Discrimination of wild and cultured european sea bass (Dicentrarchus labrax) using chemical and isotopic analyses

Recent legislation in the European Union (EC/2065/2001) requires that seafood must provide the consumer with information that describes geographical origin and production method. The present studies aimed to establish methods, based on chemical and stable isotopic analysis, that could reliably differentiate between wild and farmed European sea bass (Dicentrarchus labrax). The study measured fatty acid and isotopic compositions (delta13C and delta18O) of total flesh oil, delta15N of the glycerol/choline fraction, and compound-specific analysis of fatty acids (delta13C) by isotope ratio mass spectrometry. The sample set comprised 10 wild and 10 farmed sea bass from England (wild) and Scotland or Greece (farmed). Discrimination was achieved using fatty acid composition with 18:0, 18:2n-6, 20:4n-6, and 22:6n-3 providing the highest contributions for discrimination. Principal component analysis of the data set provided good discrimination between farmed and wild sea bass where factor 1 and factor 2 accounted for 60% of the variation in the data.     

Determination of origin of Atlantic salmon (Salmo salar): the use of multiprobe and multielement isotopic analyses in combination with fatty acid composition to assess wild or farmed origin

Variability within the stable isotope ratios in various lipidic fractions and the fatty acid composition of muscle oil has been analyzed for a large sample (171 fish) of wild and farmed Atlantic salmon ( Salmo salar) from 32 origins within Europe, North America, and Tasmania. Sampling was extended over all seasons in 2 consecutive years and included fish raised by different practices, in order to maximize the range of variation present. It is shown that two readily measured parameters, delta 15N measured on choline and delta18 O measured on total oil, can be successfully used to discriminate between fish of authentic wild and farmed origin. However, the certainty of identification of mislabeling in market-derived fish is strengthened by including the percentage of linoleic acid C18:2n-6 in the lipidic fraction. Thus, several apparent misidentifications were found. The combination of these three analytical parameters and the size of the database generated makes the method practical for implementation in official laboratories as a tool of labeling verification.     

Polyunsaturated fatty acid content of wild and farmed tilapias in Thailand: effect of aquaculture practices and implications for human nutrition

The total lipid content and fatty acid composition of the muscle tissue of tilapia (Oreochromis niloticus) and of hybrid red tilapia (Oreochromis sp.) from different culture systems and from the natural and artificial environment of Thailand were compared. Wild fish and fish reared under the most extensive conditions had a more favorable fatty acid profile for human consumption as they contained higher proportions of 18:3n-3, 20:5n-3, and 22:6n-3, higher n-3/n-6 PUFA ratios, and lower proportions of 18:2n-6. The muscle tissue of intensively cultured fish was characterized by increased fat deposition that was mainly saturated and monounsaturated fatty acids and 18:2n-6. It is undesirable for the consumer to reduce 20:5n-3 and 22:6n-3 in farmed tilapia and replace them with elevated 18:2n-6. It is recommended that the amount of 18:2n-6 in the feed of the intensively reared tilapia should be reduced by substituting vegetable oils rich in 18:2n-6 with oils rich in 18:1n-9 and/or 18:3n-3.     

Determination of authenticity, regional origin, and vintage of Slovenian wines using a combination of IRMS and SNIF-NMR analyses

The authenticity and geographical origin of wines produced in Slovenia were investigated by a combination of IRMS and SNIF-NMR methods. A total of 102 grape samples of selected wines were carefully collected in three different wine-growing regions of Slovenia in 1996, 1997, and 1998. The stable isotope data were evaluated using principal component analysis (PCA) and linear discriminant analysis (LDA). The isotopic ratios to discriminate between coastal and continental regions are the deuterium/hydrogen isotopic ratio of the methylene site in the ethanol molecule (D/H)(II) and delta(13)C values; including also delta(18)O values in the PCA and LDA made possible separation between the two continental regions Drava and Sava. It was found that delta(18)O values are modified by the meteorological events during grape ripening and harvest. The usefulness of isotopic parameters for detecting adulteration or watering and to assess the geographical origin of wines is improved only when they are used concurrently.     

