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The effect of the enrichment of sunflower oil with gamma-tocopherol on the evolution of its oxidation is the subject of this study. Sunflower oil and samples of this oil enriched with different gamma-tocopherol concentrations are submitted to accelerated storage conditions and their evolution, until total polymerization is monitored by H-1 NMR spectroscopy. The concentrations of linoleic acyl groups, of primary and of a great number of secondary oxidation compounds are determined throughout the process. These concentrations, and the times at which the main changes in them occur are analyzed to elucidate if they are valid markers of the global effect of gamma-tocopherol enrichment. It is proved for the first time that certain comparisons between concentrations of some of the compounds formed in oxidation can lead to erroneous conclusions about the effect of this enrichment. It is shown that, during a first short period of time under accelerated storage conditions, the higher the concentration of gamma-tocopherol the faster the degradation of linoleic acyl groups and the higher the concentration of hydroperoxides; after this first period this relationship is more complex. Generally, the higher the gamma-tocopherol concentration the slower the degradation of the oil, except in the first period.Practical Applications: This study provides very valuable information about the effect caused by enrichment with gamma-tocopherol on sunflower oil oxidative stability and oxidation across a very broad range of concentrations. In addition, the amount of information obtained can be of great importance from several points of view because the oxidation process has been monitored globally. This may be of interest not only to researchers involved in the analysis of oxidation mechanisms but also to those in the field of technology and edible oil legislation, and even to those worried about edible oil safety and its effect on nutrition and health. Another important feature of this study, from the practical point of view, is the methodology used because it does not involve the chemical modification of the sample and the same H-1 NMR spectrum is able to provide information about all the above-mentioned aspects. Sunflower oil enriched with different levels of gamma-tocopherol. Concentrations of primary and secondary oxidation compounds after 4 and 9 days, respectively, under accelerated storage conditions. This work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO AGL 2015-65450-R), the Basque Government (EJ-GV, IT-916-16), and the Agriculture Department of the Basque Government (PA19/02).

Fish shelf-life extension is a topic of great interest. In this study the behaviour of salted and unsalted farmed and wild European sea bass (Dicentrarchus labrax) fillets during storage was analysed through the evolution of their volatile metabolites. Farmed and wild sea bass fillets were brine-salted for 15 or 75 min, or dry-salted, vacuum-packed and stored at 4 °C for up to 1 month, and their headspaces were studied by Solid Phase Micro extraction-Gas Chromatography/Mass Spectrometry (SPME-GC/MS).; Results: At the same storage time, unsalted wild fillets contained, in general, a higher number and abundance of volatile compounds coming from microbiological or endogenous enzymatic activity than unsalted farmed ones. The more intense the salting, the lower the number and abundance of microbiological spoilage metabolites, especially in wild samples. The appearance of oxidation metabolites only in dry-salted wild samples evidences that this kind of salting provokes a certain oxidation in these samples.; Conclusions: The better performance of farmed than wild fillets suggests that salted farmed fillets, vacuum-packed and stored under refrigeration conditions, could be a successful alternative to diversify the presence of sea bass in the market. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

BACKGROUND Farmed and wild European sea bass (Dicentrarchus labrax) could be distinguished by its volatile metabolites, an issue not addressed until now. The aim of this work was to study these metabolites by solid-phase microextraction followed by gas chromatography/mass spectrometry (SPME-GC/MS). RESULTS Both farmed and wild sea bass have a great number of volatile metabolites, most of them being in low concentrations. These include alcohols, aldehydes, ketones, alkylfurans, acids, aliphatic and aromatic hydrocarbons, terpenes, sulfur and nitrogen derivatives, 2,6-di-tert-butyl-4-methylphenol and one derived compound, as well as 2,4,7,9-tetramethyl-5-decyne-4,7-diol, this latter compound presumably resulting from environmental contamination. Important differences have been detected between both types of sea bass, and also among individuals inside each group. Farmed specimens are richer in volatile metabolites than the wild counterparts; however, these latter, in general, contain a high number and abundance of metabolites resulting from microbial and enzymatic non-oxidative activity than the former. CONCLUSIONS Clear differences in the volatile metabolites of wild and farmed sea bass have been found. A great deal of valuable information on sea bass volatile metabolites has been obtained, which can be useful in understanding certain aspects of the quality and safety of raw and processed sea bass. © 2015 Society of Chemical Industry

