Olfa Ben Moussa - Academia.edu (original) (raw)
Papers by Olfa Ben Moussa
Value adding search among a selection of Tunisian fennel (Foeniculum vulgare Mill.) cultivars: Diversity assessment and selection among a local fennel germplasm
JOURNAL OF OASIS AGRICULTURE AND SUSTAINABLE DEVELOPMENT
Fennel (Foeniculum vulgare Mill.) is a very popular, aromatic, herbaceous plant that belongs to t... more Fennel (Foeniculum vulgare Mill.) is a very popular, aromatic, herbaceous plant that belongs to the Apiaceae family. It is among most important spices and medicinal species over the world. Nevertheless, in Tunisia fennel cultivation doesn't cover the local market needs. Also, fennel seeds are produced by farmers traditionally, and none of the local cultivars is named nor labelled in the market. Efforts have been deployed during the present work aiming to the characterization and valorization of genetic fennel resources. Hence, morphological diversity assessment was carried out among 62 entries of fennel acquired from different origins. Two steps principle component analysis (PCA) were applied. It came out with 7 selected cultivars of fennel representative of the initial diversity as assessed within the 62 collected fennel entries. Interestingly, among these latter, some of them exhibited particular phenotypic features linked to production traits.
Industrial Crops and Products, 2018
The basic objective of this study lies in determining the physico-chemical characteristics of Alo... more The basic objective of this study lies in determining the physico-chemical characteristics of Aloe vera gel in freshly harvested leaves, as well as evaluating its efficiency in terms of inhibiting the growth and ochratoxin A (OTA) production by Aspergillus carbonarius. The antifungal evaluation was performed by compound dissolution at the doses of 5, 10, 20, 30 and 50% in Czapek Yeast Agar medium (CYA). Our results revealed that Aloe vera gel did not display a pronounced antifungal effect on the growth of A. carbonarius. It rather showed a high antiochratoxigenic activity. Statistical analyses on growth rate of the fungus demonstrated that the main effect on mycelial growth was recorded at 50% of Aloe vera gel with an inhibition rate estimated at about 11.59%. At tested concentrations, Aloe vera gel could not totally inhibit the OTA production of fungus but only reduce it by 22.47-75.69% depending on concentration. However, this reduction was not positively correlated with the increase of the Aloe vera gel in the medium. The most important reduction on OTA synthesis was recorded at 20% of Aloe vera gel although no growth reduction was detected at this concentration. Overall, our results suggest that the concentration of Aloe vera gel should be between 20 and 30% to ensure an active inhibition of OTA production by A. carbonarius. This finding provides sound evidence that the use of Aloe vera gel as a biological pre-harvest treatment at the vineyard level is an effective, feasible and welcomed strategy.
International Journal of Dairy Technology, 2012
A Tunisian semihard Gouda-type cheese made from milk kept at 4°C for 24, 48, 72 and 96 h was moni... more A Tunisian semihard Gouda-type cheese made from milk kept at 4°C for 24, 48, 72 and 96 h was monitored during 45 days of ripening. The effect of milk refrigeration on the evolution of physicochemical parameters in relation to the quantitative variation of the microbial population during ripening of Gouda-type cheese was investigated. Microbiological and physicochemical analyses were performed on raw milk and cheese samples after curding, 2, 9, 16, 23, 30, 37 and 45 days of ripening time. The raw milk kept under refrigeration at 4°C for 96 h showed the highest microbial count and proteolysis level. The duration of storage significantly reduced the cheese yield as a result of important solubilisation casein in proteoses-peptones. Results of different nitrogenous fractions by Kjeldahl method showed enzymatic hydrolysis products of casein whose intensity depended on the maturing stage as well as the refrigeration time. Besides the evident action of the plasmin, original milk protease, on the hydrolysis of casein in soluble fractions, the proteolysis of cheese caseins is also initiated by proteolytic action of the chymosin and extracellular heat-resistant proteases notably produced by the same psychrotrophic microflora. Lactic acid bacteria starters that constitute the dominant microflora of this type of cheese are also considered as aroma precursors.
