Articles de revista
http://hdl.handle.net/2117/3784
2024-03-28T21:59:32ZDetermination of hexavalent chromium in leather by ion-exchange chromatography
http://hdl.handle.net/2117/26102
Determination of hexavalent chromium in leather by ion-exchange chromatography
Font Vallès, Joaquim; Perez Quiñones, Carmen; Reyes Farrera, María R.; Cobos, Mireia; Combalia Cendra, Felip; Marsal Monge, Agustí
The determination of traces of hexavalent chromium in leather and in leather consumer goods is carried out by ion-exchange chromatography. Samples are extracted at pH7.5-8 with a phosphate buffer, according to the method of the current ISO 17075 Standard. The extracts are filtered and analysed by HPLC using an ion-exchange stationary phase and a PDA detector, without any clean up process. An ammonium sulphate electrolyte at pH8 is used as mobile phase. The determination of the recovery yields rates from 84 to 108%. The HPLC method is compared with the current ISO 17075 Standard, which is based in the classical method of the diphenylcarbazide. The data from these results, and from those of recovery rate studies, leads us to conclude that the HPLC method is a better alternative for determining chromium (VI) in leather samples. The new method shortens the procedure of the current ISO 17075 Standard, diminishes workload, reduces the amount of laboratory wastes and its results are much more precise. HPLC is able to measure the chromium (VI) concentration of samples up to 3mg/kg, the detection limit of the current Standard
2015-01-27T11:25:37ZFont Vallès, JoaquimPerez Quiñones, CarmenReyes Farrera, María R.Cobos, MireiaCombalia Cendra, FelipMarsal Monge, AgustíThe determination of traces of hexavalent chromium in leather and in leather consumer goods is carried out by ion-exchange chromatography. Samples are extracted at pH7.5-8 with a phosphate buffer, according to the method of the current ISO 17075 Standard. The extracts are filtered and analysed by HPLC using an ion-exchange stationary phase and a PDA detector, without any clean up process. An ammonium sulphate electrolyte at pH8 is used as mobile phase. The determination of the recovery yields rates from 84 to 108%. The HPLC method is compared with the current ISO 17075 Standard, which is based in the classical method of the diphenylcarbazide. The data from these results, and from those of recovery rate studies, leads us to conclude that the HPLC method is a better alternative for determining chromium (VI) in leather samples. The new method shortens the procedure of the current ISO 17075 Standard, diminishes workload, reduces the amount of laboratory wastes and its results are much more precise. HPLC is able to measure the chromium (VI) concentration of samples up to 3mg/kg, the detection limit of the current StandardModelling extraction of white tea polyphenols: the influence of temperature and ethanol concentration
http://hdl.handle.net/2117/25526
Modelling extraction of white tea polyphenols: the influence of temperature and ethanol concentration
Peiró Sánchez, Sara; Gordon, Michael H.; Blanco Abellán, Mónica; Pérez Llamas, Francisca; Segovia Gómez, Francisco José; Almajano Pablos, María Pilar
The optimization of the extraction of natural antioxidants from white tea has fostered intensive research. This study has investigated the effects of ethanol-water mixtures, temperature and time on the extraction of polyphenols and antioxidant components from white tea. The response surface methodology was applied to identify the best extraction conditions. The best conditions to maximize the extraction of total polyphenols were: ethanol, 50%, for 47.5 min. Although the yield of polyphenols was optimal at 65 °C, the maximum antioxidant capacity was achieved with an extraction temperature of 90 °C. This study has identified the optimal conditions for the extraction of tea liquor with the best antioxidant properties. Epigallocatechin gallate, epicatechin gallate, epigallocatechin and epicatechin were extracted from white tea at concentrations up to 29.6 ± 10.6, 5.40 ± 2.09, 5.04 ± 0.20 and 2.48 ± 1.10 mg/100 g. - See more at: http://www.mdpi.com/2076-3921/3/4/684/html#sthash.DWIdO5Ua.dpuf
