Yvan Choiset - Academia.edu (original) (raw)

Papers by Yvan Choiset

Biochimica Et Biophysica Acta - Proteins And Proteomics, May 1, 2000

Von Ebner gland protein (VEGP) and odorant-binding protein (OBP) were purified from porcine lingu... more Von Ebner gland protein (VEGP) and odorant-binding protein (OBP) were purified from porcine lingual epithelium and nasal mucosa, respectively. Both VEGP and OBP preparations were homogeneous as indicated by SDS^PAGE, isoelectric focusing, gel-filtration and electrospray mass spectrometry. However, high-sensitivity differential scanning calorimetry (HS-DSC) yielded multiphasic denaturation thermograms for both proteins indicating their conformational heterogeneity. The unfolding transition of VEGP is observed at extremely high temperatures (about 110³C), which is unexpected for a protein with significant structural homology to OBP and other lipocalins. Isothermal titration calorimetry (ITC) did not detect the binding of either aspartame or denatonium saccharide to VEGP nor did it detect binding of 2-isobutyl-3-methoxypyrazine (IBMP) to OBP. Extraction of OBP with mixed organic solvents eliminated the conformational heterogeneity and the protein showed a reversible two-state transition in HS-DSC thereafter. ITC also showed that the extracted OBP was able to bind IBMP. These results imply that tightly bound endogenous ligands increase the thermal stability of OBP and block the binding of other ligands. In contrast to OBP, the extraction of VEGP with organic solvents failed to promote binding or to establish thermal homogeneity, most likely because of the irreversible denaturation of VEGP. Thus, the elucidation of the functional behaviour of VEGP is closely related to the exhaustive purging of its endogenous ligands which otherwise very efficiently mask ligand binding sites of this protein.

Journal of Food Biochemistry, Jun 15, 2012

Proteolytic activity of Lactobacillus helveticus A75 and effects of caseins hydrolysis by this st... more Proteolytic activity of Lactobacillus helveticus A75 and effects of caseins hydrolysis by this strain on their immuno-reactivity were studied. Proteases of L. helveticus A75 hydrolyzed both αS1- and β-caseins and were inhibited by serine- and metallo-proteases inhibitors. Polymerase chain reaction amplification revealed the presence of prtH gene, which was 99% identical to prtH gene of L. helveticus CNRZ 32. Effect of proteolysis of αS1- and β-caseins by L. helveticus A75 on their immunoglobulin E (IgE) binding ability was studied by an enzyme-linked immunosorbent assay with the pool of eight sera from cow milk allergy patients. The IgE binding ability of hydrolyzed proteins was lower than that of intact proteins, which indicates that hydrolysis of αS1- and β-caseins by proteases of L. helveticus A75 decreases their recognition by specific IgE. Half maximal inhibitory concentration values were 2.01 and 2.28 µg/mL for αS1- and β-casein, respectively, and increased until 9.08 and 13.65 µg/mL, respectively, after their hydrolysis by L. helveticus A75. PRACTICAL APPLICATIONS The obtained results yield new information about proteolytic activity and potential application of lactobacilli isolated from traditional Azerbaijani cheeses. Isolated strain could represent new adjunct cultures for the dairy industry.

Food Chemistry, Aug 1, 2013

Vitamin A deficiency is one of the major causes of mortality and morbidity in the developing Worl... more Vitamin A deficiency is one of the major causes of mortality and morbidity in the developing World. This deficiency can be prevented by alimentary or pharmaceutical supplementation. However, both vitamin A oxidation and isomerization should be prevented, as these phenomenons result in loss of nutritional efficacy. The aim of this study was to investigate the effect of a food protein matrix, b-lactoglobulin (b-Lg) aggregates produced by high pressure (HP), on the stabilization of b-carotene during storage and gastro-duodenal digestion and therefore on its bioavailability. In vitro gastro-duodenal digestion of b-Lg aggregates entrapping b-carotene showed that up to 12% and 33% of total b-carotene was released after peptic and pancreatic digestion, respectively. Overall, our study showed that b-Lg aggregates are efficient for caging and stabilization of b-carotene during storage and digestion. Hence, it may be an interesting approach for the protection and the delivery of vitamin A.