2,6-Di-tert-butyl-hydroxytoluene (BHT, E-321) is a synthetic phenolic antioxidant which has been widely used as an additive in the food, cosmetic, and plastic industries for the last 70 y. Although it is considered safe for human health at authorized levels, its ubiquitous presence and the controversial toxicological data reported are of great concern for consumers. In recent years, special attention has been paid to these 14 metabolites or degradation products: BHT-CH2 OH, BHT-CHO, BHT-COOH, BHT-Q, BHT-QM, DBP, BHT-OH, BHT-OOH, TBP, BHQ, BHT-OH(t), BHT-OH(t)QM, 2-BHT, and 2-BHT-QM. These derived compounds could pose a human health risk from a food safety point of view, but they have been little studied. In this context, this review deals with the occurrence, origin, and fate of BHT in foodstuffs, its biotransformation into metabolites, their toxicological implications, their antioxidant and prooxidant properties, the analytical determination of metabolites in foods, and human dietary exposure. Moreover, noncontrolled additional sources of exposure to BHT and its metabolites are highlighted. These include their carryover from feed to fish, poultry and eggs, their presence in smoke flavorings, their migration from plastic pipelines and packaging to water and food, and their presence in natural environments, from which they can reach the food chain.

This review summarizes present-day knowledge provided by proton nuclear magnetic resonance (1H NMR) concerning food lipid thermo-oxidative degradation. The food lipids considered include edible oils and fats of animal and vegetable origin. The thermo-oxidation processes of food lipids of very different composition, occurring at low, intermediate, or high temperatures, with different food lipid surfaces exposed to oxygen, are reviewed. Mention is made of the influence of both food lipid nature and degradative conditions on the thermo-oxidation process. Interest is focused not only on the evolution of the compounds that degrade, but also on the intermediate or primary oxidation compounds formed, as well as on the secondary ones, from both qualitative and quantitative points of view. Very valuable qualitative and quantitative information is provided by 1H NMR, which can be useful for metabolomic and lipidomic studies. The chemical shift assignments of spectral signals of protons of primary (hydroperoxides and hydroxides associated with conjugated dienes) and secondary, or further (aldehydes, epoxides, among which 9,10-epoxy-12-octadecenoate [leukotoxin] can be cited, alcohols, ketones) oxidation compounds is summarized. It is worth noting the ability of 1H NMR to detect toxic oxygenated α,β-unsaturated aldehydes, like 4-hydroperoxy-, 4,5-epoxy-, and 4-hydroxy-2-alkenals, which can be generated in the degradation of food lipids having omega-3 and omega-6 polyunsaturated groups in both biological systems and foodstuffs. They are considered as genotoxic and cytotoxic, and are potential causative agents of cancer, atherosclerosis, and Parkinson's and Alzheimer's diseases.

BACKGROUND: The volatile components of virgin and refined oils whose compositions were very different in terms of oleic, linoleic and linolenic acyl groups were studied by solid phase microextraction (SPME) followed by gas chromatography/mass spectrometry (GC/MS), and their composition of acyl groups was determined by proton nuclear magnetic resonance 1H NMR. The virgin oils studied were olive, linseed and walnut oils, while the refined oils were sunflower and rapeseed oils. RESULTS: Large differences were found among the headspace compositions of the virgin oils. These were due in part to compounds that could be considered as markers of different vegetable origins and manufacturing processes, but also to compounds resulting from degradative oxidation of the main acyl group components. By virtue of their being refined, fewer components were present in the refined oils, although differences in their headspaces were found owing to the presence of compounds resulting from oxidation of the determined acyl groups. CONCLUSION: The studied oils show specific characteristics regarding not only their main components, which are well known, but also their volatile components. The latter provide information on some of the processes to which oils have been submitted, on their oxidation level, on their botanical origin and on the compounds responsible for their odour. Copyright © 2011 Society of Chemical Industry

The degradation process of edible oils of very different nature, submitted to 190 °C with aeration, is studied by means of 1H nuclear magnetic resonance (NMR). In this study, no primary oxidation products, such as hydroperoxides, are detected, the signals of aldehydes being the first to be observed in the 1H NMR spectra. Differences between this degradation process and those occurring at 70 °C with aeration or under microwave action are discussed, not only in relation to the degradation rate of the different acyl groups, but also in relation to the nature and proportions of some of the degradation products generated. Oils rich in oleic acyl groups are not only more resistant to degradation than oils rich in linoleic and linolenic acyl groups, but also produce lower proportions of toxic aldehydes.

