Mercury,selenium, PCBs and fatty acids in fresh and canned fish available on the Slovenian market

In order to contribute to the general understanding of the risks and benefits of consuming fish and fish products, total mercury (THg), monomethylmercury (MeHg), polychlorinated biphenyls (PCBs), selenium (Se), n-3 and n-6 fatty acids were determined in fresh and canned fish on the Slovenian market. Furthermore, the mercury exposure of pregnant women in Slovenia was assessed by determining total mercury (THg) in hair, and through fresh and canned fish consumption obtained by a food frequency questionnaire. Based on the frequency of fish consumption and levels of MeHg, THg and PCBs determined in the present study, it can be concluded that fish available on the Slovenian market do not represent a health risk. It was also confirmed that fish are important sources of selenium and n-3 fatty acids.     

The impact of dietary oil source and frozen storage on the physical,chemical and sensorial quality of fillets from market-size red hybrid tilapia, Oreochromis sp.

Red hybrid tilapia (Oreochromis sp.) were fed one of four diets containing either fish oil, crude palm oil, palm fatty acid distillates or refined palm olein as the only added oil. Post-harvest fillet quality was then evaluated at 1, 10 and 30 weeks of frozen storage. Dietary oil source did not significantly (p > 0.05) influence the liquid holding capacity and texture of fillets but both these parameters were increased by frozen storage. Fillets from fish fed palm oil-based diets exhibited significantly higher oxidative stability during frozen storage, compared to fish fed the fish oil diet. Dietary oil source and frozen storage had little impact on sensory attributes. Unlike fillet proximate composition, fillet fatty acid composition was significantly affected by both diet and frozen storage. Total n-3 polyunsaturated fatty acids decreased significantly in the fillet lipids of all fish after 30 weeks of frozen storage.     

Fatty acid and amino acid composition of three local Malaysian Channa spp. fish

The objective of this current study was to analyze the biochemical compositions of three Malaysian Channa spp. fish. The proximate analysis revealed that the protein content of Channa lucius, Channa micropeltes and Channa striatus was 19.9%, 22.1%, 23.0% (% of dry weight), respectively. The total lipid content was generally high, ranging from 5.7% to 11.9% and crude ash ranged from 1.0% to 1.8%. The major amino acids were glutamic acid, aspartic acid and lysine, ranging from 9.7% to 21.7%, and the most abundant fatty acid in Channa spp. was C16:0, ranging from 25.6% to 30.4%. The other major fatty acids detected were C22:6, C18:1 and C18:0. The level of arachidonic acid (C20:4) was unusually high in C. striatus (19.02%). The levels of DHA in these fish would also explain the use of Channa spp., especially C. striatus, which has been used for centuries for reducing pain, inflammation and promote wound healing in Malaysia.     

Variations in essential oil and fatty acid composition during Myrtus communis var. italica fruit maturation

The essential oil and fatty acid composition of Myrtus communis var. italica fruit during its ripening was determined. The effect of the harvesting time on some physical properties of Myrtus fruits, fruit weight and moisture content, were significant. The increase of fruit weight (from 2.54 to 8.79 g% fruits) during ripeness was correlated positively with that of moisture content (from 28% to 72%). Fruit essential oil yields varied from 0.003% to 0.01% and showed a remarkable increase at 60 days after flowering to reach a maximum of 0.11%. Forty-seven volatile compounds were identified in fruit essential oils; 1,8-cineole (7.31–40.99%), geranyl acetate (1.83–20.54%), linalool (0.74–18.92%) and α-pinene (1.24–12.64%) were the main monoterpene compounds. Total fatty acid contents varied from 0.81% to 3.10% during fruit maturation and the predominant fatty acids were linoleic (12.21–71.34%), palmitic (13.58–37.07%) and oleic (6.49–21.89%) acids. The linoleic acid proportions correlated inversely with palmitic and oleic acids during all the stages of ripening.     

