A fully automated HPLC determination of the coccidiostat meticlorpindol in whole egg, egg white and yolk is described. The sample homogenate is dialysed on-line against water. The dialysate is concentrated on-line on a short reversed-phase (RP) column. The contents of this column are transferred to the reversed-phase analytical column by means of the mobile phase. Meticlorpindol is detected using an absorbance detector at 270 nm. Linear calibration graphs are obtained in the range 40-900 ng/g in whole egg and egg white (detection limit 10 ng/g) and 80-1800 ng/g in yolk (detection limit 20 ng/g). Out of 111 commercially obtained egg samples 12 contained meticlorpindol with levels varying from 10 to 433 ng/g. A group of laying hens, kept in cages, received 10 mg/kg of Lerbek (meticlorpindol and methylbenzoquate; Dow Chemical) in the feed for 10 days. Meticlorpindol residues in the eggs rose to a level of 622 ng/g. Meticlorpindol was found in the eggs until 6 days after withdrawal of the medicated feed. Another group received 110 mg/kg in the feed. Meticlorpindol residues rose to levels of 4480 ng/g in the eggs, 5880 ng/g in the egg white and 2660 ng/g in the yolk. Meticlorpindol was found in the eggs and the egg white until 14 days and in the yolk until 8 days after withdrawal of the medicated feed.
Single nucleotide polymorphisms (SNPs) can play a direct or indirect role in phenotypic expression in food allergy pathogenesis. Our goal was to quantitate the expression of SNPs in relevant cytokines that were expressed in food allergic patients. SNPs in cytokine genes IL-4 and IL-10 are known to be important in IgE generation and regulation. We examined IL-4 (C-590T), IL-4Rα (1652A/G) and IL-10 (C-627A) SNPs using real-time PCR followed by restriction fragment length polymorphism (RFLP) analysis. Our results show that the AA, AG and GG genotypes for IL-4Rα (1652A/G) polymorphisms were statistically different in radioallergosorbent test (RAST) positive versus negative patients, and although no statistically significant differences were observed between genotypes in the IL-4 (C-590T) and IL-10 (C-627A) SNPs, we observed a significant decrease in IL-4 (C-590T) gene expression and increase in IL-4Rα (1652A/G) and IL-10 (C-627A) gene expression between RAST(+) versus RAST(-) patients, respectively. We also observed significant modulation in the protein expression of IL-4 and IL-10 in the serum samples of the RAST(+) patients as compared to the RAST(-) patients indicating that changes in SNP expression resulted in altered phenotypic response in these patients.
The effects of ozone in aqueous solution on the shelf life of whole, vacuum-packaged rainbow trout, stored under refrigeration
(4±0.5°C) were studied by monitoring the microbiological, chemical and sensory changes for a period of 15 days. Vacuum-packaged
non-ozonated trout served as the control sample. Ozonation affected populations of bacteria namely, mesophilic aerobic bacteria,
Pseudomonas spp. and H2S-producing bacteria until day 11 of storage, Brochothrix thermosphacta, lactic acid bacteria and Enterobacteriaceae until day 8 of storage. Trimethylamine (TMA) values of all rainbow trout samples remained low (<3mg N/100g) until day 11
of storage, and then increased to 12.2, 8.9 and 4.7mg N/100g for the control and the samples ozonated for 60 and 90min,
respectively on day 15 of storage. Total volatile basic nitrogen (TVB-N) values remained relatively constant (20–25mg N/100g)
until day 11 of storage, but increased to 61.1, 37.6 and 39.4mg N/100g flesh for the control and ozonated specimen for 60
and 90min, respectively on day 15 of storage. Thiobarbituric acid (TBA) values remained relatively constant (1–3mg MA/kg
flesh) until day 12 of storage but increased to 8.4, 6.4 and 3.8mgMA/kg flesh on day 15 of storage for the control and the
ozonated trout for 60 and 90min, respectively. Sensory evaluation (odor, taste and texture) of cooked rainbow trout showed
a very good correlation with bacterial populations. On the basis of both sensory and microbiological data, a shelf life of
10 and 12 days was obtained for ozonated, vacuum-packaged and refrigerated rainbow trout at 60 and 90min, respectively.
