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Is Our Local Fish a Quality Food Source – an Interview with Ch. Assist. Prof. Dr. A. Merdzhanova

Dr. Merdzhanova, last week you made a public defense of your dissertation, entitled "Fatty Acid Composition of the Black Sea and Freshwater Fish Species". What is the purpose of your research?

In fact, it is part of a three-year research project of the Department of Chemistry under the Scientific Research Fund, which aimed to explore the safety and quality of the Black Sea fish species. MU - Varna won the Varna Prize with this project (2012). In my dissertation, I explore another important aspect of the research on the Black Sea fish species - their quality as a food source in the aspect of fatty acid composition. Pretty soon, a colleague from the Department is about to defend a dissertation, in which another important and interesting aspect will be explored - the content of fat-soluble vitamins in the Black Sea fish species.

What was the research about and how did you fulfill it?

The research on the content, type and quantities of fatty acids in fish species was carried out by means of a gas chromatograph with a mass detector, and their quality evaluation as foodstuffs was defined on the basis of the obtained data. Mass Detection Chromatography is a highly informative modern method of analysis that allows very precise separation and identification of fatty acids in fish lipids.

We explored 11 Black Sea fish species of commercial importance – both mass consumed and delicacy fish of the Bulgarian Black Sea coast. The selected species are some of the best-selling, well-known and on demand on the Bulgarian market - sprat, goby, shad, scad, anchovy, turbot, etc. We also explored four freshwater fish species - silver carp, carp, sheatfish and trout to make a comparison. Such a systematized study on the qualitative composition of the Bulgarian Black Sea fish species hasn't been carried out here so far. The study has also determined the energy value of 7 Black Sea fish species. The results obtained throughout the study are systematized in tables in order to facilitate their usability.

What did the results prove?

The balanced fatty acid composition is an important quality indicator of any type of food. It is well known that fatty acids are a basic structural component of lipids. They are divided into saturated, monounsaturated and polyunsaturated according to their chemical structure. The results proved that species such as bluefish, sprat, shad, scad, turbot, for example, have a very well-balanced fatty acid composition. Two of the explored freshwater fish species - silver carp and Danube carp have also shown very good results according to this indicator. Of course, these indicators depend largely on the habitat, season and other external factors.

All in all, our fish species contain nutrition lipids of high quality - 60% of them are unsaturated, the remaining 40% are saturated fatty acids, whereas 20% of the unsaturated belong to omega-3 fatty acids.

How many types of fatty acids may a certain fish species contain?

This is a popular science question. There are over 800 types of fatty acids. Thirty-four fatty acids, with a straight chain and length of C10 to C24 carbon atoms, have been identified in the analyzed species. As previously mentioned, polyunsaturated fatty acids are the most interesting, explored and biologically active ones.

What is the importance of fatty acids for the human body?

Fatty acids are an important component of the healthy diet. In recent years, a number of world health organizations have recommended an increase of fish consumption, which in turn provides an intake of high fatty acids - Omega-3, Omega-6. Recently, pregnant and lactating women have been advised to take 200 mg of docosahexaenoic omega-3 acid daily to stimulate the normal development of the fetus. It has been found out that the retina and the brain tissue contain up to 20% of this type of omega-3 acid. For example, turbot, scad, anchovy, shad, sprat and belted bonito contain a large amount of this fatty acid. It doesn't mean that the other fish species do not contain it, but if in the aforementioned species the required amount is contained in 100 g, in the rest of them it is contained in 150 g.

All in all, with this research we are trying to fill in the lack of information on fatty acid composition and thus to enrich the knowledge on the Black Sea inhabitants and in particular fish species, and the results we obtained will definitely be of use to professionals in various fields, such as nutrition and dietetics.