HAL (Le Centre pour la Communication Scientifique Directe), 2005

Food Hydrocolloids, Mar 1, 2007

Due to the combination of flexibility and amphiphilicity, in solution b-casein (b-CN) acts as a s... more Due to the combination of flexibility and amphiphilicity, in solution b-casein (b-CN) acts as a surfactant molecule. It undergoes selfassociation and forms ''micellar-like'' aggregates in aqueous media. The aim of our study was to understand the role played by the charges borne by the N-terminal part of b-CN in its association behavior. b-CN polarity was modified in order to induce new aggregation properties and to understand better the main factors defining them. An unphosphorylated wild type recombinant form (WT A 2) of b-CN has been obtained by heterologous expression in the prokaryotic host Escherichia coli. A mutant (MU A 2) form of b-CN was engineered by duplicating the first 6 N-terminal amino acids residues (RELEEL) of WT A 2 , three additional negatively charged glutamic acids replacing some of the negative charges lost by the absence of phosphorylation in prokaryotic expression system. Dynamic light scattering and fluorimetry experiments showed that recombinant and native b-CN have different behaviors in temperaturedependent association. Micellisation was impaired by the absence of phosphate groups. Mutation conferred to the protein the ability to form aggregates whose size is inversely proportional to the concentration. These different behaviors during the association processes displayed by recombinant b-CN are correlated with modifications of the temperature-induced compaction of the proteins, what was revealed by circular dichroism measurements. WT A 2 was less condensed at the air-water interface than native b-CN; this was in part reversed by the additive mutation. However, MU A 2 compensating the lack of phosphate charges in recombinant caseins forms a more cohesive monolayer at the air-water interface than do the other b-CN, which means that the mutation reinforces monomers interaction at the surface.

Anaerobe, Apr 1, 2013

The aims of this study were to characterize inhibitory activity spectra, some probiotic propertie... more The aims of this study were to characterize inhibitory activity spectra, some probiotic properties and safety of Lactobacillus curvatus A61 for its future application in production of fermented foods. The studied strain was isolated from traditional homemade cheese manufactured in Azerbaijan. The cell-free supernatant of culture of Lb. curvatus A61 inhibited the growth of tested LAB, as well as of Listeria monocytogenes and Bacillus cereus strains. The strain presented antifungal activity and inhibited the growth of Cladosporium and Fusarium ssp. during co-cultivation on agar media. PCR amplification with specific primers revealed the presence of curvacin A encoding gene in Lb. curvatus A61. Bacteriocin produced by the studied strain was heat stable and active in a broad pH range, and in the presence of Triton X-20, Triton X-80, Triton X-100, β-mercaptoethanol, Na-EDTA, SDS and NaCl. The mode of action of bacteriocin against selected indicator strains was found to be bacteriostatic. Lb. curvatus A61 was resistant to physiological concentrations of bile salts and showed high auto-aggregation ability, as well as co-aggregation ability with pathogenic L. monocytogenes strains. It was sensitive to chloramphenicol, penicillin, tetracycline, ciprofloxacin and vancomycin, but resistant to ampicillin and gentamicin.

Biochemistry, Oct 21, 1999

Nahrung, Jun 1, 2004

Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion... more Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion-exchange chromatography and reversed-phase high-performance liquid chromatography (HPLC) showed the presence of two fractions of beta-lactoglobulin but only one of alpha-lactalbumin. Gel permeation and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis allowed the calculation of the apparent molecular mass of each component, while HPLC coupled to electrospray ionisation-mass spectrometry (ESI-MS) technique, giving the exact molecular masses, demonstrated the presence of two variants A and B of ovine beta-lactoglobulin. Amino acid compositions of the two variants of beta-lactoglobulin differed only in their His and Tyr contents. Circular dichroism spectroscopy profiles showed pH conformation changes of each component. The thermograms of the different whey protein components showed a higher heat resistance of beta-lactoglobulin A compared to beta-lactoglobulin B at pH 2, and indicated high instability of ovine alpha-lactalbumin at this pH.

European Food Research and Technology, Jun 3, 2011

A collection of 147 isolates obtained from 23 samples of traditional Azerbaijani dairy products w... more A collection of 147 isolates obtained from 23 samples of traditional Azerbaijani dairy products was screened for the presence of proteolytic enzymes. Six Enterococcus faecalis strains obtained from three cheese samples have been identiWed as proteinase-producing strains, according to their ability to hydrolyze caseins. RAPD-PCR proWles of their total DNA showed diVerent patterns for strains isolated from diVerent cheese samples. The proteolytic activities of these strains were studied during their growth in milk and in non-proliferative cells system. Isolated strains were able to hydrolyze S1-, S2- ,-caseins and BLG albeit to diVerent extents, at optimal pH in the range 6.0-7.2 and optimal temperature in the range 37-45°C, depending on the strain. Proteolysis was strongly inhibited in the presence of EDTA-speciWc inhibitor of metalloproteases-but the presence of other types of proteases cannot be excluded. The potential pathogenicity of the strains was evaluated investigating the presence of the genes coding diVerent virulence factors and their resistance to antibiotics. The obtained results yield new information about technological characteristics and safety of studied Enterococci strains from Azerbaijani artisanal dairy products. Many from the isolated strains contribute certainly to the diVerences in Xavor, texture, and taste of Azerbaijani traditional cheeses and could represent new adjunct cultures for the dairy industry.

