Josep Boatella

Biological effects of oxysterols: Current status

A review of relevant literature on biological activities of oxysterols (OS) and cholesterol is presented. The data clearly demonstrate manifold biological activities, often detrimental, for OS compared with little or no such activity of a deleterious nature for cholesterol itself. Cholesterol is perhaps the single most important compound in animal tissue and, as such, it is difficult to imagine it as a toxin or hazard. In contrast, OS exhibit cytotoxicity to a wide variety of cells leading to angiotoxic and atherogenic effects; alter vascular permeability to albumin; alter prostaglandin synthesis and stimulate platelet aggregation, an important process facilitating atherosclerosis and thrombosis; alter the functionality of low density lipoprotein (LDL) receptors, possibly stimulating hypercholesterolaemia; modify cholesteryl ester accumulation in various cells, inducing foam cell formation; and enrich the LDL particle in cholesteryl esters, possibly increasing its atherogenicity. Furthermore, OS are mutagenic and carcinogenic, although some have been studied as antitumour agents based on their cytotoxic properties. Moreover, numerous studies have implicated OS in membrane and enzyme alterations that are interrelated with many of the foregoing effects. The authors find that OS deserve much more attention than cholesterol itself in terms of research activity but that unfortunately the reverse is true with regard to funding.

Analysis of olive and hazelnut oil mixtures by high-performance liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry of triacylglycerols and gas-liquid chromatography of non-saponifiable compounds (tocopherols and sterols).

We analysed the triacylglycerol, tocopherol and sterol composition of hazelnut oil, olive oil and their mixtures (90% olive oil with 10% hazelnut oil, 70% olive with 30% hazelnut oil and 50% olive oil with 50% hazelnut oil). The main triacylglycerols were 1,2,3-trioleylglycerol, 2,3-dioleyl-1-palmitoylglycerol, 2,3-dioleyl-1-linoleylglycerol and 2,3-dioleyl-1-stearoylglycerol. Non-saponfiable compounds (tocopherols and sterols) were derivatised as O-trimethylsilyl ethers. Alpha-tocopherol was the main vitamin E isomer in all samples; however, small amounts of beta-tocopherol and gamma-tocopherol were also found. Beta-sitosterol and delta5-avenasterol were the principal sterols in all samples; campesterol and stigmasterol were minor sterol compounds in all samples. Obtusifoliol, which was a major sterol in olive oil and oil mixtures, was not found in hazelnut oil. The discriminant analysis showed that hazelnut oil, olive oil and oil mixtures were clearly separated according to their triacylglycerol composition.

Nuts: source of energy and macronutrients.

On the basis of the high fat content of nuts, they are traditionally considered as foods that provide a high amount of energy. However, epidemiologic and clinical observations do not indicate an association between nut intake and increased BMI. There is a notorious variability in macronutrient composition among nuts, although they have some consistent patterns. Nuts contain all major macronutrients: protein, carbohydrate, and fat. The total protein content is relatively high, which makes them a good source of plant protein (especially for vegetarians). Although nuts contain low amounts of some essential amino acids, this is not a nutritional concern due to the complement of protein. In addition, nuts have a low lysine:arginine ratio, which is inversely associated with the risk of developing hypercholesterolemia and atherosclerosis. Carbohydrates are the second highest macronutrient in nuts in terms of total calories provided. The fat fraction is characterized by a high amount of unsaturated fatty acids and a low content of saturated fatty acids. In conclusion, the high content in unsaturated fatty acids, the low lysine:arginine ratio, and the presence of other bioactive molecules (such as fibre, phytosterols, vitamin and other antioxidants, and minerals) make the addition of nuts to healthy diets a useful tool for the prevention of cardiovascular heart diseases.

Comparison of three methods for the determination of oxysterols in spray-dried egg

Three methods for the GC determination of oxysterols (OSs) in spray-dried egg, which combine different steps of purification, are compared. In addition, the efficiency of silica cartridges in the purification of OSs using four different systems of elution with increasing polarities is studied. The absence of cholesterol oxidation during the application of the analytical procedures is checked, and the linearity of the response and the chromatographic limits of detection and quantification are established. The methods are characterized by the calculation of precision and recovery for the different OSs. The method based on saponification alone is rejected, since it shows much lower precision. The method that includes saponification and silica cartridge purification offers higher reliability than the method based on cartridge purification alone, because it shows a higher precision and larger samples can be processed, which improves the limits of detection and quantification.