Journal of Food Safety, 2012
One hundred sixty psychrotrophic lactic acid bacteria (LAB) isolated from wild and aquacultured f... more One hundred sixty psychrotrophic lactic acid bacteria (LAB) isolated from wild and aquacultured fresh fish were identified by biochemical and molecular methods using 16S-23S rRNA spacer analysis and 16S rDNA sequencing. LAB strains were characterised according to their technological properties including acidifying capacity, antibiotic resistance and proteolytic, lipolytic and enzymatic activities, as well as antimicrobial activities, against pathogenic and spoilage bacteria in order to select the most suitable strains for use as starter cultures in the biopreservation of fresh fish and seafood products. The majority of strains displayed antimicrobial activities against pathogenic bacteria (Salmonella arizonae, Staphylococcus aureus, Listeria monocytogenes, Pseudomonas aeruginosa, Escherichia coli and Aspergillus flavus) and the dominant psychrotrophic Gram-negative bacteria in fresh fish (Pseudomonas fluorescens, Aeromonas hydrophila, Pseudomonas putida and Photobacterium damselae). A total of 39 isolates of LAB isolates having the most important antimicrobial activities were selected for further properties. Low proteolytic and lipolytic activities were detected for all strains using azocasein methods and fish fat, respectively. Moreover, all strains showed acidifying activity by reducing pH to less than 4.38 at 37C after 72 h. Finally, all studied LAB were resistant to penicillin, gentamicin, colistin, ciprofloxacin, norfloxacin, nalidixic acid, erythromycin, tetracycline and streptomycin. PRACTICAL APPLICATIONS The paper presents the identification and the technological properties of lactic acid bacteria (LAB) including antimicrobial activity against pathogenic and spoilage bacteria in order to select the most suitable strains for use as starter cultures in the biopreservation of fresh fish and seafood products. Considering this, assessment of the effect of inoculation of selected LAB on microbiological and physicochemical properties of fresh fish stored at chilled temperature is necessary to guarantee adequate fresh seafood products safety. Therefore, these analyses can lead to develop better biopreservation strategy for fresh fish by the use of selected LAB strains. Huss 1996; Boularès et al. 2011a). Various food preservation techniques have been utilized to improve the microbial safety and extend the shelf life of fish in general, including freezing, dehydration, fermentation (
Characterisation and technological properties of psychotropic lactic acid bacteria strains isolated from Tunisian raw milk
Annals of Microbiology, 2008
... Olfa BEN MOUSSA1*, Melika MANKAÏ1, Khaola SETTI1, Mouna BOULARES1, Medini MAHER2, Mnasser HAS... more ... Olfa BEN MOUSSA1*, Melika MANKAÏ1, Khaola SETTI1, Mouna BOULARES1, Medini MAHER2, Mnasser HASSOUNA1 ... They were then identified by the API 50 CH system (BioMérieux, France). * Corresponding author. E-mail: olfajamel@yahoo.fr Page 2. 462 ...
Journal of Culture …
Effect of Lactococcus lactis ssp lactis inoculated in UHT skim milk on the proteolytic activity o... more Effect of Lactococcus lactis ssp lactis inoculated in UHT skim milk on the proteolytic activity of psychrotrophic strains was studied. The titration of a purified non nitrogenous fraction from refrigerated UHT milk samples, previously inoculated by 10 6 psychrotrophic strains, showed that Pseudomonas fluorescens and P. putida were the most proteolytic species. This result has also been confirmed using polyacrylamide gel electrophoresis of casein fractions extracted from refrigerated and contaminated UHT milk samples. All extracellular proteases of the studied germs revealed a decreasing affinity towards κ, β, and α s1-caseins. This bacterial proteolysis of the UHT milk caseins samples, voluntarily contaminated by each of the studied psychrotrophic strains, was significantly reduced following the addition of 10 6 CFU/ml Lactococcus, which caused, after 9 days of refrigeration, an appreciable reduction of the number of psychrotrophic germs from a minimum of 100 to 1000 times, depending on the tested strain. Our results suggest that the inhibitory effect of lactic acid bacteria on psychrotrophs is due to acidification or/and bacteriocin like production.
Revue Marocaine des Sciences Agronomiques et Vétérinaires, 2018
Our study is on the impact of the water quality of milking parlor and cattle drinking on the phys... more Our study is on the impact of the water quality of milking parlor and cattle drinking on the physico-chemical and bacteriological quality of the milk. For this, milk and water samples were collected from six farms in northern Tunisia. Results of the study showed that milk physico-chemical properties were generally within intervals close to the required standards for milk but the majority of the collected milk samples can be qualified as having poor hygienic quality. The milking parlor's cleaning water quality, based on statistical results, affected total aerobic mesophilic flora (TAMF) as well as total milk coliforms. Cows drinking water quality, based on statistical analysis, affected milk fat content. It is clear that water quality was not the only factor affecting the quality of milk. Thus, the search for sources of contamination throughout the raw milk circuit, other than the quality of drinking water and cleaning of the milking parlor, has shown that hygiene practices (prep...
Revue Marocaine des Sciences Agronomiques et Vétérinaires, 2018
Résumé Notre travail vise à étudier l’impact de la qualité de l’eau d’abreuvement et de nettoyage... more Résumé Notre travail vise à étudier l’impact de la qualité de l’eau d’abreuvement et de nettoyage de la salle de traite sur la qualité physico-chimique et bactériologique du lait. Pour se faire, on a fait la collecte des échantillons de lait et d’eau de six fermes agricoles du Nord de la Tunisie. Il ressort de cette étude que les résultats des analyses physico-chimiques du lait sont généralement compris dans des intervalles proches des normes retenues pour le lait mais la majorité des échantillons de lait collectés peuvent être qualifiés de mauvaise qualité hygiénique. La qualité de l’eau de nettoyage de la salle de traite, d’après les résultats statistiques, affecte la flore mésophile aérobie totale ainsi que les coliformes totaux du lait. Alors que la qualité de l’eau d’abreuvement, d’après les analyses statistiques, influe sur le taux de matière grasse du lait. Il apparaît clairement que la qualité de l’eau n’est pas le seul facteur qui affecte la qualité du lait. Ainsi, la reche...