Muscle lipids and fatty acid profiles of three edible fish from the Mauritanian coast: Epinephelus aeneus, Cephalopholis taeniops and Serranus scriba

Muscle lipids and fatty acids (FA) of three largely consumed seawater species of Serranidae (Epinephelus aeneus, Cephalopholis taeniops, and Serranus scriba) from the Mauritanian coast, were determined through 1 year. The lipid contents were relatively poor, ranging from 0.8% to 2.3% showing a significant seasonal dependency. Amongst the 35 FA identified, 35–51% were saturated FA (SFA), 21–33% monounsaturated FA (MUFA), and 18–34% polyunsaturated FA (PUFA). Palmitic acid was found to be the main SFA, and was seasonal dependent, with a mean value of 30.5% for E. aeneus, 27.9% for C. taeniops, and 20.9% for S. scriba. Amongst MUFA, oleic acid, with 11–16%, was the main acid in all three species. The n6 PUFA level was low, in particular for C. taeniops (1.3–1.6%), and a little higher for S. scriba (3.6–4.2%). The three species were characterised by high amounts of n3 PUFA. Amongst them, docosa-4,7,10,13,16,19-hexaenoic acid (DHA, 22:6n3) was the highest with 5–9% for C. taeniops, 13–17% for S. scriba, and 10–16% for E. aeneus. Eicosa-5,8,11,14,17-pentaenoic acid (EPA, 20:5n3), was the second highest n3 PUFA, with 4–13%.     

Feeding feedlot steers fish oil alters the fatty acid composition of adipose and muscle tissue

Sixteen steers (441±31.7kg initial body weight) consumed two high concentrate diets with either 0 or 3% fish oil to determine the impact of fish oil, an omega-3 fatty acid source, on the fatty acid composition of beef carcasses. Collected tissue samples included the Longissimus thoracis from the 6th to 7th rib section, ground 10th to 12th rib, liver, subcutaneous adipose tissue adjacent to the 12th rib, intramuscular adipose tissue in the 6th to 7th rib sections, perirenal adipose tissue, and brisket adipose tissue. Including fish oil in the diet increased most of the saturated fatty acids (P<0.01) and proportions of polyunsaturated fatty acids (P<0.06), and decreased (P<0.01) proportions of monounsaturated fatty acids. Dietary fish oil increased (P<0.01) levels of omega-3 fatty acids in sampled tissues, resulting in lower (P<0.01) omega-6:omega-3 ratios. The weight percentages of C20:5 and C22:6 in tissue may provide the recommended daily allowance for humans. Fish oil may have a role in beef niche marketing if there are no deleterious effects on consumer satisfaction.     

Seasonal variation in the fatty acid composition of three Mediterranean fish – sardine (Sardina pilchardus), anchovy (Engraulis encrasicholus) and picarel (Spicara smaris)

The total fat contents and the fatty acid compositions of three common Mediterranean fish, namely sardine (Sardina pilchardus), anchovy (Engraulis encrasicholus) and picarel (Spicara smaris) were determined at bimonthly intervals for a one-year period. The purpose of this work was to study the seasonal variation of the fatty acids in the three fish that are some of the best sources of n − 3 fatty acids. The fat and fatty acid content of the investigated fish species show a significant seasonal dependency. Two of the fish (anchovy and picarel) have the highest fat content during the late winter – spring period. On the other hand, sardine shows the highest fat concentrations during the spring-early summer period. The fish that showed the highest variation in fatty acid composition was the anchovy. The sardine was found to be the best source of n − 3 fatty acids during the one-year period (35.35 g/100 g fatty acids). Finally the picarel had the highest oleic acid content (on average, 13.89/100 g fatty acids).     

