The oils from strawberry, blackcurrant, raspberry, and apple seeds were characterized by a high content of unsaturated fatty acids (90.8%, 88.6%, 94.0%, and 86.9%, resp.). Strawberry and raspberry oils had high levels of C18:2 (45.4% and 49.0%) and
Poland is the leading European manufacturer of fruit juice, in particular concentrated apple juice. Fruit juice and drink production was 1100 thousand tons in the 2005/2006 season and varied between 900 and 1300 thousand tons in the subsequent years, whereas the amount of berries produced for juice is almost 500 thousand tons [
Seeds of berries, including strawberries, raspberries, blackcurrant, and apples, are a rich source of polyenoic fatty acids (EUFA). These acids are not synthesized in the human body and have to be supplied through diet. Human nutritionists recommend that Poles should consume diets lower in fats with the change of its structure by increasing the intake of fats that contain polyenoic fatty acids. In addition to linoleic acid (LA) and long-chain polyenoic fatty acids (LC PUFA), an important role among them is played by 18-carbon polyenoic fatty acids having a triene structure—
In addition to these fatty acids, the oils from strawberry, raspberry, blackcurrant, and apple seeds contain a number of antioxidant, anti-inflammatory, antiatherosclerotic, and anticancerous substances, including tocochromanols, carotenoids, flavonoids, phytosterols, and phenolic acids [
Recent years have seen much more intensive research on compounds that protect the body from the harmful effects of free radicals and other active forms of oxygen. Lipophilic components of vegetable oils, which show antioxidant activity and an ability to scavenge free radicals, are worthy of special notice. To date, vegetable oils rich in 18-carbon polyenoic fatty acids having a triene structure were used as pharmaceutical preparations available in capsules. However, the current oil production technology that uses cold-pressing in nitrogen gas or supercritical carbon dioxide extraction enables the oils to be obtained in almost unchanged form. They are more abundant in side compounds of high biological and antioxidant activity. Occurrence of antioxidants that inhibit unfavourable changes and knowledge of their activity and stability is essential not only to technologists but also to nutritionists. The shelf life of oils can be extended by using a variety of procedures that protect freshly extracted oils, such as limiting or eliminating oxygen contact, light exposure, and contact with prooxidative metal (copper and iron) ions, as well as supplementing the oil with oxidation inhibiting substances. Various antioxidants are used for this purpose. Efforts are made to limit the use of synthetic antioxidants on the grounds of health risks. Considerable emphasis is placed on the use of natural or nature-identical antioxidants. Their broad antioxidative properties may help to limit autoxidation of vegetable oils rich in polyenoic fatty acids having a triene structure. When they are added to the diet, they may have beneficial effects on the human body because of their free radical scavenging capacity.
In a search for new sources of these biologically valuable fats, we performed chemical analyses of oils obtained from the pressing of strawberry, raspberry, blackcurrant, and apple seeds in terms of the composition and content of fatty acids, tocopherols, tocotrienols, and phytosterols.
Oils from blackcurrant, raspberry, strawberry, and apple seeds originated from Mega-Sort company (Poland), which specializes in the drying and packaging of fruit pomace produced after extraction of fruit and vegetable juices. Pomace with about 55% moisture content, originating from Hortex company (Poland), was dried on drum driers to reduce the moisture below 10%. Dried fruit pomace was then cut and ground and the seeds were separated. The production line (Scorpion, Poland) included a chopper, a separator, and a pneumatic tunnel, in which the seeds were separated from the other parts. Oils were obtained from the seeds on a standard technological line used for cold-pressing of oilseeds (Farmet, Czech Republic) and equipped with a UNO screw press, a sedimentation tank, and board and candle filters. Seeds were subjected to a press head temperature of 55°C for 20 s. The pressed and filtered oils from raspberry and strawberry seeds were placed in dark glass containers with added N2, tightly closed, and refrigerated at 4°C until further analyses.
Gas chromatography was used to determine higher fatty acids in fruit seed oils in the form of methyl esters, following saponification of the fatty acids contained in the sample.