A GC-MS study of the composition of nine different grappas (Italian grape marc spirit) was carried out. High-weight alcohols
showed the greatest variations, while the lower congener concentrations generally were more uniform. Particularly interesting
is the presence of 1,1-diethoxy-3-methylbutane (DMB), never detected before in grappa. DMB was present in all samples, ranging
from 0.8 up to 30.6mgL−1. This latter concentration was the highest detected in an alcoholic beverage so far. A discussion on the other volatile congeners
was also reported. Principal component analysis was applied to the data and explained >80% of the whole variability. Most
grappas are grouped in a single cluster, while the other samples are completely separated. DMB, ethyl acetate, ethyl lactate,
and n-butanol are some examples of constituent able to differentiate the tested products.
Fifteen coffee samples comprising green, roasted, decaffeinated and instant coffees were analysed for their content of free and bound 3-chloropropane-1,2-diol (3-MCPD). Green coffees contained only traces of the free 3-MCPD. 3-MCPD in roasted coffees was found at the level of 10.1–18.5g/kg. The highest 3-MCPD level of 18.5g/kg was found in one instant coffee sample and in coffees with very long time application during roasting. The final colour of the roasted coffee beans was directly linked to the 3-MCPD formed, the darker beans having the greatest concentration, and arabica coffees contained lower 3-MCPD levels than robusta coffees. The level of bound 3-MCPD varied between 6g/kg (soluble coffees) and 390g/kg (decaffeinated coffee) and exceeded the free 3-MCPD level 8–33 times. Arabica coffees contained higher levels of the bound 3-MCPD than robusta coffees. The recognised precursors of 3-MCPD (salt, glycerol, lipids) were also determined and their influence on the formation of the free and bound 3-MCPD was discussed.
A study of the decay kinetics of 3-chloropropane-1,2-diol (3-MCPD) at high temperatures in aqueous model systems is reported. Data obtained over the pH range 5–6.5 and temperatures of 80–142 °C agreed well with a predicative model derived from earlier kinetic data. The results showed that 3-MCPD was unstable in aqueous solutions approaching infinite dilution at temperatures above 80 °C. Comparison of the experimental decay of 3-MCPD with that based on the kinetic parameters A (=107.73347+0.83775pHs–1) and E
a (=119.2 kJ mol–1) was good to within 20% over the temperature and pH ranged studied. A putative mechanism for the degradation reaction is discussed together with the implications for the decay and formation of 3-MCPD in food systems.
The 1,2-dicarbonyl compounds 3-deoxyglucosulose (3-DG), methylglyoxal (MGO) and glyoxal (GO) were measured for the first time in 21 honey samples as the corresponding quinoxalines after derivatization with orthophenylenediamine using RP-HPLC and UV-detection. Compared to 5-hydroxymethylfural (HMF), which was also quantified, and ranged between 0.6 and 44mg/kg, up to 100-fold higher amounts of 3-DG were found, ranging from 79 to 1,266mg/kg. During storage of honey at 35C and 45C, a linear increase of 3-DG was observed. Values for GO and MGO were in the ranges 0.2–2.7mg/kg and 0.4–5.4mg/kg respectively, and were not affected by storage. Using semi-preparative RP-HPLC, glucosone, a 1,2-dicarbonyl compound previously unknown to occur in foods was isolated from a honey sample and characterized by LC-MS and NMR spectroscopy.