The effect of replacing dietary fish oil with canola oil on fatty acid composition and expression of desaturase and elongase genes in Jade Tiger hybrid abalone

This study investigates the effect of graded substitution of dietary fish oil (FO) with canola oil (CO) on fatty acid composition and expression of Δ-6 desaturase and elongase 2 genes in the muscle of Jade Tiger hybrid abalone. The control diet contained 1.5% FO supplement (0% CO). Four other diets contained FO/CO in ratios of 3:1 (CO 25%), 1:1 (CO 50%), 1:3 (CO 75%) and 100% CO. The result demonstrated that abalone fed the diets supplemented with 25% and 50% CO showed similarly high levels of total omega-3 polyunsaturated fatty acid (n-3 PUFA), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) (P < 0.05) as the 0% CO group. The highest levels of total PUFA and total monounsaturated fatty acids were found in the 100% CO group (P < 0.05). The results also showed that Δ-6 desaturase and elongase 2 gene expression was increased in a graded manner by increasing dietary CO (P < 0.05). It was concluded that replacement of FO by CO at the levels of 25-50% can improve the contents of health-benefiting EPA and DHA in abalone.     

Direct quantification of fatty acids in dairy powders with special emphasis on trans fatty acid content

In this study a validated procedure for accurate determination of fatty acids in dairy products, with special emphasis on total trans fatty acids (TFA) content is presented. Dairy fat naturally contains 4–6% of trans fatty acids, mainly trans-octadecenoic acids (i.e. vaccenic acid), and 0.3–1.5% of conjugated linoleic acids (CLA). The proposed procedure does not require lipid extraction, and transesterification of lipids could be carried out directly on dairy products. Optimal analytical conditions have been developed to allow accurate determination of TFA content without prior fractionation of cis/trans FAME isomers by thin-layer chromatography. The methodology requires the use of a highly polar open tubular capillary column having at least 100 m length. CLA and other fatty acids from C4:0 (butyric) acid to long-chain polyunsaturated fatty acids (LC-PUFAs) could also be analyzed. Therefore, the methodology presented is versatile and could be used for both targeted analysis (e.g. determination of TFA in dairy products) and determination of the broad fatty acid profile in dairy products.     

The influence of feed supply time on the fatty acid profile of Nile tilapia (Oreochromis niloticus) fed on a diet enriched with n-3 fatty acids

The purpose of the study was to examine the fatty acid profiles of Nile tilapia (Oreochromis niloticus) submitted to different feeding times (0, 10, 20 and 30 days) on a diet enriched with n-3 fatty acids, by addition of flaxseed oil in substitution for sunflower oil. The main fatty acids detected were palmitic (C16:0), stearic (C18:0), oleic (C18:1n9), linoleic (C18:2n6) and -linolenic (C18:3n3) in all the treatments. The 30 day-fed fish presented the best values for total n-3 fatty acids, with a prominence of -linolenic acids, showing that the flaxseed oil as well as the feed supply time influenced the fatty acid profiles.     

Nutritional and sensory aspects of light lamb meat enriched in n−3 fatty acids during refrigerated storage

Fatty acid content and sensory characteristics of meat from light lambs fed three diets supplemented with different sources of n−3 fatty acids (fish oil, extruded linseed and extruded linseed plus microalgae) and a control diet during refrigerated storage have been studied. The meat from lambs fed linseed diets had the highest levels of C18:3 n−3, while animals fed fish oil had the highest long-chain n−3 polyunsaturated fatty acids (PUFA). Thus, 100 g of meat from lamb fed the fish oil diet provided 183 mg of long-chain n−3 PUFA, representing 40% of the daily recommended intake. The levels of n−3, n−6 and long-chain n−3 PUFA decreased during a 7-day storage period. The meat from lambs fed the fish oil diet had high scores of fish odour and flavour and rancid odour and flavour and the lowest overall liking. Rancid odour and flavour increased after storage, mainly in supplemented groups.     

Effects of antioxidants on heat-induced trans fatty acid formation in triolein and trilinolein

To elucidate the relation between heat-induced cis/trans isomerisation and thermal oxidative degradation of double bonds in unsaturated lipids, we investigated the effects of several edible antioxidants on these two molecular structural changes of double bonds in triolein (cis-9, 18:1) and trilinolein (cis-9, cis-12, 18:2), which were heated at 180 °C. trans Isomerisation and oxidative degradation of each cis double bond in the triacylglycerols during heating were evaluated on the basis of the increase in the amount of trans isomers and decrease in the amount of cis isomers by gas chromatography analysis. The synchronous suppression in trans isomerisation and cis deterioration of double bonds in these triacylglycerols were found by addition of antioxidants, whose inhibitory effects were associated with their kinds and concentrations. When triolein was heated in the presence of antioxidant, suppression of heat-induced trans isomerisation was directly proportional to that of cis deterioration. The results of our analysis suggested that the appropriate addition of antioxidants to edible oils during processing and cooking would facilitate the control of not only thermal oxidative degradation but also heat-induced trans isomerisation of double bonds in unsaturated lipids.     