Food Control, Apr 1, 2013

The aims of this study were to characterize bacteriocin activity, some functional and probiotic p... more The aims of this study were to characterize bacteriocin activity, some functional and probiotic properties, and to evaluate the safety of Enterococcus faecium AQ71 isolated from Azerbaijani Motal cheese. The studied strain inhibited the growth of selected tested LAB, Listeria monocytogenes and Bacillus cereus strains. PCR amplification with specific primers indicated that E. faecium AQ71 carry genes encoding enterocins P, L50A, L50B and A. Bacteriocin(s) produced by the studied strain was/were heat stable and active in a broad pH range. Triton X-20, Triton X-80, Triton X-100, b-mercaptoethanol, Na-EDTA, SDS and NaCl did not affect the antimicrobial activity of the strain. The cell free supernatants of the strain caused the lysis of cells of Lactobacillus brevis F145 and inhibited the growth of L. monocytogenes. E. faecium AQ71 was negative for the tested virulence factors and did not present multi-resistance to antibiotics. The strain was resistant to physiological concentrations of bile salts and showed good auto-aggregation ability as well as co-aggregation ability with L. monocytogenes. E. faecium AQ71 exhibited good esterase, esterase lipase, acid phosphatase and aminopeptidase activities.

Lait, May 1, 2005

The aim of this study was to investigate the angiotensin I-converting-enzyme (ACE)inhibitory acti... more The aim of this study was to investigate the angiotensin I-converting-enzyme (ACE)inhibitory activity of tryptic hydrolysates of ovine β-lactoglobulin, and of yoghurts made by using different starters. Ovine β-lactoglobulin (a mixture of variants A and B at a ratio of 50/50) was subjected to trypsin activity. The degree of hydrolysis of native whole β-lactoglobulin reached 56, 72, 93 and 95% after 1, 2, 8 and 24 h, respectively. ACE-inhibitory activity of tryptic hydrolysates increased with the time of hydrolysis, yielding 85, 88 and 92% after 2, 12 and 24 h, respectively. The determination of ACE-inhibitory activity of some tryptic peptides separated by RP-HPLC and identified by mass spectroscopy showed that the more hydrophilic peptides showed the higher activity. Yoghurts obtained by fermentation of ovine milk with four different sets of starters, and their fractions soluble or not at pH 4.6 also showed an ACE-inhibitory activity. The maximum activity was obtained in the case of insoluble fractions at pH 4.6 of yoghurts made with the set of starters YC-183. ovine milk / tryptic peptide / yoghurt / ACE-inhibitory activity

Journal of Food Science and Technology, Nov 8, 2018

The main aim of this study was to develop a continuous microwave treatment system of whey protein... more The main aim of this study was to develop a continuous microwave treatment system of whey proteins and then apply this process at 37°C, 50°C, 65°C and 70°C to achieve pepsinolysis and produce extensively hydrolysed bovine whey protein hydrolysates with low allergenic properties. The microwave process was compared to a conventional thermal treatment with similar temperature set points. Both processes were deeply analysed in terms of the thermal kinetics and operating conditions. The pepsin hydrolysates obtained by the continuous microwave treatment and conventional heating were characterized by SDS-PAGE and RP-HPLC. The allergenicity of the whey protein hydrolysates was explored using a human IgE sensitized rat basophil leukaemia cell assay. The results indicate that extensively hydrolysed whey protein hydrolysates were obtained by microwave only at 65°C and in a shorter time compared with the conventional thermal treatment. In the same temperature conditions under conventional heating, b-lactoglobulin was resistant to pepsinolysis, and 37% of it remained intact. As demonstrated by an in vitro degranulation assay using specific human IgE-sensitized rat basophils, the extensively hydrolysed whey protein obtained by microwave showed maximum degranulation values of 6.53% compared to those of the native whey protein isolate (45.97%) and hence elicited no more allergenic reactions in basophils. This work emphasizes the potential industrial use of microwave heating specific to milk protein processing to reduce their allergenicity and improve their end-use properties.