Influence of variety and geographical origin on the lipid fraction of hazelnuts (Corylus avellana L.) from Spain: (III) oil stability, tocopherol content and some mineral contents (Mn, Fe, Cu)

Abstract Induction time, acid value and α-tocopherol content of hazelnut oil and some mineral contents (manganese, iron and copper) of hazelnut kernels cultivated in Catalonia (Spain) are determined. Analysis of variance (ANOVA) showed that statistically significant differences existed for: α-tocopherol content, acid value and copper content in relation to the harvesting year of samples. Significant differences were also found for: induction time, manganese and copper contents in relation to the location of samples. On the other hand, no significant differences were found between varieties. In addition, a correlation study was performed between all parameters included in this work. A strong negative correlation was observed between linoleic acid and manganese content, and also copper content and oil stability (Rancimat).

Trans fatty acid content of human milk in Spain

The C18 fatty acid fraction of 38 samples of mature human milk from Spanish women was analyzed using capillary gas chromatography. The average content of trans fatty acids found in these samples represented 0.95% of total fatty acids. This value is lower than the percentage found in human milk from other developed countries in which the consumption of hydrogenated fat is higher. Trans fatty acid content in human milk has been related to the types of fats and oils present in the diets of the nursing mothers. According to the results obtained in this survey, we can also conclude that the amount of trans forms in breast milk lipids is lower than the trans content found in infant formulas in Spain.

DRYING CHARACTERISTICS OF THE HAZELNUT

Abstract Equilibrium moisture content isotherms for Spanish hazelnut (Corylus avellana L.) at different temperatures (30°C-80°C) were determined using static gravimetric method. Thin layer drying experiments were done with forced air circulation and were conducted with different operating conditions to determine the drying characteristics of hazelnuts. The effect of air temperature (30°C-70°C), air velocity (0.5 m/s - 2 m/s) and drying bed loading density (50 kg/m2 - 150 kg/m2) on drying of unshelled and shelled hazelnuts was studied. Six mathematical models were used to fit the experimental equilibrium moisture content data, from which the G.A.B. model was found to give the best fit. Diffusion coefficients were determined by fitting experimental thin-layer drying curves to the Ficks diffusion model. Variation of the effective diffusion coefficient with temperature was of the Arrhenius type. The Page equation was found to describe adequately the thin layer drying of hazelnut. Page equation drying paramet...

Liquid chromatographic determination of phenolic antioxidants in bakery products

A simple and rapid method for the determination of phenolic antioxidants (propyl gallate, octyl gallate, dodecyl gallate, butylated hydroxyanisole and butylated hydroxytoluene) in bakery products is described. The method involves direct extraction and liquid chromatography-UV determination. The linearity (0.9992-0.9999), resolution, precision (coefficients of variation (%) = 3.5-5.9) and recovery (40.2-95.1%) of this method are good.

INFLUENCE OF DRYING CONDITIONS ON THE HAZELNUT QUALITY. I. LIPID OXIDATION

ABSTRACT The influence of the drying conditions on the oxidation state of the lipidic fraction in hazelnut (Corylus avellana, L.) has been studied. Different hazelnut quality parameters (acidity index, KZI2 index, K270 index and oxidation stability) have been determined in unshelled and shelled hazelnuts dried under six drying air temperatures (30, 40, 50, 60, 70 and 80°). The drying experiments were done with forced air circulation, and two varieties of hazelnut were investigated, Negret and Pauetet. It has been observed that hydrolytic reactions affect dried Negret hazelnut, increasing with drying temperature. Also, drying temperatures higher than 50°C favour an increase of the rate of lipid oxidation in hazelnut, specially in shelled hazelnuts, with a decrease of the oxidation stability.

Selective gas chromatographic determination of cholesterol in eggs

A selective gas-chromatographic method is proposed for the determination of cholesterol in egg samples. The method consists of extraction of the lipid fraction and cold saponification prior to determination on a glass capillary column. The absence of cholesterol oxidation during the process was checked, and the conditions in which oxidation is avoided are discussed. The method also showed good precision (coefficient of variation=1.39%). Applying this method to different fresh and frozen egg samples, we obtained a mean content of 392 mg of cholesterol/100 g of edible portion. These values are clearly lower than the majority of results published for eggs.