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Stabilizing Marine Oils with Natural Antioxidants.

The advantages of using antioxidants in the food industry are widely recognized. Antioxidants are able to protect food products from oxidation, thereby maintaining their quality and product characteristics. Recently, as a result of the focus on healthy foods, there has been a strong increase in consumer interest in natural antioxidants. As a consequence of this trend, together with the increased use of fish oils in food applications, Kemin Food Ingredients has studied the efficacy of natural antioxidants in marine oils.

Market Trends

Because of the high degree of poly-unsaturation in their fatty acid profile, marine lipids are prone to oxidation, leading to the formation of volatile oxidation products, characterized by fishy off-flavours and off-odours. (1) As a result, the inclusion rate of marine oils in food is limited, especially in mildly flavoured products. To delay the oxidation of fish oil and increase its overall stability, the application of antioxidants is used. Traditionally, synthetic antioxidants are believed to be more effective than natural alternatives such as tocopherols and herbal extracts. However, because of an increased consumer demand for all-natural products, natural ingredients are progressively replacing synthetic antioxidants, and new, efficient natural antioxidant blends are being developed.

Positive Health Benefits of Omega-3

During recent years, consumer interest in marine oil has increased significantly, mainly because of the fact that they are rich in omega-3 fatty acids. Omega-3 fatty acids are a family of polyunsaturated fatty acids that all have a carbon double bond in the [omega]-3 position. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the most common omega-3 long-chain fatty acids found in marine oil. Omega-3 fatty acids have been shown to contribute to positive health benefits, more specifically in reducing the risk of coronary heart disease. (2) Therefore, an increasing number of food manufacturers choose to include fish oil that is rich in omega-3 fatty acids into their finished products. With the addition of these rich fatty acids, however, comes an increased need to stabilize and protect the oils from rancidity.

Natural Antioxidants Versus Synthetics

Food antioxidants can improve food quality and safety by delaying or preventing lipid oxidation of oils and fats in food products; but which antioxidant is best? The right choice depends on several factors, including product formulation, applicable food regulation constraints, antioxidant properties, sensory impact and cost. First and foremost, the antioxidant choice must meet the relevant food standards of each market--these can vary from country to country. Compliance with local regulations is non-negotiable. In some countries, strong consumer preference for natural additives has put synthetic antioxidants out of favour--despite being allowed by food laws. There are some general guidelines for choosing the correct antioxidant type. Understanding a product's capabilities will help to determine the amount that should be used. The financial impact of adding an antioxidant should be weighted against its benefits--an extended shelf-life, ensured food safety, longer marketable periods for the food product and reduced product returns, for example. These factors can all strengthen, build and maintain a brand's reputation. Natural antioxidants are, admittedly, more expensive, but an increased production cost may be justified when all the direct and indirect benefits are thoroughly analysed. The right choice of antioxidant depends on which factor is a priority to an individual customer. It should be emphasized, however, that these parameters must be clearly defined before starting any product evaluation or shelf-life study.

Antioxidants in Marine Oils

Important in the fight against the development of off-tastes and, consequently, towards shelf-life improvement are the quality of the raw material (crude, semi-refined or refined), the ability to prevent oxidation during the production process and the ability to prevent oxidation within the end-product (bottle, capsule, food matrix). Therefore, it is worthwhile finding out whether antioxidants are added to the raw materials to protect the oil during transport. The majority of the finished products that contain fish oil are currently stabilized with dl-alpha-tocopherols and/or mixed tocopherols. Next to tocopherols, although on a very limited scale, blends of rosemary extract, ascorbyl palmitate and tocopherols are also used.



As sensorial quality is a significant bottleneck for marine oil applications in functional food, the antioxidant activity of dl-alpha tocopherol has been proven to be insufficient when it comes to eliminating off-flavours. (3) As a result, innovative antioxidant concepts are being developed that significantly increase the stability of marine oils by preventing oxidation. Another point is to make sure that these antioxidants do not add an off-taste, off-smell or off-colour when added to the oil. Consequently, the development needs to be done in close co-operation with the marine oil and functional food industries.

FORTIUM brand RPT40 is a natural flavour and antioxidant combination developed by Kemin Food Ingredients for the protection of marine oils against oxidation. It contains rosemary extract, tocopherols and ascorbyl palmitate as the active ingredients. In this respect, Kemin Food Ingredients has conducted two independent ambient storage studies using an 18% EPA/12% DHA fish oil to compare the efficacy of various antioxidant blends containing natural compounds. In the first experiment, the stability of the 18/12 fish oil was tested in an accelerated OSI test method at 80[degrees]C. As seen in Figure 1, the natural antioxidant treatment with FORTIUM RPT40 resulted in a significant improvement of the oxidative stability of the fish oil. Moreover, when dosed at 0.05%, it was able to match the stability of the positive control (0.03% dl-a-tocopherol). When the fish oil was treated with 0.1% RPT40, the oxidative stability increased to a level that was even higher than that of the positive control.

