February 22, 2021

 

Nofima discovers new way of producing quality oil from raw material of mackerel fillet

 

A new refining process developed by Nofima can enable mackerel fillet producers to manufacture high-quality oil from residual raw material.

 

The project is funded by the Norwegian Seafood Research Fund (FHF) and carried out at Nofima with the institute's senior scientist, John-Erik Haugen, as the project manager.

 

Mackerel is a pelagic species of fish that has a high fat content and is rich in the essential polyunsaturated omega-3 fatty acids EPA and DHA. In the industrial production of mackerel fillets, the residual raw material has been used to make animal feed. This is due to the fact that no solutions have been established to extract and refine oil.

 

However, tasteless and odourless mackerel oil is well suited for use in health foods and functional foods due to its high content of healthy fatty acids.

 

"The main goal of the project has been to utilise the residual raw material in a better way than has previously been done, i.e. to extract the oil from the residual raw material and use it for human consumption," said Haugen. "This meant that we had to refine the oil from the residual raw material so that it became colourless and had a neutral odour and taste, and we managed to achieve just that.

 

"The refining process will provide the industry with a great amount of added value, while at the same time, being an important element of sustainability because a greater proportion of the fish is being utilised for human consumption."

 

The project will provide actors with significant values within the mackerel industry, as well as contributing to more sustainable food production. Currently, oil is not extracted from the residual raw material of mackerel, but the industry and scientists have long been aware of the potential that lies within the fish.

 

"The project has had two sub-goals. The first has been about developing a neutrally tasting oil so that it is suitable for human consumption, either in functional food or as an additive in other food products," said Haugen.

 

"The second part involves giving the industry an opportunity regarding added value, as well as increasing the sustainability aspect in terms of greater utilisation of the fish for human consumption.

 

"During the project, we have allowed Nofima's sensory panel to test the oil to ensure that the final result is what we have been aiming for, namely a completely odourless and tasteless product."

 

The refining process includes several stages of purification.

 

"Primarily, actors that handle large volumes of mackerel fillets will want to use the technology. It is also this part of the industry that has requested a solution, since the amount of residual raw material is increasing due to an ever decreasing proportion being exported as frozen whole fish," Haugen added. "Mackerel is a healthy food and I am confident about the combination of sustainability and value creation, so it will be exciting to see who first takes advantage of the technology in their operations.

 

"In order to produce the desired final product, the crude oil must undergo a number of purification stages (refining) consisting of bleaching, winterisation and deodorisation.

 

"Deodorisation is required to remove odours and flavours, and to achieve a neutral taste. Finally, antioxidants must be added to the refined oil in order to stabilise it. This is to avoid rancidity occurring during storage and to increase the shelf life of the oil."

 

During bleaching the process removes pigments, rancid elements and trace metals. Fuller's earth (a fine-grained clay mineral) is added to the oil during heating. The unwanted substances bind to the Fuller's earth which is then removed by filtration.

 

According to Nofima, mackerel oil has a high proportion of saturated fat (stearin) that solidifies at refrigerator temperatures. Winterisation, a slow cooling process, enables a fraction of stearin to solidify and to be removed through a filtration process. Saturated fat gives the oil a high melting point and removing the stearin results in a liquid oil at low temperatures.

 

During deodorisation, the process is carried out by sending water vapor through the oil at high temperature and low pressure. This stage breaks down and removes residues of oxidation products and volatile compounds that can cause unwanted odours and taste. In addition, the process removes organic pollutants.

 

During stabilisation, antioxidants are added to marine oils to avoid rancidity and increase shelf life during storage. Natural antioxidants, such as tocopherols (vitamin E) and rosemary extract, are commonly used.

 

The project's main findings are as followed:

 

- Optimisation of the bleaching process produced an almost colourless oil and with marginal effect of bleaching time over 15 minutes;

 

- Winterisation, during the refrigeration of the mackerel oil, resulted in a relatively low yield of liquid oil (olein) of 40%;

 

- Bleaching and deodorisation effectively removed up to 98% of the volatile components in the crude oil.

 

Pilot-scale refining trials have managed to produce a colourless and neutrally tasting mackerel oil that meets requirements for human consumption. Nofima said that the best effect on the stabilisation of refined mackerel oil was achieved by combining tocopherol and rosemary extract.

 

"We have developed and tested a pilot-scale refining process which means that the industry can now utilise this knowledge commercially. We believe that the results from this project will have a high utility value for the mackerel industry," said Haugen.

 

"Everything is now in place to utilise the residual raw material from mackerel in order to make high-quality oil."

 

- Nofima