bluuebunny/crossref_metadata_2025_split huggingface dataset:
A modified xylenol orange method to evaluate formation of lipid hydroperoxides during storage and processing of small pelagic fish
Authors: Eymard Sylvie , Genot Claude 
Published: September 2003

AbstractLipid oxidation causes deterioration of the quality of fatty fish during processing and storage. Its development should be evaluated by measurement of several oxidation products, among them the hydroperoxides. However, most of the methods for determining hydroperoxides already in use failed when tested on fatty fish. The objective of this study was to adapt the ferrous ion xylenol orange assay (FOX) for easy and sensitive measurement of hydroperoxides in fatty fish such as small pelagics during their storage and processing. The proposed procedure is based on the assay developed by Hermes‐Lima et al. that consists of a colourimetric assay performed directly on the methanol extract from minced fish. The reactant was replaced by Wolff's reagent (FOX2 reagent) to improve the solubility of the extract and to simplify the procedure. It was shown that absorbance should be measured at 560 nm instead of 580 nm. The method is valid between 0.3 and 0.6 absorbance units. The modified method is easy, sensitive and allowed differentiation between fresh horse mackerel samples and those stored for 12 h at 17 °C on the basis of their hydroperoxide levels.
The influence of variety and harvest time on the bitterness and phenolic compounds of olive oil
Authors: Škevin Dubravka , Rade Desanka , Štrucelj Dubravka , Mokrovšak Željko , Neđeral Sandra , Benčić Đani 
Published: September 2003

AbstractThe influence of harvest time on the intensity of bitterness and the level of phenol compounds in olive oil from the region of western Istria, obtained from 2 local (Bianchera and Busa) and one introduced, Italian variety (Leccino) was studied. Olive fruits were harvested at 3 different harvesting periods, during 4 successive crops seasons. Immediately after harvesting, the fruits were processed under the same conditions in a pilot plant. Basic quality parameters, the content of total polyphenols, o‐diphenols and the intensity of bitterness were determined in oil samples. Samples of oil obtained from the Bianchera and Busa varieties were additionally tested for stability at elevated temperature (98 °C) and under the influence of UV‐light.The results elaborated statistically showed the level of phenol compounds and the intensity of bitterness to be significantly influenced by both the harvest time and olive variety, with the influence of harvest time being more pronounced. The applied tests for accelerated deterioration of oil indicated a more rapid increase in the peroxide value in oil samples of both varieties exposed to UV‐light than in those exposed to elevated temperature. Both tests showed better stability of the oil obtained from the Bianchera variety.
1H nuclear magnetic resonance as a fast tool for determining the composition of acyl chains in acylglycerol mixtures
Authors: Guillén María D. , Ruiz Ainhoa 
Published: September 2003

AbstractSeveral samples containing different proportions of standard compounds such as tristearin, triolein, trilinolein, and trilinolenin, covering a broad range of compositions, some similar to those of edible oils, were prepared by weight. The 1H nuclear magnetic resonance (NMR) spectra of these samples were recorded and their signals were assigned. It was shown that concentrations of linolenic acyl groups close to 0.4% or higher can be detected by this technique. The area of 5 discrete proton signals of the spectrum was determined. Considering the ratio between this area and the concentration of the corresponding types of hydrogen atoms in the sample, equations calculating the proportions of the acyl groups were deduced. The high level of agreement between data coming from 1H NMR spectra and data obtained by weight shows the usefulness of this methodology. In addition, it has the advantage that it is very fast and simple in comparison with the classical methods, and does not require a chemical modification of the sample. For this reason, the described method constitutes a valuable alternative for the determination of the proportions of different acyl groups in acylglycerol mixtures, such as, for example, oils and fats.
In vivo antioxidant effect of aqueous and etheric coriander (Coriandrum sativum L.) extracts
Authors: de Almeida Melo Enayde , Bion Francisca Martins , Filho Jorge Mancini , Guerra Nonete Barbosa 
Published: September 2003