Formation of 3-chloropropane-1,2-diol (3-MCPD) from the precursors glycerol, triolein and soy lecithin in the presence of sodium chloride was studied. The precursors were reacted with sodium chloride in an emulsion stabilised with an emulsifier under conditions which modelled the thermal treatment of foods during processing. Three sets of experiments were carried out aimed to monitor the influence of various factors (NaCl, water content and temperature) on the yield of 3-MCPD. The formation of 3-MCPD strongly depended on the concentration of NaCl and reached a maximum level at about 4–7% NaCl. The highest amount of 3-MCPD was formed in media containing approximately 13–17% water. The amount of 3-MCPD increased with increasing temperature over the range 100–230C and reached its highest value at 230C. The production of 3-MCPD was also followed in models very closely related to selected foods which had been shown to have a high potential to yield 3-MCPD during processing (salami, beefburgers, processed cheese, biscuits, crackers, doughnuts). The highest levels of 3-MCPD were formed in models simulating salami as they had the highest content of both fat and salt of all the samples. The lowest amount of 3-MCPD was formed in the models simulating biscuits and crackers as they had a low salt content and, at the same time, their water content was below the optimum level.
A series of fourteen starter formula, follow-up formula, and growing-up milk produced by three manufacturers was analyzed
by for the chloropropanols 1,3-dichloropropan-2-ol (1,3-DCP), 3-chloropropane-1,2-diol (3-MCPD) and their fatty acid esters.
While none of the products contained free chloropropanols at levels exceeding the method detections limits, all of them contained
relatively high amounts of 3-MCPD esters. The latter concentrations ranged from 62 to 588μg of 3-MCPD esters (bound 3-MCPD)/kg
on the product basis and <300 (limit of quantification)—2,060μg/kg expressed on the fat basis. These concentrations were
proportional to the fat content in products as refined vegetable oils used by the manufacturers contain elevated levels of
3-MCPD esters depending on their origin and other factors. Regular intake of these products can lead to exceeding the tolerable
daily intake that has been set for free 3-MCPD. The major types of 3-MCPD esters were the symmetric diesters with palmitic
and oleic acids and asymmetric diesters with palmitic/oleic acid among which 1,2-palmitoyl, oleoyl-3-MCPD prevailed.
The polysaccharides 1,3--d-glucan and -d-mannan show numerous beneficial effects for the health of humans and animals. For several years, an increasing number of glucan- and mannan-containing products intended for food and feed applications are commercially available. For the determination of glucan and mannan contents, however, widely accepted methods have not yet been established. We have developed a practicable and reliable quantification method characterised by acidic hydrolysis with trifluoroacetic acid and subsequent determination of released d-glucose and d-mannose. The unavoidable loss of the monosaccharides due to the acidic conditions was minimised by optimisation of the hydrolysis parameters. The best conditions found were compared with literature methods in order to demonstrate the suitability. Finally, glucan and mannan contents of various commercial products were determined and compared to the specifications given by the manufacturers.
After heating N--hippuryl-L-arginine (Hip-Arg) with varying amounts of lactose for 1–4h at 100C, a previously unknown arginine derivative could be detected by RP-HPLC and UV-detection. Following semi-preparative isolation, the compound was unequivocally identified as 2-(2-benzoylamino-acetylamino)-5-[5-(3-hydroxypropyl)-4-oxo-imidazolon-2-yl]-L-ornithine (Hippuryl-PIO, Hip-PIO) by electrospray-time of flight-mass spectroscopy as well as one- and two-dimensional 1H- and 13C-nuclear magnetic resonance. Hip-PIO was exclusively formed during incubation of Hip-Arg with disaccharides containing a 1,4-glycosidic linkage. As reference for amino acid analysis, free PIO was synthesized starting from N-(tert-butoxycarbonyl)-L-arginine (t-Boc-Arg) via t-Boc-PIO and final hydrolysis with acetic acid. Preliminary evidence for the formation of protein-bound PIO, which proved to be acid-labile, was obtained using amino acid analysis with ninhydrin detection for enzymatic hydrolysates of casein samples which had been heated in the presence of lactose at 100C. The ornithinoimidazolinone PIO represents a new type of post-translational protein modification formed during food processing, which might be responsible for the major part of arginine derivatisation in disaccharide-containing foods like milk.