Tocopherols (
Gradient grade
An Agilent Series 1100 HPLC system (USA) equipped with a pump, autosampler, and fluorescence detector was used. Data were integrated using Agilent ChemStation software. Calculations were carried out using Excel. Sample preparation also involved the use of 12 mL screw-cap tubes (Schott), screw-cap bottles (15 mL), a shaker (Vortex, Germany), an ultrasound bath, and a water bath. Standards (alcohol solutions) were standardized [
Chromatographic separation was performed on a LiChroCART 250-4 Lichrospher Si 60 column (5
Oil samples (about 20 mg) were weighed into 12 mL Schott tubes with an accuracy of 0.0001 g. 1 mL of pyrogallol in ethanol (60 g/L), 0.5 mL of aqueous solution of potassium hydroxide (600 g/L), 0.5 mL of aqueous solution of sodium chloride (10 g/L), and 0.5 mL of ethanol were added to these. Vials were screw-capped, agitated on a Vortex shaker for about 10 s, and then transferred to a water bath (70°C), where the samples were saponified for 45 min. After cooling, 4 mL of aqueous solution of sodium chloride (10 g/L) was added and this was extracted twice (4 mL each) with a mixture of ethyl acetate and
The sterol content of lipids from the fruits was analysed according to the AOCS Official Method Ch 6-91 [
About 5 g of oil was weighed into a 250 mL flask with an accuracy of 0.01 g. The sample was dissolved in 50 mL of hot ethanol. Titration was performed by mixing the flask content with KOH solution in ethanol to the end point in the presence of phenolphthalein. The end point was when adding one drop of lye which caused a weak but perceivable change in colour for at least 15 s. The blank sample was titrated [
The acid value was calculated using the following formula:
About 2 g of oil was weighed with an accuracy of 0.001 g and transferred into a conical flask. The flask was filled with 10 cm3 of chloroform, mixed until the fat was completely dissolved, filled with 15 cm3 of acetic acid and 1 cm3 of KI solution, and closed with a ground-in stopper. Flask content was agitated for 1 min and then left in the dark for 5 min. 75 cm3 of distilled water (rinsing the stopper thoroughly) and 5 drops of starch solution were added to this, which after mixing was titrated with a 0.002 N solution of sodium thiosulfate. The blank sample was prepared simultaneously [
Peroxide value was calculated using the following formula:
Analysis of the chemical composition, the content of bioactive compounds, and physicochemical properties in the oils was performed in 3 replications; the results were expressed as mean and coefficients of variation (CV) (Table
Physicochemical properties of oils from strawberry, raspberry, blackcurrant, and apple seeds.
Characteristics | Strawberry seed oil | Raspberry seed oil | Blackcurrant seed oil | Apple seed oil |
---|---|---|---|---|
Content of oil (% dry matter) | 18.56 ± 0.32 | 13.52 ± 0.31 | 16.20 ± 0.29 | 20.22 ± 0.32 |
Moisture content of seeds (%) | 7.78 ± 0.11 | 6.96 ± 0.10 | 8.01 ± 0.12 | 8.84 ± 0.13 |
Acid value (mg KOH/g) | 2.09 ± 0.004 | 1.74 ± 0.002 | 4.10 ± 0.006 | 1.36 ± 0.002 |
Peroxide value (mq O2/kg) | 8.78 ± 0.02 | 8.39 ± 0.01 | 9.45 ± 0.03 | 10.59 ± 0.04 |
Values are mean± and coefficients of variation (CV).
