Influence of diets enriched with flaxseed oil on the α-linolenic, eicosapentaenoic and docosahexaenoic fatty acid in Nile tilapia (Oreochromis niloticus)

This study examined the effects of different levels of flaxseed oil in increasing the α-linolenic (LNA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids contents in tilapias raised in captivity. Nile tilapia were raised in captivity for a period of five months, receiving increasing levels (0%; 1.25%; 2.50%; 3.75% and 5.00%) of flaxseed oil in substitution for sunflower oil (control). No significant differences (P>0.05) of moisture or total lipids contents were found among fillets from tilapia fed the different diets. Analyses of the fatty acid methyl esters (FAMEs) were quantitatively measured by capillary gas chromatography against a C_23:0 internal standard. Increases of the concentration of LNA, EPA and DHA (in mg/g of total lipids), were well established in the fillets, with a significant difference (P<0.05) among all the treatments, as the replacement of the sunflower oil by flaxseed oil was increased.     

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.     

Effects of cooking and reheating methods on the fatty acid profile of sea bream treated with rosemary extract

BACKGROUND: The effects of rosemary extract on the fatty acid profile of sea bream fillets cooked by different methods (oven baking, grilling and pan frying) as well as the effects of different reheating methods (microwave and conventional oven) on the fatty acid composition of fish after frozen storage for 4 months were investigated. RESULTS: The proportion of saturated fatty acids increased only slightly in fried samples but significantly in oven‐baked and grilled samples, while the proportion of polyunsaturated fatty acids (PUFAs) increased significantly in fried samples but only slightly in oven‐baked and grilled samples. The proportion of monounsaturated fatty acids remained relatively constant after cooking. Of the fatty acids analysed, the most significant increases (P < 0.05) were observed in C18:1n‐9 and C18:2n‐6 and the most significant decreases (P < 0.05) in C14:0, C16:1, C20:5n‐3 and C22:6n‐3. Although sea bream fillets fried in sunflower oil showed an increase in PUFAs, the lowest eicosapentaenoic and docosahexaenoic acid contents were found in fried samples. CONCLUSION: Sea bream fillets treated with rosemary extract showed slower oxidation than untreated fish. Neither conventional nor microwave reheating after frozen storage for 4 months had a detrimental effect on the fatty acid profile and its stability. Copyright © 2009 Society of Chemical Industry     

Enhancement of Omega-3 Fatty Acid Content in Rainbow Trout (Oncorhynchus mykiss) Fillets

ABSTRACT:  A commercial diet for rainbow trout ( Oncorhynchus mykiss ) was supplemented with 0 (control), 8.5%, or 15.0% (w/w) of flaxseed oil (FO). Trouts were harvested on days 0, 30, 60, 90, and 120. Boneless skinless trout fillets were recovered from fish and analyzed for fatty acid profile (FAP) and total fat. While the total fat levels of fillets were not ( P > 0.05) affected by FO supplementation, the FAP was. The lowest ( P < 0.05) proportion of saturated fatty acids was obtained from 15%, followed by 8.5% FO group, and the control group. The opposite results were observed for the unsaturated fatty acids. The highest ( P < 0.05) content of omega-3 fatty acids (ω-3 FA) in fillets was determined in the 15.0%, followed by the 8.5% FO group, and the control group. While the 15.0% and 8.5% of FO supplementation increased ( P < 0.05) concentration of linolenic acid (ALA, 18:3n3) in fillets, the eicosapentaenoic (EPA, 20:5n3) and docosahexaenoic acids (DHA, 22:6n3) contents decreased ( P < 0.05). At the same time, higher ( P < 0.05) concentration of linoleic (L, 18:2n6) and lower ( P < 0.05) concentration of arachidonic acids (AN, 20:4n6) in fillets were obtained in the 15.0% FO group compared with the control group. The ω-3/ω-6 FA ratio was also improved ( P < 0.05) by supplementing basal diet with 15.0% FO. Our results suggest that trout fillets with enhanced content of ω-3 FA can be developed from trout raised in aquaculture systems fed diets supplemented with 15.0% FO. These fillets could be a basis to develop novel functional aquatic foods for some niche markets.     