Chemical composition and biological activities of fennel ( Foeniculum vulgare Mill.) essential oils and ethanolic extracts of conventional and organic seeds
Evaluation of the effect of fennel ( Foeniculum vulgare Mill) essential oil addition on the quality parameters and shelf‐life prediction of yoghurt
International Journal of Dairy Technology
Effects of Lactic Acid Bacteria and Citrus Essential Oil on the Quality of Vacuum-Packed Sea Bass (Dicentrarchus labrax) Fillets During Refrigerated Storage
Journal of Aquatic Food Product Technology
ABSTRACT The preservative effect of refrigerated and vacuum-packed sea bass (Dicentrarchus labrax... more ABSTRACT The preservative effect of refrigerated and vacuum-packed sea bass (Dicentrarchus labrax) fillets inoculated with four mixtures of lactic acid bacteria (LAB) (Lactococcus lactis, Lactobacillus plantarum, and Carnobacterium piscicola) and incorporated with citrus essential oil (CEO) was evaluated on the basis of microbiological and biochemical analysis. Initially, sea bass fillets showed high nutritional quality. During refrigerated storage, lipid contents did not show a significant decrease in any fish fillets; meanwhile, important proteolysis was observed in untreated control. In addition, results indicated that both CEO and LAB strains exhibited antimicrobial activity against spoilage, pathogenic, and fungi flora. Moreover, the total volatile bases (TVB-N) values were higher in control fillets, and the lowest TVB-N values were observed in Control CEO and C3 + CEO (30.47 ± 0.00 and 32.29 ± 1.12 mg TVB-N/100 g, respectively). Also, the levels of biogenic amines increased in all fillets without exceeding the upper limit of acceptability except for untreated control (sum of about 1396.63 ppm). Furthermore, this combined treatment ameliorated the muscle liquid-holding capacity, which improves technological properties. Overall, this treatment may open new promising opportunities for the biopreservation of fish products by enhancing the period of storage of refrigerated and vacuum-packed sea bass fillets.
Advances in Microbiology
In the present study, 20 selected Lactobacillus strains already characterized in a previous resea... more In the present study, 20 selected Lactobacillus strains already characterized in a previous research for their capability to grow in conditions simulating the intestinal environment, their resistance to antibiotics, their antibacterial activity and their adhesion capability to intestinal human Caco-2 TC7 and HT-29 MTX cell lines, were further investigated to explore more their probiotic properties. Growth behaviour in the presence of prebiotic (fructooligosaccharides (FOS) and lactulose) at a concentration of 2%, cholesterol removal by measuring the residual cholesterol in medium supplemented with cholesterol, ability to deconjugate bile salts using BSH enzyme and antioxidant activity of culture supernatant of Lactobacillus strains by ABTS .+ and DPPH methods were analyzed. All probiotic strains demonstrated important prebiotic assimilation (P > 0.05) even with OD 600 > 3 after 30 h of contact, cholesterol removal ability with maximum percentage of 57% after 24 h of contact and they were found to liberate significantly (P < 0.05) more cholic acid with maximum of 0.40 mM of sodium glycocholate, 0.33 mM of sodium taurocholate and 0.41 mM of their mixte and scavenge both radicals with 52% and 2.19% of ABTS .+ and DPPH respectively. This study confirmed the suitability of these probiotic strains for application in functional food formulations especially where cholesterol reduction and antioxidant activity in food are needed to assess possible in vivo human health benefits.
Annals of Microbiology, Mar 1, 2008
The contamination of milk by spoilage bacteria is undesirable, particularly when Gram negative ba... more The contamination of milk by spoilage bacteria is undesirable, particularly when Gram negative bacteria which produce thermo-resistant protease and lipase can grow. In this work, spoilage bacteria in refrigerated raw milk were identified, using API 20NE System. Five dominant species were found: Pseudomonas fluorescens (20%), Aeromonas hydrophila (16%), Pseudomonas cepacia (13%), Pseudomonas putida (6%) and Chryseomonas luteola (5%). On the basis of agar diffusion assays, five strains harbouring the strongest lipases activities were selected. It has been found that esterase activities are higher for each one. Effects of main environmental and nutritional factors on the esterase activity of those psychrotrophic strains were investigated. Biomass level, pH, lactose concentration and permanent agitation affected positively esterase activity of each strain. However, the addition of Tween 20 influenced it negatively. Finally, and in order to extract information from the data sets, principal components analysis was applied to the data sets. The first two principal components showed a clear discrimination between Pseudomonas fluorescens and Pseudomonas cepacia.