Chemometric discrimination among wild and cultured age-0 largemouth bass, black crappies, and white crappies based on fatty acid composition

The potential to distinguish juvenile wild from cultured fishes and to discriminate among juvenile fishes by species based on fatty acid composition was demonstrated. Statistical approaches to data evaluation included analysis of variance, correlation analysis, principal component analysis (PCA), and quadratic discriminant analysis (QDA). Differences were determined between wild and cultured fishes both within and between species and between hatcheries. Fatty acid compositions were compared among individual (not composited) specimens of wild and cultured, age-0, freshwater species: largemouth bass Micropterus salmoides, black crappies Pomoxis nigromaculatus, white crappies P. annularis, and black-nose crappies. Four fatty acids were investigated: linoleic acid (18:2n-6), linolenic acid (18:3n-3), arachidonic acid (20:4n-6), and docosahexaenoic acid (22:6n-3). Linoleic acid was the primary fatty acid used to differentiate juvenile wild from cultured fishes. Concentrations of linoleic acid were significantly different (p < 0.05) in cultured largemouth bass and black crappies from the wild counterparts. Linolenic acid concentrations were not significantly different (p < 0.05) between wild and cultured largemouth bass but were significantly different between wild and cultured black crappies. Wild largemouth bass contained higher concentrations of arachidonic acid than the cultured bass, and concentrations of docosahexaenoic acid were twice as high in wild black crappies than cultured black crappies. On the basis of four signature fatty acids, 90 of 91 juvenile fishes were correctly classified as wild or cultured; 32 of 37 wild juvenile fishes originating from the same reservoir were differentiated by species. Data from the training set were used to classify a test set of fishes as to species, source, or origin with 100% accuracy.     

Classification of gilthead sea bream (Sparus aurata) from 1H NMR lipid profiling combined with principal component and linear discriminant analysis

The combination of (1)H NMR fingerprinting of lipids from gilthead sea bream (Sparus aurata) with nonsupervised and supervised multivariate analysis was applied to differentiate wild and farmed fish and to classify farmed specimen according to their areas of production belonging to the Mediterranean basin. Principal component analysis (PCA) applied on processed (1)H NMR profiles made a clear distinction between wild and farmed samples. Linear discriminant analysis (LDA) allowed classification of samples according to the geographic origin, as well as for the wild and farmed status using both PCA scores and NMR data as variables. Variable selection for LDA was achieved with forward selection (stepwise) with a predefined 5% error level. The methods allowed the classification of 100% of the samples according to their wild and farmed status and 85-97% to geographic origin. Probabilistic neural network (PNN) analyses provided complementary means for the successful discrimination among classes investigated.     

Hydrocarbon and fatty acid composition of cheese as affected by the pasture vegetation type

The determination of the geographical origin of dairy products is an ongoing issue. In this paper the effects of botanical diversity of two pastures on the hydrocarbon and fatty acid composition of cheese fat were studied, over 2 years of experimentation. Two areas in the Italian southwestern Alpine region, dominated by Trifolium alpinum (T) and Festuca nigrescens (F) vegetation, respectively, were chosen, and milk obtained from cows grazing on these pastures was used to produce a semihard traditional cheese. Cheese samples showed a significantly different composition of most linear hydrocarbons, odd-chain (C15, C17, and C17:1) and unsaturated (trans-11,cis-15-C18:2, C18:3, C20:4n-6, C20:4n-3, and 20:5n-3) fatty acids, according to pasture type. The ratio between C(29) and C(27) linear hydrocarbons, unlike the absolute content of the single molecules, showed a good discriminating ability between the two pastures and was little affected by the natural variability due to the climatic and environmental factors.     

Fatty acid profiles of processed chicken egg yolks

The fatty acid compositions of egg yolks subjected to industrial processing treatments, namely, homogenization, pasteurization, drying, and "omega-3-enrichment", were studied. In general, the total contents of C16:0, C18:0, C18:1 n-9, and C18:2 n-6 fatty acids accounted for close to 90% of the total fatty acids. Statistical analysis of the data revealed correlations among the fatty acids; significant differences existed depending on the egg source and type of processing. Yolk samples enriched with omega-3 fatty acids clustered together owing to their higher C16:0, C16:1 n-7, C18:3 n-6, and C24:0 contents. Nonpasteurized/non-heat-treated samples formed another cluster because of their higher C18:1 n-11 and C18:1 n-9 contents, and the remaining samples formed another group due to their higher proportions of C18:0, C18:2 n-6, and C20:4 n-6. The relative proportions of essential fatty acids were similar in the four types of samples examined.     