AbstractResearch has shown that aqueous and etheric coriander extracts, composed of phenolics and carotenoids, exhibit a considerable antioxidant action. Considering the importance of natural antioxidants in the reduction of free radicals and oxidised compounds, coriander extracts obtained through sequential extraction, were administered by gavage to Wistar rats during 30 and 60 d consecutively. At the end of each experimental period, the animals were sacrificed to obtain the blood and the liver. The effect of extracts on plasma and liver lipid peroxidation was assessed by evaluation of thiobarbituric reactive substances. Initially, the aqueous extract demonstrated a superior antioxidant activity in plasma but this was replaced by the etheric extract by the end of the experiment. Of the 2 extracts, in the etheric exerted a superior antioxidant activity in both liver and plasma. The effectiveness of the extracts appears to be related to the biological material that is used (liver or plasma), furthermore to the duration of administration and the type of extract.
Unique block molecules based on glycerol skeleton as C‐3 building blocks for liquid crystals formation by self‐assembly and their future potential for the “nano‐chemistry”
Authors: Urata Kouichi 
Published: September 2003

AbstractStudies on design of liquid crystalline block molecules with non‐conventional mesophase morphoplogies have been proposed by Tschierske and co‐workers. These block molecules have a rigid core, a lateral substituent, and an alkyl chain segmenting blocks from each other. Related to this, diglyceryl alkyl ethers found by us have glycerol as a rigid core, a lateral substituent, and an alkyl chain similar to the Tschierske design. These two cases are compared with each other with regard to the relationship between the molecular structure and the liquid crystalline morphologies and other properties. Recently, new soft materials suitable for liquid crystals exhibiting self‐assembly of phase‐segregated structures have been designed. Typical examples of such “block” molecules containing glycerol having a C‐3 building block include: (i) undecyl‐glycerylether‐ modified siloxane derivatives with a siloxane segment as the rigid core and alkyl chains with 2, 3‐dihydroxypropoxy group as a hydrophilic group at a lateral or terminal position of the siloxane segment; (ii) novel hyper branched dendrimers forming the basis of polyglycerol nanocapsules with a core‐shell molecular architecture; (iii) carbon nanotubes based on cyclodextrins (CDs); (iv) polymerizable amphiphilic diacetylene‐containing phospholipids suitable for construction of functional nanocomposites. This is done by self‐assembly and polymerization of diacetylene creating a “block molecular structure” with a polyacetylene chain as a rigid core segment, the lipid headgroups as the hydrophilic segment, and terminal flexible alkyl chains. On the basis of these results, future potential of block molecules as a soft building material for liquid crystalline structures was discussed.
Oxidative flavour deterioration of fish oil enriched milk
Authors: Let Mette B. , Jacobsen Charlotte , Frankel Edwin N. , Meyer Anne S. 
Published: September 2003

AbstractThe oxidative deterioration of milk emulsions supplemented with 1.5 wt‐% fish oil was investigated by sensory evaluation and by determining the peroxide value and volatile oxidation products after cold storage. Two types of milk emulsions were produced, one with a highly unsaturated tuna oil (38 wt‐% of n‐3 fatty acids) and one with cod liver oil (26 wt‐% of n‐3 fatty acids). The effect of added calcium disodium ethylenediaminetetraacetate (EDTA) on oxidation was also investigated. Emulsions based on cod liver oil with a slightly elevated peroxide value (1.5 meq/kg) oxidised significantly faster than the tuna oil emulsions, having a lower initial peroxide value (0.1 meq/kg). In the tuna oil emulsions the fishy off‐flavour could not be detected throughout the storage period. Addition of 5—50 ppm EDTA significantly reduced the development of volatile oxidation products in the cod liver oil emulsions, indicating that metal chelation with EDTA could inhibit the decomposition of lipid hydroperoxides in these emulsions. This study showed that an oxidatively stable milk emulsion containing highly polyunsaturated tuna fish oil could be prepared without significant fishy off‐flavour development upon storage, provided that the initial peroxide value was sufficiently low.
Determination and certification of the relative mass fractions of triglycerides and cholesterol in pure and adulterated butter oil
Authors: Zeleny Reinhard , Schimmel Heinz 
Published: September 2003

