Solid-phase microextraction method for the determination of volatile compounds associated to oxidation of fish muscle

5 tablas, 5 figurasA procedure for the determination of volatile compounds derived from lipid oxidation of fish muscle samples is presented. Analytes are concentrated on a solid-phase microextraction fiber employed in the headspace mode (HS-SPME), and selectively determined using gas chromatography in combination with mass spectrometry (GC–MS). The influence of several parameters on the efficiency of microextraction such as type of fiber, volume of sample, time, temperature, salting-out effect and stirring was systematically investigated. A saline extraction of fish muscle followed by incubation on a Carboxen-polydimethylsiloxane fiber during 30 min at 60 °C gave the most effective and accurate extraction of the analytes. Quantification of them was performed by MS in the selected ion monitoring mode and by the internal standard method. Satisfactory linearity, repeatability and quantification limits were achieved under these conditions. The method was applied to the determination of the volatile compounds associated to oxidation of Atlantic horse mackerel (Trachurus trachurus) minced muscle and excellent correlations were obtained with chemical indexes for monitoring lipid oxidation as peroxide value and thiobarbituric acid reactive substances. This combined technique is fast, simple, sensitive, inexpensive and useful to monitor target compounds associated to fish rancidity as 1-penten-3-ol, 2,3-pentanedione or 1-octen-3-olThis work was performed within the research project PPQ2003-06602-C04-03 and the Integrated Research Project SEAFOODplus, contract No FOOD-CT-2004-506359. The financing of this work by the Spanish Ministry of Science and Technology and the European Union is gratefully acknowledgedPeer reviewe

Diseño de ingredientes antioxidantes de origen natural y su aplicación en la estabilización de productos derivados de la pesca

335 páginasMinisterio de Ciencia y Tecnología, proyectos PPQ2003-06602 C04-03 y AGL-2006-12210-C03-01SEAFOODplus, FOOD-CT-2004-506359Peer reviewe

Phytochemistry of heather (Calluna vulgaris (L.) Hull) and its altitudinal alteration

11 páginas, 2 figuras, 3 tablas.-- The final publication is available at www.springerlink.comCalluna vulgaris (L.) Hull (heather) is the only species within the genus Calluna (Ericaceae). It is a dominant species of heather communities and can be found in most parts of Europe and Northern America from lowland up to alpine regions. Common heather is traditionally used to treat urinary tract disturbances and inflammatory related disorders. This review covers the current knowledge on phytochemical investigations of C. vulgaris which revealed a complex pattern of flavonoid glycosides including acetylated compounds as well as other classes of phenolics (chromones, procyanidins and simple phenols). Recently, an acetophenone (rodiolinozide) was identified. C. vulgaris occurs in habitats comprising several altitudinal zones which makes it an attractive species to study the variation of its metabolic profiles in wild populations growing under different climatic Calluna vulgaris (L.) Hull (heather) is the only species within the genus Calluna (Ericaceae). It is a dominant species of heather communities and can be found in most parts of Europe and Northern America from lowland up to alpine regions. Common heather is traditionally used to treat urinary tract disturbances and inflammatory related disorders. This review covers the current knowledge on phytochemical investigations of C. vulgaris which revealed a complex pattern of flavonoid glycosides including acetylated compounds as well as other classes of phenolics (chromones, procyanidins and simple phenols). Recently, an acetophenone (rodiolinozide) was identified. C. vulgaris occurs in habitats comprising several altitudinal zones which makes it an attractive species to study the variation of its metabolic profiles in wild populations growing under different climatic conditions. Within phenolic compounds, flavonols showed significant differences in samples collected at different altitudes with increased levels of quercetin glycosides at higher altitudes whereas no significant correlation could be found for caffeoyl quinic acids and the dihydroflavonol glycoside callunin. Expanding such investigations to different species and different geographical areas should give a more accurate picture of suitable marker compounds within the group of phenolics in order to detect adaptive processes in high altitude plants. Furthermore, investigations on the specific patterns of phenolics at cellular and subcellular level and their variation due to factors like enhanced solar radiation and low temperature should be expandedWe are grateful for financial support by the Faculty of Natural Sciences, University of Graz, and the Dr. Heinrich-Jo¨rg and the Gandolph-Doelter foundationsPeer reviewe

Galloylation and Polymerization: Role of Structure to Antioxidant Activity of Polyphenols in Lipid Systems