2015-01-14T17:46:52ZPeiró Sánchez, SaraGordon, Michael H.Blanco Abellán, MónicaPérez Llamas, FranciscaSegovia Gómez, Francisco JoséAlmajano Pablos, María PilarThe optimization of the extraction of natural antioxidants from white tea has fostered intensive research. This study has investigated the effects of ethanol-water mixtures, temperature and time on the extraction of polyphenols and antioxidant components from white tea. The response surface methodology was applied to identify the best extraction conditions. The best conditions to maximize the extraction of total polyphenols were: ethanol, 50%, for 47.5 min. Although the yield of polyphenols was optimal at 65 °C, the maximum antioxidant capacity was achieved with an extraction temperature of 90 °C. This study has identified the optimal conditions for the extraction of tea liquor with the best antioxidant properties. Epigallocatechin gallate, epicatechin gallate, epigallocatechin and epicatechin were extracted from white tea at concentrations up to 29.6 ± 10.6, 5.40 ± 2.09, 5.04 ± 0.20 and 2.48 ± 1.10 mg/100 g. - See more at: http://www.mdpi.com/2076-3921/3/4/684/html#sthash.DWIdO5Ua.dpufIsocyanate toughening of pCBT/organoclay nanocomposites with exfoliated structure and enhanced mechanical properties
http://hdl.handle.net/2117/24875
Isocyanate toughening of pCBT/organoclay nanocomposites with exfoliated structure and enhanced mechanical properties
Abt, Tobias Martin; Bou Serra, Jordi; Sánchez Soto, Miguel
Cyclic butylene terephthalate (CBT (R)) is an interesting matrix material for the preparation of nanocomposites due to its very low, water-like melt viscosity which favours clay exfoliation. Nevertheless, polymerized CBT (pCBT) is inherently brittle. This paper reports the preparation of isocyanate-toughened nanocomposites made from CBT and organo-modified montmorillonite. The role of the organoclay as reinforcement and the polymeric isocyanate (PMDI) as toughening agent on the properties of pCBT was studied. The organoclay increased the stiffness and strength by up to 20% whereas the PMDI improved the deformation behaviour. However, the PMDI did not affect the degree of clay dispersion or exfoliation and flocculated-intercalated structures were observed. The compatibility between the pCBT matrix and clay was further increased by preparing PMDI-tethered intercalated organoclay. The modified organoclay then exfoliated during ring-opening polymerization and yielded true pCBT/clay nanocomposites. This work demonstrates that reactive chain extension of CBT with a polyfunctional isocyanate is an effective method to obtain toughened pCBT nanocomposites. Moreover, isocyanates can enhance the compatibility between pCBT and nanofiller as well as the degree of exfoliation.
2014-11-27T18:00:32ZAbt, Tobias MartinBou Serra, JordiSánchez Soto, MiguelCyclic butylene terephthalate (CBT (R)) is an interesting matrix material for the preparation of nanocomposites due to its very low, water-like melt viscosity which favours clay exfoliation. Nevertheless, polymerized CBT (pCBT) is inherently brittle. This paper reports the preparation of isocyanate-toughened nanocomposites made from CBT and organo-modified montmorillonite. The role of the organoclay as reinforcement and the polymeric isocyanate (PMDI) as toughening agent on the properties of pCBT was studied. The organoclay increased the stiffness and strength by up to 20% whereas the PMDI improved the deformation behaviour. However, the PMDI did not affect the degree of clay dispersion or exfoliation and flocculated-intercalated structures were observed. The compatibility between the pCBT matrix and clay was further increased by preparing PMDI-tethered intercalated organoclay. The modified organoclay then exfoliated during ring-opening polymerization and yielded true pCBT/clay nanocomposites. This work demonstrates that reactive chain extension of CBT with a polyfunctional isocyanate is an effective method to obtain toughened pCBT nanocomposites. Moreover, isocyanates can enhance the compatibility between pCBT and nanofiller as well as the degree of exfoliation.Use of lyophilised and powdered Gentiana lutea root in fresh beef patties stored under different atmospheres
http://hdl.handle.net/2117/24797
Use of lyophilised and powdered Gentiana lutea root in fresh beef patties stored under different atmospheres
Azman, Nurul Aini Binti Mohd; Gordon, Michael H.; Skowyra, Monika; Segovia Gómez, Francisco José; Almajano Pablos, María Pilar
Gentiana lutea
root is a medicinal herb that contains many active compounds which contribute to physiological
effects, and it has recently attracted much attention as a natural source of antioxidants. The aim of this study was to evaluate
the effects on the colour, pH, microbial activities, sensory quality and resistance to lipid oxidation (through the thiobarbituric
acid method) during storage of beef patties containing different concentrations of
