-
-
2.9
1.2
-


-
-
-
1.4
3.5


-
-
-
-
-


1.5
1.3
-
-
0.8


22.4
32.9
48.4
36.8
45.4


35.4
46.2
40.5
18.0
37.4


32.0
34.2
42.9
32.9
35.5


48.0
0.0
31.0
37.0
15.8


42.7
31.7
24.2
32.0
21.3


2.0
2.0
0.1
1.7
0.4


2.0
0.3
-
4.0
1.1


3.1
3.7
3.1
3.2
0.5


1.1
2.9
0.3
2.0
2.9


1.2
2.7
1.4
0.9
1.2

Others; includes C14:0, C16:1 and C22:0

Fig.1. Brassica accessions thar revealed high seed yield per plant in 1997 season.

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