Proceeding from the fact that the seeds of Roselle plant are full of nutritional constituents, however in Egypt and Libya, they are often discarded as a by-product, this study aims to evaluate the nutritional composition of Roselle seeds grown in Egypt and Libya as a source of oil and protein besides making a comparison between whole chemical composition of Roselle seeds grown in both countries. Ground of whole Egyptian and Libyan Roselle seeds powder contained high amount of protein (31.02% ± 0.93% and 28.67% ± 0.45%), crude fat (21.6% ± 0.66% and 16.94% ± 0.86%) and total ash (6.89% ± 0.11% and 5.60% ± 0.10%), respectively. However, Egyptian seeds have moisture content, protein, crude fat and total ash higher than Libyan seeds. Crude oil from Egyptian seeds had high refractive index and iodine value in comparison with crude oil from Libyan seeds. There were no remarkable differences between both seeds in acidity percent, unsaponifiable matters percent and saponification value. Linoleic, oleic and palmitic acids were the major fatty acid constituents in Egyptian Roselle seeds. Meanwhile linolenic, linoleic, oleic, stearic, palmitoleic and palmitic acids were the major fatty acid constituents in Libyan Roselle seeds. Crude oil from Egyptian seeds had higher percent of unsaturated fatty acids than crude oil from Libyan seeds. Unsaponifiable matters constituents for extracted oil from Egyptian seeds were free from n-pentacosane (C 25) and rich in n-hexacosane (C 26). Oil from both seeds had the same content of Beta sito-sterol and stigma-sterol. Both seeds were rich in glutamic acid, aspartic acid, arginine and leucine. Libyan seeds were rich in essential amino acids in comparison with Egyptian seeds. Finally nutritional comparison of Roselle seeds variation depends on the variety, location and environmental conditions during cultivation. Roselle seeds are a good source for extraction of oil and protein. Protein from Roselle seeds could be used as a supplement material for poor food in lysine.
Seeds are however one of the cheapest food sources. Researchers have confirmed the nutritional usefulness of seeds [
In Egypt and Libya, seeds of Roselle plant are discarded as a by-product. Nutritional composition of Roselle seeds variation depends on the variety, location and environmental conditions where the seeds were cultivated [
Two kilograms of each Roselle seeds from Libya and Egypt were sun dried, ground, sieved, through mesh screen, packed in polyethylene bags and stored in a deep freezer at −20˚C until analysis. Moisture content was determined directly after grounding and sieving before storage.
Oil was extracted by soaking the prepared seeds in petroleum ether (40˚C - 60˚C). The ratio of solvent to crushed seeds was 3:1. The crushed seeds soaked in solvent for 24 hours with shaking. Miscella (mixed oil with solvent) was removed from seeds by filtration through wattman filter paper No. 1. The soaking was repeated three times. Solvent was removed from collected miscella by using of rotary evaporator at 40˚C under vacuum. Oil was stored in dark bottle in deep freezer at −20˚C until analysis.
Moisture content of seeds powder was determined using air-oven method. Ash content was determined by incinerating at 550˚C until constant weight was achieved. Total nitrogen and protein content were determined based on kjeldahl method using the conversion factor of 6.25. Lipids were determined by using soxhelt method. All of the above determinations were carried out based on methods as mentioned previously in A.O.A.C. [
Refractive index, specific gravity, acidity, saponification value, iodine value, peroxidase value, Thiobarbituric acid (T.B.A) value and unsaponifiable matters were determined according to the methods described in A.O.C.S. [
(1) Separation of Fatty Acid
Fatty acids were separated and change to methyl esters according to the methods described by [
(2) Preparation of Diazomethane
Diazomethane was prepared from methylamine hydrochloride as reported by [
Methylamine solution (100 ml) was placed in stoppered 500 ml flask and concentrated hydrochloric acid (78 ml) and water added to bring the total weight to 250 g. Urea (150 g) was introduced and mixture was boiled gently under reflux for 200 min and vigorously for 15 min, the solution was cooled to room temperature, then sodium nitrite (55 g) was added at 0˚C.