G. lutea.
Fresh beef patties were formulated
with 0–5gkg
-
1
of
G. lutea
and 0 or 0.5gkg
-
1
of ascorbic acid and packed in two different atmospheres, Modified Atmosphere
1 (MAP1) and Modified Atmosphere 2 (MAP2), and stored at 4
±
1
°
C for 10 days. MAP1 contained 20:80 (v/v) O
2
:CO
2
and MAP2
contained 80:20 (v/v) O
2
:CO
2
2014-11-21T12:32:25ZAzman, Nurul Aini Binti MohdGordon, Michael H.Skowyra, MonikaSegovia Gómez, Francisco JoséAlmajano Pablos, María PilarGentiana lutea
root is a medicinal herb that contains many active compounds which contribute to physiological
effects, and it has recently attracted much attention as a natural source of antioxidants. The aim of this study was to evaluate
the effects on the colour, pH, microbial activities, sensory quality and resistance to lipid oxidation (through the thiobarbituric
acid method) during storage of beef patties containing different concentrations of
G. lutea.
Fresh beef patties were formulated
with 0–5gkg
-
1
of
G. lutea
and 0 or 0.5gkg
-
1
of ascorbic acid and packed in two different atmospheres, Modified Atmosphere
1 (MAP1) and Modified Atmosphere 2 (MAP2), and stored at 4
±
1
°
C for 10 days. MAP1 contained 20:80 (v/v) O
2
:CO
2
and MAP2
contained 80:20 (v/v) O
2
:CO
2Characterization of phytochemicals in petals of different colours from viola × wittrockiana gams and their correlation with antioxidant activity
http://hdl.handle.net/2117/24100
Characterization of phytochemicals in petals of different colours from viola × wittrockiana gams and their correlation with antioxidant activity
Skowyra, Monika; Calvo, Maria Isabel; Gallego Iradi, María Gabriela; Azman, Nurul Aini Binti Mohd; Almajano Pablos, María Pilar
A study to establish relationship between the petal colour, extraction solvent, phenolic, flavonoid, anthocyanin content and antioxidant activity in three varieties of Viola × wittrockiana (yellow, red and violet) is reported in this article. Identification and quantification of flavonoids and anthocyanins using HPLC-DAD-ESI-MS is also presented. The antioxidant activity was studied by four different analytical assays: the measurement of scavenging capacity against ABTS+ and DPPH free radicals, oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP). The violet petals were the most active in all solvents employed for extraction and also showed higher total phenolic, flavonoid and anthocyanin content in comparison with red and yellow ones. Fourteen constituents were identified by HPLC coupled with diode-array detection (DAD) and mass spectrometry (ESI-MS), ten of them were flavonoids and four anthocyanins. The major compounds found in violet pansy were rutin, violanthin and violanin. Aqueous extract of violet pansy can be regarded as a suitable candidate to serve as a radical scavenging agent that could be used in functional foods.