15 pagesMany polyphenols are present in foods and nature as individual congeners, but also polymerized in oligomeric and polymeric entities. Flavanols and their condensed polymers, proanthocyanidins, are widespread components in green tea, red wine, cocoa, grape seeds and pine bark, with an extremely variable number of polyphenolic residues (polymerization degree) and galloyl moieties (galloylation). Polymerization and galloylation are key structural elements in the healthy outcome and antioxidant activity of polyphenols. The present chapter résumés how size and composition diversity, particularly polymerization and galloylation, influence the physicochemical properties relevant for the antioxidant activity of polyphenols in foods and biological systems: the radical scavenging ability, chelation on redox active metals, interfacial partitioning, redox capacity to regenerate, or to be regenerated by co-antioxidants and to inactivate/active pro-oxidants. To evaluate these structural-activity relationships, the physicochemical properties of polyphenols, evaluated either in vitro or in situ in biological systems, will be assessed together with their antioxidant efficiency in food and biological lipid systemsN

Development of a solid-phase microextraction method for determination of volatile oxidation compounds in fish oil emulsions

11 páginas, 8 figuras, 5 tablasHeadspace solid-phase microextraction (HS-SPME) is proposed for isolating and determining the headspace volatiles formed during oxidation of fish-oil-in-water emulsions. Three different fiber coatings were tested and compared for sensitivity and reproducibility. A carboxen/polydimethylsiloxane (CAR-PDMS) fiber coating was found to be the most suitable for the analysis of emulsion volatiles. The main factors affecting the microextraction process on CAR-PDMS were then evaluated by a factorial design: amount of sample, time and temperature of extraction and stirring. The incubation of 0.5 g of emulsion at 60 °C during 30 min leads to the most effective extraction of volatiles associated with lipid oxidation of fish oil emulsions. The HS-SPME method coupled with GC–MS allowed the qualitative and quantitative analysis of the volatiles derived from oxidation of real fishoil enriched foods such as milk and mayonnaise. The method here proposed is very fast and simple and yields high sensitivity, with good repeatability for all target compounds.This work was performed within the research project PPQ2003-06602-C04-03 and the Integrated Research Project SEAFOODplus, contract No FOOD-CT-2004-506359. The financing of this work by the Spanish Ministry of Science and Technology and the European Union is gratefully acknowledged.Peer reviewe

Determination of ascorbic and dehydroascorbic acid in lean and fatty fish species by high-performance liquid chromatography with fluorometric detection

6 páginas, 4 figuras, 2 tablasAscorbic acid (AA) and dehydroascorbic acid (DHAA) were analysed in fish muscle by high performance liquid chromatography (HPLC) coupled with fluorescence determination using 4,5-dimethyl-ophenilenediamine (DMPD) as a derivative agent. The use of the DMPD in combination with isobutanol extraction eliminated many matrix interferences and increased significantly the specificity and sensitivity of the method. A strong pH dependence in the derivatization reaction was also demonstrated. Satisfactory results in terms of sensitivity, stability and reproducibility were obtained. The analyses demonstrated that the relative ratio of AA and DHAA in post-mortem fish muscle differs among fish species and seems to be related with the susceptibility to oxidation.This work was performed within the research project PPQ2003-06602-C04-03 and the Integrated Research Project SEAFOODplus, contract no. FOOD-CT-2004-506359. The financing of this work by the Spanish Ministry of Science and Technology and the European Union is gratefully acknowledged. J. Iglesias acknowledges his doctoral grant from CSIC (Consejo Superior de Investigaciones Científicas).Peer reviewe

Determination of carbonyl compounds in fish species samples with solid-phase microextraction with on-fibre derivatization

8 páginas, 4 tablas, 3 figurasHeadspace solid-phase microextraction (HS-SPME) with on-fibre derivatization has been applied for determining volatile carbonyl compounds in fish muscle samples associated to different species and technological treatments. o-2,3,4,5,6-(Pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) has been used as derivatization reagent and the formed oximes were determined by gas chromatography coupled to mass spectrometry (GC–MS). The method has been optimised for improving the extraction–derivatization of analytes. Factors as the type of fibre, salting-out effect, incubation temperature and time, stirring and sample volume have been evaluated. The technique combines the typical advantages of SPME (economical, solventless, minimal sample handling or suitability for routine analysis) with a very high sensitivity using low quantities of sample (only 0.5 g of muscle). The comparison with an optimised and validated SPME method without derivatization showed excellent results in terms of sensitivity and selectivity since several compounds, as those associated to technological processes were detected in the different fish samples only after carbonyl derivatization.The financing of this work by the Spanish Ministry of Science and Technology and the European Union is gratefully acknowledged.Peer reviewe

Capacity of reductants and chelators to prevent lipid oxidation catalyzed by fish hemoglobin