Two aqueous smoke flavourings were obtained, on a laboratory scale, from mixtures of oak wood sawdust (Quercus sp.) and sawdust of the aerial parts of thyme (Thymus vulgaris L.) or sage (Salvia lavandulifolia Vahl.) (8:2, w[sol ]w, respectively). The acidity and composition of these preparations were determined in this study. The presence of thyme or sage in the starting material influences the acidity and composition of these two smoke flavourings. Both flavourings contain the same main components (aldehydes, ketones, diketones, acids, esters and furan and pyran derivatives, alkyl aryl ethers, and phenol, guaiacol, pyrocatechol, syringol and their alkyl derivatives and some anhydro-sugars), which are well-known typical smoke components. In addition they contain some terpenic derivatives, such as linalool, camphor, endo-borneol and 2,5-bornanedione and a large group of nitrogenated derivatives in low concentrations, coming from the aromatic plants. These compounds contribute floral and herbaceous as well as burnt and roasted notes to these smoke flavourings and all those associated properties to these specific compounds. Copyright © 2005 John Wiley & Sons, Ltd.

The oxidation process of olive, hazelnut, and peanut oils at 70°C with circulating air has been studied by means of 1H NMR. The evolution of the process, including the rate of degradation of the acyl groups and of formation and degradation of primary oxidation products, as well as the rate of formation of secondary oxidation products such as aldehydes, is commented on and compared with the oxidation of oils rich in polyunsaturated acyl groups. Differences that are due not only to the rate of the processes but also to the nature and concentration of the generated aldehydes are observed. Oils rich in monounsaturated acyl groups generate smaller amounts of the geno-and cytotoxic oxygenated aldehydes than oils rich in polyunsaturated acyl groups.

The oxidation process of rapeseed, walnut and linseed oils, rich sources of linolenic acyl groups, was studied by means of 1 H nuclear magnetic resonance spectroscopy. The visible changes in some spectrum signals, especially in those of methylic, allylic and bis-allylic hydrogen atoms, provide information about the degradation of the different acyl groups throughout the oxidation process. The rate of the changes produced in the three oils was compared, not only in relation to the rate of degradation of the different acyl groups, but also to both the formation and degradation of primary as well as to the formation of secondary oxidation products. Among the secondary oxidation products, the study was focused on the formation of aldehydes, their nature and evolution throughout the oxidation process of these three oils. The formation of n-alkanals, trans-2-alkenals, trans,trans-2,4-alkadienals, as well as of the well known geno- and cytotoxic 4,5-epoxy-, 4-hydroperoxy- and 4-hydroxy-trans-2-alkenals, was proved to take place.

The oxidation process of sunflower and corn oils at 70 °C with circulating air has been studied by means of 1H nuclear magnetic resonance (NMR). The changes produced in the two oils are compared not only in relation to the rate of degradation of acyl groups but also with reference to both the rate of formation and degradation of primary oxidation products as well as the rate of formation of secondary oxidation products such as aldehydes. Special attention is paid to the evolution of the different kinds of aldehydes formed throughout the process. The great ability of these oils to produce geno- and cytotoxic aldehydes under the above conditions is proved. Moreover, peroxide and anisidine values of corn oil throughout its oxidation process have also been determined and the results obtained have been compared with those provided by the 1H NMR spectra, showing good agreement. Copyright © 2005 Society of Chemical Industry

The usefulness of 1 H nuclear magnetic resonance (NMR) for studying oil oxidation processes was tested. Refined sesame oil was submitted to oxidative conditions at 70 °C with circulating air, and the status of the sample was studied daily by 1 H NMR. This technique permits the determination of the proportions of the acyl groups in the oil throughout the oxidation process and, at the same time, allows monitoring of the formation and degradation of primary oxidation compounds, as well as of the formation of secondary oxidation products. Generation of the geno- and cyto-toxic oxygenated aldehydes 4-hydroxy-, 4-hydroperoxy- and 4,5-epoxy-trans-2-alkenal was proved.