The effect of a flaxseed oil-enhanced diet on the product quality of farmed brook trout (Salvelinus fontinalis) fillets

Abstract: The effects of dietary modification with flaxseed oil‐enhanced (Flax) feed on the product quality of brook trout fillets were examined. Trout were fed a commercial feed supplemented with fish oil (CD) or flaxseed oil (Flax) for 165 d before harvesting. Proximate composition and fatty acid profile were determined on fillets. Quality parameters of the raw fillets were examined over the storage period by measuring color (L*, a*, b*), muscle pH, and thiobarbituric acid reactive substances test. Evaluations on the cooked fillets included sensory evaluation with triangle tests and a paired preference test. There were no differences in proximate composition between the groups; however, the total omega‐3 fatty acids were greater in Flax fillets (P < 0.05). Diet and day were shown to interact in their effect on whiteness, pH, and lipid oxidation (P < 0.05); however, linear regression did not determine that malondialdehyde concentration was associated with time in either diet type implying that lipid oxidation in the vacuum‐packed fish was controlled at storage temperatures (4°C). Sensory panelists were able to choose the odd sample in a replicated triangle test analyzed using the β‐binomial model, and there was preference for Flax fillets (P < 0.05). Results indicate that a Flax‐enhanced diet would have favorable effects on product quality of farmed brook trout.     

Polyunsaturated fatty acid levels in rat tissues after chronic treatment with dietetic oils

BACKGROUND: The essential fatty acids can be helpful in the prevention of several pathologies. The purpose of this study was to quantify the major n‐3 and n‐6 fatty acids in tissues of rats fed with flaxseed oil and with a dietetic oil in order to evaluate how their chronic supplementation could influence the correspondent in vivo levels and to study the effectiveness of the dietetic oil compared to flaxseed oil. RESULTS: Fatty acids were successfully extracted from biological samples, subjected to derivatization procedure and analysed by high‐performance liquid chromatography with UV detection under gradient elution mode. The developed method showed good linearity, precision and accuracy, with recoveries ranging from 89% to 92%. Animals treated with flaxseed and dietetic oils showed enhanced levels of n‐3 fatty acids compared to control groups, with significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid in the brain and in the adipose tissue of the dietetic group compared to the flaxseed group. CONCLUSION: The obtained data underline that the tested oils can effectively enhance the tissue levels of n‐3 fatty acids and therefore they could be successfully used in the dietetic treatment of lipid‐related diseases. Copyright © 2011 Society of Chemical Industry     

Effects of differences in diet and seasonal changes on the fatty acid composition in fillets from farmed and wild sea bream (Sparus aurata L.) and sea bass (Dicentrarchus labrax L.)

The effects of dietary fatty acids and seasonal variation on the fatty acid profiles of farmed and wild sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) were determined by analysis of their fillets. Farmed sea bream and sea bass were fed on the same commercial feeds all year. Fatty acid profiles in the fillets reflected the fatty acid profiles of the commercial feeds. The predominant fatty acids in the trial feeds, fillets of farmed and wild sea bream and sea bass were 16:0, 18:1n‐9, 18:2n‐6, 20:5n‐3 and 22:6n‐3. The fatty acid profiles in the fillets of farmed sea bream and sea bass did not differ (P > 0.05) except in the winter season compared with those of their wild counterparts. However, the content of eicosapentaenoic acid (20:5n‐3), docosahexaenoic acid (22:6n‐3) in the fillets of the farmed and wild sea bass were significantly (P < 0.05) higher than the farmed and wild sea bream. The wild sea bream had significantly (P < 0.05) higher total saturated fatty acid and monounsaturated fatty acid (MUFA) levels, and lower total n‐6 and n‐3 polyunsaturated fatty acid (PUFA) levels in winter than in the summer and spring seasons. Similarly, in the fillets of wild sea bass, total n‐3 PUFA levels were significantly (P < 0.05) lower, and the MUFA levels were higher in winter than in the other seasons. These results indicate that the farmed fish fillets were good sources of n‐3 PUFA in each of the three seasons. However, wild fish were good sources of n‐3 PUFA in the spring and summer.     