Biooils are biologically the most valuable plant fats due to their composition that reflects the actual structure of all substances found in the seeds from which the oil was extracted. The WHO/FAO Codex Alimentarius Commission provided a definition of biooil that corresponds to virgin oil and determines the conditions for its extraction. Only mechanical extraction methods that ensure high quality of biooils are allowed. Pressing of oilseeds using hydraulic or screw press at low temperature regimes is therefore the only expression method. The procedures allowed to remove impurities from oil include water washing and centrifugation as well as sedimentation and filtration. No phospholipids, tocopherols, sterols, or carotenoids are removed from these oils. The high quality of these oils is conditional on the use of selected, fully mature seeds. The moisture content of the seeds obtained was in the range of 7.5–9.5%. Most oil was found in apple seeds, followed by strawberry, blackcurrant, and raspberry seeds (20.2, 18.5, 16.2, and 13.5%, resp.). These results are confirmed by the findings of other authors [
In addition to lifestyle and living conditions, diet is one of the most important determinants of our health and well-being. Advances in understanding the action of diet ingredients that may have a beneficial effect on the human body made it possible to design and produce food with specific health-promoting effects, rich in various bioactive components. Among these, polyenoic fatty acids are important, which play a significant role in preventing metabolic diseases of modern civilization. Polish fat products (oils, margarines, spreads, 100% fats) contain small amounts of
Oils considered a rich source of PUFA having a triene structure (
Composition of fatty acids in oils from strawberry, raspberry, blackcurrant, and apple seeds (% of total fatty acids).
Fatty acids | Strawberry seed oil | Raspberry seed oil | Blackcurrant seed oil | Apple seed oil |
---|---|---|---|---|
C 10 | 0.01 | 0.00 | 0.01 | 0.00 |
C 16 | 6.20 | 4.19 | 9.63 | 9.50 |
C 16:1 ( |
0.25 | 0.14 | 0.17 | 0.00 |
C 18 | 1.89 | 1.19 | 1.39 | 1.82 |
C 18:1 ( |
15.51 | 11.70 | 12.09 | 29.36 |
C 18:2 ( |
45.45 | 49.01 | 38.64 | 55.54 |
0.04 | 0.04 | 18.54 | 0.34 | |
C 18:3 ( |
29.05 | 33.02 | 13.57 | 0.85 |
C 18:4 ( |
0.00 | 0.00 | 3.58 | 0.00 |
C 18:2 (CLA) c9-c11 | 0.00 | 0.00 | 0.11 | 0.00 |
C 20 | 0.91 | 0.45 | 0.21 | 1.56 |
C 20:1 | 0.27 | 0.00 | 1.26 | 0.57 |
C 20:2 ( |
0.11 | 0.00 | 0.49 | 0.09 |
C 20:4 ( |
0.00 | 0.00 | 0.01 | 0.00 |
C 22 | 0.12 | 0.13 | 0.07 | 0.18 |
C 22:1 | 0.08 | 0.04 | 0.07 | 0.07 |
C 22:5 ( |
0.10 | 0.09 | 0.14 | 0.11 |
C 22:6 (DHA) ( |
0.00 | 0.01 | 0.01 | 0.01 |
SFA | 9.14 | 5.95 | 11.32 | 13.06 |
UFA | 90.86 | 94.05 | 88.68 | 86.94 |
PUFA |
45.60 | 49.05 | 57.68 | 55.97 |
PUFA |
29.16 | 33.12 | 17.30 | 0.96 |
PUFA |
15.63 | 1.48 | 3.33 | 58.30 |
The analysed oils were found to be high in
In the analysed oils, the highest concentrations of tocols were identified in raspberry and blackcurrant seed oils (301.9 and 229.5 mg/100 g) and lower levels in apple and strawberry seed oils (143.6 and 58.4 mg/100 g, resp.). The dominant isomers of tocopherols in oils from raspberry, blackcurrant, and strawberry seeds were
Tocochromanol (tocopherol and tocotrienol) content of oils from strawberry, raspberry, blackcurrant, and apple seeds.