2014-09-18T11:21:11ZSkowyra, MonikaCalvo, Maria IsabelGallego Iradi, María GabrielaAzman, Nurul Aini Binti MohdAlmajano Pablos, María PilarA study to establish relationship between the petal colour, extraction solvent, phenolic, flavonoid, anthocyanin content and antioxidant activity in three varieties of Viola × wittrockiana (yellow, red and violet) is reported in this article. Identification and quantification of flavonoids and anthocyanins using HPLC-DAD-ESI-MS is also presented. The antioxidant activity was studied by four different analytical assays: the measurement of scavenging capacity against ABTS+ and DPPH free radicals, oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP). The violet petals were the most active in all solvents employed for extraction and also showed higher total phenolic, flavonoid and anthocyanin content in comparison with red and yellow ones. Fourteen constituents were identified by HPLC coupled with diode-array detection (DAD) and mass spectrometry (ESI-MS), ten of them were flavonoids and four anthocyanins. The major compounds found in violet pansy were rutin, violanthin and violanin. Aqueous extract of violet pansy can be regarded as a suitable candidate to serve as a radical scavenging agent that could be used in functional foods.Avocado seeds: extraction optimization and possible use as antioxidant in food
http://hdl.handle.net/2117/23601
Avocado seeds: extraction optimization and possible use as antioxidant in food
Segovia Gómez, Francisco José; Peiró Sánchez, Sara; Gallego Iradi, María Gabriela; Mohd Azman, Nurul Aini; Almajano Pablos, María Pilar
Consumption of avocado (Persea americana Mill) has increased worldwide in recent years. Part of this food (skin and seed) is lost during processing. However, a high proportion of bioactive substances, such as polyphenols, remain in this residue. The primary objective of this study was to model the extraction of polyphenols from the avocado pits. In addition, a further objective was to use the extract obtained to evaluate the protective power against oxidation in food systems, as for instance oil in water emulsions and meat products. Moreover, the possible synergy between the extracts and egg albumin in the emulsions is discussed. In Response Surface Method (RSM), the variables used are: temperature, time and ethanol concentration. The results are the total polyphenols content (TPC) and the antiradical power measured by Oxygen Radical Antioxidant Capacity (ORAC). In emulsions, the primary oxidation, by Peroxide Value and in fat meat the secondary oxidation, by TBARS (Thiobar bituric acid reactive substances), were analyzed.
The RSM model has an R 2 of 94.69 for TPC and 96.7 for ORAC. In emulsions, the inhibition of the oxidation is about 30% for pure extracts and 60% for the combination of extracts with egg albumin. In the meat
burger oxidation, the formation of TBARS is avoided by 90%
2014-07-24T10:03:50ZSegovia Gómez, Francisco JoséPeiró Sánchez, SaraGallego Iradi, María GabrielaMohd Azman, Nurul AiniAlmajano Pablos, María PilarConsumption of avocado (Persea americana Mill) has increased worldwide in recent years. Part of this food (skin and seed) is lost during processing. However, a high proportion of bioactive substances, such as polyphenols, remain in this residue. The primary objective of this study was to model the extraction of polyphenols from the avocado pits. In addition, a further objective was to use the extract obtained to evaluate the protective power against oxidation in food systems, as for instance oil in water emulsions and meat products. Moreover, the possible synergy between the extracts and egg albumin in the emulsions is discussed. In Response Surface Method (RSM), the variables used are: temperature, time and ethanol concentration. The results are the total polyphenols content (TPC) and the antiradical power measured by Oxygen Radical Antioxidant Capacity (ORAC). In emulsions, the primary oxidation, by Peroxide Value and in fat meat the secondary oxidation, by TBARS (Thiobar bituric acid reactive substances), were analyzed.
The RSM model has an R 2 of 94.69 for TPC and 96.7 for ORAC. In emulsions, the inhibition of the oxidation is about 30% for pure extracts and 60% for the combination of extracts with egg albumin. In the meat
burger oxidation, the formation of TBARS is avoided by 90%Extraction of antioxidants from borage (Borago officinalis L.) leaves—Optimization by response surface method and application in oil-in-water emulsions
http://hdl.handle.net/2117/23599
Extraction of antioxidants from borage (Borago officinalis L.) leaves—Optimization by response surface method and application in oil-in-water emulsions
Segovia Gómez, Francisco José; Lupo, Bryshila; Peiró Sánchez, Sara; Gordon, Michael H.; Almajano Pablos, María Pilar
Borage (Borago officinalis L.) is a typical Spanish plant. During processing, 60% are leaves. The aim of this work is to model and optimize the extraction of polyphenol from borage leaves using the response surface method (RSM) and to use this extract for application in emulsions. The responses were: total polyphenol content (TPC), antioxidant capacity by ORAC, and rosmarinic acid by HPLC. The ranges of the variables temperature, ethanol content and time were 50–90 °C, 0%–30%–60% ethanol (v/v), and 10–15 min. For ethanolic extraction, optimal conditions were at 75.9 °C, 52% ethanol and 14.8 min, yielding activity of 27.05 mg GAE/g DW TPC; 115.96 mg TE/g DW in ORAC and 11.02 mg/L rosmarinic acid. For water extraction, optimal activity was achieved with extraction at 98.3 °C and 22 min, with responses of 22.3 mg GAE/g DW TPC; 81.6 mg TE/g DW in ORAC and 3.9 mg/L rosmarinic acid. The significant variables were ethanol concentration and temperature. For emulsions, the peroxide value was inhibited by 60% for 3% extract concentration; and 80% with 3% extract concentration and 0.2% of BSA. The p-anisidine value between the control and the emulsion with 3% extract was reduced to 73.6% and with BSA 86.3%, and others concentrations had similar behavior.