Influence des conditions de culture sur l'àctivité protéolytique extracellulaire de souches psychrotrophes isolées à partir du lait cru tunisien réfrigéré : Leur caractérisation enzymatique par le système API ZYM
Industries Alimentaires Et Agricoles, 2005
L'influence de certaines conditions de culture sur l'activite proteolytique extracellulai... more L'influence de certaines conditions de culture sur l'activite proteolytique extracellulaire de cinq souches de bacteries psychrotrophes appartenant aux genres Pseudomonas et Aeromonas, prealablement isolees a partir du lait cru refrigere a + 4 °C, est etudiee en utilisant une matrice d'experiences. Ainsi, les effets des principaux parametres d'environnement et intrinseques du milieu de culture sur l'activite de proteases extracellulaires thermostables sont mesures. L'activite proteolytique extracellulaire est optimale pour une concentration en caseine autour de 3 a 5 %, des valeurs comprises entre un pH de 6 et un pH de 8 et une temperature de culture d'environ 37 °C. Par ailleurs, l'activite des proteases est maximale pour une concentration bacterienne comprise entre 10 4 et 10 7 ufc.ml -1 selon les souches. De plus, la recherche de certaines activites enzymatiques, a l'aide de la micro-methode API ZYM, montre que toutes les souches psychrotrophes etudiees sont egalement dotees d'activites aminopeptidasiques, phosphohydrolytiques, phosphatasiques et esterasiques importantes.
Functional in vitro screening of Lactobacillus strains isolated from Tunisian camel raw milk toward their selection as probiotic
Small Ruminant Research, 2016
Tweenty probiotic lactic acid bacteria (LAB) strains from Tunisian camel raw milk were identified... more Tweenty probiotic lactic acid bacteria (LAB) strains from Tunisian camel raw milk were identified among a collection of 177 isolates. The selected strains were able to tolerate pH 2, pepsin, pancreatin and bile salts, as restrictive criteria for probiotic potential. LAB strains were identified using 16S rRNA gene sequencing. Fourteen isolates belonged to the species Lactobacillus fermentum and six to Lactobacillus plantarum. None of this LAB showed mucin degradation or hemolytic activity, while proving resistant to a series of clinically antibiotics. All strains have antibacterial activity against Listeria monocytogenes, Staphylococcus aureus and Escherchia coli. However, only 18 strains inhibited Salmonella thyphimirium. The L. fermentum strains showed an important level of adhesion to human Caco-2 and HT29-MTX epithelial cells. Our work suggests that camel raw milk is valuable source of probiotic bacteria with functional characters of intestinal lactobacilli. These bacteria may be further used in probiotic applications.
Advances in Microbiology
One hundred strains isolated from bovine raw milk, obtained from different farms, were subjected ... more One hundred strains isolated from bovine raw milk, obtained from different farms, were subjected to different in vitro stress typical of gastrointestinal tract. Twelve strains were able to tolerate pepsin at pH 2, pancreatin and bile salts (0.3%). These bacteria were identified using 16S rRNA gene sequencing. Eight isolates were Lactobacillus plantarum and four were Lactobacillus fermentum. They were not able to degrade mucin and they were γ-haemolytic. All strains had antibacterial activity against Staphylococcus aureus, Listeria monocytogenes and Salmonella thyphimirium. However, only six strains inhibited Escherchia coli. All these showed ability for autoaggregation and/or hydrophobicity properties. They were also characterized in respect to their technological properties. Important acidification and low proteolytic and lipolytic capacities were detected for all strains. In addition, they were able to produce exopolysaccharides and grow at hot and cold temperatures. These bacteria may be used further for manufacturing of functional foods and confirming their suitability as probiotic starter cultures.
African Journal of Biotechnology, Apr 17, 2013
Indirect semi-skimmed ultra high temperature (UHT) milk was made from refrigerated milk preserved... more Indirect semi-skimmed ultra high temperature (UHT) milk was made from refrigerated milk preserved by the lactoperoxidase system (LPS). The effect of the LPS on the physicochemical and biochemical properties of UHT milk during storage period of 6 months at 30°C was assessed. The levels of soluble nitrogen at pH 4.6 and non protein nitrogen in all UHT milk samples increased during storage. However, control UHT milk, manufactured with refrigerated milk which LPS was not activated; showed the highest values (p < 0.01). Less hydrophobic amino acids concentrations, such as found in nitrogen soluble fraction, were lower in activated LPS UHT milk. Also, bacterial proteinase activities, measured using ophthaldialdehyde (oPA) as substrate, increased during storage. They were found higher in control UHT milk than in treated milk (p < 0.01). However, a decrease of total fatty acids in UHT milk, dependent on time of storage and LPS activation, was found during UHT milk storage.
