In order to preserve krill’s “unique health and nutritional properties,” krill oil extraction should take place as soon as possible after the krill have been caught, according to Dimitri Sclabos, general manager of Tharos Co., a Chilean-based krill consultancy.
Sclabos claims that a new at-sea extraction process for Antarctic krill (Euphausia superba) developed by Tharos enables krill oil to be produced on board the catching vessel in less than two hours after the krill have been brought on board.
“Compared to current krill oils which are all manufactured on land using either dried krill meals or frozen krill previously produced at sea, Tharos’ krill oils are manufactured entirely on board from fully traceable, freshly captured raw krill,” he said. “The process is 100 percent chemical and solvent-free.
“This unique concept provides the health and food industries with a highly competitively priced krill oil that preserves krill’s original nutritional and medical properties. There is no lipid oxidation, no aftertaste, no burping problems, and no residual solvent material,” he said.
“The process extracts the entire phospholipids’ profile of raw fresh krill, preserving the natural omega-3 content and the high content of the pure and natural antioxidant, astaxanthin.”
Tharos said it has identified three stages that krill go through after capture and death when stored at about 0 degrees Celsius under very specific conditions, which emphasize why it is better for phospholipids’ enriched krill oils to be manufactured at sea.
Before rigor mortis sets in, which takes 1-2 hours after catching, the tiny crustacean is transparent and its carapace is shiny, its color varying from brick to pale pink with a green to yellow spot (due to its diet of phytoplankton). Once in storage, krill gradually becomes an opaque opal pink in color.
The krill softens after 2-3 hours, although the neck (the part between the head and the thorax) becomes firm and arched. The inner fat becomes more acidic so the oil becomes rancid and old, and the solubility of salt-soluble proteins drops.
The third stage, which sets in after about four hours, sees severe autolysis, or self digestion by the krill’s own enzymes. As a result of the ensuing hydrolysis, valuable lipids are lost and there is a sharp increase in non-protein substances and harmful volatile nitrogen bases.
For krill stored for more than five hours, in addition to the autolysis, microbial spoilage takes place.
Acceleration of autolytic degradation is also impacted by the capture volume of each trawl. For large tows (more than 10 tons) there is long term damage resulting in a significant loss of proteins and the acceleration of hydrolysis.
When captured using a continuous pumping system instead of the regular net/gear system, there are no problems with krill being crushed in the net and they arrive at the processing line almost alive.
The nature of the post-mortem changes for krill are similar to those for other crustaceans, but occur much faster, according to Sclabos. “The water content [of krill] is higher and there is very high enzymatic activity even at very low temperatures. In our lab we have seen [enzymatic] activity at below 70 degrees Celsius.”
Not surprisingly the length of time in which krill are stored in a fishing vessel’s hold and the temperature at which the krill are held, can accelerate microbial spoilage and the formation of nitrogen-containing volatiles.
Sclabos said that the new Tharos process works perfectly well on South Antarctic krill caught during either its normal low or high fat seasons, producing both phospholipids and triglyceride-enriched krill oils, and also human food and animal feed grade dried krill meals in parallel.
As Tharos’ krill oil is obtained entirely onboard the catching vessel, and with a high processing yield, the financial margin for the vessel is very attractive, according to Sclabos. In addition there is no requirement to provide processing facilities on land. “All this combines to provide competitive final prices for the consumer.”
There is a huge and very lucrative market for krill oil in the U.S. and Western Europe, so to obtain a high quality product at a reasonable price will be very welcome.