Although it is well known that arginine side chains of proteins become extensively modified in the course of the advanced Maillard reaction, to date only few possible arginine derivatives are known. Recently, N-δ-[5-(3-hydroxypropyl)-4-oxo-imidazolon-2-yl]-l-ornithine (PIO) was identified as a new arginine derivative, formed exclusively from the side-chain of peptide-bound arginine and degradation products of oligosaccharides with 1,4-glycosidic linkages. In the present paper, a previously unknown C5 dicarbonyl compound, namely 3,4-dideoxypentosulose (3,4-DDPS), was isolated by means of semi-preparative RP-HPLC as the corresponding chinoxaline after heating lactose followed by trapping the 1,2-dicarbonyl compound with o-phenylenediamine. Identification was achieved using LC–MS as well as 1H- and 13C-NMR. Synthesis of 3,4-DDPS as the corresponding 2-hydroxy-dihydro-pyran-3-one proved the structure analysis. During heating of N-α-hippuryl arginine (Hip-Arg) with 2-hydroxy-dihydro-pyran-3-one, Hip-PIO was formed as the only arginine derivative. The formation of 3,4-DDPS from oligosaccharides with 1,4-glycosidic linkages follows a new and quantitatively important pathway of carbohydrate degradation in foods.
The performance of Lactobacillus sanfranciscensis TMW 1.392 and its levansucrase deletion mutant TMW 1.392Δlev in wheat dough was compared. The effects of both strains on
dough and bread characteristics were determined in order to find benchmarks for in situ production of exopolysaccharides (EPS).
Growth and acidification were lower in doughs prepared with the Δlev mutant than in those employing the wild type. Extensogram
resistance of the dough was reduced and extensibility increased with the addition of L.sanfranciscensis levan. Added EPS positively influenced water absorption, bread volume and firming of the crumb. In situ production of EPS
was not sufficient to achieve the same positive effects of EPS, as they partially overlapped with effects resulting from enhanced
acidification. Control doughs were made to separate effects of predough, EPS and different metabolism/acidification. High
acetic acid levels decreased extensibility and volume. High lactic acid levels negatively influenced crumb hardness and firming
kinetics. The use of knock out mutants proved helpful to judge overall performance of a strain, although the interpretation
of specific effects must consider all changes in its metabolism.
plantarum FST1.7 has been recently shown to produce antifungal compounds, which improve the shelf life of wheat bread. In the present
study, this strain was investigated for its ability to improve the quality and shelf life of gluten-free bread. Effects of
incorporation of sourdough fermented by strain FST1.7 into a gluten-free bread mixture were compared to those obtained with
sourdough fermented by the non-antifungal strain Lactobacillus sanfranciscensis TMW1.52 as well as to those obtained with chemically or non-acidified batters. Fundamental rheological tests revealed that
the addition of sourdough to the gluten-free mix led to an increase in firmness and increase in elasticity overtime (P<0.05). Bread characteristics such as pH, total titratable acidity, and crumb hardness (5-day storage) were evaluated. Results
showed that the biologically acidified gluten-free breads were softer after 5days than the chemically acidified gluten-free
breads (P<0.001). Antifungal challenge tests employing conidial suspensions of Fusarium
culmorum were carried out using the sourdough, non-acidified batter and bread. The rate of mould growth for the fungal species used
was retarded by L.plantarum FST 1.7 when compared to the controls. In conclusion, the results of this study indicate that L.plantarum FST1.7 can be used to produce gluten-free bread with increased quality and shelf life.
Minor fatty acids (iso- and anteiso-fatty acids, vaccenic acid, elaidic acid) in foodstuff (seafood, milk, and dairy products)
were analyzed by gas chromatography with electron ionisation mass spectrometry in the selected ion monitoring mode (GC/EI-MS-SIM).