International Journal of Food Microbiology, Dec 1, 2016

Fungal growth in bakery products represents the most frequent cause of spoilage and leads to econ... more Fungal growth in bakery products represents the most frequent cause of spoilage and leads to economic losses for industrials and consumers. Bacteria, such as lactic acid bacteria and propionibacteria, are commonly known to play an active role in preservation of fermented food, producing a large range of antifungal metabolites. In a previous study (Le Lay et al., 2016), an extensive screening performed both in vitro and in situ allowed for the selection of bacteria exhibiting an antifungal activity. In the present study, active supernatants against Penicillium corylophilum and Aspergillus niger were analyzed to identify and quantify the antifungal compounds associated with the observed activity. Supernatant treatments (pH neutralization, heating and addition of proteinase K) suggested that organic acids played the most important role in the antifungal activity of each tested supernatant. Different methods (HPLC, mass spectrometry, colorimetric and enzymatic assays) were then applied to analyze the supernatants and it was shown that the main antifungal compounds corresponded to lactic, acetic and propionic acids, ethanol and hydrogen peroxide, as well as other compounds present at low levels such as phenyllactic, hydroxyphenyllactic, azelaic and caproic acids. Based on these results, various combinations of the identified compounds were used to evaluate their effect on conidial germination and fungal growth of P. corylophilum and Eurotium repens. Some combinations presented the same activity than the bacterial culture supernatant thus confirming the involvement of the identified molecules in the antifungal activity. The obtained results suggested that acetic acid was mainly responsible for the antifungal activity against P. corylophilum and played an important role in E. repens inhibition.

HAL (Le Centre pour la Communication Scientifique Directe), Mar 6, 2012

International audienc

HAL (Le Centre pour la Communication Scientifique Directe), 2005

Ovine β-lactoglobulin (BLG, a mixture of variants A and B at a ratio of 46/54) and α-lactalbumin ... more Ovine β-lactoglobulin (BLG, a mixture of variants A and B at a ratio of 46/54) and α-lactalbumin (ALA) were subjected to pepsin activity. The degree of peptic hydrolysis of native whole BLG reached 63%, 74%, 82% and 87% after 2, 4, 8 and 20 h hydrolysis, respectively. BLG ...

Proceedings of the Nutrition Society, 2013

Revue Francaise D Allergologie, Apr 1, 2015

ABSTRACT Introduction Les probiotiques peuvent influencer le microbiote intestinal et moduler les... more ABSTRACT Introduction Les probiotiques peuvent influencer le microbiote intestinal et moduler les réponses immunitaires. Ils peuvent donc être des outils qui peuvent prévenir ou atténuer certaines pathologies impliquant le système immunitaire intestinal, telles que les allergies. À cet effet, l’objectif de notre travail était d’évaluer l’effet protecteur de Lactobacillus plantarum chez des souris BALB/c immunisées à la β-Lg. Méthodes Trente souris Balb/c ont été réparties en trois groupes de 10 souris chacun. Pendant 18 jours, les animaux du 1er groupe (témoin négatif) et du 2e groupe (témoin positif) recevaient une solution saline, tandis que le 3e groupe recevait L. plantarum par intubation orale. Ensuite les souris des groupes 2 et 3 ont été sensibilisées par voie intrapéritonéale à la β-Lg. Au 35e jour d’immunisation, les souris ont été sacrifiées. Les taux sériques des IgG, IgE, IgG1 et IgG2a anti-β-Lg ont été déterminés par dosage Elisa et une étude histologique a été réalisée sur des fragments jéjunaux afin d’évaluer le degré d’inflammation. Résultats Chez le groupe traité avec les probiotiques, l’immunisation a entraîné une faible production des IgG, IgG2a et IgE sériques anti-β-Lg (p < 0,0001) en comparant avec le groupe témoin positif. L’étude histologique de l’épithélium intestinal montre que les villosités des souris du groupe traité sont longues (48,87 ± 0,87 μm) avec une infiltration lymphocytaire intra-épithéliale très peu marquée comparativement au témoin négatif. Discussion L. plantarum protège les souris contre l’allergie à la β-Lg. Cela peut être dû à la génération des substances qui peuvent être reconnues par les récepteurs de l’hôte et induire des voies de signalisation aboutissant à leurs effets bénéfiques. Conclusion L. plantarum protège l’intégrité de l’épithélium intestinal en exerçant un rôle bénéfique sur la structure de l’épithélium et tempère la réponse allergénique à la bêta-lactoglobuline.