Farmed salmon fillets were dry-salted for 24 h. Both salted and unsalted samples were submitted to oxidative conditions at 50 °C in an oven with circulating air. Lipids of both samples were extracted daily from aliquots and studied by Fourier transform infrared spectroscopy. The infrared spectra of salmon lipids are similar to those of vegetable edible oils, with differences in the frequency and absorbance of some bands due to their different acyl group compositions. The infrared spectra of salted and unsalted fish lipid samples remain unchanged during a period of time, which is shorter for the salted salmon. After this period, changes in the frequency and absorbance of some bands of the spectrum are observed owing to the presence of oxidation products. Therefore the reduction in the oxidative stability of farmed salmon lipids caused by the dry-salting process is proved and the usefulness of this technique for studying the oxidative stability of fish lipid samples as well as their oxidation degree is shown. Copyright © 2004 Society of Chemical Industry

1H NMR spectra of 66 samples of edible oils from 14 different botanical origins were acquired. Assignment of signal spectra to the different types of hydrogen atoms was made and the areas of the signals determined. Considering that the area of the signals of the spectra is proportional to the number of hydrogen atoms of each type in the sample, it is possible to calculate not only the iodine value, but also the proportion of different acyl groups from the data. Determination of both parameters requires only a few minutes and one spectroscopic run. Classical methodology however, requires two separate wet methods for determining the unsaturation degree (iodine value) and the proportions of different acyl groups; both of them involve chemical transformations of the sample and considerable time and cost. Determination of acyl group proportions in samples by 1H NMR, which was validated with mixtures of standard triglycerides, provides accurate results and is able to detect small differences between samples of very similar composition.

Several samples containing different proportions of standard compounds such as tristearin, triolein, trilinolein, and trilinolenin, covering a broad range of compositions, some similar to those of edible oils, were prepared by weight. The 1H nuclear magnetic resonance (NMR) spectra of these samples were recorded and their signals were assigned. It was shown that concentrations of linolenic acyl groups close to 0.4% or higher can be detected by this technique. The area of 5 discrete proton signals of the spectrum was determined. Considering the ratio between this area and the concentration of the corresponding types of hydrogen atoms in the sample, equations calculating the proportions of the acyl groups were deduced. The high level of agreement between data coming from 1H NMR spectra and data obtained by weight shows the usefulness of this methodology. In addition, it has the advantage that it is very fast and simple in comparison with the classical methods, and does not require a chemical modification of the sample. For this reason, the described method constitutes a valuable alternative for the determination of the proportions of different acyl groups in acylglycerol mixtures, such as, for example, oils and fats.

Three oil samples obtained from sacha inchi (Plukenetia volubilis L.) seeds were studied by means of FTIR and 1H NMR. Frequency data of the most significant bands of the IR spectrum of this oil are given. These data show that sacha inchi oil has a high degree of unsaturation. The same fact is deduced from the ratio between the absorbance of the bands due to the stretching vibrations of the cis olefinic CH double bonds at 3010.5 cm−1 and to the methylene symmetrical stretching vibrations at 2855.1 cm−1. The proportions of monounsaturated, polyunsaturated, and saturated acyl groups were predicted from the frequency of some IR bands, and these were in satisfactory agreement with the values obtained through FAME generation and their quantification by GC. Likewise, simple observation of the 1H NMR spectra provided a great deal of information about sacha inchi oil, with regard not only to the relative proportions of the different acyl groups but also to their nature. Thus, the presence of γ-linolenic acyl groups was discounted. Furthermore, the area of some 1H NMR signals was used to determine the proportion of saturated and mono-, di-, and triunsaturated acyl groups, which also were in satisfactory agreement with the values obtained by classical methods. IR and 1H NMR determinations take very little time in comparison with classical methods and do not require chemical manipulation or transformation of the sample. A comparison was also made between the compositions of sacha inchi and linseed oil. Both oils are important sources of the healthful n−3 linolenic acyl groups, and sacha inchi also contains high proportions of the n−6 linoleic acyl groups.