Value adding search among a selection of Tunisian fennel (Foeniculum vulgare Mill.) cultivars: Diversity assessment and selection among a local fennel germplasm
JOURNAL OF OASIS AGRICULTURE AND SUSTAINABLE DEVELOPMENT
Fennel (Foeniculum vulgare Mill.) is a very popular, aromatic, herbaceous plant that belongs to t... more Fennel (Foeniculum vulgare Mill.) is a very popular, aromatic, herbaceous plant that belongs to the Apiaceae family. It is among most important spices and medicinal species over the world. Nevertheless, in Tunisia fennel cultivation doesn't cover the local market needs. Also, fennel seeds are produced by farmers traditionally, and none of the local cultivars is named nor labelled in the market. Efforts have been deployed during the present work aiming to the characterization and valorization of genetic fennel resources. Hence, morphological diversity assessment was carried out among 62 entries of fennel acquired from different origins. Two steps principle component analysis (PCA) were applied. It came out with 7 selected cultivars of fennel representative of the initial diversity as assessed within the 62 collected fennel entries. Interestingly, among these latter, some of them exhibited particular phenotypic features linked to production traits.
Industrial Crops and Products, 2018
The basic objective of this study lies in determining the physico-chemical characteristics of Alo... more The basic objective of this study lies in determining the physico-chemical characteristics of Aloe vera gel in freshly harvested leaves, as well as evaluating its efficiency in terms of inhibiting the growth and ochratoxin A (OTA) production by Aspergillus carbonarius. The antifungal evaluation was performed by compound dissolution at the doses of 5, 10, 20, 30 and 50% in Czapek Yeast Agar medium (CYA). Our results revealed that Aloe vera gel did not display a pronounced antifungal effect on the growth of A. carbonarius. It rather showed a high antiochratoxigenic activity. Statistical analyses on growth rate of the fungus demonstrated that the main effect on mycelial growth was recorded at 50% of Aloe vera gel with an inhibition rate estimated at about 11.59%. At tested concentrations, Aloe vera gel could not totally inhibit the OTA production of fungus but only reduce it by 22.47-75.69% depending on concentration. However, this reduction was not positively correlated with the increase of the Aloe vera gel in the medium. The most important reduction on OTA synthesis was recorded at 20% of Aloe vera gel although no growth reduction was detected at this concentration. Overall, our results suggest that the concentration of Aloe vera gel should be between 20 and 30% to ensure an active inhibition of OTA production by A. carbonarius. This finding provides sound evidence that the use of Aloe vera gel as a biological pre-harvest treatment at the vineyard level is an effective, feasible and welcomed strategy.
International Journal of Dairy Technology, 2012
A Tunisian semihard Gouda-type cheese made from milk kept at 4°C for 24, 48, 72 and 96 h was moni... more A Tunisian semihard Gouda-type cheese made from milk kept at 4°C for 24, 48, 72 and 96 h was monitored during 45 days of ripening. The effect of milk refrigeration on the evolution of physicochemical parameters in relation to the quantitative variation of the microbial population during ripening of Gouda-type cheese was investigated. Microbiological and physicochemical analyses were performed on raw milk and cheese samples after curding, 2, 9, 16, 23, 30, 37 and 45 days of ripening time. The raw milk kept under refrigeration at 4°C for 96 h showed the highest microbial count and proteolysis level. The duration of storage significantly reduced the cheese yield as a result of important solubilisation casein in proteoses-peptones. Results of different nitrogenous fractions by Kjeldahl method showed enzymatic hydrolysis products of casein whose intensity depended on the maturing stage as well as the refrigeration time. Besides the evident action of the plasmin, original milk protease, on the hydrolysis of casein in soluble fractions, the proteolysis of cheese caseins is also initiated by proteolytic action of the chymosin and extracellular heat-resistant proteases notably produced by the same psychrotrophic microflora. Lactic acid bacteria starters that constitute the dominant microflora of this type of cheese are also considered as aroma precursors.