For this purpose, lipids were obtained by accelerated solvent extraction (ASE) and the fatty acid constituents were converted
into methyl esters. Instead of the determination of the relative contribution of the minor fatty acids to the sum of all fatty
acids detected (the so-called 100% method), we exclusively quantified the minor fatty acids, which was possible by using two
types of internal standards (IS-1 and IS-2). For recovery checks during the extraction and/or the transesterification step
we added the novel 10,11-dichloroundecanoic acid (DC-11:0) as IS-1. DC-11:0, which has never been detected in foodstuff, was
synthesized by electrophilic addition of chlorine to 10-undecenoic acid (11:1n-10). The novel IS eluted in the range of 23:0 from the polar GC column used and showed the same properties as fatty acids in
foodstuff during sample preparation. Recovery rate of DC-11:0 was generally >96% in the various samples analyzed. Ethyl esters
(FAEE) of a12:0, a14:0, a15:0, a16:0, a17:0, and a18:0 (IS-2) were added to both the external standard (a quantitative mixture
of methyl esters of methyl-branched fatty acids and 18:1n-9trans) in order to determine their response factors relative to FAEE and to the food samples. With this technique, (only) methyl-branched
fatty acids (MBFAs) as well as vaccenic acid (18:1n-7) and elaidic acid (18:1n-9trans) were quantified in a range of dairy products (including twelve cheeses) and seafood. All samples were analyzed in triplicates,
and good standard deviations (concentrations 0.002–5g/100g; standard deviations 0.00–0.03) were obtained in all cases. MBFAs
were detected in all samples analyzed. The highest content of MBFAs (3.0g/100g) was determined in red-smear of romadur cheese.
In all except two cheeses, i17:0 was the most abundant MBFA. The highest amount of 18:1n-9trans was found in feta (2.84g/100g) whereas 0.03g/100g in big eye snapper (Pricanthus tayenus) marked the lowest record of this minor fatty acid. Seal oil contained the highest amount of 18:1n-7 with 5.00g/100g, whereas emmental cheese was the sample with the lowest content of this monoenoic fatty acid. The combination
of suitable IS and a sensitive GC/EI-MS-SIM method proved to be well suited for the quantification of minor fatty acids in
foodstuff. When only a set of fatty acids is going to be analyzed, this method is less time consuming compared to “100% methods”
and less prone to false results due to the higher selectivity of GC/MS compared to GC in combination with flame ionisation
Protein hydrolysates are of a significant interest, due to their potential application as a source of bioactive peptides in
nutraceutical and pharmaceutical domains. The present study was focused on bovine hemoglobin hydrolysate obtained with pig
pepsin in the presence of 30% ethanol. This hydrolysate was fractioned by reversed-phase high-performance liquid chromatography
(RP-HPLC) into 12 major fractions (F1–F12). All fractions were analyzed by ESI/MS and ESI/MS/MS, in order to characterize and identify the peptides in these fractions.
This hydrolysis permitted to generate a new serial of bioactive peptides with both antimicrobial and ACE inhibitory activities.
Identified peptides were TKAVEHLDDLPGALSELSDLHAHKLRVDPVNFKLLSHSLL, LDDLPGALSELSDLHAHKLRVDPVNFKLLSHSL, KLLSHSL, and LLSHSL
corresponding respectively to the 67-106, 73-105, 99-105, and 100-105 fragments of the α chain of bovine hemoglobin. They
were the first found from bovine hemoglobin. These purified peptides have an antibacterial activity against four bacteria
strains: Kocuria luteus A270, Listeria innocua, Escherichia coli, and Staphylococcus aureus with a MIC between 187.1 and 35.2μM. On the other hand, these peptides displayed at the same time ACE inhibitory activity
with an IC50 range from 42.55 to 1,095μM.
KeywordsBovine hemoglobin–Hydrolysis–Antimicrobial peptides–ACE inhibitory activity
Around 10 million tons of grape pomace containing 38–52% (on a dry matter basis) seeds was produced each year in the world,
so how utilize these residual matters has been receiving great attention. In this study, 11S globulin-like protein (GSG) was
isolated and purified from grape (Vitis vinifera L.) seeds by two consecutive cation exchange and size exclusion chromatography. A yield of 10mg the protein from 1kg seeds
was obtained. The apparent molecular mass of the native GSG was found to be about 300kDa. The protein consisted of two subunits
with molecular masses of 25.5 and 40.0kDa, respectively. MADLI-TOF–MS result showed that they were distinct from each other.
