Aplicaciones de columnas capilares polares termoestables en cromatografía gaseosa

The composition, the effect of processing and storage, and the overall quality of food lipids can be evaluated by gas chromatography (GC). GC analyses are carried out on non-polar or polar capillary columns, which separate the various lipid components according to their polarity and boiling points. However, there are components with high-boiling points that require higher temperatures in order to be better resolved. Thermostable polar GC columns with a relatively low column bleeding, can be used for this scope. These columns generate GC traces with different separation characteristics, which can lead to the identification of components that cannot be completely resolved with non-polar GC columns. Thermostable polar GC columns are suitable for the separation of different lipid classes and can be utilised for a fast screening of the total unsaponifiable matter of the oil or lipid extract. A series of examples for the analysis of food lipids with thermostable polar GC columns, are here described.La composición, el efecto del procesamiento y el almacenamiento, y la calidad total de los alimentos grasos se pueden evaluar por cromatografía de gases (GC). El análisis cromatográfico se lleva a cabo con columnas capilares polares y apolares que separan los diferentes componentes lipídicos de acuerdo a su polaridad y punto de ebullición. Sin embargo, existen componentes con altos puntos de ebullición que requieren temperaturas más elevadas para lograr una mejor separación. Las columnas polares termoestables de cromatografía de gases con un “sangrado” relativamente bajo, se pueden usar para esta actividad. Estas columnas generan cromatogramas con características diferentes que pueden conducir a la identificación de componentes que no pueden ser completamente resueltos con columnas no polares. Las columnas polares termoestables de cromatografía de gases son óptimas para la separación de las diferentes clases de lípidos y pueden ser usadas para una visión rápida del total de la materia insaponificable del aceite o extracto lipídico. En este artículo se describen una serie de ejemplos de análisis de los lípidos de diferentes alimentos, llevados a cabo con columnas termoestables de cromatografía de gases

Milk and butter. From the Neolithic to the current nutritional aspects

The evolution in the history of nutrition knowledge towards dairy products, is strictly related to the socio-cultural development of humans. In fact, milk and butter have accompanied humans since ancient times, which traces of the consumption of such products are dated back about the earliest times after the last (glaciation) ice age, while the application for extra nutritional uses, such as cosmetics and ceremonial rites, are reported in the writings of the Old Testament. Even in Italy, before the Roman Empire, were known rudimentary techniques of production and storage of dairy products. But only with the advent of the Etruscans, and the Romans later, that the use of milk and dairy products reach a wide diffusion in several applications. Since the advent of Christ until today, milk and its derivatives have maintained a privileged place in the human diet, but it is only with the advent of modern medicine and new findings in lipidic chemistry that emerged multiple biological and nutritional properties, very important for human health. After a short summary of the ancient history of the milk and butter, the role of dairy products in cancer, in hypercholesterolemia, and cardiovascular disease are reported. Moreover, the current opinions on saturated fatty acids, the role of polyunsaturated fatty acids and their lipid mediators obtained by the action of cyclooxygenase, lipoxygenase and the cytochrome P450 enzymes, are treated. Even if sometimes mistreated, the milk, but most of all its high fat content derivatives such as butter, is a rich source of biologically active compounds that foster a controversial action against neolplastic and cardiovascular disease. These compounds, mainly contained in the lipid fraction, for the more obvious relationships that exist between nutrition and health status, have been the subject in the last decades of intense scientific investigation in which there were expressed lights and shadows, but recognizing that not all fats are harmful and further thorough studies are necessary, in particular, on the derived lipid mediators. This will allow a significant progress based on new scientific evidences, further orienting researchers and clinicians on evidencebased nutritional science

Formation of the 5,6-epoxy derivatives of 7-liydroxy-cholesteryl 3β-acetates during peroxidation of cholesteryl acetate.

The thermal peroxidation of cholesteryl acetate (CA) generates many compounds, most of which have been identified in previous studies. The trimethylsilyl (TMS) derivatives of the thermodegradation products of the single hydroperoxides of CA (7α- and 7β-) gave GCMS spectra that were almost identical to those of the thermal peroxidation of CA, except for four compounds that were only detected as TMS derivatives. These substances were identified by comparing their mass spectra and their GC retention time against those of the four synthesized isomers of the epoxy-hydroxy derivatives of CA. The presence of a considerable amount of epoxy-hydroxy derivates of CA, especially at low-temperature degradations, provides an explanation for the formation of other substances that have been previously identified

Constituyentes volátiles y estabilidad oxidativa de aceites vírgenes de oliva: influencia del batido de la pasta de aceitunas.

Olive crushing, olive-paste kneading and separation of the oil the most important technological steps in olive oil production since they directly influence the future quality of the product. The contact between the oil and the olive-paste increases lipolysis and lipid oxidation, which are mainly due to the highly-active lipases present in the paste and the lipoxygenase action, respectively. The choice of the technological parameters is directly related to the oil future stability and its organoleptic characteristics. This study confirms and emphasizes the fact that the oxidative degradation, simultaneously with the well-known formation of the flavor compounds, is related to the time required for the separation of the oil-water emulsion. Loss of the natural antioxidants (minor polar components) by an oxidative effect was demonstrated to be also influenced by the time required for oil separation.La molienda de aceitunas, el batido de la pasta y la separación del aceite de oliva producen una serie de transformaciones en las características del aceite que posteriormente será extraído. Es sabido que la formación de distintos componentes del aroma del aceite derivan de reacciones oxidativas enzimáticas. El contacto entre el aceite y la pasta de aceitunas incrementa la lipolisis y la oxidación lipídica, debido a un incremento de la actividad de las lipasas presentes en la pasta y a una acción lipoxigenásica respectivamente. La elección de los parámetros tecnológicos está en relación directa con la futura estabilidad y las características organolépticas del aceite. En este trabajo se confirma la formación de tales compuestos evidenciándose la degradación oxidativa del aceite en relación al tiempo de batido empleado. Se demuestra también una pérdida de antioxidantes (componentes polares menores) por efectos oxidativos en modo proporcional al tiempo de batido

Volatile constituents and oxidative stability of virgin olive oils: influence of the kneading of olive-paste.