The 1H nuclear magnetic resonance (NMR) spectra of 36 edible oil samples of 15 different botanical origins were recorded with a 300 MHz instrument using deuterated chloroform as solvent. The assignment of each of their peaks was made by comparison with those of standard compounds, tristearin, triolein, trilinolein and trilinolenin. For the first time, certain spectral regions of interest, conveniently expanded, together with the chemical shifts of their peaks, are given for 15 oil samples of different botanical origin. The usefulness of each of these spectral regions in the differentiation of oils is discussed. It is shown that 1H NMR spectra can be considered as the fingerprint of each oil sample. It is proved that they provide a great deal of information which permits discrimination between oils of different composition. This discrimination can be made in many cases with the naked eye by observation of certain spectral signals, without any other additional determinations. © 2003 Society of Chemical Industry

Solid phase microextraction followed by gas chromatographylmass spectrometry of raw and smoked black bream and rainbow trout was carried out. The volatile components of the raw fish belong to a limited number of groups of compounds. Raw black bream has a higher presence of acids than raw trout, while the latter contains more alcohols, hydrocarbons, esters and phenol derivatives; both contain similar concentrations of saturated aldehydes. The volatiles of the smoked fish basically comprise the compounds also detected in the raw fish together with others produced during the processing. Smoke components detected in both smoked fish species were mainly phenol, guaiacol and syringol derivatives, ketones, acetic acid and some polycyclic aromatic hydrocarbons. Smoked black bream contained a higher number and higher concentrations of smoke components than smoked rainbow trout. Large variations in concentrations of smoke components in the smoked fish samples indicated that the smoking process had not been totally homogeneous. The presence of autoxidatively derived compounds, such as unsaturated aldehydes, was mainly detected in some smoked bream samples, showing that this degradation process is not occurring homogeneously. The usefulness of the applied techniques for the study of volatile components of raw and smoked fish is shown. Le but de cette etude est d'etablir s'il existe des differences entre les composes volatils d'especes tres differentes de poissons dans des conditions d'alimentation et d'environnement differents. Elle determine aussi dans quelle mesure le procede de fumage modifie la composition de ces composes dans chacune des especes. L'utilite des techniques de microextraction en phase solide et de chromatographie gazeuse / spectrometrie de masse pour l'evaluation des composes volatils dans ces produits est demontree.

The oxidation of a broad collection of commercial edible oils, including extra virgin olive, olive, sesame, sunflower, corn, unknown seed, soybean, safflower, rapeseed, peanut and walnut oils, was monitored by Fourier transform infrared spectroscopy. Samples were kept in a convection oven with air circulating at 70 °C. Duplicate spectra were collected each day of the experiment by applying a film of pure oil between two KBr disks. The frequency and absorbance of each infrared band were automatically registered by a macro program. Ratios between absorbances of different bands of the spectra were calculated. Changes in frequency values of different bands and in ratios between absorbances of some bands allow different stages of the oxidation process to be distinguished as well as determining their oxidative stability in a simple and fast way, showing the usefulness of this technique in monitoring oil oxidation processes. © 2000 Society of Chemical Industry

The common components found in smoke flavourings are carbonyl derivatives, acids, esters and lignin monomers such as alkyl-aryl ethers and phenol derivatives. Recently the presence of lignin dimers has been noted. In addition to these compounds, lignin trimers and new lignin dimers have been detected in the brown layer left by a smoke flavouring on the wall of the receptacle in which it was contained; these compounds tend to migrate towards the wall of the container and have not been previously described as smoke or smoke flavouring components. Lignin trimers and dimers are important in the preservation of smoked foods for their known high antioxidant activity, even higher than that of the lignin monomers. The mass spectral data of a large number of lignin trimers and dimers are given and can be useful for future studies of smoke flavourings and smoked food as well as in beverage studies and for the characterisation of woods to be used in the beverage industry. © 1999 Society of Chemical Industry

