Biomedical subjects

P Paseiro-Losada

Publications and source records attributed to P Paseiro-Losada.

10 recordsLinked to original sources

PubMed2005

Profiling flavor compounds of potato crisps during storage using solid-phase microextraction.

Headspace solid-phase microextraction (HS-SPME) was studied as a solvent free alternative method for the extraction and characterisation of volatile compounds in stored potato crisps by capillary gas chromatography coupled with mass detection. Better results were obtained when extraction was carried out at 70 degrees C using a divinylbenzene (DVB)-carboxen (CAR)-polydimethylsiloxane fiber. The fiber was exposed for 20 min (extraction time) to the sample headspace, immediately after an equilibrium time of 5 min (time needed to reach the equilibrium between sample and above headspace). A total of 31 compounds were identified in oxidised potato crisps and resulted mainly from the degradation/rearrangement of lipids and carbohydrates.

Gas Chromatography-Mass Spectrometry↗

PubMed2004

Determination of hexanal as indicator of the lipidic oxidation state in potato crisps using gas chromatography and high-performance liquid chromatography.

Hexanal (an oxidative state indicator) formed in the headspace of potato crisps during storage was evaluated using two different procedures. First, solid-phase microextraction, an innovative sampling preparation methodology was used. It consisted on the absorption of analytes directly from samples and subsequent thermal desorption on the gas chromatograph (GC) injector. Then, a reversed-phase high-performance liquid chromatographic technique (HPLC) was employed to quantify hexanal in the form of 2,4-dinitrophenylhydrazone derivative. Methods were evaluated in what concerns to validation parameters such as linearity, repeatibility and detection limit. GC (LOD = 1 ng/ml) method resulted in more sensitive method than HPLC (LOD = 9 ng/ml). The most suitable technique for hexanal measurement was selected.

Aldehydes↗

PubMed2004

Comparison between high-performance liquid chromatography and gas chromatography methods for fatty acid identification and quantification in potato crisps.

A reversed-phase high performance liquid chromatographic (RP-HLPC) method was compared with a gas chromatography-flame ionization detection (GC-FID) method for determining fatty acids in potato crisps. Different extraction procedures were used. Fatty acids were quantified by linear regression. Both methods presented good precision (R.S.D. < or = 5.88%) and recovery (> or = 82.31%). The precision using HPLC method was slightly better than for GC-FID method. There was good agreement between the fatty acid composition of potato crisps analysed by both methods. For most purposes the HPLC method would be better. However, when more fatty acids need to be analysed, GC is a more suitable method.

Chromatography, Gas↗

PubMed2004

Determination of the uronic acid composition of seaweed dietary fibre by HPLC.

A high-performance liquid chromatographic (HPLC) method is described for determination of the ratio of beta-d-mannuronic acid to alpha-l-guluronic acid (M/G ratio) in dietary fibre of edible seaweeds. Total dietary fibre (TDF) content was determined gravimetrically. The TDF fraction was hydrolysed with 12 m and 1 m H(2)SO(4), then neutralized with AG 4 x 4 resin. The uronic acids were separated in a Tracer Extrasil SAX 5 micro m column (25 cm x 4 mm) at 35 degrees C, with 2 mm KH(2)PO(4) containing 5% methanol as mobile phase at a fl ow rate of 1.5 mL/min. The detection wavelength was UV 210 nm. The chromatographic identifications of beta-d-mannuronic acid and alpha-l-guluronic acid were confirmed by liquid chromatography-mass spectrometry (LC-MS). The method precision was 1.4% for beta-d-mannuronic acid and 3.5% for alpha-l-guluronic acid. The method was used to determine M/G ratio in canned seaweeds (Saccorhiza polyschides and Himanthalia elongata) and in dried seaweeds (H. elongata, Laminaria ochroleuca, Undaria pinnatifida, Palmaria sp. and Porphyra sp.).

Chromatography, High Pressure Liquid↗

PubMed2004

An HPLC method for the quantification of sterols in edible seaweeds.

This study presents an HPLC method for the quantification of sterols in edible seaweeds. Sterols were identified by HPLC/mass spectrometry (HPLC-MS) in positive APCI mode. The samples were saponified by refluxing with 1 m ethanolic KOH, and the non-saponifiable fraction was extracted with hexane. Sterols were quantified by HPLC with UV detection (HPLC-UV), on a 15 x 0.4 cm Kromasil 100 C(18) 5 micro m column (mobile phase 30:70 v/v methanol:acetonitrile; fl ow rate 1.2 mL/min; column temperature 30 degrees C; detection wavelength 205 nm). Method repeatability for fucosterol was good (coefficient of variation 2.4%). Sterol contents were determined in canned or dried brown seaweeds (Himanthalia elongata, Undaria pinnatifida, Laminaria ochroleuca) and red seaweeds (Palmaria sp., Porphyra sp.). The predominant sterol was fucosterol in brown seaweeds (83-97% of total sterol content; 662-2320 micro g/g dry weight), and desmosterol in red seaweeds (87-93% of total sterol content; 187-337 micro g/g dry weight).

Chromatography, High Pressure Liquid↗

PubMed2004

Simultaneous determination of thiamine and riboflavin in edible marine seaweeds by high-performance liquid chromatography.