La molienda de aceitunas, el batido de la pasta y la separacion del aceite de oliva producen una serie de transformaciones en las caracteristicas del aceite que posteriormente sera extraido. Es sabido que la formacion de distintos componentes del aroma del aceite derivan de reacciones oxidativas enzimaticas. El contacto entre el aceite y la pasta de aceitunas incrementa la lipolisis y la oxidacion lipidica, debido a un incremento de la actividad de las lipasas presentes en la pasta y a una accion lipoxigenasica respectivamente. La eleccion de los parametros tecnologicos esta en relacion directa con la futura estabilidad y las caracteristicas organolepticas del aceite. En este trabajo se confirma la formacion de tales compuestos evidenciandose la degradacion oxidativa del aceite en relacion al tiempo de batido empleado. Se demuestra tambien una perdida de antioxidantes (componentes polares menores) por efectos oxidatives en modo proporcional al tiempo de batido

Effets de la formation de la pourriture acide sur la composition de la fraction lipidique des différentes parties du grain de Vitis vinifera cv. Fortana

On a étudié par comparaison la composition de la fraction lipidique des différentes parties de grains de Vitis vinifera sains et attaqués par la pourriture acide.Des différences considérables ont été révélées entre les extraits des différents types d'échantillons de pulpe + peau en ce qui concerne les paramètres suivants: teneur en lipide, composition des triglycérides, composition des acides gras. Par contre, la fraction lipidique des deux échantillons de pépins était très semblable.Les composants principaux ainsi que leur répartition quantitative caractéristique correspondent aux résultats publiés dans une étude précédente. On a mis en évidence l'aldéhyde oléanoique qui n'était présente que dans quelques échantillons de pulpe + peau en même temps que l'acide correspondant et l'erythrodiol.Effects of sour rot on the composition of the lipid fraction of different parts of grapevine berries ( Vitis vinifera cv. Fortana)The composition of the lipid fraction of the various parts of berries of Vitis vinifera, healthy and infected by sour rot, have been compared. Notable differences became evident among the extracts of the various samples of pulp + skin with respect to the following parameters: lipid contens, composition of triglycerides and composition of fatty acids. The composition of the lipid fraction of the two samples of grape seeds, however, turned out to be very similar.The principal components and their quantitative distribution characteristics corresponded with the results reported in a preceding work. Oleanoic aldehyde has been identified which, together with the corresponding acid and erythrodiole, was only present in the samples of pulp + skin

Levels of phytosterol oxides in enriched and nonenriched spreads: application of a thin-layer chromatography-gas chromatography methodology

The content of phytosterol oxidation products (POPs) in enriched and nonenriched commercial spreads was evaluated by thin-layer chromatography-gas chromatography (TLC-GC). Oxides of beta-sitosterol, campesterol, and stigmasterol were produced by thermo-oxidation (7-hydroxy, 7-keto, and epoxy derivatives) and chemical synthesis (triol derivatives), which were then separated and identified by TLC-GC. Their identification was further confirmed by GC-mass spectrometry (GC-MS). The total amounts of phytosterols found were 6.07 and 0.33 g/100 g of sample in phytosterol-enriched and nonenriched spread, respectively, whereas the total POPs contents were 45.60 and 13.31 mg/kg of sample in the enriched and nonenriched products. The main POPs found were the 7-keto derivatives of all phytosterols analyzed; 7-ketositosterol was the most abundant one (14.96 and 5.93 mg/kg of sample in phytosterol-enriched and nonenriched spread). No beta-epoxy and triol derivatives were detected in both types of samples. The enriched spread presented a lower phytosterol oxidation rate (0.07%) than the nonenriched one (0.41%)

Thermo-oxidation of cholesterol: effect of the unsaturation degree of the lipid matrix

The influence of the unsaturation degree of different triacylglycerols (tristearin, triolein, trilinolein and trilinolenin) on cholesterol oxidation at 180 °C, was evaluated. Cholesterol degraded faster when heated alone than in the presence of triacylglycerols; moreover, the more unsaturated the matrix, the slower the degradation of cholesterol. Both cholesterol and triacylglycerols degradation fit a first order kinetic model (R(2)>0.9), except for the tristearin sample. Cholesterol oxidation products (COPs) and peroxides were formed during the heating treatment. The presence of any type of lipid matrix postponed and decreased the maximum concentration of both oxidation parameters. Maximum total COPs concentrations were achieved at 20 min in neat cholesterol, 120 min in tristearin and triolein and 180 min in polyunsaturated matrix samples. 7-Ketocholesterol was the main COP in most cases during the whole heating treatment. Both the presence of triacylglycerols and their unsaturation degree inhibited cholesterol thermooxidation at 180 °C