7 páginas, 5 figurasThe efficiency of different reductants (reduced glutathione, ascorbic acid, and catalase) and metal chelators [ethylenediaminetetraacetic acid (EDTA), citric acid, sodium tripolyphosphate (STPP), and adenosine-5′-triphosphate (ATP)] to inhibit lipid oxidation promoted by fish hemoglobin was investigated. The inhibitory activity on hemoglobin-catalyzed lipid oxidation was also evaluated for grape oligomeric catechins (proanthocyanidins), which have both reducing and chelating properties. The antioxidant activity was studied in two different lipid oxidation models, liposomes and washed minced fish muscle. Grape proanthocyanidins were found to be significantly more effective than other reductants to prevent hemoglobin-mediated lipid oxidation in both liposomes and washed fish muscle. Reduced glutathione was also efficient to retard lipid oxidation at the same molarity in washed fish muscle, whereas catalase and ascorbic acid showed a lower antioxidant activity. Metal chelators were less active than reductants, and consequently, the former were necessarily evaluated at much higher concentration than grape proanthocyanidins and reducing compounds. STPP was found to be the iron chelator with the strongest efficiency to delay hemoglobin-mediated lipid oxidation followed by EDTA. Citric acid and ATP were ineffective in retarding lipid oxidation in both systems. Grape proanthocyanidins provided the most extensive protection to preserve hemoglobin at ferrous state in washed fish muscle. Our results draw attention to the greater capacity of reducing compounds to prevent fish hemoglobin-mediated lipid oxidation in comparison with iron chelators, suggesting that the free radical scavenging and/or reduction of ferrylHb species are crucial actions to avoid the pro-oxidant capacity of fish hemoglobinThis investigation has been supported by the Spanish Ministry of Science (Grant AGL2006-12210-C03-01).Peer reviewe

Contribution of Galloylation and polymerization to the antioxidant activity of polyphenols in fish lipid systems

9 páginas, 1 esquema, 5 figuras, 5 tablasPolyphenolic fractions extracted from pine (Pinus pinaster) bark, grape (Vitis vinifera) pomace, and witch hazel (Hamamelis virginiana) bark were selected for investigating the influence of the number of phenolic units, polymerization, and the content of esterified galloyl residues (galloylation) on their efficacy for inhibiting lipid oxidation in fish lipid enriched foodstuffs. Experiments carried out with nongalloylated pine bark fractions with different polymerization degrees demonstrated that the number of catechin residues per molecule modulates their reducing and chelating properties in solution. In real food systems such as bulk fish oil and fish oil-in-water emulsions, the efficacy against lipid oxidation was highly dependent on the physical location of the antioxidant at the oxidative sensitive sites. The lowest polymerized fractions were the most efficient in bulk fish oil samples, whereas proanthocyanidins with an intermediate polymerization degree showed the highest activity in fish oil-in-water emulsions. Galloylation did not influence the antioxidant effectiveness of proanthocyanidins in bulk fish oils. The presence of galloyl groups favored the antioxidant activity of the polyphenols in emulsions, although results indicated that a high degree of galloylation did not improve significantly the activity found with medium galloylated proanthocyanidins. The results obtained in this research provide useful information about the relationship between structure and antioxidant activity in order to design antioxidant additives with application in fish oil-enriched functional foods.This work was performed within the research project AGL-2006-12210-C03-01. The financing by the Spanish Ministry of Science and Technology is gratefully acknowledged.Peer reviewe

Contribution of Galloylation and polymerization to the antioxidant activity of polyphenols in fish lipid systems

9 páginas, 1 esquema, 5 figuras, 5 tablasPolyphenolic fractions extracted from pine (Pinus pinaster) bark, grape (Vitis vinifera) pomace, and witch hazel (Hamamelis virginiana) bark were selected for investigating the influence of the number of phenolic units, polymerization, and the content of esterified galloyl residues (galloylation) on their efficacy for inhibiting lipid oxidation in fish lipid enriched foodstuffs. Experiments carried out with nongalloylated pine bark fractions with different polymerization degrees demonstrated that the number of catechin residues per molecule modulates their reducing and chelating properties in solution. In real food systems such as bulk fish oil and fish oil-in-water emulsions, the efficacy against lipid oxidation was highly dependent on the physical location of the antioxidant at the oxidative sensitive sites. The lowest polymerized fractions were the most efficient in bulk fish oil samples, whereas proanthocyanidins with an intermediate polymerization degree showed the highest activity in fish oil-in-water emulsions. Galloylation did not influence the antioxidant effectiveness of proanthocyanidins in bulk fish oils. The presence of galloyl groups favored the antioxidant activity of the polyphenols in emulsions, although results indicated that a high degree of galloylation did not improve significantly the activity found with medium galloylated proanthocyanidins. The results obtained in this research provide useful information about the relationship between structure and antioxidant activity in order to design antioxidant additives with application in fish oil-enriched functional foods.This work was performed within the research project AGL-2006-12210-C03-01. The financing by the Spanish Ministry of Science and Technology is gratefully acknowledged.Peer reviewe