Comparative assessment of proximate composition,physicochemical parameters,fatty acid profile and mineral content in farmed and wild rainbow trout (Oncorhynchus mykiss)

This study was conducted to determine differences between farmed and wild rainbow trout in terms of proximate and fatty acid composition, physicochemical parameters and mineral content. Fat content of farmed fish fillets was higher, while moisture content was lower than wild fish. However, wild fish had higher pH value and water‐holding capacity comparing to farmed fish. The muscle lipids of farmed fish contained higher proportions of 20:0, 18:1n‐9 and 20:1n‐9; and lower proportions of 18:2n‐6, 20:2cis, 18:3n‐3, 20:3n‐6, 20:4n‐6, 20:5n‐3 and 22:6n‐3 fatty acids than wild fish. The percentage of total saturated fatty acids (SFAs) was similar in both fish. Total polyunsaturated fatty acids (PUFAs), n‐3 PUFAs and n‐3/n‐6 PUFAs ratio were higher in the wild fish comparing to farmed fish, whereas its total monounsaturated fatty acids (MUFAs) and n‐6 PUFAs contents were lower. Among the seventeen minerals analysed in fish flesh, differences existed between farmed and wild rainbow trout in Ca and Fe contents. Moreover, toxic trace minerals (As, Cd, Pb and Hg) were all present in amounts below their toxic levels. The differences observed between farmed and wild fish may be attributed to the diet constituents and environmental conditions of the fish.     

EVALUATION OF PROCESSING, PRESERVATION AND CHEMICAL AND FATTY ACID COMPOSITION OF NILE TILAPIA WASTE

In this experiment, the heads of Nile tilapia were used as a raw material to produce flour through cooking, grinding, drying and sieving processes. The flour obtained was stored for 90 days in a refrigerator and shelf time was monitored by chemical methods (acid number [AN] and thiobarbituric acid [TBA] test), fatty acid composition and microbiological methods. The proximate composition was: moisture (6.01%), ash (19.38%), proteins (38.41%) and total lipids (35.46%). Thirty-six fatty acids were found in the lipidic fraction. The predominant ones were 16:0, 18:1n-9 and 18:2n-6. The fatty acids of the series n-3, 18:3n-3 (alpha-linolenic acid), 18:2n-6 (linolenic acid), 20:5n-3 (eicosapentaenoic acid) and 22:6n-3 (docosahexaenoic acid) were found in smaller proportion. No changes were detected in the flour stored for 90 days as to polyunsaturated fatty acids and microbiological analysis. The AN remained constant up to 60 days of storage and TBA values increased throughout the 90-day storage.

PRACTICAL APPLICATIONS

Waste Nile tilapia heads are not commonly used in human feeding and, therefore, are discarded. In this experiment, Nile tilapia heads were used as a raw material to produce tilapia flour; it was stored in a refrigerator and the shelf time was monitored for 3 months by chemical and microbiological methods. The flour is a caloric food, has high lipid content with omega-3 fatty acids, minerals, proteins and can be used as human feeding.     

Influence of diets enriched with different vegetable oils on the fatty acid profiles of snail Helix aspersa maxima

The proximate analyses and fatty acid profiles of snail (Helix aspersa maxima) muscle submitted to different feedings with diets enriched with 3% of different vegetable oils (canola, soybean, flaxseed, sunflower, maize and rice) were analysed. The lowest value of lipids was in the snail muscle of the treatment enriched with soybean oil. The main fatty acids detected were palmitic (C16:0), oleic (C18:1n9) and linoleic (LA, C18:2n6) in all treatments. The highest value for linolenic acid (LNA, C18:3n3) was observed in muscle of snail fed with enriched diet of flaxseed (oil also high in LNA).     

