Preparation and stabilization of food-grade marine oils

Details Preparation and stabilization of food-grade marine oils Preparation and stabilization of food-grade marine oils

2001-04-05

2003-09-23

Paden, Carolyn (Department: 1761)

Food or edible material: processes, compositions, and products

Inhibiting chemical or physical change of food by contact...

Treating liquid material

C426S417000, C426S541000, C426S601000

Reexamination Certificate

active

06623774

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to processes for preparing and stabilizing food-grade marine oils.
BACKGROUND OF THE INVENTION
Marine oils have attracted substantial interest as a source of n-3 long-chain polyunsaturated fatty acids (LCPUFA), particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are of dietary significance. These LCPUFA contain 5 or 6 double bonds which render them prone to atmospheric oxidation accompanied by a fishy taste and smell. The increasing interest in LCPUFA has prompted research into methods of stabilizing fish oils against oxidation and off-flavor development
Refined marine oils are initially free from a fishy taste and smell but reversion through oxidation occurs rapidly. Many attempts have been made to stabilize such oils by the addition of different anti-oxidants or mixtures thereof. However, all these attempts have failed so far, cf. R. J. Hamilton et al., Journal of American Oil and Chemist's Society (JAOCS), Vol. 75, no. 7, p. 813-822, (1998). Accordingly, there is a need for a process for stabilizing marine oils over a long period of time in a simple and economical way, where, even after a long period of storage, no fishy taste and smell occur.
Fully or partially refined marine oil which has been treated with silica and stabilized by incorporation in the thus-treated oil of a mixture of lecithin, ascorbyl palmitate, and alpha-tocopherol in accordance with the procedure described in EP 612 346 and its U.S. counterpart U.S. Pat. No. 5,855,944 (U.S. Pat. No. 5,855,944) reportedly displays excellent Rancimat stability and good application performance for health food supplements. In a particular embodiment of the procedure described in EP 612 346/U.S. Pat. No. 5,855,944, the filly or partially refined marine oil is treated with silica having a surface area greater than 500 m
2
/g, and the silica-treated oil is then subjected to a soft vacuum steam deodorization at a temperature between about 140° C. and about 210° C.; then lecithin, ascorbyl palitate and a tocopherol in the ratio of 6-3: 4-2: 8-4 are incorporated in the thus-treated oil, whereby the resulting stabilization is reported to last for several months. In dairy applications, such as yogurt and milk drinks, however, the so-treated and stabilized oil develops a strong fishy smell and taste.
Refined marine oil which has been treated with an adsorbent such as silica and stabilized with 0.1% deodorized rosemary extract (HERBALOX “O”, available from Kalsec, Inc. of Kalanmazoo, Mich.) and sage extract in a manner analogous to the procedure described in EP 340 635 reportedly has a hereby taste and smell which can be detected in food applications. This hereby taste and smell reportedly suppresses the taste and smell of fish. In dairy applications, the use of as little as 0.03% of HERBALOX “O” and sage extract in the marine oil results in a very strong hereby taste and smell which prevents the use of this oil in these applications.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a process for preparing and stabilizing food-grade marine oil which includes treating marine oil with silica optionally in the presence of carbon, vacuum steam deodorizing the marine oil at a temperature between about 140° C. and about 210° C. in the presence of 0.1-0.4% rosemary or sage extract, and, optionally, adding 0.01-0.03% ascorbyl palmitate and 0.05-0.2% mixed tocopherol to the marine oil after the deodorizing.
DETAILED DESCRIPTION OF THE INVENTION
It has now surprisingly been found in accordance with the present invention that marine oil which has been treated with silica in accordance with the procedure described in EP 612 346/U.S. Pat. No. 5,855,944 can be stabilized over a long period of time without the occurrence of fishy taste and smell by vacuum steam deodorization at a temperature between about 140° C. and about 210° C., in the presence of 0.1-0.4% of deodorized rosemary or sage extract. The treating of the oil with silica may be by combining (i.e., adding or mixing the oil with silica). The treatment of the oil with silica can suitably be carried out in one embodiment by contacting the oil with the silica in a silica-filled column or stirred reactor vessel or a combination thereof Batch, semi-batch or continuous operation is feasible. Silica having a surface area of more than 500 m
2
/g is suitably used. It is preferred to carry out this treatment at about room temperature, although lower or, especially, higher temperatures may also be used if desired. Further, it is preferred to perform this embodiment under the atmosphere of an inert gas, especially nitrogen. The contact time between the oil and the silica can be varied within wide limits and can be a few seconds to several days. In this connection, the flow rate at which the oil passes through the silica in a column procedure will depend on factors such as the type and particle size of the chosen silica, the dimensions of the column and the like.
In another embodiment, an oil/solvent miscella is passed through a silica column The solvent is preferably a food grade approved apolar solvent, preferably a hydrocarbon and especially hexane. This embodiment can be carried out, for example, by dissolving the oil in the solvent to provide a solution containing about 20-60%, preferably 33%, oil by weight, passing the solution through silica in a column or stirred reactor vessel or a combination thereof using a ratio of miscella to silica of 20:1 to 5:1, preferably 15:1, (wt./wt.), filtering and then removing the solvent by distillation. Here again, the contact time between oil and the silica can be varied within wide limits and can be a few seconds to several days.
The treatment with silica described hereinbefore can also be carried out in the presence of carbon. The carbon which is used is preferably dried or substantially freed from water 2a before or during the process and, furthermore, preferably has a surface area of more than 1100 m
2
/g. Examples of suitable carbons are those available as NORIT, e.g. NORIT CA1, and similar activated carbons.
The fully refined marine oil used in the present invention is one which has been neutralized, bleached and deodorized in a conventional manner. The oil can be, for example, menhaden oil, herring oil, sardine oil anchovy oil, pilchard oil, tuna oil, shark oil, hake oil, etc., or a blend of two or more of these oils.
Factors associated with the fishy taste and smell of a marine oil are not well defined. In order to obtain more information as to which factors are responsible for the fishy taste and smell, 21 oil samples were analyzed in detail as shown and discussed below. Samples 1-10 used in these analytical proceedings are commercially available standard fish oils from suppliers throughout the world and are regarded as being “aged” because of the delays in refining them further in accordance with the procedure described in EP 612 346/U.S. Pat. No. 5,855,944, whereas samples 11-15 are refined fish oils where it is known that both the extraction and refining have been performed immediately after the fish have been caught or with minimum delay only. Samples 16-17 are oils of fungal origin Samples 18-21 have been produced from commercially available fish oils in accordance with the procedure described in EP 612 346/U.S. Pat. No. 5,855,944 in which, however, a special short path distillation step has been included at the start of the process to trap smell molecules for use as described below. The purpose to this wide trawl (diversified catch) is to have as representative a range as possible of refined oils containing EPA and DHA.
Table 1 records the influence of the acid value, the EPA and, respectively, DHA content, the color and the pro-oxidant iron and copper levels on sensory responses of a trained panel to the 21 oil samples described above.
The analysis for the determination of the EPA and DHA content and, respectively, the proxidant iron and copper levels were performed according to analytical methods known in the art. For determining the ac

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