Revue Francaise D Allergologie, Apr 1, 2014

HAL (Le Centre pour la Communication Scientifique Directe), Sep 3, 2012

Biochimica Et Biophysica Acta - Proteins And Proteomics, May 1, 2000

Von Ebner gland protein (VEGP) and odorant-binding protein (OBP) were purified from porcine lingu... more Von Ebner gland protein (VEGP) and odorant-binding protein (OBP) were purified from porcine lingual epithelium and nasal mucosa, respectively. Both VEGP and OBP preparations were homogeneous as indicated by SDS^PAGE, isoelectric focusing, gel-filtration and electrospray mass spectrometry. However, high-sensitivity differential scanning calorimetry (HS-DSC) yielded multiphasic denaturation thermograms for both proteins indicating their conformational heterogeneity. The unfolding transition of VEGP is observed at extremely high temperatures (about 110³C), which is unexpected for a protein with significant structural homology to OBP and other lipocalins. Isothermal titration calorimetry (ITC) did not detect the binding of either aspartame or denatonium saccharide to VEGP nor did it detect binding of 2-isobutyl-3-methoxypyrazine (IBMP) to OBP. Extraction of OBP with mixed organic solvents eliminated the conformational heterogeneity and the protein showed a reversible two-state transition in HS-DSC thereafter. ITC also showed that the extracted OBP was able to bind IBMP. These results imply that tightly bound endogenous ligands increase the thermal stability of OBP and block the binding of other ligands. In contrast to OBP, the extraction of VEGP with organic solvents failed to promote binding or to establish thermal homogeneity, most likely because of the irreversible denaturation of VEGP. Thus, the elucidation of the functional behaviour of VEGP is closely related to the exhaustive purging of its endogenous ligands which otherwise very efficiently mask ligand binding sites of this protein.

Journal of Food Biochemistry, Jun 15, 2012

Proteolytic activity of Lactobacillus helveticus A75 and effects of caseins hydrolysis by this st... more Proteolytic activity of Lactobacillus helveticus A75 and effects of caseins hydrolysis by this strain on their immuno-reactivity were studied. Proteases of L. helveticus A75 hydrolyzed both αS1- and β-caseins and were inhibited by serine- and metallo-proteases inhibitors. Polymerase chain reaction amplification revealed the presence of prtH gene, which was 99% identical to prtH gene of L. helveticus CNRZ 32. Effect of proteolysis of αS1- and β-caseins by L. helveticus A75 on their immunoglobulin E (IgE) binding ability was studied by an enzyme-linked immunosorbent assay with the pool of eight sera from cow milk allergy patients. The IgE binding ability of hydrolyzed proteins was lower than that of intact proteins, which indicates that hydrolysis of αS1- and β-caseins by proteases of L. helveticus A75 decreases their recognition by specific IgE. Half maximal inhibitory concentration values were 2.01 and 2.28 µg/mL for αS1- and β-casein, respectively, and increased until 9.08 and 13.65 µg/mL, respectively, after their hydrolysis by L. helveticus A75. PRACTICAL APPLICATIONS The obtained results yield new information about proteolytic activity and potential application of lactobacilli isolated from traditional Azerbaijani cheeses. Isolated strain could represent new adjunct cultures for the dairy industry.

Food Chemistry, Aug 1, 2013

Vitamin A deficiency is one of the major causes of mortality and morbidity in the developing Worl... more Vitamin A deficiency is one of the major causes of mortality and morbidity in the developing World. This deficiency can be prevented by alimentary or pharmaceutical supplementation. However, both vitamin A oxidation and isomerization should be prevented, as these phenomenons result in loss of nutritional efficacy. The aim of this study was to investigate the effect of a food protein matrix, b-lactoglobulin (b-Lg) aggregates produced by high pressure (HP), on the stabilization of b-carotene during storage and gastro-duodenal digestion and therefore on its bioavailability. In vitro gastro-duodenal digestion of b-Lg aggregates entrapping b-carotene showed that up to 12% and 33% of total b-carotene was released after peptic and pancreatic digestion, respectively. Overall, our study showed that b-Lg aggregates are efficient for caging and stabilization of b-carotene during storage and digestion. Hence, it may be an interesting approach for the protection and the delivery of vitamin A.

