Analysis and Identification of Seabuckthorn oil of different origin

 

Prof. Dr. Mörsel, Jörg-Thomas, Technical University of Berlin Germany

Silke Steen, UBF Untersuchungs- Beratungs- Forschungslaboratorium GmbH, Germany

 

Abstract

Seabuckthorn is known as an unique source of high valued oils. The chemical properties of these oils, seed and pulp oil are not fully known. To determine the chemical composition experiments has been carried out and a great nnumber of oil samples has been analysed. The analysis of the major components, fatty acid profile, chemical values and the content of trace constituents strongly depends on the isolation method. Especially vitamin contents, carotenoide contents and quality parameters like acid values strongly differs between the samples. Among the non - glyceride substances a new group of sterylglycosides has been identified.

Keywords

Seabuckthorn, pulp oil, seed oil, fatty acid composition, statistical data, carotenoid, tocopherol, sterylglycoside, hippophaë rhamnoides

Introduction

Seabuckthorn (hippophaë rhamnoides) is a plant known for more than two thousand years in Asia. Its also widely spread about Europe, especially along the sea coasts and on surface mining residual areas. In the 1970th great activities has been developed to plant seabuckthorn in farms for juice and oil production in the former GDR. Today there over 200 ha orchards and additional wild areas with Seabuckthorn. The oil of seabuckthorn has been used in natural medicine for long times. Several positive effects to skin are well known but not complete clarified. Nevertheless knowledge about the oil is uncomplete. Data from literature vary in a wide range. This may be caused by the unknown technology or methods used for oil isolation, as well as deriving from different species..

As known there are two oils produced from the berries seed oil and fruit (pulp) oil. The composition of the latter one is of greater interest because of the high content of palmitoleic acid, tocoperols, carotenoids and sterols. On the international market products of different origins, qualities and properties can be found. Weve monitored the import and inland production of Seabuckthorn pulp and kernel oil for several years. Today there are oils produced by solvent or supercritical extraction, by extraction with other natural oils (e.g. sunflower oil), by melting out or by enzymatic methods. Thus the obtained oils differ not only by the yield but also in the content of valuable constituents.

Especially mixtures between both oils sometimes in combination with edible oils like sunflower oil produce a great variety of products. Prices on the international market strongly depend on the quality and purity of the product. Due to this strong technological influence its necessary to identify seabuckthorn oils on the base of practical oil composition and statistical data. Therefore its necessary to have detailed information on the composition, the range of characteristic parameters and medium values. A further knowledge on the chemical composition will give an better opportunity to identify adulterations of oils.

Methods and Materials

Seabuckthorn berries from German plants (harvest 1998 to 2002) were used to produced the oil by enzymatic fluidization of the berries (mostly varieties Hergo and Leikora). The technology used succeeded to achieve oils with good taste and odour. After fluidisation the oil is separated by centrifugation and dried under vacuum. The residue (kernels) is used for crushing. In comparison to these products samples from import market (origin Europe and Asia) has been analysed by the same way.

Fatty acid composition has been determined by GC on a Shimadzu GC 14a with SP 2380 GC capillary column 30m (Supelco). Transesterification has been carried out with Triemthylsulfoniumchloride (DGF method C-VIIIe, C VI 10a, 1999).

Determination of peroxide value, acid value and unsaponificable matter has been carried out by standard methodes (DGF method C-III). The determination of carotenoides was done by spectroscopy. b -carotene and other carotenoides were differentiated by there absorption maximum, non-polar carotenoids were separated by chromatography on silica (DGF method, 1999).

Tocopherols were determination after pre-concentration by cryo-crystallisation on an Shimadzu HPLC LC 9a using normal phase chromatography (Lichrosorb Si60 250mm/4mm) with isooctane : ethylacetate 96:4 (Koswig, Mörsel 1990). Data were calculated by external standard method, reference material: tocopherol isomer mixture Merck KG Darmstadt.

Sterole concentrations were determined by GC with FID on Carlo Erba GC with OV 105 capillary column 30m x 0,1 mm x 0,2 m. Samples were saponified according to AOCS method and silylated with BSTFA by the DGF standard method (DGF 1999) Quantification was done with the internal standard 5-a cholestane added before saponification.

Oxydative stability has been estimated by Swift Test performed by the method of Hardorn and Zürcher (1974) with Ranzimatä by Metrohm Swiss. Reaction temperature therefor was 110 C and 20 l air per hour.

The identification of sterylglycosides was carried out after precipitation with acetone from the crude oil. The precipitate was dissolved in diethylether hexane and further separated by silic acid column chromatography (300 mm x 15mm) with gradient elution ether / methanol with increasing polarity. Sterole containing fractions were hydrolysed with methanol / hydrochloric acid to yield the free sterole, the sugar and sometimes fatty acids. The elementary constituents were further characterised by chromatography (see above) or with enzymatic methods. (details will be published separately)

Results

The fatty acid concentration was relatively constant over a long period and didnt strongly depend from the habitat. The concentration of palmitoleic and palmitic acid were in general higher than 30% the one of stearic acid lower than 1%. The fatty acid composition is given in Table 1.

