CPUT, SU researchers combine forces to delve into snoek's nutrient value

To fish lovers, wintertime in the Cape equals freshly caught snoek. Now is therefore a good time to consider the nutritional value of eating this relatively low-cost medium-sized type of marine fish. According to a new study published in the South African Journal of Science, a snoek's meat is quite high in protein and important omega-3 fatty acids, but low in fat.

The findings from the study is part of ongoing research into the quality and value of snoek and other South African marine fish species. It was conducted by Ms Suné Henning, a lecturer in food science and technology at the Cape Peninsula University of Technology (CPUT), and meat scientist Prof Louw Hoffman, holder of the South African Research Chair in Meat Science: Genomics to Nutriomics based at Stellenbosch University.

Only a handful of studies have been done on the nutritional contents of South African marine fish species, while even fewer older ones have specifically looked at raw and cooked Cape snoek.

In the current study, Henning and Hoffman established that Cape snoek is a low-fat fish that has a fat content of less than 4%. This is in line with the fat contents of pink salmon (Oncorhynchus gorbusha) fillets.

Snoek is among others high in the "good" fatty acid eicosapentaenoic acid (EPA) and the omega 3 fatty acid docosahexaenoic acid (DHA). The EPA content of the fat of raw snoek is 9,11%, and for the fat of cooked snoek it is 10,13%. The DHA content of the fat of raw snoek is 19,7%, and 20.28% for the fat of cooked snoek.

In all it has a high protein content of 24,5%, which is higher than that of other marine fish species such as European hake (Merluccius merluccius), seabass (Dicentrarchus labrax) and cod (Gadus morhua callarias), or freshwater fish species, such as rainbow trout (Oncorhynchus mykiss) and catfish (Clarias gariepinus).

"Cape snoek is often seen as a low-value fish, but it is in fact a healthy, relatively cheap high-protein, low fat food source that is high in 'good' omega-3 fatty acids," Henning summarises the findings.

"Snoek is therefore an important and healthy source of protein," adds Hoffman.

They further established that cooking reduces the amount of moisture available in the flesh, but increases the protein content.

For the purposes of the current study, the research team focused on establishing the proximate analysis parameters of raw and cooked snoek. Proximate analysis is often used by food scientists to determine the major nutrients or components in a food source. They do so by assessing the moisture, ash, crude protein, crude fat and carbohydrate contents of a product – be it raw or processed.

"Proximate analysis also helps food scientists to understand the quality aspects and sensory evaluations of raw materials, as well as aspects such as the perception of consumers and the product's eventual shelf life," explains Henning.

There are many methods by which snoek or any other piece of fish can be prepared – be it microwave cooking, steaming, "braaing" or oven baking. "It is therefore important to know what the specific proximate analysis parameters are of snoek, because these ultimately have an influence on the nutrient value of the fish that will be eaten," says Henning, who is also studying the effect that different cooking techniques have on the proximate and fatty acid profiles of snoek.

"The aim of this study was to determine the proximate and fatty acid compositions of raw and cooked Cape snoek. We wanted to quantify its nutritional value and make the information available to consumers and processors, so that it can be used as part of the nutritional tables of South African foodstuffs and in academic databases," Prof Hoffman explains.

The research team analysed the flesh samples of ten flecked Cape snoek (Thyrsites atun) at the laboratory of the Department of Animal Sciences at Stellenbosch University.

As part of ongoing postgraduate research collaboration and support between CPUT and SU, Henning and Hoffman have combined their efforts over the past seven years to study aspects of snoek and other types of fish as a food source. In this regard MTech students from CPUT who are investigating aspects of fish meat regularly make use of the research facilities available at Stellenbosch University's Department of Animal Sciences, home of SARChI Research Chair.

Reference: Henning, S.S. & Hoffman, L.C. (2017). Proximate and fatty acid composition of cooked South African Cape snoek (Thyrsites atun), South African Journal of Science, May 2017