Application of multielement stable isotope ratio analysis to the characterization of French, italian, and spanish cheeses

The stable isotope ratios (delta13C, delta15N, and delta34S of casein and delta13C and delta18O of glycerol) measured by IRMS of French, Italian, and Spanish cheeses are presented and discussed. Variability factors such as animal-feeding regimen, geographical origin, and climatic and seasonal conditions were studied to check the possibilities of cheese characterization offered by each isotopic parameter. Delta13C values of both casein and glycerol appeared to be strongly correlated to the amount of maize in the animal diet. Delta15N and delta34S of casein proved to be mostly influenced by the geoclimatic conditions of the area (aridity, closeness to the sea, altitude). Delta18O of glycerol was more dependent on the geographical origin of the cheeses and on climatic/seasonal parameters. By applying a multivariate stepwise canonical discriminant analysis, good discrimination possibilities for the different European cheeses were obtained, confirmed by the classification analysis, when >90% of the samples were correctly reclassified.     

Up-regulated desaturase and elongase gene expression promoted accumulation of polyunsaturated fatty acid (PUFA) but not long-chain PUFA in Lates calcarifer, a tropical euryhaline fish, fed a stearidonic acid- and γ-linoleic acid-enriched diet

The limited activity of Δ6 fatty acid desaturase (FAD6) on α-linolenic (ALA, 18:3n-3) and linoleic (LA, 18:2n-6) acids in marine fish alters the long-chain (≥C(20)) polyunsaturated fatty acid (LC-PUFA) concentration in fish muscle and liver when vegetable oils replace fish oil (FO) in aquafeeds. Echium oil (EO), rich in stearidonic acid (SDA, 18:4n-3) and γ-linoleic acid (GLA, 18:3n-6), may enhance the biosynthesis of n-3 and n-6 LC-PUFA by bypassing the rate-limiting FAD6 step. Nutritional and environmental modulation of the mechanisms in LC-PUFA biosynthesis was examined in barramundi, Lates calcarifer , a tropical euryhaline fish. Juveniles were maintained in either freshwater or seawater and fed different dietary LC-PUFA precursors present in EO or rapeseed oil (RO) and compared with FO. After 8 weeks, growth of fish fed EO was slower compared to the FO and RO treatments. Irrespective of salinity, expression of the FAD6 and elongase was up-regulated in fish fed EO and RO diets, but did not lead to significant accumulation of LC-PUFA in the neutral lipid of fish tissues as occurred in the FO treatment. However, significant concentrations of eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (ARA, 20:4n-6), but not docosahexaenoic acid (DHA, 22:6n-3), appeared in liver and, to a lesser extent, in muscle of fish fed EO with marked increases in the phospholipid fraction. Fish in the EO treatment had higher EPA and ARA in their liver phospholipids than fish fed FO. Endogenous conversion of dietary precursors into neutral lipid LC-PUFA appears to be limited by factors other than the initial rate-limiting step. In contrast, phospholipid LC-PUFA had higher biosynthesis, or selective retention, in barramundi fed EO rather than RO.     

Authentication of vegetable oils by bulk and molecular carbon isotope analyses with emphasis on olive oil and pumpkin seed oil

The authenticity of vegetable oils consumed in Slovenia and Croatia was investigated by carbon isotope analysis of the individual fatty acids by the use of gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/IRMS), and through carbon isotope analysis of the bulk oil. The fatty acids from samples of olive, pumpkin, sunflower, maize, rape, soybean, and sesame oils were separated by alkaline hydrolysis and derivatized to methyl esters for chemical characterization by capillary gas chromatography/mass spectrometry (GC/MS) prior to isotopic analysis. Enrichment in heavy carbon isotope ((13)C) of the bulk oil and of the individual fatty acids are related to (1) a thermally induced degradation during processing (deodorization, steam washing, or bleaching), (2) hydrolytic rancidity (lipolysis) and oxidative rancidity of the vegetable oils during storage, and (3) the potential blend with refined oil or other vegetable oils. The impurity or admixture of different oils may be assessed from the delta(13)C(16:0) vs. delta(13)C(18:1) covariations. The fatty acid compositions of Slovenian and Croatian olive oils are compared with those from the most important Mediterranean producer countries (Spain, Italy, Greece, and France).     