Journal of Food Safety, 2012
One hundred sixty psychrotrophic lactic acid bacteria (LAB) isolated from wild and aquacultured f... more One hundred sixty psychrotrophic lactic acid bacteria (LAB) isolated from wild and aquacultured fresh fish were identified by biochemical and molecular methods using 16S-23S rRNA spacer analysis and 16S rDNA sequencing. LAB strains were characterised according to their technological properties including acidifying capacity, antibiotic resistance and proteolytic, lipolytic and enzymatic activities, as well as antimicrobial activities, against pathogenic and spoilage bacteria in order to select the most suitable strains for use as starter cultures in the biopreservation of fresh fish and seafood products. The majority of strains displayed antimicrobial activities against pathogenic bacteria (Salmonella arizonae, Staphylococcus aureus, Listeria monocytogenes, Pseudomonas aeruginosa, Escherichia coli and Aspergillus flavus) and the dominant psychrotrophic Gram-negative bacteria in fresh fish (Pseudomonas fluorescens, Aeromonas hydrophila, Pseudomonas putida and Photobacterium damselae). A total of 39 isolates of LAB isolates having the most important antimicrobial activities were selected for further properties. Low proteolytic and lipolytic activities were detected for all strains using azocasein methods and fish fat, respectively. Moreover, all strains showed acidifying activity by reducing pH to less than 4.38 at 37C after 72 h. Finally, all studied LAB were resistant to penicillin, gentamicin, colistin, ciprofloxacin, norfloxacin, nalidixic acid, erythromycin, tetracycline and streptomycin. PRACTICAL APPLICATIONS The paper presents the identification and the technological properties of lactic acid bacteria (LAB) including antimicrobial activity against pathogenic and spoilage bacteria in order to select the most suitable strains for use as starter cultures in the biopreservation of fresh fish and seafood products. Considering this, assessment of the effect of inoculation of selected LAB on microbiological and physicochemical properties of fresh fish stored at chilled temperature is necessary to guarantee adequate fresh seafood products safety. Therefore, these analyses can lead to develop better biopreservation strategy for fresh fish by the use of selected LAB strains. Huss 1996; Boularès et al. 2011a). Various food preservation techniques have been utilized to improve the microbial safety and extend the shelf life of fish in general, including freezing, dehydration, fermentation (
Characterisation and technological properties of psychotropic lactic acid bacteria strains isolated from Tunisian raw milk
Annals of Microbiology, 2008
... Olfa BEN MOUSSA1*, Melika MANKAÏ1, Khaola SETTI1, Mouna BOULARES1, Medini MAHER2, Mnasser HAS... more ... Olfa BEN MOUSSA1*, Melika MANKAÏ1, Khaola SETTI1, Mouna BOULARES1, Medini MAHER2, Mnasser HASSOUNA1 ... They were then identified by the API 50 CH system (BioMérieux, France). * Corresponding author. E-mail: olfajamel@yahoo.fr Page 2. 462 ...
Journal of Culture …
Effect of Lactococcus lactis ssp lactis inoculated in UHT skim milk on the proteolytic activity o... more Effect of Lactococcus lactis ssp lactis inoculated in UHT skim milk on the proteolytic activity of psychrotrophic strains was studied. The titration of a purified non nitrogenous fraction from refrigerated UHT milk samples, previously inoculated by 10 6 psychrotrophic strains, showed that Pseudomonas fluorescens and P. putida were the most proteolytic species. This result has also been confirmed using polyacrylamide gel electrophoresis of casein fractions extracted from refrigerated and contaminated UHT milk samples. All extracellular proteases of the studied germs revealed a decreasing affinity towards κ, β, and α s1-caseins. This bacterial proteolysis of the UHT milk caseins samples, voluntarily contaminated by each of the studied psychrotrophic strains, was significantly reduced following the addition of 10 6 CFU/ml Lactococcus, which caused, after 9 days of refrigeration, an appreciable reduction of the number of psychrotrophic germs from a minimum of 100 to 1000 times, depending on the tested strain. Our results suggest that the inhibitory effect of lactic acid bacteria on psychrotrophs is due to acidification or/and bacteriocin like production.
Revue Marocaine des Sciences Agronomiques et Vétérinaires, 2018
Our study is on the impact of the water quality of milking parlor and cattle drinking on the phys... more Our study is on the impact of the water quality of milking parlor and cattle drinking on the physico-chemical and bacteriological quality of the milk. For this, milk and water samples were collected from six farms in northern Tunisia. Results of the study showed that milk physico-chemical properties were generally within intervals close to the required standards for milk but the majority of the collected milk samples can be qualified as having poor hygienic quality. The milking parlor's cleaning water quality, based on statistical results, affected total aerobic mesophilic flora (TAMF) as well as total milk coliforms. Cows drinking water quality, based on statistical analysis, affected milk fat content. It is clear that water quality was not the only factor affecting the quality of milk. Thus, the search for sources of contamination throughout the raw milk circuit, other than the quality of drinking water and cleaning of the milking parlor, has shown that hygiene practices (prep...
Revue Marocaine des Sciences Agronomiques et Vétérinaires, 2018
Résumé Notre travail vise à étudier l’impact de la qualité de l’eau d’abreuvement et de nettoyage... more Résumé Notre travail vise à étudier l’impact de la qualité de l’eau d’abreuvement et de nettoyage de la salle de traite sur la qualité physico-chimique et bactériologique du lait. Pour se faire, on a fait la collecte des échantillons de lait et d’eau de six fermes agricoles du Nord de la Tunisie. Il ressort de cette étude que les résultats des analyses physico-chimiques du lait sont généralement compris dans des intervalles proches des normes retenues pour le lait mais la majorité des échantillons de lait collectés peuvent être qualifiés de mauvaise qualité hygiénique. La qualité de l’eau de nettoyage de la salle de traite, d’après les résultats statistiques, affecte la flore mésophile aérobie totale ainsi que les coliformes totaux du lait. Alors que la qualité de l’eau d’abreuvement, d’après les analyses statistiques, influe sur le taux de matière grasse du lait. Il apparaît clairement que la qualité de l’eau n’est pas le seul facteur qui affecte la qualité du lait. Ainsi, la reche...