2014-07-24T09:44:08ZSegovia Gómez, Francisco JoséLupo, BryshilaPeiró Sánchez, SaraGordon, Michael H.Almajano Pablos, María PilarBorage (Borago officinalis L.) is a typical Spanish plant. During processing, 60% are leaves. The aim of this work is to model and optimize the extraction of polyphenol from borage leaves using the response surface method (RSM) and to use this extract for application in emulsions. The responses were: total polyphenol content (TPC), antioxidant capacity by ORAC, and rosmarinic acid by HPLC. The ranges of the variables temperature, ethanol content and time were 50–90 °C, 0%–30%–60% ethanol (v/v), and 10–15 min. For ethanolic extraction, optimal conditions were at 75.9 °C, 52% ethanol and 14.8 min, yielding activity of 27.05 mg GAE/g DW TPC; 115.96 mg TE/g DW in ORAC and 11.02 mg/L rosmarinic acid. For water extraction, optimal activity was achieved with extraction at 98.3 °C and 22 min, with responses of 22.3 mg GAE/g DW TPC; 81.6 mg TE/g DW in ORAC and 3.9 mg/L rosmarinic acid. The significant variables were ethanol concentration and temperature. For emulsions, the peroxide value was inhibited by 60% for 3% extract concentration; and 80% with 3% extract concentration and 0.2% of BSA. The p-anisidine value between the control and the emulsion with 3% extract was reduced to 73.6% and with BSA 86.3%, and others concentrations had similar behavior.A dehydration process for ovine hide to obtain a new collagenous material
http://hdl.handle.net/2117/23590
A dehydration process for ovine hide to obtain a new collagenous material
Ollé Otero, Lluís; Sorolla, Silvia; Casas Solé, Concepció; Bacardit Dalmases, Anna
The aim of the present work is to develop a dehydration process for ovine hide to obtain a new collagenous material for use in the leather industry. What is obtained through this new process is a dry and very porous collagenous substrate which allows the application of tanning chemicals by immersion
in aqueous solutions. When compared to existing, traditional processes, economic and environmental advantages are obtained from the use of this new material. More specifically, the new process results
in reductions in water use (18%), chemical use (39%), and process time (11%)
2014-07-23T09:39:33ZOllé Otero, LluísSorolla, SilviaCasas Solé, ConcepcióBacardit Dalmases, AnnaThe aim of the present work is to develop a dehydration process for ovine hide to obtain a new collagenous material for use in the leather industry. What is obtained through this new process is a dry and very porous collagenous substrate which allows the application of tanning chemicals by immersion
in aqueous solutions. When compared to existing, traditional processes, economic and environmental advantages are obtained from the use of this new material. More specifically, the new process results
in reductions in water use (18%), chemical use (39%), and process time (11%)Radical Scavenging of White Tea and Its Flavonoid Constituents by 2 Electron Paramagnetic Resonance (EPR) Spectroscopy
http://hdl.handle.net/2117/23582
Radical Scavenging of White Tea and Its Flavonoid Constituents by 2 Electron Paramagnetic Resonance (EPR) Spectroscopy
Azman, Nurul Aini Binti Mohd; Peiró Sánchez, Sara; Fajarí, Lluís; Julià, Luis; Almajano Pablos, María Pilar
White tea (WT) presents high levels of catechins, which are known to reduce oxidative stress. WT is the least processed tea, unfermented and prepared only from very young tea leaves. The subject of this paper is the use of the spin trap method and electron paramagnetic resonance (EPR) spectroscopy as the analytical tool to measure, for the first time, the radical scavenging activity of WT and its major catechin components, epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG), against the methoxy radical, using ferulic acid as antioxidant pattern. The antioxidant activity has been measured by the decrease of the intensity of the spectral bands of the adduct DMPO–OCH3 in the EPR with the amount of antioxidant in the reactive mixture. Tea leaves and buds were extracted with waterless methanol. It has been proved that tea compounds with more antiradical activity against methoxy radical are those with the gallate group, EGCG and ECG.