Effect of the polyunsaturated fatty acid composition of beef muscle on the profile of aroma volatiles

The effect of n-3 polyunsaturated fatty acids (PUFAs) in beef muscle on the composition of the aroma volatiles produced during cooking was measured. The meat was obtained from groups of steers fed different supplementary fats: (i) a palm-oil-based control; (ii) bruised whole linseed, which increased muscle levels of alpha-linolenic (C18:3 n-3) and eicosapentaenoic acid (EPA, C20:5 n-3); (iii) fish oil, which increased EPA and docosahexaenoic acid (C22:6 n-3); (iv) equal quantities of linseed and fish oil. Higher levels of lipid oxidation products were found in the aroma extracts of all of the steaks with increased PUFA content, after cooking. In particular, n-alkanals, 2-alkenals, 1-alkanols, and alkylfurans were increased up to 4-fold. Most of these compounds were derived from the autoxidation of the more abundant mono- and di-unsaturated fatty acids during cooking, and such autoxidation appeared to be promoted by increased levels of PUFAs.     

褐藻糖胶对黄颡鱼幼鱼中脂肪酸的影响

为研究褐藻糖胶作为饲料添加剂对黄颡鱼幼鱼脂肪酸的影响,选取大小、体重相近的黄颡鱼幼鱼,随机分为对照组和试验组,对照组饲喂不添加褐藻糖胶的基础饲料,试验组饲喂添加0.1%褐藻糖胶的饲料,采用气相色谱质谱联用技术(GC-MS)分析不同喂养时间(1、2、4、8周)下试验组和对照组黄颡鱼幼鱼脂肪酸含量的变化。结果表明,黄颡鱼幼鱼体内共检测出15个总脂肪酸(TFA)和17个游离脂肪酸(FFA)。方差分析结果表明,黄颡鱼幼鱼TFA中C18:1 (n-9)、C20:4(n-5)和C22:6 (n-3)具有交互作用,而大部分FFA间都存在交互作用。喂养时间对黄颡鱼幼鱼脂肪酸有显著影响(P<0.05),随着喂养时间的延长,游离的单不饱和脂肪酸(MUFA)含量呈先减少后增加趋势,而总MUFA含量呈先增加后减少趋势;黄颡鱼幼鱼游离脂肪酸和总脂肪酸中饱和脂肪酸(SFA)均呈先增加后减少趋势,而多不饱和脂肪酸(PUFA)呈先下降后升高趋势。0.1%褐藻糖胶对黄颡鱼幼鱼TFA中C18:1 (n-9)、C20:4(n-5)和C22:6 (n-3)含量影响显著(P<0.05),对FFA组分含量的影响均显著(P<0.05),试验组黄颡鱼幼鱼SFA含量高于对照组,MUFA含量低于对照组,PUFA在喂养第2周时高于对照组,喂养第8周时低于对照组。此外,黄颡鱼幼鱼C20:3(n-3)/C22:6(n-3)的比值小于0.4,且喂养0.1%褐藻糖胶第8周时,黄颡鱼幼鱼C22:6(n-3)和C20:4(n-5)含量明显高于对照组,说明褐藻糖胶有益于黄颡鱼产卵和孵化,有助于黄颡鱼幼鱼的发育生长。本研究结果为黄颡鱼的健康养殖提供了基础数据。     

Triacylglycerol and fatty acid compositions of French virgin olive oils. Characterization by chemometrics

