Prooxidant effect of α-tocopherol on soybean oil. Global monitoring of its oxidation process under accelerated storage conditions by 1H nuclear magnetic resonance.

The effect of adding α-tocopherol in proportions ranging from 0.002 to 5% in weight on the oxidative stability of soybean oil was studied. For the first time, the oxidation process under accelerated storage conditions including evolution of the molar percentages of the several types of oil acyl groups, and formation and evolution of various kinds of oxidation products comprising hydroperoxides, hydroxy-dienes and other alcohols, epoxides, aldehydes and keto-dienes, was followed by 1H nuclear magnetic resonance. It is proved that, except in the lowest proportion, α-tocopherol not only exerts a prooxidant effect on soybean oil but also modifies its oxidation pathway, affecting the oxidation products generation rate, their nature, relative proportions and concentrations. It is noticeable that the highest α-tocopherol concentrations induce the generation of some toxic compounds at earlier stages of the thermoxidation process and sometimes in higher concentration, such as certain oxygenated α,ß-unsaturated aldehydes and monoepoxides derived from linoleic groups.

Contamination of cheese by polycyclic aromatic hydrocarbons in traditional smoking. Influence of the position in the smokehouse on the contamination level of smoked cheese.

This paper sets out to determine the polycyclic aromatic hydrocarbon (PAH) contamination degree of a traditionally smoked cheese: Herreño cheese, which comes from one of the Canary Islands. Its PAH profile is thoroughly studied by means of gas chromatography-mass spectrometry in SIM mode, and compared with that of an unsmoked cheese. Furthermore, a parameter not previously studied is evaluated, namely the influence of the position of the individual cheeses in the smokehouse on their PAH contamination level. Heavy PAH, among which are included most of the carcinogens, are very scarce and their concentrations low. In fact, benz[a]anthracene, together with chrysene+triphenylene, are the only heavy PAH detected in all of the smoked samples studied. The concentration of benzo[a]pyrene, detected only in 1 of the samples, is below the limit established in Spain for the rind of smoked cheese. In contrast, high concentrations of light PAH have been found, especially of naphthalene and its alkyl derivatives, whose effect on human health is not yet well established. The results derived from the analysis of the PAH profile suggest the potential usefulness of certain ratios between some pairs of PAH (phenanthrene/anthracene, naphthalene/acenaphthylene) to provide information on the PAH contamination source. Furthermore, differences have been found, depending on the position of the cheeses in the smokehouse, those placed in the path followed by the smoke being more contaminated. Therefore, the findings of this study could help in improving the design of smokehouses, to decrease the PAH contamination degree of smoked cheese.

Laboratory appraisal of organic carbon changes in mixtures made with different inorganic wastes.

Mixtures of organic and inorganic wastes were incubated to examine the changes in organic C (OC) contents. An anaerobic sludge and a CaO-treated aerobic sludge, with OC concentrations of 235 and 129 gkg(-1), were used. The inorganic wastes used - referred to as "conditioners" - were shot blasting scrap, fettling, Linz-Donawitz slag, foundry sand (FS), and fly ash from wood bark combustion (FA). The total OC (TOC) and KMnO(4)(-) oxidized OC were determined. DTA-TGA profiles and FTIR spectra were also obtained. Mixtures made with the FS contained significantly lower (P<0.05) amounts of TOC (45 gkg(-1)) than the rest of mixtures, which was attributed to the non-existence of reactive surfaces in the conditioner and the increased aeration induced by this material. Those made with FA contained significantly higher (P<0.05) amounts of TOC (170 gkg(-1)), which was attributed to: (i) the addition of an extra source of C - black carbon (BC) - in the FA, and (ii) the inhibition of mineralization from the compounds present in this conditioner (e.g., amorphous aluminosilicates, BC). The results highlight the importance of the characteristics of the conditioners on the fate of the OM originating from the sludges.

Occurrence of polycyclic aromatic hydrocarbons in artisanal Palmero cheese smoked with two types of vegetable matter.