Tocochromanols | Strawberry seed oil | Raspberry seed oil | Blackcurrant seed oil | Apple seed oil |
---|---|---|---|---|
Tocopherols (mg/100 g): | ||||
|
2.46 ± 0.8 | 65.61 ± 14.5 | 84.32 ± 7.5 | 41.75 ± 1.5 |
|
nd | 3.83 ± 5.4 | 4.44 ± 2.4 | 62.77 ± 1.3 |
|
49.02 ± 0.6 | 193.58 ± 29.9 | 117.88 ± 13.8 | 13.60 ± 2.4 |
|
6.15 ± 0.7 | 32.17 ± 13.3 | 18.41 ± 4.6 | 21.28 ± 3.3 |
Tocotrienols (mg/100 g): | ||||
|
nd | 1.84 ± 2.5 | 1.67 ± 0.9 | 1.21 ± 0.6 |
|
nd | nd | nd | nd |
|
0.85 ± 0.6 | 4.18 ± 2.2 | 2.07 ± 1.2 | 3.05 ± 1.7 |
|
nd | 0.71 ± 0.7 | 0.78 ± 0.6 | nd |
|
||||
Sum of tocols (mg/100 g) | 58.48 ± 5.7 | 301.92 ± 2.3 | 229.57 ± 23.1 | 143.66 ± 3.5 |
nd (not detected), limit of quantitative for each tocol is 0.5 mg/100 g.
Values are mean± and coefficients of variation (CV).
The tocopherol content of oils from blackcurrant and raspberry seeds was comparable to commercial oils rich in tocopherol, that is, maize and soybean oils at 162 and 180 mg/100 g oil, respectively [
In most vegetable oils, sterols are the principal component of unsaponifiable substances, whose content in blackcurrant and borage oil is 1.2% [
Phytosterol content of oils from apple, blackcurrant, strawberry, and raspberry seeds (
Phytosterols | Apple |
Blackcurrant |
Strawberry |
Raspberry |
---|---|---|---|---|
Campesterol | 219.8 ± 16.4 | 513.4 ± 5.7 | 328.9 ± 12.4 | 254.7 ± 20.2 |
Stigmasterol | 13.2 ± 13.1 | 44.6 ± 3.0 | 97.9 ± 2.5 | 60.7 ± 3.7 |
Sitosterol | 2629.3 ± 168.5 | 3637.3 ± 225.7 | 2656.6 ± 95.14 | 3341.9 ± 32.7 |
Sitostanol | 249.9 ± 56.8 | 300.9 ± 36.3 | 291.9 ± 10.7 | 364.6 ± 18.4 |
Avenasterol | 347.8 ± 6.3 | 124.2 ± 3.4 | 47.5 ± 3.2 | 80.3 ± 2.4 |
D7-Stigmasterol | 0 | 76.2 ± 9.2 | 108.2 ± 3.7 | 94.7 ± 5.6 |
Cycloartenol | 0 | 775.6 ± 26.9 | 642.7 ± 25.3 | 449.8 ± 21.2 |
D7-Avenasterol | 0 | 146.4 ± 6.1 | 158.7 ± 9.2 | 66.6 ± 5.2 |
24-Methylene-cycloartenol | 0 | 931.9 ± 47.7 | 99.9 ± 12.6 | 523.8 ± 17.1 |
Citrostadienol | 0 | 274.5 ± 10.5 | 210.7 ± 13.4 | 147.0 ± 3.2 |
|
||||
Sum of phytosterols | 3460.0 | 6824.9 | 4643.1 | 5384.1 |
Values are mean± and coefficients of variation (CV).
Chromatographic analysis of the oils revealed 10 different phytosterols. Oils from blackcurrant, raspberry, strawberry, and apple seeds contain considerable amounts of phytosterols. The richest sources of phytosterols were blackcurrant seed oil (6824.9
The dominant compound in the analysed oils was sitosterol, whose content ranged from 2630
The oils obtained from strawberry, blackcurrant, raspberry, and apple seeds are a rich source of essential unsaturated fatty acids (EUFA), tocochromanols and phytosterols, which could find wide application in the cosmetic, pharmaceutical, and food industries.
The native oils from strawberry, raspberry, blackcurrant, and apple seeds can be regarded as special oils (biooils), which, due to their possible nutraceutical effects, could find broader use not only in the cosmetic but also in the food industry. They could find special application in the design and production of foods with specific health-promoting effects, rich in various bioactive components helpful in preventing metabolic diseases of modern civilization.
The authors declare that there is no conflict of interests regarding the publication of this paper.