There is no data concerning the fatty acid and triacylglycerol composition of French virgin olive oil. Thus, these compositions were determined using 564 samples coming from four olive harvests (1998-1999 to 2000-2001). Among these 564 samples, 372 came from the four main French cultivars (Aglandau, Cailletier, Picholine, and Salonenque) and from both of the oldest French protected designations of origin: "Nyons" (cv. Tanche) and "Vallée des Baux". The fatty acid compositions took the different isomeric monounsaturated fatty acids (C16:1 and C18:1) into account. The eicosenoic acid is gondoic acid (20:1n-9) and was determined by dimethyl disulfide adduct using GC/MS. The use of propionitrile as a mobile phase for the HPLC analysis of the triacylglycerols led to better resolutions between triacylglycerols than those resolutions obtained with the mix of solvents recommended by the normalized method (acetone/acetonitrile). Of the samples, 88 had a 9-heptadecenoic acid level (17:1n-8) higher than 0.3% and 33 had a linolenic acid level higher than 0.9%, which are maximal values accepted by the International Olive Oil Council and the European Union. A linear discriminant analysis was carried out on 372 samples with the SAS system and particularly with STEPISC and CANDISC procedures. Variables (n = 37) representing the different fatty acids, the sum of saturated, monounsaturated, and polyunsaturated fatty acids, squalene, and triacylglycerols were used, thus allowing us to classify samples into six groups defined with 100% of well classified samples. These results constitute an original data bank that can be used to identify the origin of virgin olive oils.     

Trans fatty acid analyses in samples of marine origin: the risk of false positives

At conditions commonly applied for trans fatty analyses by gas chromatography, fatty acids naturally occurring in marine lipids may overlap chromatographically with C16 and C18 trans fatty acids and lead to false positives. Elution patterns were studied by tracking retention indices at shifting temperature conditions on two cyanopropyl-coated capillary columns. Most overlaps can be avoided by selecting the right chromatographic conditions, but it was not possible to find a single condition that eliminates the risk of overlap between trans fatty acids and interferents. In total, 17 compounds were identified as potential interferents, and the amounts of these compounds were quantified in various samples of marine origin. The interferents that will most likely contribute to incorrect assessments of trans fatty acids in marine lipids are probably 18:3 n-4 and 18:1 n-11.     

Comparison of lipid content and Fatty Acid composition in the edible meat of wild and cultured freshwater and marine fish and shrimps from china

The lipid content and fatty acid composition in the edible meat of twenty-nine species of wild and cultured freshwater and marine fish and shrimps were investigated. Both the lipid content and fatty acid composition of the species were specified due to their unique food habits and trophic levels. Most of the marine fish demonstrated higher lipid content than the freshwater fish, whereas shrimps had the lowest lipid content. All the marine fish and shrimps had much higher total n-3 PUFA than n-6 PUFA, while most of the freshwater fish and shrimps demonstrated much lower total n-3 PUFA than n-6 PUFA. This may be the biggest difference in fatty acid composition between marine and freshwater species. The cultured freshwater fish demonstrated higher percentages of total PUFA, total n-3 PUFA, and EPA + DHA than the wild freshwater fish. Two freshwater fish, including bighead carp and silver carp, are comparable to the marine fish as sources of n-3 PUFA.     

Fatty acid profile of table olives and its multivariate characterization using unsupervised (PCA) and supervised (DA) chemometrics

The fatty acid composition of 67 commercial presentations of table olives was determined. The most abundant fatty acids, in decreasing order of presence, were C18:1, C16:0, C18:2 n-6, and C18:0. The ranges, expressed as grams of fatty acids per 100 g of edible portion, for the different nutritional fractions were as follows: saturated fatty acids, 2.07-5.99; monounsaturated fatty acids, 5.67-19.42; polyunsaturated fatty acids, 0.52-3.87; and trans-fatty acids, 0.08-0.44. Principal component analysis of the matrix of the fatty acid composition led to the deduction of new factors. The first accounted for 55.10% of the total variance and was mainly related to C16:10, C18:0, C20:0, C22:0, C24:0, C18:1, C18:1t, and C20:1. The second factor accounted for 10.33% of variance and was related to C16:1 and C18:2 n-6. They did not permit differentiation among elaboration types or cultivars. However, discriminant analysis was successfully applied for this objective. The fatty acids that most contributed to discriminate among elaboration styles were C17:1, C18:1, C16:0, C17:0, and C18:0 (function 1) and C17:0, C17:1, C20:0, C16:0, C18:1, and C24:0 (function 2). In the case of cultivars, they were C20:0, C18:1, C17:1, C18:2 n-6, C18:1t, and C18:2t (function 1); C18:2 n-6, C18:1, C16:0, C20:0, C18:0, and C18:2t (function 2); and C17:0, C18:3 n-3, and C17:1 (function 3). Results from this study have shown differences among the fatty acid composition and fat content of the diverse commercial presentations of table olives, which can be applied in predictive and classification discriminant analysis.     