AbstractPure butter oil and adulterated butter oil (5% coconut oil added) were certified for the relative mass fractions of triglycerides C24‐C54 and cholesterol by employing a reference method defined in EC‐regulation 454/95 based on gas chromatographic separation of the triglycerides on packed or capillary columns. Four data sets each of packed‐column and capillary‐column methods were accepted and utilised to establish the certified values. Technical evaluation of the data revealed that calibration is a critical issue in terms of composition of the calibrant and possible precipitation. Recalculations of submitted data were carried out, which mainly involved linear interpolation to calculate the response factors of components not present in the calibrant. This procedure decreased the overall variation of results. Data derived from capillary‐column methods differing in column length, diameter, coating, and temperature program were found to be comparable to those obtained by the more uniform packed‐column methods as regards precision, repeatability, and obtained S‐values. The presented results shall provide a basis to further refine the existing reference method.
On‐line LC‐NMR‐MS characterization of sesame oil extracts and assessment of their antioxidant activity
Authors: Dachtler Markus , van de Put Frans H. M. , v. Stijn Frans , Beindorff Christiaan M. , Fritsche Jan 
Published: September 2003

AbstractSesame lignans were isolated by solvent extraction and subsequently purified by solvent crystallization from crude, unroasted sesame oil, and a sesame oil deodorizer distillate. In addition, an aliquot of the purified sesame oil extract was treated with camphorsulfonic acid to obtain a sesaminol‐enriched extract. The sesame lignan composition of the extracts was characterized by on‐line liquid chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling (LC‐NMR‐MS). The effect of the sesame oil extracts as well as pure sesame lignans and γ‐tocopherol on the oxidative stability of sunflower oil (lignan‐free) was studied by the Rancimat assay. The Rancimat assay revealed the following oxidative stability order: sesame oil extract < sesame oil deodorizer distillate < sunflower oil (no added sesame oil extracts) < sesamol < sesaminol‐enriched sesame oil extract. In addition, the radical‐scavenging capacity of these extracts was assessed by the Trolox® equivalent antioxidant capacity (TEAC) assay. The TEAC assay revealed a slightly different AOX activity order: sesamin < sesame oil extract < sesaminol‐enriched sesame oil extract < sesamol. In conclusion, the sesaminol‐enriched extract revealed strong antioxidant activity and is therefore suitable to increase the oxidative stability of edible oils high in polyunsaturated fatty acids.
3, 4‐Dihydroxymandelic acid amides of alkylamines as antioxidants for lipids
Authors: Ley Jakob P. , Bertram Heinz‐Jürgen 
Published: September 2003

AbstractThe antioxidative and radical scavenging activity of the 3, 4‐dihydroxymandelic acid (DHMA) amides of hexylamine, 2‐ethylhexylamine, octylamine, and cyclohexylamine was determined by several physicochemical test systems. The amides were synthesized by protecting group‐free coupling of in situ prepared N‐hydroxysuccinimidylester of DHMA and the amines. The radical scavenging activity was determined using the DPPH (2, 2‐diphenyl‐1‐picrylhydrazyl) method and by quenching superoxide anions generated using a horse radish peroxidase/H2O2 system. In the DPPH assay, all amides show higher radical scavenging activity (EC50 0.09‐0.12 mol/molDPPH) compared to the standard antioxidants ascorbic acid (EC50 0.27 mol/molDPPH) and tocopherol (EC50 0.25 mol/molDPPH). The amides are also more potent superoxide radical scavengers (IC50 < 600 nm) than standard ascorbic acid (IC50 700 nm). Activity against lipid peroxidation was determined by accelerated autoxidation of highly unsaturated oils and squalene using the Rancimat. Again, the antioxidative potentials of the DHMA amides against lipid oxidation as determined by the Rancimat, are at least equal or higher compared to the standard lipid antioxidants tocopherol, BHT, BHA, and ascorbylpalmitate (concentration in soybean oil 0.05%, all other oils 0.025%, squalene 0.005%). In squalene, an equi‐amount mixture of DHMA octylamide and α‐tocopherol shows a synergistic effect. Last but not least, the amides are able to protect an emulsion of linoleic acid/β‐carotene against oxidation initiated by N, N‐azodiisobutyramidine dihydrochloride (IC50 0.19‐0.77 mmol/l, ascorbic acid > 0.9, tocopherol 0.08). The DHMA octylamide in combination with ascorbic acid shows a synergistic antioxidative effect in the emulsion model. In conclusion, the new alkylamides of DHMA are easy to synthesize, potent radical scavengers and protect lipids, in particular the highly unsaturated, both in bulk and in emulsions against autoxidation.
Numeric Simulation of Ion‐Site Association Effects in Ion‐Selective Electrode Response
Authors: Mikhelson Konstantin N. 
Published: September 2003