Quality characteristics of Dutch-style fermented sausages manufactured with partial replacement of pork back-fat with pure, pre-emulsified or encapsulated fish oil

Dutch-style fermented sausages were manufactured with 15% and 30% pork back-fat substitution by pure or commercial encapsulated fish oil, either added as such or as pre-emulsified mixture with soy protein isolate. Adding commercial encapsulated fish oil was the most important factor influencing the chemical composition. The fat content was not significantly different between products (p > 0.05). The n−6/n−3 ratio decreased from 8.49 in controls to 0.90-2.47 in modified products. Lipid oxidation parameters (propanal and hexanal) showed much higher values for sausages with pure fish oil than for products with encapsulated oil. For the latter, lipid oxidation was similar to controls. Products with encapsulated or pre-emulsified oil were significantly firmer than products from other treatments in physical and sensory analysis (p < 0.05). Overall, it is technologically feasible to enrich dry fermented sausages with n−3 fatty acids from fish oil and the application of commercial encapsulated fish oil seems to be the best in retaining overall quality.     

Chemical,amino acid and fatty acid composition of Sterculia urens L. seed

The chemical, amino acid and fatty acid compositions of Sterculia urens seeds are reported. The cotyledons were found to be rich in protein (30.88%) and lipids (39.2%). The major amino acids in defatted Sterculia urens cotyledon flour (DSCF) were determined as glutamic acid, arginine and aspartic acid. Cysteine, methionine, tyrosine and histidine were observed in minor quantities. The ratio of essential to non-essential amino acids was observed to be 0.45. Among the essential amino acids, isoleucine was found to be higher than the reported FAO/WHO requirements. The GC-FID and GC–MS analysis revealed that the major fatty acids of the total lipid were stearic acid (31.72%), linoleic acid (28.83%) and palmitic acid (26.79%). Eicosadienoic acid (4.98%) and eicosatrienoic acid (2.96%) were also found in the total lipid.     

Total lipid content, fatty acids and 4-desmethylsterols accumulation in developing fruit of Pistacia lentiscus L. growing wild in Tunisia

This research has determined oil, fatty acid and sterol contents of the Tunisian Pistacialentiscus (Lentisc) fruits during maturation. Low oil accumulation was observed during the first 35 days after the fruiting (DAF) date (from 1.83% to 2.57%). After that, two phases were distinguished (35th until the 60th and 105th to the 145th DAF), where the rate of oil accumulation increased significantly. At the last stage of maturation, the lentisc fruits had the highest percentage of lipid content, 42.54%. The changing profile of fatty acids during maturation had been marked mainly by an increase in oleic acid content (from 19.49% to 50.72%) paralleling a decrease in linoleic acid content (from 42.5% to 21.75%). At the 15th DAF, the alpha-linolenic acid was found with a maximum of 13.81%. At full maturity, the main fatty acids were oleic acid, followed by palmitic and linoleic acid. Other fatty acids were present in trace proportions, such as palmitoleic, stearic, linolenic, gadoleic and arachidic acid. In all stages of ripening only four sterols were identified and quantified. β-Sitosterol was the major 4-desmethylsterol in samples tested, followed by campesterol. Cholesterol and stigmasterol were detected in trace amounts. During the first stage of ripening, the amount of total sterols was about 5.19/100 g of oil. It decreased to 0.43/100 g in the last stage. Sitosterol and campesterol showed nearly the same profile during the ripening of P. lentiscus fruit which could be linked to the relation between these compounds during their biosynthesis.     