N-terminal amino acid sequence of the 40.0kDa subunit is RQQTSRQQKE. Amino acid composition analyses indicated that GSG contained
all eight essential amino acids, while lysine was the first limiting amino acids. To the best of our knowledge, this is the
first report on the purification of 11S globulin-like protein from Vitis vinifera L. seeds.
Puroindoline a and b (Pina, Pinb) form the molecular basis of bread wheat grain hardness. Varieties with a softer endosperm and a wild genotype, in which
both Pina and Pinb were present, seemed to produce less damaged starch flour than hard varieties, where Pin mutations occurred and changed the starch rheological properties. The functional property of starch samples extracted from
wheat varieties with different Pin alleles was evaluated. Starch morphology was characterized by scanning electron microscopy and laser light scattering. Thermal
properties were evaluated by differential scanning calorimetry. Amylose content, starch damage and rapid visco-analyser (RVA)
parameters were also determined. Significant variations (P<0.05) were identified between different Pin variants for the distribution pattern of starch granule volume, amylose content, starch damage, RVA viscosity breakdown and
retrogradation, gelatinisation transition temperatures and enthalpies. Hard genotypes presented higher medium diameter granules
and lower enthalpic values. However, the differences detected are more evident among varieties that present both Pina and Pinb, than among those presenting only one of the two (a or b).
The combination of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) and gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-P-IRMS) is applied to the authenticity assessment of cinnamaldehyde from various sources. For that reason, cinnamon oils were self-prepared by steam distillation from three different varieties of cinnamon bark on the market, C. ceylanicum (ceylon), C. cassia (cassia) and C. burmanii (cassia vera). Furthermore, the so-called wood cinnamon was investigated, which is produced from the outer bark of older branches of cinnamon of minor quality. Self-prepared oils were analysed from commercial cinnamon powder. In addition several commercial samples of cinnamon oil and cinnamaldehyde, some of them declared to be natural, were investigated.
13CV-PDB values of cinnamaldehyde were determined and characteristic authenticity ranges were deduced, allowing the differentiation between synthetic and natural samples. By correlation of both the
13CV-PDB values, characteristic authenticity ranges were defined for ceylon, cassia and wood cinnamon. The
13CV-PDB values of cassia vera samples are in the range of cassia. By comparing the
2V-SMOW values of different self-prepared samples (ground bark, distillate) of cinnamon determined by TC/EA-IRMS with the corresponding GC-IRMS values, online GC-IRMS methods are proved to be essential in the authentication of complex natural products.
More than 50 authentic EU data bank wines from Germany (vintages: 2003, 2004 and 2006) have been extracted by liquid–liquid extraction with a mixture of cyclohexane and 2-methyl-2-propanol. The δ13C values of the extracted wine ethanol and other co-extracted higher alcohols have been determined by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). The stable isotope ratios of wine ethanol obtained by liquid–liquid extraction were compared with those obtained after distillation according to the official EU method. No significant differences of the isotope ratios of ethanol measured by the two compared methods were found (R
2 = 0.972), thus it was concluded that no significant isotope effect during sample preparation occurred. Additionally, the 13C/12C isotope ratios of the major co-extracted alcohols, e.g. 2-methylpropan-1-ol, 2- and 3-methylbutan-1-ol, butan-2,3-diol and 2-phenyl-1-ethanol were determined and set in relation to the δ13C values of the corresponding extracted wine ethanol. Also, high correlations between their isotope ratios (e.g. 2,3-methylbutan-1-ol R
2 = 0.829) were found. The key benefits of the introduced liquid–liquid extraction are the time- and cost-saving determination of δ13C values of wine ethanol, the small amount of sample needed for the extraction and additionally the potential analysis of the co-extracted higher alcohols which could be valuable for the detection of fraud.