2014-07-22T11:35:48ZAzman, Nurul Aini Binti MohdPeiró Sánchez, SaraFajarí, LluísJulià, LuisAlmajano Pablos, María PilarWhite tea (WT) presents high levels of catechins, which are known to reduce oxidative stress. WT is the least processed tea, unfermented and prepared only from very young tea leaves. The subject of this paper is the use of the spin trap method and electron paramagnetic resonance (EPR) spectroscopy as the analytical tool to measure, for the first time, the radical scavenging activity of WT and its major catechin components, epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC), and epigallocatechin-3-gallate (EGCG), against the methoxy radical, using ferulic acid as antioxidant pattern. The antioxidant activity has been measured by the decrease of the intensity of the spectral bands of the adduct DMPO–OCH3 in the EPR with the amount of antioxidant in the reactive mixture. Tea leaves and buds were extracted with waterless methanol. It has been proved that tea compounds with more antiradical activity against methoxy radical are those with the gallate group, EGCG and ECG.Screening of antioxidant activity of Gentian Lutea root and its application in Oil-in-Water Emulsions
http://hdl.handle.net/2117/23532
Screening of antioxidant activity of Gentian Lutea root and its application in Oil-in-Water Emulsions
Mohd Azman, Nurul Aini; Segovia Gómez, Francisco José; Martínez Farré, Francesc Xavier; Gil Moya, Emilio; Almajano Pablos, María Pilar
Gentiana Lutea root (G. Lutea) is a medicinal herb, traditionally used as a bitter tonic in gastrointestinal ailments for improving the digestive system. The active principles of G. Lutea were found to be secoiridoid bitter compounds as well as many other active compounds causing the pharmacological effects. No study to date has yet determined the potential of G. Lutea antioxidant activity on lipid oxidation. Thus, the aim of this study was to evaluate the effects of an extract of G. Lutea on lipid oxidation during storage of an emulsion. G. Lutea extracts showed excellent antioxidant activity measured by DPPH scavenging assay and Trolox equivalent antioxidant capacity (TEAC) assays. An amount of 0.5% w/w G. Lutea lyophilise was able to inhibit lipid oxidation throughout storage (p < 0.05). A mixture of G. Lutea with 0.1% (w/w) BSA showed a good synergic effect and better antioxidant activity in the emulsion. Quantitative results of HPLC showed that G. Lutea contained secoiridoid-glycosides (gentiopiocroside and sweroside) and post column analysis displayed radical scavenging activity of G. Lutea extract towards the ABTS radical. The results from this study highlight the potential of G. Lutea as a food ingredient in the design of healthier food commodities
2014-07-17T07:14:50ZMohd Azman, Nurul AiniSegovia Gómez, Francisco JoséMartínez Farré, Francesc XavierGil Moya, EmilioAlmajano Pablos, María PilarGentiana Lutea root (G. Lutea) is a medicinal herb, traditionally used as a bitter tonic in gastrointestinal ailments for improving the digestive system. The active principles of G. Lutea were found to be secoiridoid bitter compounds as well as many other active compounds causing the pharmacological effects. No study to date has yet determined the potential of G. Lutea antioxidant activity on lipid oxidation. Thus, the aim of this study was to evaluate the effects of an extract of G. Lutea on lipid oxidation during storage of an emulsion. G. Lutea extracts showed excellent antioxidant activity measured by DPPH scavenging assay and Trolox equivalent antioxidant capacity (TEAC) assays. An amount of 0.5% w/w G. Lutea lyophilise was able to inhibit lipid oxidation throughout storage (p < 0.05). A mixture of G. Lutea with 0.1% (w/w) BSA showed a good synergic effect and better antioxidant activity in the emulsion. Quantitative results of HPLC showed that G. Lutea contained secoiridoid-glycosides (gentiopiocroside and sweroside) and post column analysis displayed radical scavenging activity of G. Lutea extract towards the ABTS radical. The results from this study highlight the potential of G. Lutea as a food ingredient in the design of healthier food commodities