HAL (Le Centre pour la Communication Scientifique Directe), 2005

Food Hydrocolloids, Mar 1, 2007

Due to the combination of flexibility and amphiphilicity, in solution b-casein (b-CN) acts as a s... more Due to the combination of flexibility and amphiphilicity, in solution b-casein (b-CN) acts as a surfactant molecule. It undergoes selfassociation and forms ''micellar-like'' aggregates in aqueous media. The aim of our study was to understand the role played by the charges borne by the N-terminal part of b-CN in its association behavior. b-CN polarity was modified in order to induce new aggregation properties and to understand better the main factors defining them. An unphosphorylated wild type recombinant form (WT A 2) of b-CN has been obtained by heterologous expression in the prokaryotic host Escherichia coli. A mutant (MU A 2) form of b-CN was engineered by duplicating the first 6 N-terminal amino acids residues (RELEEL) of WT A 2 , three additional negatively charged glutamic acids replacing some of the negative charges lost by the absence of phosphorylation in prokaryotic expression system. Dynamic light scattering and fluorimetry experiments showed that recombinant and native b-CN have different behaviors in temperaturedependent association. Micellisation was impaired by the absence of phosphate groups. Mutation conferred to the protein the ability to form aggregates whose size is inversely proportional to the concentration. These different behaviors during the association processes displayed by recombinant b-CN are correlated with modifications of the temperature-induced compaction of the proteins, what was revealed by circular dichroism measurements. WT A 2 was less condensed at the air-water interface than native b-CN; this was in part reversed by the additive mutation. However, MU A 2 compensating the lack of phosphate charges in recombinant caseins forms a more cohesive monolayer at the air-water interface than do the other b-CN, which means that the mutation reinforces monomers interaction at the surface.

Anaerobe, Apr 1, 2013

The aims of this study were to characterize inhibitory activity spectra, some probiotic propertie... more The aims of this study were to characterize inhibitory activity spectra, some probiotic properties and safety of Lactobacillus curvatus A61 for its future application in production of fermented foods. The studied strain was isolated from traditional homemade cheese manufactured in Azerbaijan. The cell-free supernatant of culture of Lb. curvatus A61 inhibited the growth of tested LAB, as well as of Listeria monocytogenes and Bacillus cereus strains. The strain presented antifungal activity and inhibited the growth of Cladosporium and Fusarium ssp. during co-cultivation on agar media. PCR amplification with specific primers revealed the presence of curvacin A encoding gene in Lb. curvatus A61. Bacteriocin produced by the studied strain was heat stable and active in a broad pH range, and in the presence of Triton X-20, Triton X-80, Triton X-100, β-mercaptoethanol, Na-EDTA, SDS and NaCl. The mode of action of bacteriocin against selected indicator strains was found to be bacteriostatic. Lb. curvatus A61 was resistant to physiological concentrations of bile salts and showed high auto-aggregation ability, as well as co-aggregation ability with pathogenic L. monocytogenes strains. It was sensitive to chloramphenicol, penicillin, tetracycline, ciprofloxacin and vancomycin, but resistant to ampicillin and gentamicin.

Biochemistry, Oct 21, 1999

Nahrung, Jun 1, 2004

Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion... more Ovine whey proteins were fractionated and studied by using different analytical techniques. Anion-exchange chromatography and reversed-phase high-performance liquid chromatography (HPLC) showed the presence of two fractions of beta-lactoglobulin but only one of alpha-lactalbumin. Gel permeation and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis allowed the calculation of the apparent molecular mass of each component, while HPLC coupled to electrospray ionisation-mass spectrometry (ESI-MS) technique, giving the exact molecular masses, demonstrated the presence of two variants A and B of ovine beta-lactoglobulin. Amino acid compositions of the two variants of beta-lactoglobulin differed only in their His and Tyr contents. Circular dichroism spectroscopy profiles showed pH conformation changes of each component. The thermograms of the different whey protein components showed a higher heat resistance of beta-lactoglobulin A compared to beta-lactoglobulin B at pH 2, and indicated high instability of ovine alpha-lactalbumin at this pH.

European Food Research and Technology, Jun 3, 2011

A collection of 147 isolates obtained from 23 samples of traditional Azerbaijani dairy products w... more A collection of 147 isolates obtained from 23 samples of traditional Azerbaijani dairy products was screened for the presence of proteolytic enzymes. Six Enterococcus faecalis strains obtained from three cheese samples have been identiWed as proteinase-producing strains, according to their ability to hydrolyze caseins. RAPD-PCR proWles of their total DNA showed diVerent patterns for strains isolated from diVerent cheese samples. The proteolytic activities of these strains were studied during their growth in milk and in non-proliferative cells system. Isolated strains were able to hydrolyze S1-, S2- ,-caseins and BLG albeit to diVerent extents, at optimal pH in the range 6.0-7.2 and optimal temperature in the range 37-45°C, depending on the strain. Proteolysis was strongly inhibited in the presence of EDTA-speciWc inhibitor of metalloproteases-but the presence of other types of proteases cannot be excluded. The potential pathogenicity of the strains was evaluated investigating the presence of the genes coding diVerent virulence factors and their resistance to antibiotics. The obtained results yield new information about technological characteristics and safety of studied Enterococci strains from Azerbaijani artisanal dairy products. Many from the isolated strains contribute certainly to the diVerences in Xavor, texture, and taste of Azerbaijani traditional cheeses and could represent new adjunct cultures for the dairy industry.