An aqueous smoke flavouring from Thymus vulgaris L was obtained. The qualitative and quantitative composition of its dichloromethane extract was studied by gas chromatography and gas chromatography/mass spectrometry. In addition to the common smoke components such as aldehydes, ketones, diketones, esters, acids, furan and pyran derivatives, alkyl aryl ethers, phenol, guaiacol and syringol derivatives, some terpenic compounds were detected. Differences between this aqueous liquid smoke and others from various kinds of wood are due not only to the absence or presence of some compounds but also to the proportions of the different groups of components present in the mixture. Some aldehydes, esters, guaiacol and its derivatives and terpenic compounds contribute to the overall odour of this liquid smoke more significantly than the ketones, furan and pyran derivatives, acids, phenol and its derivatives and syringol. The yield in smoke components obtained from the pyrolysis of Thymus vulgaris L at 488 °C is of a similar order to that obtained from other woods. © 1999 Society of Chemical Industry

Twelve sets of olive oil mixed with various edible seed oils in different proportions were made. The seed oils used were sunflower, corn, walnut, rapeseed, soybean, safflower, peanut, wheat germ, and sesame oil. These samples have very different proportions of saturated, mono- and polyunsaturated acyl groups, and of minor components. Fourier transformed infrared spectra of these blends were recorded from films of the oil samples between two discs of KBr. Taking into account the close relationships found previously between the frequency data of some specific bands and the composition of the oil samples, frequency data of all samples were collected and used in equations that relate frequency and composition predicting the percentage by weight of saturated, mono- and polyunsaturated acyl groups in the samples. The predicted values were compared with those derived from the combination of chemical and gas-chromatographic methods and a high degree of agreement was found. The presence of small amounts of seed oil in olive oil is shown by a small variation in the values of the frequencies of specific bands of the spectra, resulting from a smaller proportion of mono-unsaturated acyl groups than in pure olive oil. On the other hand, the frequency of the maximum absorbance between 915 cm–1 and 904 cm–1 also indicates the proportion of seed oil in the blend up to levels of 5% or up to 8% of seed oil in olive oil, depending on the nature of the seed oil. This methodology could give information about the composition of blends of edible oils in a very fast and simple way. Die Nutzlichkeit mancher Frequenzen aus Fourier-transformierten Infrarot-spektroskopischen Banden fur die Bestimmung der Zusammensetzung von esbaren Olmischungen Zwolf Serien von Olivenol gemischt mit einigen esbaren Pflanzenolen wurden in verschiedenen Verhaltnissen hergestellt. Die Pflanzenole waren Sonnenblumenol, Maisol, Walnusol, Rapsol, Sojaol, Farberdistelol, Erdnusol, Weizenkeimol und Sesamol. Diese Proben hatten unterschiedliche Anteile an gesattigten, einfach und mehrfach ungesattigten Acylgruppen und an Minorverbindungen. Fourier-transformierte Infrarotspektren dieser Mischungen wurden aus Filmen von Olproben zwischen zwei KBr-Scheiben aufgenommen. Die Frequenzdaten aller Proben wurden gesammelt, um den prozentualen Gewichtsanteil von gesattigten, mono- und polyungesattigten Acylgruppen in den Proben vorauszusagen; dabei wurden die fruher gefundenen Beziehungen zwischen der Frequenz einiger spezifischen Banden und der Zusammensetzung der Olproben berucksichtigt. Die vorausgesagten Werte wurden mit denjenigen aus chemischen und gaschromatographischen Methoden verglichen, und ein hoher Grad an Ubereinstimmung wurde festgestellt. Die Anwesenheit einer kleinen Pflanzenolmenge im Olivenol wurde durch eine kleine Anderung der Frequenzwerte von spezifischen Banden des Spektrums gezeigt, was durch den kleineren Anteil an einfach gesattigten Acylgruppen verglichen mit reinem Olivenol bedingt ist. Andererseits zeigt die Frequenz der Maximum-Absorption zwischen 915 cm–1 und 904 cm–1 auch den Anteil des Pflanzenols im Gemisch bis zu Mengen von 5% oder 8% an Pflanzenol in Olivenol, abhangig von der Natur des Pflanzenols. Diese Methodik konnte auf sehr schnelle und einfache Weise Auskunft uber die Zusammensetzung der Mischungen von Pflanzenol mit Olivenol geben.

