Product Development

Pacific Agri-Food Research Centre of Agriculture and Agri-Food Canada at Summerland, British Columbia began sea buckthorn research a few years ago. The objective is to develop technology for commercial sea buckthorn production and value-added products in North America. Production problems include thorniness, harvest difficulties due to lack of abscission of berries which are firmly attached to the branches, tree size, establishment of a pruning system, disease, insect and pest control, and the need for a mechanical harvester.

Thorniness:

Almost all Hippophae species start to develop thorns (5 cm) on two- or three-year-old plants. This characteristic is undesirable if harvesting is done by hand. Testing for new selections without thorns are underway in combination with selection for fruit size, yield, nutraceutical value, and oil content.

Berry Persistence:

The transformation of the raw sea buckthorn berry into a sophisticated product requires appropriate harvest, transportation, holding, and storage procedures. Berries persist on the branches all winter due to the absence of an abscission layer and firm berry attachment to the fruiting branch has enormous difficulties for harvest. The total labor cost estimated for harvesting a sea buckthorn orchard of 4 ha was 58% of the total cumulative production costs over 10 years (Schroeder et al. 1996).

Studies are underway to determine if ethephon [(2-chloroethyl) phosphonic acid], an ethylene generator which reduces berry removal force in sour cherries and many other fruit crops, will be effective in sea buckthorn. Preliminary results indicated that ethephon can reduce berry removal force marginally if it was applied 10 days before havest.

Tree Size Control:

Shrubs of most of the Hippophae species can reach 4 m in height and require a proper pruning system to maintain manageable height and shape.

Diseases, Insects, and Pests:

At the present time, few pests or diseases on sea buckthorn have been reported. The most damaging insect is green aphids, rose leaf roller, gypsy moth, gall tick, comma-shaped scale, fruit fly, and caterpillars. Diseases reported on sea buckthorn are verticillium wilt, fusarium wilt, damping off, brown rot, and scab. The pests which cause damage to sea buckthorn include deer, birds, mice, and rats. However, since sea buckthorn is a new cultivated crop, there are no registered pesticides or fungicides. Research is underway in Canada to find the best chemical and organic control measures.

Harvesting:

Prototype harvesters, available commercially in Germany, are based upon the principle of cutting off the fruit branch (Gaetke and Triquart 1992; Olander 1995). Since sea buckthorn sets fruit on second year wood, harvesting by this method means that a harvest can be obtained only every other year which is economically unsuitable for most of the farmers in North America.

In some countries, sea buckthorn is harvested in the winter after berries have frozen, however, the loss of moisture and vitamins involved with waiting for the first seasonal freeze may be unacceptable in some circumstances and flavor is unacceptable. In Canada, the most successful methods of mechanical harvesting have involved shaking the individual branches of the shrub in situ to dislodge the berries, without any damage if the berries are not overripe, causing them to fall into a catcher placed around the base of the tree.

Postharvest Handling and Storage:

Sea buckthorn berries when overripe carry a strong musky odor with rancid taste, detectable even in the field. Washing may reduce or change the odor (Beveridge et al. 1999). To avoid this problem, berries must be harvested at the correct stage, quickly transported to the processing plant, and be cooled immediately to temperatures around 4°C to retard growth of microorganisms

If the berries are to be stored more than a few days, they should be frozen, preferably by individual quick freezing techniques. The berries are thawed and processed to products as required on demand. Juice extracted by pressing or centrifugal techniques must be stored under refrigeration and requires pasteurization and freezing for long term storage. Alternatively fruit may be processed into pasteurized or sterilized finished products and stored in that form at room temperature. The shelf life even of sterilized product is limited but improved in refrigerated storage.

Juice:

The fruit of the sea buckthorn plant weighs between 270 and 480 mg and averages 350 mg depending upon cultivar and maturity (Li 1999). Pressing these berries yields 60% to 85% juice. Juice yield of 67% has been reported derived from centrifugal methods (Heilscher and Lorber 1996). The juice is very high in organic acids as reflected in the high levels of titratable acidity, and has a low pH (near 2.7). Quantitatively the most important organic acid is malic acid, but there several other minor acids have been reported (Beveridge et al. 1999). Protein levels are fairly high for a fruit juice and this probably explains the fact that sea buckthorn juice is a cloudy or opalescent product.

Vitamin C content has been reported as high as 600 mg/100 g of fruit. Vitamin E content is 160 mg/100 g of fruit (Bernath and Foldesi 1992). Pulp and seeds contain triglyceride oils with important medicinal value such as superoxide dismutase activity in mice, which enhance the activity of NK cells in tumor bearing mice (Dai et al. 1987; Chen 1991; Degtyareva et al. 1991).

Oil:

Here are two sources of oil in sea buckthorn fruit: the seed which contains 15% (w/w) oil and the pulpy fruit parts surrounding the seed which contains 48% oil (T.S.C. Li, unpubl. data). Both pulp and seed oils from sea buckthorn vary in vitamin E content depending on whether derived from seed oil (64.4 to 92.7 mg/100 g seed), juice oil (216 mg/100 g berry), or from the pulp after juice and seed removal (481 mg/100 g berry). Carotenoids also vary depending upon the source of the oil.