AbstractEffects in ion‐selective electrode response and selectivity, caused by ion‐site association in membranes are studied by means of numeric simulations based on a generalized model, which does not rely on a certain degree of the dissociation of electrolytes in membranes. The variability of the experimental values of the potentiometric selectivity coefficients is considered in view of the association in membranes. The reasons why the “dissociation approach” often fits experimental data are also discussed. A novel version of segmented sandwich membrane method is proposed for direct potentiometric measurements of ion‐site association constants in membranes, and preliminary experimental results are presented.
Highly Selective PVC‐Membrane Electrodes Based on Three Derivatives of (Tetraphenylporphyrinato)Cobalt(III) Acetate for Determination of Trace Amounts of Nitrite Ion
Authors: Shamsipur Mojtaba , Javanbakht Mehran , Hassaninejad Ali Reza , Sharghi Hashem , Ganjali Mohammah Reza , Mousavi Mir Fazlollah 
Published: September 2003

AbstractThree different para‐substituted derivatives of (tetraphenylporphyrinato) cobalt(III) acetate were examined as suitable ionophores for the preparation of polymeric membrane (PME) and coated graphite (CGE) nitrite‐selective electrodes. The electrodes revealed a Nernstian behavior over very wide NO2− ion concentration ranges (1.0×10−6−1.0×10−1 M for the PME and 5.0×10−8−5.0×10−2 M for the CGE based on the p‐isopropyl derivative) and very low detection limits (8.0×10−7 M for the PME and 2.0×10−8 M for the CGE). The potentiometric response is independent of the pH of solution in the pH range 4.5–7.0. The electrodes manifest advantages of relative long lifetime, fast response and, most important, good selectivities relative to a wide variety of inorganic and organic anions. In fact the selectivity behavior and detection limit of the proposed NO2− ion‐selective electrodes show great improvements compared to the previously reported electrodes for nitrite ion. The proposed PMEs and CGEs can be used for at least 2 and 4 months, respectively, without any divergence in potentials. The electrodes were successfully applied to the determination of nitrite ion in different real samples such as sausage, milk, flour and cheese.
Spectral Imaging and Electrochemical Study on the Response Mechanism of Ionophore‐Based Polymeric Membrane Amperometric pH Sensors
Authors: Long Robert , Bakker Eric 
Published: September 2003

AbstractThe response features of amperometric ionophore‐based chemical sensors were evaluated in regular ion‐selective membranes, poly(vinyl chloride) plasticized with o‐nitrophenyl octyl ether, with a H+‐selective chromoionophore as model ionophore. Direct imaging experiments upon discrete applied voltage pulses revealed that the diffusion coefficients in such membranes are very similar to that found in membranes under zero current conditions, at about 10−8 cm2 s−1. In the potential range that defines the limiting current, it was found by these imaging experiments that the ionophore is saturated at the membrane surface, as expected. The observed concentration profiles could be well described with established diffusion theory. At more extreme potentials, the observed diffusion profiles were different, and could be explained by the extraction of additional, uncomplexed hydrogen ions into the membrane phase. The results were correlated to the amperometric response behavior of the same electrodes. At the limiting current, Cottrell fits were performed, and similar diffusion coefficients were found as in the imaging experiments. The pH‐dependent normal pulse voltammetric responses were analyzed in terms of their half wave potential, and found to show a Nernstian pH response, suggesting that they function in close analogy to their potentiometric counterparts. The breakdown of Nernstian pH response at low pH is explained by extraction of electrolyte into the membrane under these conditions, which renders the interface non‐polarizable and leads to loss of voltammetric features. The results adequately support the previously published response mechanism of such ionophore‐based amperometric sensors, including the origin of the limiting current, the capability of such membranes to be responsive to ion activities, the requirement of applying baseline potentials between pulses, and the reason for the altered selectivity at extreme potentials.
Copper Ion Selective Membrane Electrodes Based on Some Schiff Base Derivatives
Authors: Sadeghi S. , Eslahi M. , Naseri M. A. , Naeimi H. , Sharghi H. , Shameli A. 
Published: September 2003