Heterotrophic growth and nutritional aspects of the diatom Cyclotella cryptica (Bacillariophyceae): Effect of some environmental factors

To investigate the nutritional value of the diatom Cyclotella cryptica (Reimann, Lewin, and Guillard) as an alternative feed for use in the aquaculture industry, the heterotrophic growth characteristics and resultant fatty acid profile of the microalga were studied when cultivated under a variety of controlled salinity and temperature conditions. In addition, the effects of pH on the growth characteristics were also studied. The maximum specific growth rate was affected by initial pH and cultivation temperature, but not by salinity. The optimal pH and temperature ranges for growth were 7.2 to 8.1 and 22.5 to 25.0 °C, respectively. Lipid accumulation and the fatty acid composition were also affected by cultivation temperature and salinity. The optimal temperature range and salinity level for lipid accumulation were 18.0 to 25.0 °C and 11.2 psu, respectively. In all cases the fatty acid distribution was similar, with the most abundant fatty acids being palmitic acid (16:0), palmitoleic acid (16:1 n-7), stearidonic acid (18:4 n-3, SDA), eicosapentaenoic acid (20:5 n-3, EPA), and decosahexaenoic acid (22:6 n-3, DHA).     

Roles of lipid oxidation and pH on properties and yellow discolouration during storage of film from red tilapia (Oreochromis niloticus) muscle protein

Protein-based films prepared from red tilapia (Oreochromis niloticus) washed and unwashed mince solubilised at pH 3 and 11 were prepared and characterised. Tensile strength (TS) of films from washed mince was greater than that of films prepared from unwashed mince for both pH used (P < 0.05). TS of films prepared at pH 3 was higher than that of films prepared at pH 11 for both of washed and unwashed mince (P < 0.05). Film from washed mince with pH 3 showed the highest TS, while that from unwashed mince with pH 11 had the lowest TS with the highest elongation at break (EAB) (P < 0.05). Films from washed mince had the lower value of thiobarbituric acid reactive substances (TBARS) than did those from unwashed counterpart, regardless of pH used. Nevertheless, TBARS was much higher in films prepared at acidic pH, compared with those prepared at alkaline pH. During storage of 20 days at room temperature, films became yellowish as evidenced by the increases in b^∗ and ΔE^∗-values. Films prepared at pH 11 showed the higher b^∗ and ΔE^∗-values than did those prepared at pH 3, especially for those from unwashed mince. However, films prepared from washed mince at pH 3 showed higher b^∗ and ΔE^∗-values than did those prepared at pH 11 (P < 0.05). Films generally had the increase in TS but the decreases in water vapour permeability (WVP), film solubility and protein solubility after 20 days of storage (P < 0.05). Therefore, lipid oxidation more likely played a role in yellow discolouration of fish muscle protein film, mainly by providing the carbonyl groups involved in Maillard reaction, while pH regulated the rate of reaction.     

Preparation of eicosapentaenoic acid concentrates from sardine oil by Bacillus circulans lipase

An extracellular lipase derived from Bacillus circulans, isolated from marine macroalga, Turbinaraia conoides, was used to prepare n-3 polyunsaturated fatty acid (PUFA) concentrates from sardine oil triglycerides. The enzyme was purified 132-fold with specific activity of 386 LU/mg. The purified lipase was able to enrich sardine oil with 37.7 ± 1.98% 20:5n-3 and 5.11 ± 0.14% 18:3n-3 in the triglyceride fraction after 3 h of hydrolysis. Lower hydrophobic constants of n-3 fatty acids (18:3n-3_logP = 5.65; 20:5n-3_logP = 5.85, respectively) than n-6 (20:4n-6_logP = 6.16) resulted in higher hydrolytic resistance of the former toward lipase, leading to their enrichment in the triglyceride fraction. Lipase-catalysed hydrolysis of sardine oil for 3 h, followed by urea complexation, provided free fatty acids containing 51.3 ± 4.65% 20:5n-3. The purified methyl ester of 20:5n-3 (68.29 ± 2.15%) from the urea concentrate was attained by chromatography on argentated neutral alumina.