A mixture of 300 g crushed ice and 50 g concentrated sulfuric acid was prepared in 1500 ml beaker surrounded by bath of ice and salt. Cold methyl urea-nitrite solution was added slowly with mechanical stirring at such rate, that the temperature did not rise above 0˚C. The crystalline nitrosomethyl urea was filtered at once then drained well and dried in vacuum desiccator. Aqueous potassium hydroxide solution (60 ml, 50% w/w) and ether (200 ml) were placed in 500 ml round bottomed flask. The mixture was cooled to 5˚C, then nitrosomethyl urea (20.6 g) and ether (80 ml) were added. The ethereal layer was separated using separating funnel and dried over pellets of potassium hydroxide for 2 - 3 h.
(3) Identification and Determination of Fatty Acid by Gas Liquid Chromatography (GLC)
Fatty acids were identified and determined by GLC according to the method described by [
The unsaponifiable matters were fractionated by using GLC according to the method described by [
The Amino acids profile was determined according to the method described by Cohen et al. [
Proximate analysis and crude oil properties were expressed as mean of three replicates ± standard deviation according to the method described by Steel et al. [
Results in
Components (%) | Egyptian Seed3 | Libyan Seed3 |
---|---|---|
Moisture | 9.25 ± 0.35 | 5.32 ± 0.39 |
Crude Fat | 21.60 ± 0.66 | 16.94 ± 0.86 |
Protein | 31.02 ± 0.93 | 28.67 ± 0.45 |
Total Ash | 6.89 ± 0.11 | 5.60 ± 0.10 |
Soluble Ash | 2.29 ± 0.04 | 1.62 ± 0.04 |
Insoluble Ash | 4.60 ± 0.11 | 2.98 ± 0.08 |
Carbohydrates2 | 36.37 ± 2.02 | 43.47 ± 1.98 |
1Light read seeds; 2Nitrogen Free Extract; 3Values are expressed as mean ± SD of three replicates.
It could be noticed that seeds contained high amounts of crude oil and protein than cotton seeds which used in Egypt for oil production. We can conclude that Roselle seeds consider as a good and economic source for healthy edible oil and protein production [
Results in
Results in
The ratio of unsaturated to saturated fatty acids for Egyptian Roselle seeds was 3:1 the results are in a good agreement with that reported by [
Properties | Egyptian Seed** | Libyan Seed** |
---|---|---|
Refractive Index | 1.4777 ± 0.0005 | 1.4675 ± 0.0005 |
Specific Gravity | 0.8995 ± 0.0006 | 0.9199 ± 0.0049 |
Acidity (%)* | 0.67 ± 0.028 | 0.68 ± 0.02 |
Unsaponifiable Matters (%) | 0.81 ± 0.02 | 0.80 ± 0.03 |
Saponification Value | 197 ± 3.0 | 197.93 ± 2.09 |
Iodine Value | 115 ± 2.57 | 93.70 ± 2.04 |
Peroxide Value | 6.51 ± 1.54 | 7.51 ± 1.6 |
T.B.A Value | 1.04 ± 0.03 | 1.04 ± 0.03 |
*As oleic acid; **Values are expressed as mean ± SD of three replicates.
