“Stability has been an issue with krill powder in the past. This has limited the growth of the product as the customer often requires that the product can be offered for sale at room temperature,” Inge Bruheim, chief scientific officer at the Norwegian biotech company, told NutraIngredients.
The studies – the first to investigate the long term storage stability of krill powder – were performed in collaboration with NOFIMA (the Norwegian Institute of Food, Fisheries and Aquaculture Research) and Denmark Technical University, with financial support from the Norwegian Research Council. The results showed that Rimfrost’s krill powder is stable over extended periods at room temperature and that minimal degradation takes place.
Derived from Antarctic krill – a shrimp-like marine crustacean – krill powder is rich in omega-3s, protein and astaxanthin.
Omega-3 fatty acids impart health benefits due to the number and positions of double bonds in their chemical structure. In krill, the omega-3 fatty acids are primarily bound in phospholipids, which studies show make them more bioavailable than when present as triacylglycerol in fish oil.
Omega-3: boon and bane
However, this very structure that gives them a health advantage also renders them susceptible to oxidation.
Due to the instability of the omega-3s and the activity of endogenous enzymes, immediate processing after catch is necessary. Rimfrost deploys enzymatic hydrolysis to stabilise its fresh krill after harvest. It does this by inactivating the endogenous proteases, thus reducing the risk of oxidation and resulting in the formation of bioactive peptides.
“This low temperature process in combination with vacuum drying ensures that the krill granulate produced has a minimal degree of oxidation. Our krill powder also contains a high level of natural antioxidants such as vitamin E and astaxanthin, which further contributes to its high stability. It is well known that lipid oxidation will fuel further lipid oxidation in a viscous cycle,” explained Bruheim.
He added that he was not aware of any other methods that could be used effectively, saying “micro-encapsulation will not provide a 100% pure krill powder as opposed to ours where all components are derived from krill”.
In the NOFIMA study, the stability of Rimfrost’s Pristine krill powder was assessed over two years at room temperature. The results showed that the concentration of astaxanthin decreased over time, but there was no significant change in the levels of other ingredients, including the fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).
The second study, carried out in conjunction with Denmark Technical University and published in the European Journal of Lipid Science and Technology, investigated the stability of krill powder when stored up to a year at room temperature. Stability was assessed by changes in concentrations of lipid classes, antioxidants, pyrroles and volatiles.
This found that some oxidation and hydrolysis occured, evidenced by an increase in free fatty acids and some volatiles, along with a decrease in antioxidants, vitamin E in the form of tocopherol and astaxanthin.
However the researchers concluded that “overall, oxidation was not severe and packaging the krill powder in vacuum increased the oxidative stability of krill powder, as determined by the higher content of astaxanthin and tocopherol”.
These two studies have confirmed the stability of Rimfrost’s krill powder at room temperature for a year and potentially longer. However, prolonged exposures to temperatures above 25ºC and direct sunlight should be avoided, advised Bruheim.
He added that stability tests carried out in refrigerated conditions had shown astaxanthin to be even more stable at lower temperatures.
Whilst Rimfrost has no plans for further stability tests, the company is embarking on more research projects.
“The next research from us will be clinical data documenting the safety and efficacy of our krill powder as a food supplement,” confirmed Bruheim.
European Journal of Lipid Science and Technology
2016, 118, 0000–0000 1 DOI: 10.1002/ejlt.201600085
“Quality changes of Antarctic krill powder during long term storage”
Authors: Nina Skall Nielsen, Henna Fung Sieng Lu, Inge Bruheim and Charlotte Jacobsen