Effect of chitosan–Jicama starch coating on changes in qualities of fresh Nile tilapia (Oreochromis niloticus) fillets during ice storage

The effect of chitosan (0.5%)/Jicama starch (0%–4%)‐based edible coating on the quality of Nile tilapia (Oreochromis niloticus) fillets was evaluated over ice storage time. All samples were periodically analysed for pH value, thiobarbituric acid (TBA), total volatile basic nitrogen (TVB‐N), electrical conductivity (EC), total viable counts (TVC), total psychrotrophic counts (TPC), drip loss, colour, hardness and sensory characteristics. Results demonstrated that the quality of Nile tilapia fillets was preserved by the film containing chitosan and/or Jicama starch. Compared with chitosan coating alone (0.5% chitosan/0.25% glycerol) (P < 0.05), T3 (0.5% chitosan/1% Jicama starch/0.25% glycerol) had a better effect on the drip loss, TBA, TVC, TPC, hardness and sensory characteristics of the samples, thus indicating that low Jicama starch concentration (1%) enriched the coating ability of chitosan in extending the shelf life of Nile tilapia fillets.     

LIPID CHANGES IN FROZEN STORED FILLETS FROM PRE- AND POSTSPAWNED HAKE (MERLUCCIUS HUBBSI MARINI)

The lipid composition of frozen stored fillets from pre‐ and postspawned hake was studied. The total lipid (TL) content in the chloroform/methanol extract from unfrozen postspawned hake was four times higher than that of prespawned fish. After freezing, the TL content of postspawning hake muscle remained unchanged whereas the TL extracted from prespawning fish muscle increased about 90%. The TL extractability of muscle from fish in both different gonadal conditions was not affected by frozen storage. Lipolysis in frozen stored fillets from prespawned hake occurs principally by hydrolytic action on phospholipids (PL), and phosphatidylcholine was the main PL hydrolyzed. Triacylglycerols were the main substrates hydrolyzed in frozen stored fillets from postspawned hake. Freezing and frozen storage affected polyenoics and n‐3 fatty acids (FA). The decrease in the contents of n‐3 FA in fillets from postspawned hake was lower than that observed in fillets from prespawned fish.     

Impact of UV‐C Light on the Fatty Acid Profile and Oxidative Stability of Nile Tilapia (Oreochromis niloticus) Fillets

The influence of different ultraviolet (UV‐C) doses (0.103 and 0.305 J/cm²) was investigated by instrumental color parameters, pH, lipid, and protein oxidations, fatty acids (FA) composition and biogenic amines (BAs) in Nile tilapia fillets during 11 d at 4 ± 1 °C. The UV‐C treatment increased (P < 0.05) a^* values and protein oxidation in a dose‐dependent manner, and delayed (P < 0.05) the formation of BAs over the course of the storage period. L^* values and lipid oxidation were not influenced (P > 0.05) by UV‐C light. Fillets treated with a low UV‐C dose exhibited greater (P < 0.05) total polyunsaturated fatty acid (PUFA) than their untreated counterparts. Therefore, a low UV‐C dose can be recommended in tilapia fillets as an alternative processing method to control pH and BAs, as well as improve the total PUFA amount and overall nutritional quality.     

The effects of fish oil-enriched diets on growth,feed conversion and fatty acid content of red hybrid tilapia, Oreochromis sp.

Juvenile, red hybrid tilapia were fed diets containing cod liver oil (0%, 4%, 8%, 12% of total diet) substituted against corn oil. After 10 weeks, no significant differences between treatments were seen in weight gain, specific growth rate, feed conversion ratio, whole body or dorsal muscle (fillet) proximate composition. Gas chromatography revealed significant differences in the total n-3 content and fatty acid profiles of dorsal muscle. The total n-3 content of dorsal muscle increased from 7.6% to 18.6%, total n-6 content fell from 37.5% to 12.9% and docosahexanaenoic acid increased from 5.8–16.1% of total fatty acids, in fish fed 0% and 12% fish oil, respectively. The retention of eicosapentaenoic acid was low in all dietary groups, possibly indicating selective use as a substrate for β-oxidation. The results demonstrate the potential to enhance the total n-3 fatty acids and docosahexaenoic acid in tilapia fillets by increasing dietary fish oil.     

