Mónica Narváez-Rivas

A new high-performance liquid chromatographic method with evaporative light scattering detector for the analysis of phospholipids. Application to Iberian pig subcutaneous fat

A new method for the analysis of phospholipids by normal-phase HPLC is described using a silica column. Addition of ammonia and triethylamine to a gradient based on chloroform/methanol/water promoted a good and rapid separation of phospholipid classes (20 min run). The use of an evaporative light scattering detector permitted an accurate analysis of a mixture of phospholipids. Calibration curves were linear within different range for each phospholipid class. The LOD and LOQ obtained were below 0.03 and 0.05 mg kg⁻¹ for all cases, respectively. Besides, a new method for the separation of phospholipids from total lipids before HPLC analysis by a solid-phase extraction (SPE) with Si cartridges has been developed. This methodology gave a good recovery ranging from 97 to 117%. The method was validated with a standard mixture of phospholipids. This method has been applied to characterize the phospholipid fraction of subcutaneous fat from Iberian pig. Cardiolipin, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylcholine, and sphingomyelin have been described for first time in these samples. The fatty acid composition of the different phospholipid classes and their HPLC electrospray ionization mass spectrometry have been used for characterizing the molecular species present in each one.

Authentication of fattening diet of Iberian pigs according to their volatile compounds profile from raw subcutaneous fat.

AbstractThe composition of volatile components of subcutaneous fat from Iberian pig has been studied. Purge and trap gas chromatography−mass spectrometry has been used. The composition of the volatile fraction of subcutaneous fat has been used for authentication purposes of different types of Iberian pig fat. Three types of this product have been considered, montanera, extensive cebo and intensive cebo. With classification purposes, several pattern recognition techniques have been applied. In order to find out possible tendencies in the sample distribution as well as the discriminant power of the variables, principal component analysis was applied as visualisation technique. Linear discriminant analysis (LDA) and soft independent modelling by class analogy (SIMCA) were used to obtain suitable classification models. LDA and SIMCA allowed the differentiation of three fattening diets by using the contents in 2,2,4,6,6-pentamethyl-heptane, m-xylene, 2,4-dimethyl-heptane, 6-methyl-tridecane, 1-methoxy-2-propanol, isopropyl alcohol, o-xylene, 3-ethyl-2,2-dimethyl-oxirane, 2,6-dimethyl-undecane, 3-methyl-3-pentanol and limonene. FigureIberian pigs in outdoor rearing system (Montanera)

Changes in the Fatty Acid and Triacylglycerol Profiles in the Subcutaneous Fat of Iberian Ham during the Dry-Curing Process

In this study, we have evaluated the changes that occur in the profiles of total fatty acids and triacylglycerols during the dry-curing process (730 days) of Iberian ham. The subcutaneous adipose tissues of six hams obtained from three Iberian pigs fed on acorns were analyzed periodically during the processing time (from the raw to the dry-cured samples), including postsalting, drying, and ripening stages. The environmental conditions were also registered. The curing process significantly decreased (p < 0.01) the relative percentages of total polyunsaturated fatty acids, including C18:2n-6 and C18:3n-3 and, therefore, significantly increased (p < 0.05) the level of monounsaturated fatty acids. The triglycerides containing 0-2 double bonds showed an increase during the curing process. On the contrary, the more unsaturated ones (3-5 double bonds) suffered a significant decrease. We have postulated that these changes could also be due to polymerization and oxidation reactions that affect the triacylglycerols and besides the fatty acids. In general, most fatty acids and triacylglycerols reversed the trend by about 500-600 days of processing.