Fatty Acid | Egyptian Seeds (%) | Libyan Seeds (%) |
---|---|---|
Myristic Acid (C14:0) | 2.19 | 5.24 |
Palmitic Acid (C16:0) | 18.15 | 12.70 |
Palmitoleic Acid (C16:1) | 2.00 | 13.39 |
Stearic Acid (C18:0) | 4.09 | 15.97 |
Oleic Acid (C18:1) | 33.31 | 16.50 |
Linoleic Acid (C18:2) | 38.17 | 17.50 |
Linolenic Acid (C18:3) | 2.09 | 18.70 |
US:S Ratio | 3:1 | 2:1 |
Results for unsaponifiable matters constituents in crude oil from Egyptian and Libyan seeds indicated that both seeds have the same constituents and percentage, results are given in
Except that oil from Egyptian seeds was free from n-pentacosane (C25) and had high percent of n-hexacosane (C26) in comparison with oil from Libyan seeds. Hydrocarbons n-triacontane (C30), n-hentriacontane (C31), n-tetracosane (C24), n-tricosane (C23) and stigma sterols were the major unsaponifiable matters constituents in crude Roselle oil from both Egyptian and Libyan seeds. Crude oil from both seeds is considered as vegetable oil was rich in phytosterols [
Data in
Components | Egyptian Seeds (%) | Libyan Seeds (%) |
---|---|---|
n-undecane (C11) | 1.35 | 1.35 |
n-dodecane (C12) | 2.35 | 2.35 |
n-tridecane (C13) | 1.13 | 1.13 |
n-tetradecane (C14) | 2.51 | 2.51 |
n-pentadecane (C15) | 1.98 | 1.98 |
n-hexadecane (C16) | 2.13 | 2.13 |
n-heptadecane (C17) | 2.46 | 2.46 |
n-octadecane (C18) | 1.67 | 1.67 |
n-nonadecane (C19) | 2.36 | 2.36 |
n-eicosane (C20) | 2.20 | 2.20 |
n-heneicosane (C21) | 3.28 | 3.28 |
n-docosane (C22) | 1.62 | 1.62 |
n-tricosane (C23) | 4.59 | 4.59 |
n-tetracosane (C24) | 5.74 | 5.74 |
n-pentacosane (C25) | - | 1.45 |
n-hexacosane (C26) | 3.11 | 1.66 |
n-heptacosane (C27) | 1.48 | 1.48 |
n-octacosane (C28) | 2.23 | 2.23 |
n-triacontane (C30) | 21.48 | 21.00 |
n-hentriacontane (C31) | 21.49 | 21.97 |
n-dotriacontane (C32) | 2.02 | 2.02 |
Cholesterol | - | - |
Stigmasterol | 4.21 | 4.21 |
Beta-sito-sterol | 1.62 | 1.62 |
Amino Acids | Egyptian Seeds % | Libyan Seeds % | FAO/WHO |
---|---|---|---|
Essential Amino Acids | |||
Threonine | 4.86 | 2.64 | 4.0 |
Valine | 3.26 | 5.33 | 5.0 |
Methionine | 1.13 | 0.71 | 3.5 |
Isoleucine | 3.24 | 4.65 | 4.0 |
Leucine | 7.32 | 6.93 | 7.0 |
Tyrosine | 3.64 | 6.31 | |
Phenylalanine | 5.09 | 4.77 | 6.0 |
Lysine | 5.37 | 3.02 | 5.5 |
Histidine | 2.97 | 5.43 | ||
---|---|---|---|---|
Tryptophan | 0.37 | 1.20 | ||
Cystine | 2.64 | 2.61 | ||
Total | 39.89 | 43.60 | ||
Non-Essential Amino Acids | ||||
Aspartic | 10.73 | 10.26 | ||
Serine | 4.40 | 2.88 | ||
Glutamic Acid | 21.30 | 19.87 | ||
Proline | 4.14 | 0.15 | ||
Glycine | 4.27 | 8.20 | ||
Alanine | 4.69 | 5.41 | ||
Arginine | 10.58 | 9.63 | ||
Total | 60.11 | 56.40 | ||
E/N Ratio | 0.6636 | 0.7730 | ||
E/T Ratio | 0.3989 | 0.4360 | ||
1st Limiting Amino Acid | Tryptophan | Proline | ||
2nd Limiting Amino Acid | Methionine | Methionine | ||
3rd Limiting Amino Acid | Cystine | Tryptophan | ||
that of the FAO reference protein [
Roselle seeds are a good source for extraction of protein and oil. Roselle seeds vary in nutritional composition depending on the location and environmental conditions during cultivation. Protein from Roselle seeds could be used as a supplement agent of food mixture for poor lysine sources. Roselle seeds still need further investigation for oil properties and protein quality for human nutrition practices.