Change in proximate, amino acid and fatty acid contents in muscle tissue of rainbow trout (Oncorhynchus mykiss) after cooking

Changes in proximate, amino acid and fatty acid composition of farmed, commercially important rainbow trout (Oncorhynchus mykiss) after conventional and microwave cooking were analysed. Rainbow trouts cooked in microwave ovens had statistically significant higher total protein, total fat, and ash than electrical oven‐cooked samples. The amounts of essential and nonessential amino acids were not different between cooking methods, but the difference between raw and cooked samples was significant. Lysine, leusine, methionine, threonine, valine, arginine and histidine were found most in microwave‐cooked rainbow trouts whereas isoleucine, tyrosine and phenylalanine were found most in electrical oven‐cooked samples. As total saturated fatty acid and total monounsaturated fatty acids amount were not statistically different between the cooking methods, the difference between raw and cooked fillets was found statistically significant (P < 0.05). There was no statistically significant difference between raw and cooked fillets in total n‐3 and n‐6 contents.     

Quality Properties,Fatty Acids,and Biogenic Amines Profile of Fresh Tilapia Stored in Ice

This work determines quality properties and fatty acids content of Nile tilapia (Oreochromis niloticus) stored in ice for 21 d. The quality properties consist of thiobarbituic acid (TBA), total volatile basic nitrogen (TVB‐N), trimethylamine (TMA), and microbiological analysis (total viable count (TVC), total coliform, Salmonella and Staphylococcus aureus) and determination of biogenic amines content (histamine, cadaverine, putrescine, spermine, spermidine, 2‐phenylethylamine, agmatine, tyramine, and ammonia). Moreover, the fat, moisture, and ash composition as well as fatty acids profile have also been analyzed. The TBA, TVB‐N, and biogenic amines analysis showed rather low levels of spoilage even after 21 d of storage. The microbiological analysis, however, showed that tilapia was unsuitable for consumption after just 10 d. The fat, ash, moisture, and fatty acids profile analysis showed that tilapia is not a good source of n?3 fatty acids. The research indicated that the microbiological analysis was the best method to establish spoilage of tilapia stored in ice, of all analytical methods performed in this study.     

Fatty acid composition in some selected marine fish species living in Turkish waters

The muscle fatty acid (FA) composition of 12 selected marine fish species living in Turkish waters was determined. FA profiles of muscle were compared in terms of total and individual saturated (SFAs) and unsaturated fatty acids. Total SFA, monounsaturated fatty acid (MUFA), n‐3 polyunsaturated fatty acid (n‐3 PUFA) and n‐6 polyunsaturated fatty acid (n‐6 PUFA) contents as well as n‐3/n‐6 FA and eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) ratios differed (P < 0.01) in all fish species. Palmitic acid (16:0) among total SFAs, oleic acid (18:1n‐9) among MUFAs, DHA (22:6n‐3) among n‐3 PUFAs and 18:2n‐6 and 20:4n‐6 among n‐6 PUFAs were the most abundant FAs. The ratio of n‐3/n‐6 PUFA contents, indicating the availability of n‐3 PUFAs that are beneficial for human health, ranged from 2.67 to 12.61. The EPA/DHA ratio was between 0.17 and 0.83 in the marine fish species studied. Copyright © 2005 Society of Chemical Industry     

Effects of feeding micronised flaxseed on yield and composition of milk from Holstein cows