Palmero cheese is a fresh smoked cheese from the Isle of Palma (Canary Islands), manufactured with goat's milk. To guarantee its safety, the occurrence of polycyclic aromatic hydrocarbons (PAH) in artisanal Palmero cheese smoked with 2 types of vegetable matter (almond shells and dry prickly pear) was studied. The determination of PAH includes extraction and clean-up steps, followed by separation, identification, and quantification of PAH by gas chromatography-mass spectrometry in selected ion-monitoring mode. The most abundant PAH are those with 2 and 3 aromatic rings. Although the highest total PAH concentrations corresponded to the cheeses smoked with almond shells, the degree of PAH contamination of the cheeses studied was lower than that found in other cheeses smoked in the traditional way. The nature of the vegetable material used for smoking seemed to have an influence on the type of PAH formed, especially on alkylderivatives and some light PAH. However, despite the artisanal, and consequently variable, production process of these cheeses, many similarities have been found among their PAH profiles. In fact, relatively constant relationships are observed between the concentrations of certain pairs of PAH. Benzo(a)pyrene was only present in 2 samples, and in much lower concentrations than the maximum allowed legal limits. Therefore, according to the results obtained, it appears that it is possible to obtain a safe product without renouncing the artisanal character or the sensory properties of this type of cheese.

Components detected by means of solid-phase microextraction and gas chromatography/mass spectrometry in the headspace of artisan fresh goat cheese smoked by traditional methods.

The study of the headspace components of fresh smoked goat cheese, was carried out by means of solid-phase microextraction using a polyacrylate fiber followed by gas chromatography/mass spectrometry. The samples studied were six artisan Palmero cheeses manufactured following traditional methods and smoked using pine needles. The cheese regions studied were exterior, interior, and a cross section. In total, more than 320 components were detected, the exterior region being the richest in components, among which were acids, alcohols, esters, hydrocarbons, aldehydes, ketones, furan and pyran derivatives, terpenes and sesquiterpenes, nitrogen derivatives, phenol, guaiacol and syringol derivatives, ethers, and others. In addition to typical cheese components, typical smoke components were also detected; these latter were present especially in the headspace of the exterior region and only those in significant concentrations in the exterior region were also detected in the interior. The main components were acids and phenolic derivatives. These latter compounds play an important role in the flavor of this cheese, and their relative proportions together with the presence of specific smoke components derived from pine leaves may be considered of interest in order to distinguish this cheese from others smoked with different vegetable matter.

Carbohydrate and nitrogenated compounds in liquid smoke flavorings.

Commercial smoke flavorings were extracted with dichloromethane and the remaining aqueous phase was evaporated at room temperature; the residues obtained were dissolved in methanol and studied by gas chromatography/mass spectrometry. The composition of these residues was totally different from that of the dichloromethane extracts, constituting a small number of compounds that were also detected in the dichloromethane extract, as well as a large number of compounds not described before as components of either smoke for food smoking or smoke flavorings. Among those compounds not previously described there are some furan, pyran, and phenolic derivatives, as well as some pyridine and carbohydrate derivatives. The main component of these fractions is 1,6-anhydro-beta-D-glucopyranose, or levoglucosan. Likewise, aqueous residues of liquid smoke flavorings, prepared at a laboratory scale from beech, vine shoots, thyme, and sage, were studied in the same way. These contained compounds of the same groups cited above, but showed clear differences. The aqueous residue of beech smoke flavoring was the most similar to that of the commercial smoke flavorings. The aqueous residues of vine shoots, thyme, and sage smoke flavorings contained a lower number of furan, pyran, and carbohydrate derivatives and a higher number of nitrogenated derivatives. Instead of levoglucosan, the main component was an unidentified compound, present in all samples, included in the carbohydrate derivatives group. In the samples studied, the influence of the vegetal source on the composition of the aqueous fraction has been shown. In the future, attention must be paid to the functionality of these smoke components.

Influence of the moisture content on the composition of the liquid smoke produced in the pyrolysis process of Fagus sylvatica L. wood.

The pyrolysis of several samples of sawdust of Fagus sylvatica L. wood with different moisture contents was carried out, keeping all other smoke generation parameters constant. However, parameters such as smoke production length and maximum temperature reached were affected by the moisture content of the sample and varied in the different pyrolytic runs. The acidity and the composition of the liquid smokes obtained were determined, this latter by means of gas chromatography/mass spectrometry and gas chromatography with flame ionization detection. The acidity and composition of the liquid smoke produced were affected not only by the moisture content of the sawdust sample but also by the smoke generation length and by the temperature of the process. The highest yields in components were produced from samples with low moisture content that underwent a short pyrolytic process. Some compounds, with important properties from an organoleptic and preservative point of view, were not generated from samples with high moisture content. Equations that closely relate yield of the total components or of groups of components or of individual components with parameters such as moisture content, length of the process, and temperature were obtained; these equations predict yield data of liquid smoke components with a satisfactory degree of approximation.