María D. Guillén

Infrared spectroscopy in the study of edible oils and fats

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.

Bioavailability and risk assessment of orally ingested polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs) are a family of toxicants that are ubiquitous in the environment. These contaminants generate considerable interest, because some of them are highly carcinogenic in laboratory animals and have been implicated in breast, lung, and colon cancers in humans. These chemicals commonly enter the human body through inhalation of cigarette smoke or consumption of contaminated food. Of these two pathways, dietary intake of PAHs constitutes a major source of exposure in humans. Although many reviews and books on PAHs have been published, factors affecting the accumulation of PAHs in the diet, their absorption following ingestion, and strategies to assess risk from exposure to these hydrocarbons following ingestion have received much less attention. This review, therefore, focuses on concentrations of PAHs in widely consumed dietary ingredients along with gastrointestinal absorption rates in humans. Metabolism and bioavailability of PAHs in animal models and the processes, which influence the disposition of these chemicals, are discussed. The utilitarian value of structure and metabolism in predicting PAH toxicity and carcinogenesis is also emphasized. Finally, based on intake, disposition, and tumorigenesis data, the exposure risk to PAHs from diet, and contaminated soil is presented. This information is expected to provide a framework for refinements in risk assessment of PAHs from a multimedia exposure perspective.

High resolution 1H nuclear magnetic resonance in the study of edible oils and fats

Abstract In this paper a review of the applications of high resolution 1 H NMR to the study of edible oils and fats is reported. Aspects such as sample preparation and acquisition parameters are treated. The assignment of the 1 H NMR signals of the major and minor components of unoxidized and of thermally stressed edible oils and fats is given. The usefulness of this technique in the determination of degree of unsaturation and of the proportion of the different acyl groups, is examined. In addition, the capability of this technique to assess the quality and genuineness of olive oil and to detect adulterations is discussed. Finally, its contribution in the study of the oxidation of edible oils and fats and its effectiveness to determine not only primary but also secondary oxidation products, and also oxidative stability is shown.

Some of the most significant changes in the Fourier transform infrared spectra of edible oils under oxidative conditions

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

Study of the volatile composition of an aqueous oak smoke preparation

An aqueous smoke flavouring from oak (Quercus sp.) sawdust was obtained on the laboratory scale. Its qualitative and quantitative composition was studied by gas chromatography after previous extraction. A high number of compounds (215) was detected. In addition to the well-known smoke components, others, only recently described as smoke components, were also detected. In the first group there are aldehydes, ketones, diketones, esters, alcohols, acids, furan and pyran derivatives, syringol, guaiacol, phenol and pyrocatechol derivatives, alkyl and aryl ethers; in the second group the presence of some furan and pyran derivatives is noteworthy, as well as a significant number of lignin dimers in low proportion, a considerable number of anhydrosugars in very high proportion and some nitrogenated derivatives in low proportions. Differences between this oak aqueous liquid smoke and others previously obtained from several woods, under similar operative conditions, 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 preparation.

Toxic Oxygenated α,β-Unsaturated Aldehydes and their Study in Foods: A Review

The oxidation of lipids containing polyunsaturated omega-3 or omega-6 acyl groups, such as docosahexenoic, eicosapentenoic, linolenic, arachidonic, or linoleic groups, and of the corresponding fatty acids, generates among other compounds α,β -unsaturated aldehydes supporting different functional groups containing oxygen, which can be named oxygenated α,β -unsaturated aldehydes (Oα β UAs). These compounds can be produced in cells and tissues of living organisms or in foods during processing or storage, and from these latter can be absorbed through the diet. In the last few years, Oα β UAs are receiving a great deal of attention because they are being considered as possible causal agents of numerous diseases, such as chronic inflammation, neurodegenerative diseases, adult respiratory distress syndrome, atherogenesis, diabetes, and different types of cancer. This review deals with the nature of the different kinds of Oα β UAs detected until now, their reactivity and consequent biological activity; the several pathways proposed for their formation; the current knowledge about the influence of both oxidative conditions and lipids nature in the rate of formation and yield of each kind of Oα β UAs in edible oils; the methods described until now to determine the presence in foods of some of these compounds, such as 4-hydroxy-trans-2-nonenal, 4-hydroxy-trans-2-octenal, 4-hydroxy-trans-2-hexenal and 4-oxo-trans-2-hexenal; and finally, the levels found of some of them in several foods.

Characterisation of the essential oils of some cultivated aromatic plants of industrial interest

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).

Study of the composition of the different parts of a Spanish Thymus vulgaris L. plant

Abstract The yield and composition of the dichloromethane extracts of leaves, flowers and stems of Thymus vulgaris L. growing in northeastern Spain have been studied. The yield obtained from leaves and flowers is much higher than that obtained from stems. This plant has a chemotype different from those previously known for Thymus vulgaris L. The fraction of the dichloromethane extract from leaves and flowers, studied by gas chromatography/mass spectrometry, shows that these tissues have higher concentrations of terpene hydrocarbons, oxygen terpene derivatives, sesquiterpene hydrocarbons, oxygen sesquiterpene derivatives, saturated aliphatic hydrocarbons and phytosterol derivatives than the stems. However, aldehydes with large number of carbon atoms have been found in higher concentrations in stems than in flowers and leaves. These extracts from different parts of Thymus vulgaris L. also show the presence of a large number of flavonoids and vitamin E, compounds of great interest in food industry for their antioxidant activity. Leaves and flowers of this plant are of interest as flavourings, as well as being natural antioxidants for the food industry.

Texture profile analysis of meat products treated with commercial liquid smoke flavourings

Abstract The texture of two meat products (salted pork loin and salted bacon) treated with two commercial liquid smoke flavourings (immersion for 30 s in either F1 or F2) was examined by instrumental texture profile analysis after 15, 30 and 90 days of storage. The two flavourings caused changes to the texture parameters of the products. Smoke flavouring F1, which is poor in carbonyl compounds, modified the cohesiveness, springiness and gumminess of the loin, and the hardness, fracturability and springiness of the bacon. Smoke flavouring F2, which is rich in carbonyl compounds, caused changes in springiness and gumminess of the loin, and of all the investigated texture parameters in bacon. Generally, significant changes occurred over time on the texture attributes evaluated.

Polycyclic aromatic compounds: Extraction and determination in food

Polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic compounds (PACs) in general, comprise the largest class of known environmental carcinogens. Reports of some studies of total diet in a number of developed countries indicate that food constitutes an important source of exposure of man to PACs, although other authors have shown the need to develop accurate data, in order that the overall public health hazard may be effectively evaluated and controlled. In this context, this review aims to give an overview of methods used to determine the PAC content of foodstuffs. At first, the nature, classification and derived compounds of PAHs are considered. Likewise, the occurrence of PAHs in processed and in non-processed foods is shown. The main causes are environmental contamination and the utilization of procedures which give rise to the presence of PACs during the processing, preservation, and packaging of foods. Octanol: water partition coefficients of PACs and their relationships with some properties, such as aqueous solubility and bioaccumulation, are considered. The solubility of complex mixtures of PACs in several organic solvents and the different methods for extraction and isolation of the PAC-fraction from foodstuffs are reviewed. The methodologies used for the separation, identification and quantitative determination also are briefly considered.