The yield and composition of the volatile fraction of the dichloromethane extract of the aerial parts of a Spanish wild growing plant, Thymus vulgaris L., have been studied. The main components are 1,8-cineole and linalool, a chemotype not described before in Thymus vulgaris L. Oxygenated terpene derivatives constitute 42% of the total components; saturated hydrocarbons of high molecular weight, 25%; oxygenated sesquiterpene derivatives, monoterpene and sesquiterpene hydrocarbons, 4%, 3% and 1.6% respectively. In addition, some fatty acids, aldehydes, phytosterols, flavanones, vitamin E and other compounds have also been detected. © 1998 John Wiley & Sons, Ltd.

Fourteen samples of edible oils and lard have been studied by means of Fourier transform infrared spectroscopy. The spectra were recorded from a film of pure oil or lard between two discs of KBr. The bands of the spectra were assigned to different functional group vibrations. The frequencies of some bands have constant values, independent of the nature of the sample. However, frequencies of other bands, some of them in the fingerprint region, depend greatly on the sample composition. Equations obtained from frequency of these bands and composition data are valuable to predict the proportions of saturated, monounsaturated and polyunsaturated acyl groups in oils and lard.

The use of infrared spectroscopy in the study of fats and oils is reviewed. The importance of the mid-infrared region in the study of lipids is shown. Differences between dispersive and Fourier-transform infrared techniques are commented on and the experimental methods used in the handling of oil and fat samples are reported. The assignment of oil and fat bands of mid-infrared spectra is made, and the usefulness of this technique to characterise oils and fats and to detect adulterations is reviewed. The application of spectroscopic data to determine the degree of unsaturation or iodine value, trans- double bonds content, free fatty acid content, average chain length or saponification number, solid fat content, as well as peroxide and anisidine values, is commented on. Also, the importance of this technique for monitoring oxidation processes is shown. © 1997 SCI.

Vitis vinifera L shoots and Fagus sylvatica L wood were used to obtain aqueous smoke flavouring preparations. Both flavourings have a gold colour and pleasant odour. The flavour components of both samples are extracted with dichloromethane. The identification and quantitation of the components of the extracts are carried out by means of gas chromatography/mass spectrometry, and gas chromatography with flame ionisation detection. In both preparations carbonyl derivatives are in higher concentrations than phenol derivatives. Compounds that confer sweet, burnt and pungent flavours are in higher concentrations in the Vitis vinifera L shoots smoke flavouring, and compounds that give smoky flavours are in higher concentrations in the Fagus sylvatica L wood smoke flavouring. Ratios between the concentrations of the main components are proposed as parameters in order to characterise smoke and smoke flavourings, manufactured under specific conditions, from a specific wood. Finally, the yield of some components from a fixed amount of wood is also given.

The compositions of the essential oils of Rosmarinus officinalis L, Salvia lavandulifolia V and Lavandula latifolia M, obtained by steam distillation from plants cultivated in the northeast of Spain, have been studied by gas chromatography and gas chromatography/mass spectrometry. The essential oil of rosemary appears to be more complex and richer in flavour notes than other previously studied Spanish rosemary oils, and has an intermediate ratio of α-pinene and of 1,8-cineole in relation to essential oils of rosemary of different geographical origins, but higher proportions of camphor, verbenone and linalool. The essential oil of sage has proportions of 1,8-cineole, camphor, endo-borneol, trans-caryophyllene and α-humulene closer to commercial Salvia officinalis L than to other Spanish sages of different geographical locations, and the difference from commercial Salvia officinalis L is due principally to the higher ratio of terpene hydrocarbons and the lower proportion of thujone in the Spanish sage studied here. The essential oil of the spike lavender has the same main components and similar proportions as other Spanish wild and commercial spike lavender essen-tial oils, but shows differences in the nature of the minor components (rhodinol fraction).

Kovats retention indices for a series of linear, branched, and cyclic alkanes on squalane at any temperature, and on other stationary phases of different polarity at a given temperature, are related to physicochemical properties of the solutes, such as boiling point and molar refraction, by multiple regression analysis. The equations found permit calculation of the Kovats retention index for all alkanes, with standard deviations close to experimental error. The same equations can also be used for calculating the physicochemical parameters they contain.