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Abstract. The fat soluble vitamins, as well as n3 and n6 fatty acids (FA) are essential compounds of fish lipids and exclusively provided by the diet. Fish is sometimes eaten raw, but it is usually thermal processed before consumption. Temperature processing of fish tissue enhances its taste, inactivates pathogenic microorganisms and increases its shelf life. The fat soluble vitamins (vitamins A, D 3 and E) and fatty acids are considered to be susceptible to oxidation during heating (cooking) process. The aim of the present study was to evaluate the effect of steaming (10 min at 90 o C) and frying (5 min on the each side with sunflower oil) on fat soluble vitamins and fatty acids composition in Horse mackerel (Trahurus mediterraneus) fish fillets. Vitamins A, D 3 and E were analyzed simultaneously using RP-HPLC. The fatty acid composition was analyzed by GC-MS. The amounts of vitamin A (retinol) in cooked fish fillets (for both heat treatments) decreased significantly, compared to their content in the raw samples. In contrast vitamin D 3 (cholecalciferol) content affects only by steaming, while changes on vitamin E (alpha-tocopherol) was observed solely after frying process. The highest content of monounsaturated fatty acids (MUFA) were observed after steaming, whereas fried samples presented higher values of polyunsaturated fatty acids (PUFA) due to significant increase in linoleic acid (C18:2n6). During steaming did not reduce significant n3 and n6 PUFA levels, while frying caused a large reduction of n3 PUFAs. The ratio of n3/n6 was markedly lower in fried samples than in raw and steamed mackerel. In conclusion the Black Sea Horse Mackerel is a good source of vitamin D 3 , vitamin E and n3 PUFAs. After steaming and frying process there were minimum losses in the contents of cholecalciferol and alpha-tocopherol, while retinol was reduced nearly a half. The process of frying affects most significantly three fatty acids groups, whereas after steaming was observed little influence on fatty acids profile.

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The fatty acid compositions of three Black Sea fish species turbot (Pseta maxima), red mullet (Mullus barbatus ponticus) and garfish (Belone belone) were investigated. This species are considered as preferred for consumption in Bulgaria. Lipid extraction was done according to the Bligh and Dyer method. The fatty acid composition was determined by GC/MS. The saturated fatty acids amounts were 38.32 % for turbot, 35.44 % red mullet and 42.90% for garfish. Monounsaturated fatty acids were found in lowest level in comparison with other groups for garfish (23.65%) and turbot (24.85%) while for red mullet they have a highest value -37.56%. Omega 3 polyunsaturated fatty acids as eicosapentaenoic (C 20:5 omega 3, EPA) and docosahexaenoic (C 22:6 omega 3, DHA) acids were found in highest levels in turbot (22.26%) and garfish (21.80%) and in lowest values of red mullet (9.35%). The results showed that the fish examined are good source of omega 3 polyunsaturated fatty acids, resulting in a very favourable omega 3 / omega 6 ratios, especially in turbot and garfish.

Many studies suggest that marine molluscs are one of the most important dietary sources of fat soluble vitamins (E, D3 and A) and essential fatty acids (FA). The most commercially important species from the Bulgarian Black Sea are the Black mussel, rapana and shrimp. There is scarce information in the scientific literature about fat soluble vitamins and FA composition of these Black Sea molluscs. The aims of the present study are to determine and compare fat soluble vitamins content as well as relative daily intake, FA composition and atherogenic index (IA), thrombogenicity index (IT) and flesh-lipid quality index (FLQ) in wild Black Sea mussel (Mytilus galloprovincialis), rapana (Rapana venosa) and shrimp (Crangon crangon). Fat soluble vitamins were analysed simultaneously using RP-HPLC system. The FA profile was analysed by GC-MS. All of the analysed samples presented significant amounts of vitamin E, followed by vitamin A and D3. Black Sea molluscs are excellent sources of fat soluble vitamins, especially for vitamin D3 - one survey provides more than 100% of the RDI established in Bulgaria. The FA composition of total lipids showed significant differences and the present study revealed that SFA content was significantly higher than MUFA (p<0.001) and PUFA (p<0.001) (SFA>PUFA>MUFA) in shrimp and mussel whereas rapana showed opposite trends (PUFA>SFA>MUFA). The omega6/omega3 and PUFA/SFA ratios of the analysed species were greater than the FAO/WHO recommendations.

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Shellfish aquaculture has become an increasingly important factor in Bulgarian economy in the recent years. Marine biotoxins, produced by some phytoplankton species, may accumulate in mussels and present an important challenge in commercialization of shellfish. The aim of this study was to determine the occurrence and variability of hydrophilic toxinsparalytic shellfish poisoning (PSP) and amnesic shellfish poisoning (ASP) as well as lipophilic toxinsincluding diarrheic shellfish poisoning (DSP), pectenotoxins (PTXs) and yessotoxins (YTXs) in plankton, wild and farmed mussel samples from the Southern Black Sea coast, an important shellfish farming area in spring 2017. PSP toxins were determined by HPLC with postchromatographic oxidation and fluorescence detection and domoic acid and lipophilic toxins by liquid chromatograph coupled to tandem mass spectrometry. DA and pectenotoxin-2 were detected in plankton, wild and farmed mussel samples. Yessotoxins were detected only in cultivated mussels and no PSP toxins were detected. The occurrence of phycotoxins differed over both space and time. Toxin profile includes prevalent domoic acid, scarce presence of pectenotoxin-2 and yessotoxins in the samples.