Enantioselective gas chromatography and/or 13C/12C isotope ratio analysis are suitable tools for the authenticity assessment of the fusel alcohols, 2- and 3-methylbutanol
(1 and 2, respectively). The chiral compound, 1 is biosynthesised almost completely as the (S)-enantiomer, regardless of which carbohydrate source is used for fermentation. The type of CO2 fixation and some plant-specific influences were of prime importance to the 13C/12C isotope ratios of the starting materials in alcoholic fermentation, and the δ13C values of 1 and 2 differed significantly. In general, the δ13C values of 2 were about 4–5ö lower than those of 1 produced via the same fermentation process. 13C/12C isotope ratio analysis results can be used to determine between fusel alcohols produced from different sources, and provides
a new and valuable method of authenticity assessment.
We applied PCR–RFLP (Polymerase Chain Reaction – Restriction Fragment Length Polymorphism) analysis to identify seven gadoid
species of different biogeographical origin and commercial relevance, namely Gadus morhua (Atlantic ocean); Trisopterus minutus capelanus, Trisopterus minutus minutus, Molva elongata, Phycis blennoides, Micromesistius poutassou (Atlantic ocean and Mediterranean sea); Theragra chalcogramma (Pacific ocean). Two DNA fragments belonging to mitochondrial 12S and 16S rRNA genes of about 430 and 630bp, respectively,
were isolated by PCR amplification. Their direct sequencing showed a significant genotypic diversity among gadoid species,
useful for species identification. Digestion of 16S rRNA gene PCR fragment with MvaI or Bsh1285I restriction enzymes, followed by agarose gel electrophoresis of the cleaved products, yielded specific restriction profiles
that enabled direct, visual identification of the species analyzed. This PCR–RFLP method allowed a clear and rapid discrimination
of the gadoid species studied.
To reveal the role of primary products of lipid peroxidation during soy protein oxidation process, oxidative modification
of soy protein by 13-hydroperoxyoctadecadienoic acid (13-HPODE) generated by lipoxygenase-catalyzed oxidation of linoleic
acid was investigated in this article. Incubation of soy protein with increasing concentration of 13-HPODE resulted in generation
of protein carbonyl derivatives and loss of protein sulfhydryl groups. Circular dichroism spectra indicated that exposure
of soy protein to 13-HPODE led to loss of α-helix structure. Effect of oxidation on tertiary structure was demonstrated by
surface hydrophobicity and tryptophan fluorescence. Surface hydrophobicity gradually decreased, accompanied by loss and burial
of some tryptophan residues. The results of surface hydrophobicity and tryptophan fluorescence implied that aggregation was
induced by oxidation. Size exclusion chromatogram indicated that the extent of aggregation was increased in a 13-HPODE dose-dependent
manner. Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that non-disulfide linkages were involved in aggregate
formation, and β-conglycinin was more vulnerable to 13-HPODE than glycinin.
13C nuclear magnetic resonance spectroscopy has been applied to select the processing conditions for tuna sterilisation. The
work aimed to determine the heating times and retort temperatures required to guarantee a particular degree of microbiological
sterility, but also to provide maximum nutrients and/or the retention of quality factors. Quality assessment was made on the
basis of lipid degradation, hydrolysis and oxidation, and the estimation of the nutritional value (n-3 fatty acid content).
Treatments involving the highest temperatures for the shortest times led to a final food with the highest n-3 fatty acid content
and the lowest lipid degradation.
The enantiomeric ratios of the chiral polychlorinated biphenyls 2, 2′, 3, 5′, 6-pentachlorobiphenyl (PCB 95) and 2, 2′, 3,
4′, 5′, 6-hexachlorobiphenyl (PCB 149) were determined in human milk samples by multidimensional gas chromatography, using
two different achiral columns for preseparation and a chiral column for enantiomeric separation. Detection was carried out
by electron capture detection and by mass spectrometry in the single ion monitoring mode. For PCB 95 a slight enrichment of
the first eluted peak was determined whereas PCB 149 is present as racemate.