Food Control, Apr 1, 2013

The aims of this study were to characterize bacteriocin activity, some functional and probiotic p... more The aims of this study were to characterize bacteriocin activity, some functional and probiotic properties, and to evaluate the safety of Enterococcus faecium AQ71 isolated from Azerbaijani Motal cheese. The studied strain inhibited the growth of selected tested LAB, Listeria monocytogenes and Bacillus cereus strains. PCR amplification with specific primers indicated that E. faecium AQ71 carry genes encoding enterocins P, L50A, L50B and A. Bacteriocin(s) produced by the studied strain was/were heat stable and active in a broad pH range. Triton X-20, Triton X-80, Triton X-100, b-mercaptoethanol, Na-EDTA, SDS and NaCl did not affect the antimicrobial activity of the strain. The cell free supernatants of the strain caused the lysis of cells of Lactobacillus brevis F145 and inhibited the growth of L. monocytogenes. E. faecium AQ71 was negative for the tested virulence factors and did not present multi-resistance to antibiotics. The strain was resistant to physiological concentrations of bile salts and showed good auto-aggregation ability as well as co-aggregation ability with L. monocytogenes. E. faecium AQ71 exhibited good esterase, esterase lipase, acid phosphatase and aminopeptidase activities.

Lait, May 1, 2005

The aim of this study was to investigate the angiotensin I-converting-enzyme (ACE)inhibitory acti... more The aim of this study was to investigate the angiotensin I-converting-enzyme (ACE)inhibitory activity of tryptic hydrolysates of ovine β-lactoglobulin, and of yoghurts made by using different starters. Ovine β-lactoglobulin (a mixture of variants A and B at a ratio of 50/50) was subjected to trypsin activity. The degree of hydrolysis of native whole β-lactoglobulin reached 56, 72, 93 and 95% after 1, 2, 8 and 24 h, respectively. ACE-inhibitory activity of tryptic hydrolysates increased with the time of hydrolysis, yielding 85, 88 and 92% after 2, 12 and 24 h, respectively. The determination of ACE-inhibitory activity of some tryptic peptides separated by RP-HPLC and identified by mass spectroscopy showed that the more hydrophilic peptides showed the higher activity. Yoghurts obtained by fermentation of ovine milk with four different sets of starters, and their fractions soluble or not at pH 4.6 also showed an ACE-inhibitory activity. The maximum activity was obtained in the case of insoluble fractions at pH 4.6 of yoghurts made with the set of starters YC-183. ovine milk / tryptic peptide / yoghurt / ACE-inhibitory activity

Journal of Food Science and Technology, Nov 8, 2018

The main aim of this study was to develop a continuous microwave treatment system of whey protein... more The main aim of this study was to develop a continuous microwave treatment system of whey proteins and then apply this process at 37°C, 50°C, 65°C and 70°C to achieve pepsinolysis and produce extensively hydrolysed bovine whey protein hydrolysates with low allergenic properties. The microwave process was compared to a conventional thermal treatment with similar temperature set points. Both processes were deeply analysed in terms of the thermal kinetics and operating conditions. The pepsin hydrolysates obtained by the continuous microwave treatment and conventional heating were characterized by SDS-PAGE and RP-HPLC. The allergenicity of the whey protein hydrolysates was explored using a human IgE sensitized rat basophil leukaemia cell assay. The results indicate that extensively hydrolysed whey protein hydrolysates were obtained by microwave only at 65°C and in a shorter time compared with the conventional thermal treatment. In the same temperature conditions under conventional heating, b-lactoglobulin was resistant to pepsinolysis, and 37% of it remained intact. As demonstrated by an in vitro degranulation assay using specific human IgE-sensitized rat basophils, the extensively hydrolysed whey protein obtained by microwave showed maximum degranulation values of 6.53% compared to those of the native whey protein isolate (45.97%) and hence elicited no more allergenic reactions in basophils. This work emphasizes the potential industrial use of microwave heating specific to milk protein processing to reduce their allergenicity and improve their end-use properties.