Nine multiparous Holstein cows were used in three 3 × 3 Latin squares to investigate the effects of feeding unheated and micronised flaxseed on milk yield and milk fatty acid composition. Three diets were formulated to meet the nutrient requirement of dairy cows in early lactation: a control diet with no added flaxseed (NFS), an unheated flaxseed diet (UFS) and a micronised flaxseed diet (MFS). The level of flaxseed in UFS and MFS was 70 g kg^?1 of the diet dry matter (DM). Feeding flaxseed to dairy cows had no effect on DM intake or milk yield. However, energy‐corrected milk was higher (P < 0.05) for cows fed MFS than for those fed UFS or NFS. Supplemental flaxseed reduced (P < 0.05) the milk fat percentage without affecting the concentration of milk protein or milk lactose. However, the yield of milk components was not affected by feeding flaxseed. The concentrations of short‐chain (C_4:0 to C_12:0) and medium‐chain (C_14:0 to C_17:0) fatty acids were decreased (P < 0.05) while those of long‐chain fatty acids (C_18:0 to C_18:3) were increased (P < 0.05) in the milk of cows fed UFS and MFS compared with cows fed NSF. Feeding flaxseed to dairy cows can alter the milk fatty acid composition, but only minor effects on milk fatty acid composition can be expected by feeding micronised versus unheated flaxseed. Copyright © 2003 Society of Chemical Industry     

Egg yolk fatty acid profile in relation to dietary fatty acid concentrations

BACKGROUND: The health benefits of n‐3 fatty acids have led to much research on manipulating the fatty acid composition of animal‐derived foods. In this study, two experiments were conducted to investigate the interaction of dietary fatty acids on egg yolk fatty acid concentrations. In experiment I, 32 dietary treatments with three replicates of three birds each were fed for 35 days. Diets were prepared by mixing one type of fish oil with four vegetable oils in different proportions. In experiment II, three different types and two levels of fish oil in combination with two vegetable oils were tested under the same conditions as in experiment I. RESULTS: In experiment I the results showed that the egg yolk saturated (SFA) and monounsaturated (MUFA) fatty acid concentration was determined by the dietary SFA, MUFA and 18:2n‐6 content. The egg 18:2n‐6 concentration was mainly explained by the dietary inclusion of 18:2n‐6 and negatively by the dietary MUFA content. The egg C18:3n‐3, C20:5n‐3 and C22:6n‐3 concentration is almost exclusively determined by their direct supply from the diet. The egg 20:4n‐6 concentration was inversely proportional to the long‐chain n‐3 polyunsaturated fatty acid content of the diet. The results of experiment II showed that the egg yolk C20:5n‐3 and C22:6n‐3 concentration was determined by both the level of dietary fish oil (1 or 2%) and the C20:5n‐3/C22:6n‐3 ratio in the fish oil. CONCLUSION: The results of this study demonstrated that the direct dietary supply of fatty acids is the most important factor determining the egg yolk fatty acid composition, in particular for the n‐3 fatty acids. The interaction effect from other dietary fatty acids was in general small. Copyright © 2011 Society of Chemical Industry     

Fatty acid composition,including isomeric profile of conjugated linoleic acid,and cholesterol in Mertolenga‐PDO beef

This paper describes the fatty acid composition, including the isomeric distribution of conjugated linoleic acid (CLA), total lipids and cholesterol in longissimus dorsi (LD) and semitendinosus (ST) muscles of Mertolenga beef from young bulls reared according to Protected Designation of Origin (PDO) specifications. Mertolenga purebred young bulls (n = 30) were raised in a semi‐extensive production system, including a finishing period on concentrate feeds for the last 5 or 3 months (October and June samplings, respectively). Mertolenga‐PDO beef showed seasonal changes in the levels of some fatty acids (including the predominant 18:2n‐6), sums of trans fatty acids and n‐3 polyunsaturated fatty acids, some CLA isomers (t11,t13, t11,c13 and t10,c12), sums of geometric groups of CLA isomers and total cholesterol. In addition, significant differences were obtained between LD and ST muscles for most of the analysed parameters. From a nutritional perspective, beef‐PDO from June seems to be more healthful than that from October as a consequence of its lower n‐6/n‐3 ratio. Moreover, the results suggest that the polyunsaturated fatty acid/saturated fatty acid ratio in the ST muscle is consistently above the recommended guideline for human diets, although the values were below that guideline for the LD muscle. Taken together, the data indicate that, although the finishing period of Mertolengo young bulls on concentrate attenuates most of the beneficial grass effects on meat fat throughout the year, beef‐PDO from late spring is of greater nutritional value than that from early autumn. Copyright © 2006 Society of Chemical Industry