The results from the second experiment are presented in Figure 2. They show that at a dose level of 0.8%, RPT40 was able to match the oxidative stability of the positive control (a synthetic antioxidant blend of dl-a-tocopherol, TBHQ and BHT). In view of the increasing trend of replacing synthetic antioxidants with natural alternatives, it is clear that FORTIUM RPT40 is an excellent candidate when applied at the appropriate dosage.

Moreover, peroxide values (PV) and thiobarbituric acid reactive substances (TBARS) were compared for an untreated control, a positive control (0.03% alpha tocopherol) and a treatment with FORTIUM RPT40, applied at levels ranging from 0.05-0.08%. PV values and TBARS for all treatments were lower (P<0.05) than the untreated control starting from Day 10 and 17, respectively (Table I). Furthermore, our study showed that the PV values for RPT40 were significantly lower (P<0.05) than the positive control from Day 14 onward.


General Conclusion

These results demonstrate that RPT40--a product based on ascorbyl palmitate with natural rosemary extract and tocopherols as the active compounds--is effective at delaying oxidation in marine oils. This will increase the usage potential of stabilized fish oil in various food products. In addition, it was shown that the product combination, with its natural ingredients, could delay oxidation as effectively as synthetic antioxidants when applied at the appropriate dosage.


(1.) E.N. Frankel, et al., "Oxidative Stability of Fish and Algae Oils Containing Long-Chain Polyunsaturated Fatty Acids in Bulk and in Oil-in-Water Emulsions," J. Agric. Food Chem. 50(7), 2094-2099 (2002).

(2.) US Food and Drug Administration, "FDA Announces Qualified Health Claims for Omega-3 Fatty Acids" ( news/2004/NEW01115.html), 8 September 2004.

(3.) E. Kulas, E. Olsen and R.G. Ackman, "Effect of [alpha]-, [gamma]-, and [delta]-Tocopherol on the Distribution of Volatile Secondary Oxidation Products in Fish Oil," Eur. J. Lipid Sci. Technol. 104, 520-529 (2002).

For more information

Katrien Pardons, PhD, Associate

Scientist, and Kelly De Vadder, Marketing Assistant

Kemin Food Ingredients BVBA

Atealaan 4i, B-2200 Herentals


T. +32 14 283 660

FORTIUM[R] brand RPT40 is a registered trademark of Kemin Industries, Inc., Iowa, USA.
Table I: Oxidative stability of 18/12 fish oil samples during storage
at room temperature expressed as peroxide value (a) and thiobarbituric
acid reactive substances (b). (Positive control * consists of 0.03%

Time (days) Negative Positive RPT40 RPT40
 Control Control * (-0.05%) (-0.08%)

 2 7.0 (a) 6.6 (a) 7.8 (a) 8.4 (a)
 4 8.0 (a) 7.3 (a) 7.7 (a) 9.0 (a)
 10 15.4 (a) 14.2 (a) 11.7 (a) 11.4 (a)
 14 23.0 (a) 20.8 (a) 13.6 (a) 13.7 (a)
 17 24.6 (a) 22.7 (a) 15.0 (a) 13.2 (a)
 23 36.2 (a) 34.1 (a) 21.8 (a) 17.2 (a)
 29 51.9 (a) 47.5 (a) 30.2 (a) 23.1 (a)
 37 71.9 (a) 65.8 (a) 43.4 (a) 26.0 (a)
 43 86.4 (a) 75.2 (a) 55.9 (a) 31.0 (a)

Time (days) Negative Positive RPT40 RPT40
 Control Control * (-0.05%) (-0.08%)

 2 0.6 (b) 0.5 (b) 0.5 (b) 0.6 (b)
 4 1.3 (b) 0.8 (b) 0.7 (b) 0.7 (b)
 14 0.6 (b) 0.4 (b) 0.5 (b) 0.3 (b)
 17 1.6 (b) 0.7 (b) 0.8 (b) 0.5 (b)
 23 6.7 (b) 4.2 (b) 4.0 (b) 2.6 (b)
 29 14.0 (b) 3.3 (b) 2.3 (b) 3.1 (b)
 37 16.8 (b) 6.9 (b) 5.8 (b) 3.0 (b)
 43 14.1 (b) 11.1 (b) 4.6 (b) 2.8 (b)
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Title Annotation:antioxidants
Author:Pardons, Katrien; De Vadder, Kelly
Publication:Nutraceutical Business & Technology
Article Type:Report
Geographic Code:4EUBL
Date:Jul 1, 2007
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