The seed oils are highly unsaturated with up to 73% or more of the fatty acids making up the oil being linoleic or linolenic (Oomah et al. 1999). Pulp oil is more saturated with about 38% of the fatty acids being palmitic, and 50% of the fatty acids being palmitoleic acid. The difference between seed and pulp oil seems to lie in the relatively high content of C16 fatty acids in the pulp oil and the relatively high proportion of C18 fatty acids in the seed oil.

Phytosterols:

Phytosterols are plant sterols with structures related to cholesterol and which are capable of lowering plasma cholesterol on consumption by humans. Elevated blood cholesterol is one of the well established risk factors for coronary heart disease and lowering this indicator can presumably impact heart disease incidence (Thurnham 1999). Phytosterols are the major constituents of the unsaponifiable fraction of sea buckthorn oils. The major phytosterol in sea buckthorn oil is sitosterol (b-sitosterol), with 5-avenasterol second in quantitative importance. Other phytosterols are present in relatively minor quantities.

Juice Extraction:

If fresh pressed juice is allowed to stand one or two days it will separate into three phases: an upper floating particulate phase, a center liquid portion, and a sinking particulate sediment. This separation is undesirable from a consumer point of view (Kleinschmidt et al. 1996)

If pulp oil is left in the juice, it will result in the formation of an oil layer on the juice surface, creating an oil ring that remains on the package surface after the juice is removed. This oil ring remaining on the package is unsightly and undesirable. Centrifugal reduction of the juice oil content below about 0.1% will eliminate the floating oil problem. As the oil is removed by the disk stack centrifuge, the coarse sediment will be sedimented to the bottom of the bowl and can be removed automatically by the dislodging mechanisms present in the centrifuge (Beveridge et al. 1999). Alternatively the crushed berries or extracted juice may be treated with a preparation containing pectinmethylesterase (PME) (Lui and Lui 1989), or perhaps treated with one of the many commercially available hydrolytic enzyme preparations.

For preservation purposes, it is necessary that the juice be sterilized/pasteurized. High-temperature-short-time (HTST) processes of 80C for several seconds are preferred (Liu and Lui 1989). This is because the juice is somewhat delicate and will sustain a loss of flavor and develop an off-flavor if heated beyond the conditions indicated. Furthermore, vitamin C is destroyed by heating so maximum retention is promoted by HTST processing.

The juice turns brown after about 6 months and this browning is reduced under non-oxidative conditions. Reducing storage temperatures to 4°C prolongs storage life (Zhou and Chen 1989) and enzymes and sunlight are important sources of browning initiation.

Normally, sea buckthorn juice is an opalescent, to very turbid juice depending upon the amount of suspended solids remaining after centrifugation. However, ultra filtration may be used to remove all particulate and produce a clear juice (Bock et al. 1990; Heilscher and Lorber 1996). The ultra filtration membrane can have a molecular weight cutoff of 100,000 or more and the process produces an oil-free permeate and an oil-rich retentate which can be utilized for production of pulp oil rich in vitamin E and a solid material rich in carotenoids which may be used as an isolation source for the pigment or as a dietary supplement.

Oil Extraction:

Sea buckthorn offers two possibilities for oil extraction. Pulp oil exists in the juice pulp and is isolated as a cream layer by centrifugal technology. The usual methods for manufacturing oil commercially require countercurrent (usually) extraction of the oil bearing material, seed or pulp, with an organic solvent, commonly hexane (Weiss 1963, 1970).

Increasingly, consumers are demanding fewer residues in their foods. Newer extraction techniques such as supercritical fluid extraction (SCE) especially carbon dioxide under high pressure can be used to reduce oil residues. Sea buckthorn oil may be a secondary product since it is a specialty oil used in medicine, as a nutraceutical supplement, and in cosmetics (Beveridge et al. 1999).

Pigment:

A pigment termed “sea buckthorn yellow” can be extracted from sea buckthorn waste material. The waste material could be the press cake remaining after juice extraction or the sediments remaining after centrifugation. In one process the pigment is extracted with low concentrations of alcohol (Chen et al. 1995; Liu et al. 1989) after concentrating the suspension. The waste material is spray dried to yield a yellow powder. It contains flavones but also, carotene and vitamin E. Supercritical CO2 has also been used to extract a yellow coloring material from sea buckthorn waste. Pressure had the greatest influence on extraction with yields increasing with extraction pressure. A yield of 64% total carotenoids was achieved under processing conditions of 60 MPA (Messerschmidt et al. 1993).

Teas:

Sea buckthorn leaves contain nutrients and bioactive substances. These include flavonoids (Chen et al. 1991), carotenoids, free and esterified sterols, triterpenols, and isoprenols (Goncharova and Glushenkova 1996). Numerous products can be made from the air dried leaves including teas and tea powders.

Animal Feed:

One potentially large market for sea buckthorn, are nutraceutical products for animals. The large volume of waste material from sea buckthorn, such as leaves, fruit, pulp, and seed residues from juice and oil extraction, could be developed into a value-added product. Sea buckthorn leaves contain approximately 15% protein and berry and seed residues still contain valuable chemical substances at low concentrations.