Chemical composition and biological activities of fennel ( Foeniculum vulgare Mill.) essential oils and ethanolic extracts of conventional and organic seeds
Evaluation of the effect of fennel ( Foeniculum vulgare Mill) essential oil addition on the quality parameters and shelf‐life prediction of yoghurt
International Journal of Dairy Technology
Effects of Lactic Acid Bacteria and Citrus Essential Oil on the Quality of Vacuum-Packed Sea Bass (Dicentrarchus labrax) Fillets During Refrigerated Storage
Journal of Aquatic Food Product Technology
ABSTRACT The preservative effect of refrigerated and vacuum-packed sea bass (Dicentrarchus labrax... more ABSTRACT The preservative effect of refrigerated and vacuum-packed sea bass (Dicentrarchus labrax) fillets inoculated with four mixtures of lactic acid bacteria (LAB) (Lactococcus lactis, Lactobacillus plantarum, and Carnobacterium piscicola) and incorporated with citrus essential oil (CEO) was evaluated on the basis of microbiological and biochemical analysis. Initially, sea bass fillets showed high nutritional quality. During refrigerated storage, lipid contents did not show a significant decrease in any fish fillets; meanwhile, important proteolysis was observed in untreated control. In addition, results indicated that both CEO and LAB strains exhibited antimicrobial activity against spoilage, pathogenic, and fungi flora. Moreover, the total volatile bases (TVB-N) values were higher in control fillets, and the lowest TVB-N values were observed in Control CEO and C3 + CEO (30.47 ± 0.00 and 32.29 ± 1.12 mg TVB-N/100 g, respectively). Also, the levels of biogenic amines increased in all fillets without exceeding the upper limit of acceptability except for untreated control (sum of about 1396.63 ppm). Furthermore, this combined treatment ameliorated the muscle liquid-holding capacity, which improves technological properties. Overall, this treatment may open new promising opportunities for the biopreservation of fish products by enhancing the period of storage of refrigerated and vacuum-packed sea bass fillets.
Advances in Microbiology
In the present study, 20 selected Lactobacillus strains already characterized in a previous resea... more In the present study, 20 selected Lactobacillus strains already characterized in a previous research for their capability to grow in conditions simulating the intestinal environment, their resistance to antibiotics, their antibacterial activity and their adhesion capability to intestinal human Caco-2 TC7 and HT-29 MTX cell lines, were further investigated to explore more their probiotic properties. Growth behaviour in the presence of prebiotic (fructooligosaccharides (FOS) and lactulose) at a concentration of 2%, cholesterol removal by measuring the residual cholesterol in medium supplemented with cholesterol, ability to deconjugate bile salts using BSH enzyme and antioxidant activity of culture supernatant of Lactobacillus strains by ABTS .+ and DPPH methods were analyzed. All probiotic strains demonstrated important prebiotic assimilation (P > 0.05) even with OD 600 > 3 after 30 h of contact, cholesterol removal ability with maximum percentage of 57% after 24 h of contact and they were found to liberate significantly (P < 0.05) more cholic acid with maximum of 0.40 mM of sodium glycocholate, 0.33 mM of sodium taurocholate and 0.41 mM of their mixte and scavenge both radicals with 52% and 2.19% of ABTS .+ and DPPH respectively. This study confirmed the suitability of these probiotic strains for application in functional food formulations especially where cholesterol reduction and antioxidant activity in food are needed to assess possible in vivo human health benefits.
Annals of Microbiology, Mar 1, 2008
The contamination of milk by spoilage bacteria is undesirable, particularly when Gram negative ba... more The contamination of milk by spoilage bacteria is undesirable, particularly when Gram negative bacteria which produce thermo-resistant protease and lipase can grow. In this work, spoilage bacteria in refrigerated raw milk were identified, using API 20NE System. Five dominant species were found: Pseudomonas fluorescens (20%), Aeromonas hydrophila (16%), Pseudomonas cepacia (13%), Pseudomonas putida (6%) and Chryseomonas luteola (5%). On the basis of agar diffusion assays, five strains harbouring the strongest lipases activities were selected. It has been found that esterase activities are higher for each one. Effects of main environmental and nutritional factors on the esterase activity of those psychrotrophic strains were investigated. Biomass level, pH, lactose concentration and permanent agitation affected positively esterase activity of each strain. However, the addition of Tween 20 influenced it negatively. Finally, and in order to extract information from the data sets, principal components analysis was applied to the data sets. The first two principal components showed a clear discrimination between Pseudomonas fluorescens and Pseudomonas cepacia.