This study presents a high-performance liquid chromatography (HPLC) method for simultaneous determination of thiamine and riboflavin and the results of its application to a number of edible seaweeds that are sampled in dried form (Himanthalia elongata, Laminaria ochroleuca, Undaria pinnatifida, Palmaria sp., and Porphyra sp.) or as canned food (H. elongata and Saccorhiza polyschides). Samples are prepared by acid and enzymatic hydrolysis. Optimized conditions for reversed-phase HPLC with fluorescence detection are as follow: column, Kromasil 100 C18; column temperature, 35 degrees C; mobile phase, a 72:28 (v/v) mixture of 0.005 M ammonium acetate (pH 6.7)-methanol; and flow rate, 1.35 mL/min. With these conditions, recovery is 95.52% for thiamine and 90.08% for riboflavin, and the method precision (relative standard deviation) is 2.66% for thiamine and 2.21% for riboflavin. On a dry weight basis, thiamine contents range from 0.14 microg/g in dried H. elongata to 2.02 microg/g in dried Porphyra and riboflavin contents from 0.31 microg/g in canned H. elongata to 6.15 microg/g in dried Porphyra.

Chromatography, High Pressure Liquid↗

PubMed2003

Evaluating the migration of ingredients from active packaging and development of dedicated methods: a study of two iron-based oxygen absorbers.

The behaviour of two commercial oxygen-scavenging products with respect to migration of active ingredients into foodstuffs was investigated. Migrants were identified, and by using appropriate analytical methods, migration was determined in a variety of liquid, solid or gelled food simulants and foods. Simulants were chosen to cover a range of water activities and viscosities. Foods and the gelled food simulant agar were packed with and without vacuum, and with the oxygen scavenger in various locations relative to the packed food. The main migrants, as identified by X-ray fluorescence spectrometry, infrared spectroscopy and scanning electron microscopy with energy-dispersive spectrometry were Na(+) and Cl(-) in non-acidic aqueous simulants, and Na(+), Cl(-) and Fe(2+) in 3% acetic acid. Migration into aqueous simulants exceeded the current European Union limit for total migration from plastic materials (assumed to be currently applicable to these systems) and was probably excessive by any reasonable standard. However, neither oxygen scavenger appeared to release significant quantities of migrants into solid foods when the scavenger was properly located in the package and the packing process does not favour the contents becoming wet by water released from the food.

Acetic Acid↗

PubMed2003

Determination of bisphenol A in, and its migration from, PVC stretch film used for food packaging.

Bisphenol A (BPA) is used as an additive in polyvinyl chloride (PVC) products, including stretch films used for food packaging. The BPA contents were investigated of several brands of stretch film bought locally but marketed internationally or throughout Spain and which were presumably produced at different manufacturing plants. Their major components were identified by FTIR (Fourier Transform Infrared Spectrometry) and horizontal attenuated total reflectance, and the migration of BPA from these materials into the standard European Union food simulants was determined by high-performance liquid chromatography (HPLC) using both fluorescence (FL) and ultraviolet (UV) detection, the identity of the analyte being confirmed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The two HPLC detection methods had different detection limits (30 microg x l(-1) for UV, 3 microg x l(-1) for FL), but afforded virtually identical BPA determinations for the samples tested. BPA contents ranging from 40 to 100 mg x kg(-1) were found in three of the five PVC-based films analysed, and a content of 500 mg x kg(-1) was found in a fourth; for these determinations, extraction into acetonitrile was used. In standard tests of migration into water, 3% acetic acid and olive oil over 10 days at 40 degrees C, migration from a given film was in all cases greatest into olive oil. Migration from the films with non-zero BPA contents ranged from 3 to 31 microg x dm(-2), values higher than those reported for many other food-contact materials, but lower than the European Union specific migration limit for BPA. PVC stretch film nevertheless may make a significant contribution to contamination of foodstuffs by BPA, and should be taken into account in estimating BPA intake or exposure to this substance.

Benzhydryl Compounds↗

PubMed2002

High-performance liquid chromatographic determination of alpha-tocopherol in macroalgae.

A high-performance liquid chromatographic (HPLC) method for the microscale determination of alpha-tocopherol in macroalgae is reported. The method includes microscale saponification and extraction with n-hexane. The presence of alpha-tocopherol in macroalgae samples was confirmed by HPLC-MS. Alpha-tocopherol levels as determined in samples by HPLC with UV and fluorescence detection did not differ significantly; however, fluorescence detection has a higher sensitivity (detection limit 10.4 ng/ml, vs. 104 ng/ml with UV detection), as well as good precision (relative standard deviation 1.81%) and recovery (94.3%). Fluorescence detection is also faster. We used this method to determine the alpha-tocopherol contents of four commercial macroalgae products from northwest Spain as part of nutritional studies in dehydrated Himanthalia elongata and Laminaria ochroleuca, and also in canned Himanthalia elongata and Saccorhiza polychides.

Chromatography, High Pressure Liquid↗

PubMed1998

m-Xylylenediamine determination in the official EU aqueous food simulants.

European Union directive 90/128/EEC prescribes a specific migration limit of 0.05 mg/kg for the aliphatic diamine m-xylylenediamine (m-XDA) into food or food simultants, but there is no generally accepted method of analysis available for compliance testing with the given restriction. A method is described for the determination of m-XDA monomer in the following food simulants: distilled water, 3% (w/v) acetic acid, and 15% (v/v) ethanol. The method is appropriate for the quantitative determination of m-XDA at a minimum level of 0.020 mg/kg in these food simulants. Detection limits are in the range of 0.004 to 0.010 mg m-XDA per kilogram food simulant (depending on the type of food simulant). The method should also be applicable to other aqueous food simulants. m-XDA in aqueous simulant test samples is determined by high-performance liquid chromatography with fluorescence detection following derivatization with fluorescamine. Quantitation is relative to external standards. The identity of m-XDA may be confirmed by the presence of a second peak in the chromatograms obtained from samples derivatized with less fluorescamine or by comparison with authentic samples.

Food Analysis↗