Subcutaneous fat triacylglycerols profile from iberian pigs as a tool to differentiate between intensive and extensive fattening systems

Triacylglycerols of subcutaneous fat of Iberian pigs reared on two different feeding systems, extensive and intensive, have been determined by gas chromatography with a flame ionization detector. Analyses were performed on a column coated with a bonded stationary phase (50% phenyl-50% methylpolysiloxane) with hydrogen as the carrier gas. Lipids were extracted by melting the subcutaneous fat in a microwave oven and then filtering and dissolving in hexane. A total amount of 1995 samples from several campaigns were considered. Palmitoyl-stearyl-oleoyl glycerol and palmitoyl-dioleoyl glycerol were the most abundant triacylglycerols found in the samples. A study on the discriminating power of the triacylglycerols to differentiate samples according to the pig feeding system was performed. By using the triacylglycerols as chemical descriptors, principal component analysis, linear discriminant analysis, and soft independent modeling of class analogy were applied. Dioleoyl-linoleoyl glycerol and oleoyl-dilinoleoyl glycerol were the most discriminating variables. Variable-variable plots of these two glycerols allow separation of the samples according to their content.

A new SPE/GC-fid method for the determination of cholesterol oxidation products. Application to subcutaneous fat from Iberian dry-cured ham

A new method for the isolation and analysis of cholesterol oxidation products (COPs) using solid phase extraction (SPE) and silica columns was developed using gas chromatography-flame ion detection (GC-FID). The method comprises of saponification and liquid-liquid extraction of the unsaponifiable fraction prior to the isolation and derivatization of the COPs to trimethylsilyl ethers. The COPs used in this study are cholestane-5α-6α-epoxide, cholestane-3β-5α-6β-triol, 25-hydroxycholesterol and 5-cholesten-3β-ol-7-one. In order to identify the COPs fraction a GC-ion-trap-mass spectrometry experiment were conducted using authentic standards to verify the presence of the COPs. The method was effective at rapidly separating the COPs (25 min run). Calibration curves were linear with the LODs and LOQs bellow 0.03 and 0.07 mgkg(-1) for all cases, respectively. This methodology gave a total recovery for every compound that was used in the study. Betulin was used as an internal standard to monitor the recovery. The method was validated with a standard mixture of COPs. The method has been applied to characterize the COP fraction of subcutaneous fat from Iberian dry-cured ham. Cholestane-5α-6α-epoxide, cholestane-3β-5α-6β-triol, 25-hydroxycholesterol and 5-cholesten-3β-ol-7-one have been identified for the first time in these samples.

Authentication of fattening diet of goat kid according to their fatty acid profile from perirenal fat

Fatty acids of forty-two samples of perirenal fat of goat kids reared on three different feeding systems: goat milk (B), milk replacer (R) and milk-based starter (F) have been analyzed by Gas Chromatography flame ionization detector. The lipids were extracted by melting of perirenal fat in a microwave oven. The fat was then filtered and dissolved in hexane. This analysis was performed on a column (100 m x 0.25 mm i.d. and 0.25 microm film thickness) coated with a polar stationary phase HP-88 and flame ionization detector was used. Hydrogen (25 psi inlet constant pressure) was used as carrier gas. Programmed temperature was kept at 175 degrees C and held isothermally for 10 min, and was then raised to 205 degrees C at a rate of 3 degrees C/min and held isothermally for 10 min. By using the fatty acids as chemical descriptors, pattern recognition techniques were applied to differentiate between goat milk, milk replacer and milk-based starter fattening diet of goat kid. C18:2 and C18:3 acids were found to be the most differentiating variables.

Characterization of Lipids in Femoral Atheroma from Diabetic Patientsand Their Use as Clinical Descriptors

In this work, a solid phase extraction (SPE) method is used to separate the different lipid fractions of atheroma plaque from diabetic human patients for their subsequent analysis. Sixteen fatty acids, seventeen triacylglycerols, eleven diacylglycerols being each of them as 1,2- and 1,3-isomers, two free fatty acids, 1-monoolein and seven phospholipid classes were identified. The discriminating power of the different compounds characterized has been studied in order to use them as clinical descriptor. Linear Discriminant Analysis has been applied for such purposed, diacylglycerols being the most useful compounds giving models with a total classification when sex, dyslipidemia, heart attack and stage of atheroma from patients were considered. This methodology has been used to highlight the differences between sex and age of the patients, as well as to find out differences between patients with different diseases such as dyslipidemia, heart attack, metabolic syndrome and renal failure.