Influence des conditions de culture sur l'àctivité protéolytique extracellulaire de souches psychrotrophes isolées à partir du lait cru tunisien réfrigéré : Leur caractérisation enzymatique par le système API ZYM
Industries Alimentaires Et Agricoles, 2005
L'influence de certaines conditions de culture sur l'activite proteolytique extracellulai... more L'influence de certaines conditions de culture sur l'activite proteolytique extracellulaire de cinq souches de bacteries psychrotrophes appartenant aux genres Pseudomonas et Aeromonas, prealablement isolees a partir du lait cru refrigere a + 4 °C, est etudiee en utilisant une matrice d'experiences. Ainsi, les effets des principaux parametres d'environnement et intrinseques du milieu de culture sur l'activite de proteases extracellulaires thermostables sont mesures. L'activite proteolytique extracellulaire est optimale pour une concentration en caseine autour de 3 a 5 %, des valeurs comprises entre un pH de 6 et un pH de 8 et une temperature de culture d'environ 37 °C. Par ailleurs, l'activite des proteases est maximale pour une concentration bacterienne comprise entre 10 4 et 10 7 ufc.ml -1 selon les souches. De plus, la recherche de certaines activites enzymatiques, a l'aide de la micro-methode API ZYM, montre que toutes les souches psychrotrophes etudiees sont egalement dotees d'activites aminopeptidasiques, phosphohydrolytiques, phosphatasiques et esterasiques importantes.
Functional in vitro screening of Lactobacillus strains isolated from Tunisian camel raw milk toward their selection as probiotic
Small Ruminant Research, 2016
Tweenty probiotic lactic acid bacteria (LAB) strains from Tunisian camel raw milk were identified... more Tweenty probiotic lactic acid bacteria (LAB) strains from Tunisian camel raw milk were identified among a collection of 177 isolates. The selected strains were able to tolerate pH 2, pepsin, pancreatin and bile salts, as restrictive criteria for probiotic potential. LAB strains were identified using 16S rRNA gene sequencing. Fourteen isolates belonged to the species Lactobacillus fermentum and six to Lactobacillus plantarum. None of this LAB showed mucin degradation or hemolytic activity, while proving resistant to a series of clinically antibiotics. All strains have antibacterial activity against Listeria monocytogenes, Staphylococcus aureus and Escherchia coli. However, only 18 strains inhibited Salmonella thyphimirium. The L. fermentum strains showed an important level of adhesion to human Caco-2 and HT29-MTX epithelial cells. Our work suggests that camel raw milk is valuable source of probiotic bacteria with functional characters of intestinal lactobacilli. These bacteria may be further used in probiotic applications.
Advances in Microbiology
One hundred strains isolated from bovine raw milk, obtained from different farms, were subjected ... more One hundred strains isolated from bovine raw milk, obtained from different farms, were subjected to different in vitro stress typical of gastrointestinal tract. Twelve strains were able to tolerate pepsin at pH 2, pancreatin and bile salts (0.3%). These bacteria were identified using 16S rRNA gene sequencing. Eight isolates were Lactobacillus plantarum and four were Lactobacillus fermentum. They were not able to degrade mucin and they were γ-haemolytic. All strains had antibacterial activity against Staphylococcus aureus, Listeria monocytogenes and Salmonella thyphimirium. However, only six strains inhibited Escherchia coli. All these showed ability for autoaggregation and/or hydrophobicity properties. They were also characterized in respect to their technological properties. Important acidification and low proteolytic and lipolytic capacities were detected for all strains. In addition, they were able to produce exopolysaccharides and grow at hot and cold temperatures. These bacteria may be used further for manufacturing of functional foods and confirming their suitability as probiotic starter cultures.
African Journal of Biotechnology, Apr 17, 2013
Indirect semi-skimmed ultra high temperature (UHT) milk was made from refrigerated milk preserved... more Indirect semi-skimmed ultra high temperature (UHT) milk was made from refrigerated milk preserved by the lactoperoxidase system (LPS). The effect of the LPS on the physicochemical and biochemical properties of UHT milk during storage period of 6 months at 30°C was assessed. The levels of soluble nitrogen at pH 4.6 and non protein nitrogen in all UHT milk samples increased during storage. However, control UHT milk, manufactured with refrigerated milk which LPS was not activated; showed the highest values (p < 0.01). Less hydrophobic amino acids concentrations, such as found in nitrogen soluble fraction, were lower in activated LPS UHT milk. Also, bacterial proteinase activities, measured using ophthaldialdehyde (oPA) as substrate, increased during storage. They were found higher in control UHT milk than in treated milk (p < 0.01). However, a decrease of total fatty acids in UHT milk, dependent on time of storage and LPS activation, was found during UHT milk storage.