AbstractA series of Schiff base derivatives were studied to characterize their abilities as a copper ion carrier in PVC membrane electrodes. The electrode based on 2,2′‐[4,4′diphenyl‐methanebis(nitrilomethylidyne)]‐bisphenol exhibits a Nernstian response for copper ions over the activity range 8.0×10−6−1.0×10−1 mol L−1 with detection limit of about μ mol L−1 of copper ion in comparison with two other Schiff bases. The response time, pH effect and other characteristics of the electrodes were studied in a static mode. The effect of the methyl group substitute on Schiff base structure with SO2 bridging group in different positions with respect to OH group was studied. The results show that behavior of the electrodes is not considerably influenced by the position of methyl substitute. The selectivity coefficients were determined with modified fixed interference method (FIM) and matched potential method (MPM). The proposed electrodes comparatively show good selectivity with respect to alkali, alkaline earth and some transition metal ions. The electrodes were used for the determination of copper in black tea, multivitamin and mineral capsule and as an indicator electrode in potentiometric titration of copper ion.
Ion‐Partitioning Bulk Membrane CHEMFET as Highly Sensitive Calcium Probe
Authors: Moschou Elizabeth A. , Chaniotakis Nikolas A. 
Published: September 2003

AbstractThe development of a novel, highly sensitive calcium CHEMFET‐based sensor system is presented. The CHEMFET utilizes a bulk phase ion‐partitioning membrane as the chemical recognition element while the signal transduction is achieved via a pH‐ISFET. The ion‐partitioning membrane is doped with two different ionophores, one selective to calcium, and the other to protons. Calcium ions partitioned into the bulk of the membrane phase will displace protons of equal charge out of the membrane for electroneutrality reasons, and towards the pH‐ISFET's gate, generating the observed signal. It is shown that the increase of the calcium to proton carrier concentration ratio in the membrane phase, the use of a strong calcium ionophore, and a weak proton carrier contribute to the increase of the sensor sensitivity. The performance of the optimized Ca‐CHEMFET is evaluated by the successful determination of the free calcium ion activity in blood serum samples.
Modification of a Thin Gold Film with Boronic Acid Membrane and Its Application to a Saccharide Sensor Based on Surface Plasmon Resonance
Authors: Soh Nobuaki , Sonezaki Makoto , Imato Toshihiko 
Published: September 2003

AbstractA study of the response behavior of saccharides to surface plasmon resonance (SPR) based sensor, in which a boronic acid membrane‐modified thin gold film was used as a sensor chip is described. The following three procedures were used in the modification of the sensor chip: first, 3‐aminophenylboronic acid (3‐APB) was coupled with 11‐mercaptoundecanoic acid to form a self‐assembled monolayer (SAM) on the gold film of the sensor chip, second, 3‐APB was immobilized on the sensor chip by electrochemical polymerization, and third, the sensor chip was coated with a vinyl polymer by the radical polymerization of vinylphenylboronic acid. SPR responses were measured in a flow system, where the above three types of sensor chip were assembled in the flow cell of the SPR sensor. The SPR responses caused by the interaction between the boronic acid membrane modified on the sensor chip and saccharides were evaluated by measurement of an angle shift of the SPR sensor. A weak response was observed for the SPR sensor using the sensor chip modified with SAM and the electropolymerized membrane, while the sensor chip modified with the vinylboronic acid polymer membrane showed a selective and enhanced response to saccharides. From the SPR response for the latter sensor, the findings indicate that the interaction between the boronic acid membrane on the sensor chip and the saccharides was in the order glucose<mannose<galactose<fructose. Namely, the interaction between the boronic acid and cis‐diol moiety in the saccharides appears to be stronger in the order 2,3‐cis‐diol<3,4‐cis‐diol<1,2‐cis‐diol. The adsorption behavior of sorbose to the sensor chip modified with the boronic acid polymer membrane followed the Freundlich‐type adsorption isotherm. The electrochemical polymerization of 3‐APB on the gold film of the SPR sensor chip was monitored in situ by combining an SPR system with an electrochemical analyzer system.