Fatty acid composition and antioxidant levels in muscle tissue of different Mediterranean marine species of fish and shellfish

The levels of hydrophilic, lipophilic, and enzymatic antioxidants, as well as the fatty acids composition, of triglyceride and phospholipid fractions were determined in the muscle tissue of 21 species of teleosts, 3 species of cephalopods, and 6 species of crustaceans, just caught from the central Tyrrhenian Sea (Mediterranean Sea). The enzymatic activities and the levels of low-molecular-weight antioxidants, and the percentages of fatty acids, showed marked interspecies differences. Our results showed that total polyunsaturated fatty acids (21.7-61.5%) were the highest, followed by saturated (16.9-41.3%) and monounsaturated (9.1-42.8%) fatty acids. The total n-3 fatty acids content (16.6-57.1%) was found to be higher than the total n-6 fatty acids content (4.1-10.6%). All of the species studied had an n-3/n-6 ratio of more than 1, confirming the great importance of fish and shellfish as a significant dietary source of n-3 polyunsaturated fatty acids and their beneficial role in the Mediterranean type of diet.     

Dietary lipid source modulates in vivo fatty acid metabolism in the freshwater fish, Murray cod (Maccullochella peelii peelii)

The aim of the present investigation was to quantify the fate of C18 and long chain polyunsaturated dietary fatty acids in the freshwater fish, Murray cod, using the in vivo, whole-body fatty acid balance method. Juvenile Murray cod were fed one of five iso-nitrogenous, iso-energetic, semipurified experimental diets in which the dietary fish oil (FO) was replaced (0, 25, 50, 75, and 100%) with a blended vegetable oil (VO), specifically formulated to match the major fatty acid classes [saturated fatty acids, monounsaturated fatty acids, n-3 polyunsaturated fatty acids (PUFA), and n-6 PUFA] of cod liver oil (FO). However, the PUFA fraction of the VO was dominated by C18 fatty acids, while C20/22 fatty acids were prevalent in the FO PUFA fraction. Generally, there was a clear reflection of the dietary fatty acid composition across each of the five treatments in the carcass, fillet, and liver. Lipid metabolism was affected by the modification of the dietary lipid source. The desaturation and elongation of C18 PUFAs increased with vegetable oil substitution, supported by the occurrence of longer and higher desaturated homologous fatty acids. However, increased elongase and desaturase activity is unlikely to fulfill the gap observed in fatty acid composition resulting from decreased highly unsaturated fatty acids intake.     

不同产地海带脂肪酸组成的比较分析

为比较分析不同产地海带的脂肪酸组成,本研究采用溶剂法对海带总脂提取条件进行优化,并通过气相色谱-质谱技术对福州、宁波和青岛3个产地海带的总脂脂肪酸组成进行比较分析。结果表明,二氯甲烷-甲醇法提取海带总脂的效率较高,是海带总脂提取的理想方法;福州、宁波和青岛海带的总脂含量依次为0.75%、0.69%和0.86%,且无显著差异。从海带总脂中共鉴定出30种脂肪酸,以 C16:0、C18:1n-9、C20:4n-6(AA)和C20:5n-3(EPA)为主,且3个产地海带在脂肪酸组成上存在显著差异。福州产地海带中的C20:4n-6和C20:5n-3含量分别为10.12%、6.18%,其中C20:4n-6含量显著高于宁波(9.41%)和青岛(8.77%),C20:5n-3含量显著低于宁波(8.13%)和青岛(9.40%),进而使3个产地海带中的n-3 PUFA、n-6 PUFA、n-3/n-6、EPA+AA和EPA/AA等指标存在显著差异。本研究结果为不同产地海带总脂提取、脂肪酸比较分析及营养评价提供了一定的理论依据。