Table 1 Fatty acid composition of seabuckthorn pulp oil and seed oil

fatty acid

Medium pulp oil

SD

medium seed oil

SD

[%]

[%]

myristic

0,3

0,36

0,11

0,2

palmitic acid

33,0

5,67

20,5

5,67

palmitoleic acid

34,2

6,35

1,4

2,1

stearic acid

0,3

0,24

13,4

1,5

oleic acid

28,4

2,64

15,2

1,5

linoleic acid

3,3

1,94

28,5

3,5

linolensäure

1,0

0,62

22,0

4,8

The results clearly shows that only fatty acids occurring in higher concentration are suitable markers for identification of adulterated oils. In Comparison seed oil results from literature are listed too [Bat 1993].

In addition the distribution of the main fatty acids within the triglyceride was determined after enzymatic hydrolysis of the pulp oil. Fatty acid compositon is shown in Table 2.

 

Table 3 Physical and chemical properties of seabuckthorn pulp oil

parameter

medium

RSD

density 20 C

g/ml

0,8967

2,8%

refraction

1,466818

0,1%

unsaponificable matter

%

2,06

25,4%

acid value

mg KOH/g

9,5

72,8%

peroxide value

mequ./kg

1,0

184,2%

Ranzimat 110C, 20 l/h

h

29,0

64,4%

 

Table 4 Composition of the unsaponificable matter of seabuckthorn pulp oil

medium

SD

RSD

sterols

15,6 mg/100g

5,5 mg/100g

35,2%

tocopherols

3,7 mg/100g

3,2 mg/100g

87,1%

carotenoides

19,7 mg/100g

20,7 mg/100g

104,7%

fatty alcohols

14,8 mg/100g

3,9 mg/100g

26,4%

hydrocarbons

21,5 mg/100g

12,8 mg/100g

59,2%

polymer substances

26,9 mg/100g

19,7 mg/100g

73,2%

Steroles were found in an concentration of about 0,3%. Analysis of the composition showed that b -sitosterole is the major constituent. The concentration of carotenoids is strongly varying. Concentration between 80 to 200 mg/kg were found. The amount of b -carotene within the total carotenoides vary between 35 % and 90 % with a medium value at 58 %. This analysis had been performed by photometric determination. It has to be taken in consideration that a separation by absorption maximum only in part can be achieved. Oils produced by melting out from the dried berries shows strongly higher concentration. The pulp oils are general of high stability. Swift tests showed induction periods at 110 C over 30h, maximum values of 65 hours were observed. It should be mentioned that samples of fresh pressed seed oil also showed considerable stability. But this situation changed already after short term storage drastically, the oils became unstable.

Differences between pulp and seed oil may depend on samples or on biochemical factors. The general concentration in the pulp oil and in the seed oil are in the same range but the degree of unsaturation of the seed oil is 2.5 fold higher than in the pulp. This causes the instability of the seed oil.

During storage of pulp oil we mentioned a sedimentation of an insoluble matter. Further investigation were done to identify acetone insoluble matter isolated from the oil. The first results indicated only a small amount of phospholipids. A highly nonpolar compound was isolated from this fraction first results indicated that this could be a highly esterified sterylglycoside. We determined the composition after hydrolysis. The results indicated that this should be a highly esterified sterylgycoside. Further investigation will focus on this substance.

 

Conclusions

The results shows that a few of the investigated properties is suitable to detect adulterations of seabuckthorn oil with other oils. So its possible to identify mixtures of pulp and seed oil. In our opinion the concentration of palmitoleic acid of a pure pulp oil should be greater than 20 % and the one of linolenic acid below 2 %. Density and refraction index are very stable parameters and should be used for checking the identity of oils. Carotenoid- and steroleconcentration arent suitable indicators for this question. Triglyceride analysis can be helpful to ensure quality of products. For international trade parameters of seed and pulp oil should be defined to protect consumers and manufacturers for deception. Our results agree with data from other sources of seabuckthorn pulp and seed oil and from the literature. The naturally and technologically caused differences are significant and have strong consequences for commerce.

 

References

Koswig, S. and J.-Th. Mörsel, Die Nahrung 34(1990) 89-91

Mörsel, J.-Th. and K. Seifert, Laborpraxis (1996) 84-87

DGF Einheitsmethoden, Wissenschaftliche Verlagsgesellschaft Stuttgart 1999

AOCS Sandard Methods, Champaign, 1998

Hardorn, H. and K. Zürcher, Dtsch. Lebensmittelrdsch.70(1974) 57 pp.

Bat, S. and U. Tannert, SÖFW 119 (1993) 29-31