International Journal of Food Microbiology, Dec 1, 2016

Fungal growth in bakery products represents the most frequent cause of spoilage and leads to econ... more Fungal growth in bakery products represents the most frequent cause of spoilage and leads to economic losses for industrials and consumers. Bacteria, such as lactic acid bacteria and propionibacteria, are commonly known to play an active role in preservation of fermented food, producing a large range of antifungal metabolites. In a previous study (Le Lay et al., 2016), an extensive screening performed both in vitro and in situ allowed for the selection of bacteria exhibiting an antifungal activity. In the present study, active supernatants against Penicillium corylophilum and Aspergillus niger were analyzed to identify and quantify the antifungal compounds associated with the observed activity. Supernatant treatments (pH neutralization, heating and addition of proteinase K) suggested that organic acids played the most important role in the antifungal activity of each tested supernatant. Different methods (HPLC, mass spectrometry, colorimetric and enzymatic assays) were then applied to analyze the supernatants and it was shown that the main antifungal compounds corresponded to lactic, acetic and propionic acids, ethanol and hydrogen peroxide, as well as other compounds present at low levels such as phenyllactic, hydroxyphenyllactic, azelaic and caproic acids. Based on these results, various combinations of the identified compounds were used to evaluate their effect on conidial germination and fungal growth of P. corylophilum and Eurotium repens. Some combinations presented the same activity than the bacterial culture supernatant thus confirming the involvement of the identified molecules in the antifungal activity. The obtained results suggested that acetic acid was mainly responsible for the antifungal activity against P. corylophilum and played an important role in E. repens inhibition.

HAL (Le Centre pour la Communication Scientifique Directe), Mar 6, 2012

International audienc

HAL (Le Centre pour la Communication Scientifique Directe), 2005

Ovine β-lactoglobulin (BLG, a mixture of variants A and B at a ratio of 46/54) and α-lactalbumin ... more Ovine β-lactoglobulin (BLG, a mixture of variants A and B at a ratio of 46/54) and α-lactalbumin (ALA) were subjected to pepsin activity. The degree of peptic hydrolysis of native whole BLG reached 63%, 74%, 82% and 87% after 2, 4, 8 and 20 h hydrolysis, respectively. BLG ...

Proceedings of the Nutrition Society, 2013

Revue Francaise D Allergologie, Apr 1, 2015

ABSTRACT Introduction Les probiotiques peuvent influencer le microbiote intestinal et moduler les... more ABSTRACT Introduction Les probiotiques peuvent influencer le microbiote intestinal et moduler les réponses immunitaires. Ils peuvent donc être des outils qui peuvent prévenir ou atténuer certaines pathologies impliquant le système immunitaire intestinal, telles que les allergies. À cet effet, l’objectif de notre travail était d’évaluer l’effet protecteur de Lactobacillus plantarum chez des souris BALB/c immunisées à la β-Lg. Méthodes Trente souris Balb/c ont été réparties en trois groupes de 10 souris chacun. Pendant 18 jours, les animaux du 1er groupe (témoin négatif) et du 2e groupe (témoin positif) recevaient une solution saline, tandis que le 3e groupe recevait L. plantarum par intubation orale. Ensuite les souris des groupes 2 et 3 ont été sensibilisées par voie intrapéritonéale à la β-Lg. Au 35e jour d’immunisation, les souris ont été sacrifiées. Les taux sériques des IgG, IgE, IgG1 et IgG2a anti-β-Lg ont été déterminés par dosage Elisa et une étude histologique a été réalisée sur des fragments jéjunaux afin d’évaluer le degré d’inflammation. Résultats Chez le groupe traité avec les probiotiques, l’immunisation a entraîné une faible production des IgG, IgG2a et IgE sériques anti-β-Lg (p < 0,0001) en comparant avec le groupe témoin positif. L’étude histologique de l’épithélium intestinal montre que les villosités des souris du groupe traité sont longues (48,87 ± 0,87 μm) avec une infiltration lymphocytaire intra-épithéliale très peu marquée comparativement au témoin négatif. Discussion L. plantarum protège les souris contre l’allergie à la β-Lg. Cela peut être dû à la génération des substances qui peuvent être reconnues par les récepteurs de l’hôte et induire des voies de signalisation aboutissant à leurs effets bénéfiques. Conclusion L. plantarum protège l’intégrité de l’épithélium intestinal en exerçant un rôle bénéfique sur la structure de l’épithélium et tempère la réponse allergénique à la bêta-lactoglobuline.

Revue Francaise D Allergologie, Apr 1, 2014

HAL (Le Centre pour la Communication Scientifique Directe), Sep 3, 2012