Browsing by Author "Teixeira, Paula C."
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- Antimicrobial effects of a microemulsion and a nanoemulsion on enteric and other pathogens and biofilmsPublication . Teixeira, Paula C.; Leite, Gonçalo M.; Domingues, Ricardo J.; Silva, Joana; Gibbs, Paul A.; Ferreira, João PauloSome microemulsions and nanoemulsions may have antimicrobial properties and be effective anti-biofilm agents. We examined the abilities of two fine emulsions, designated BCTP and TEOP, to inactivate suspensions of vegetative cells of Salmonella spp. Escherichia coli 0157:H7 (VT-), Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes. BCTP is an O/W nanoemulsion of soybean oil and tri-n-butyl phosphate emulsified with Triton X-100, while TEOP is an O/W microemulsion of ethyl oleate with Tween 80 as emulsifier and n-pentanol as a co-emulsifier. BCTP was effective in reducing the cell numbers of L. monocytogenes, while TEOP was effective against all five organisms investigated. The abilities of these emulsions to reduce preformed biofilms of the five bacteria were also investigated. With the exception of the biofilm formed by L. monocytogenes, which surprisingly was not significantly affected by BCTP, all biofilms were inhibited by both BCTP and TEOP.
- Application of an impedimetric technique for the detection of lytic infection of salmonella spp. by specific phagesPublication . Amorim, Lara R. P.; Silva, Joana G. L.; Gibbs, Paul A.; Teixeira, Paula C.This study was performed to evaluate the adaption of the impedimetric method to detect the lytic infection by Salmonella-specific bacteriophages and to provide a higher selectivity to this rapid method in detecting Salmonella spp. by using specific agents. Three bacteriophages and twelve strains of Salmonella spp. were tested. Each of the twelve strains was used separately to inoculate TSB together with each one of the phages. The inoculumconcentration was between 106 and 107 cfu/mL, at a cell: phage ratio of 1 : 100. From the sample analysis, based on conductance (G)measurements (37◦C), the infection could be detected, by observation of both detection-time delay and distinct curve trends. The main conclusions were that kinetic detection by impedance microbiology with phage typing constitutes a method of determining whether a test microorganism is sensitive to the bacteriophage and a method to evaluate whether a lytic bacteriophage is present in a sample, by affecting bacterial growth rate/metabolic change
- Could modifications of processing parameters enhance the growth and selection of lactic acid bacteria in cold-smoked salmon to improve preservation by natural meansPublication . Tomé, Elisabetta; Gibbs, Paul A.; Teixeira, Paula C.Several smoking conditions were examined with the objective of enhancing the numbers of lactic acid bacteria (LAB) by natural means in vacuum-packaged cold-smoked salmon during 21 days of storage at 5C. Three combinations of salting, drying, and smoking were used: (i) dry salting time of salting (2 or 6 h); (ii) wet salting (6 h) dry salting (6 h) with mor without sugar; and (iii) wet salting (6 h) dry salting (6 h) different times of smoking (2 or 6 h of drying and 2 or 6 h of smoking). Two batches were processed for each set of conditions. Determinations of pH and salt content in the water phase were carried out for products in each treatment. Microbiological analyses (total viable count, total LAB, Lactobacillus spp., and Enterobacteriaceae) also were conducted at the beginning of storage (t0) and after 21 days of refrigerated storage (t1). There were differential increases in total LAB and lactobacilli during the storage period according to the treatment performed. The most effective treatment to enhance LAB growth was 6 h of dry salting with sugar, 6 h of drying, and 2 h of smoking. These salting-drying-smoking conditions also selected the LAB as the dominant flora at the end of the storage period. The LAB promoted by these processing parameters seem to be potentially useful protective cultures because of their anti-Listeria activity. From the results of this research, we conclude that it is possible to enhance the growth of LAB in general and that of inhibitory strains in particular by suitable choices of processing parameters.
- Exploring the development of a clean-label vegan burger enriched with fermented microalgaePublication . Bassani, Joseane C.; Martins, Valter F. R.; Barbosa, Joana; Coelho, Marta; Sousa, Clara; Steffens, Juliana; Backes, Geciane T.; Pereira, Hugo; Pintado, Manuela E.; Teixeira, Paula C.; Morais, Alcina M. M. B.; Morais, Rui M. S. C.Haematococcus pluvialis and Porphyridium cruentum are red microalgae with high biotechnological potential due to their rich composition of bioactive compounds. However, their intense flavor limits their application in food products. This study evaluated the impact of fermentation with Lactiplantibacillus plantarum (30 ?C for 48 h; LAB-to-biomass ratio of 0.1:1; 106 CFU/mL) on the physicochemical and functional properties of H. pluvialis and P. cruentum biomasses. Particular attention was given to antioxidant activity (ABTS and ORAC assays), color, amino acid profiles, and volatile organic compound (VOC) profiles, all of which may influence sensory characteristics. Results demonstrated that non-fermented H. pluvialis exhibited significantly higher antioxidant activity (AA) than P. cruentum. After fermentation, H. pluvialis showed an ABTS value of 3.22 ± 0.35 and an ORAC value of 54.32 ± 1.79 µmol TE/100 mg DW, while P. cruentum showed an ABTS of 0.26 ± 0.00 and an ORAC of 3.11 ± 0.13 µmol TE/100 mg DW. Total phenolic content (TPC) of fermented H. pluvialis and P. cruentum was 1.08 ± 0.23 and 0.18 ± 0.026 mg GAE/100 mg DW, respectively. Both AA and TPC increased after fermentation. Fermentation also significantly affected biomass color. FTIR analysis showed intensification of protein and carbohydrate vibrational bands post-fermentation. GC-MS analysis of VOCs showed that P. cruentum contained 42 VOCs before fermentation, including trans-?-ionone, 4-ethyl-6-hepten-3-one, hexanal, and heptadienal, which are responsible for fishy and algal odors. Fermentation with Lb. plantarum significantly reduced these compounds, lowering trans-?-ionone to 0.1453 mg/L and eliminating 4-ethyl-6-hepten-3-one entirely. H. pluvialis contained 22 VOCs pre-fermentation; fermentation eliminated hexanal and reduced heptadienal to 0.1747 ± 0.0323 mg/L. These changes contributed to improved sensory profiles. Fermentation also induced significant changes in the amino acid profiles of both microalgae. The fermented biomasses were incorporated into vegan burgers made from chickpea, lentil, and quinoa. Color evaluation showed more stable and visually appealing tones, while texture remained within desirable consumer parameters. These findings suggest that Lb. plantarum fermentation is an effective strategy for improving the sensory and functional characteristics of microalgal biomass, promoting their use as sustainable, value-added ingredients in innovative plant-based foods.
- Growth control of listeria innocua 2030c on vacuum-packaged cold-smoked salmon by lactic acid bacteriaPublication . Tomé, Elisabetta; Gibbs, Paul A.; Teixeira, Paula C.Five bacteriocin-producing lactic acid bacteria (LAB): Enterococcus faecium ET05, Lactobacillus curvatus ET06, L. curvatus ET30, L. deldrueckii ET32 and Pediococcus acidilactici ET34, selected by their capacity for growth and producing inhibition in vitro at high salt-on-water content, low temperature and anaerobic atmosphere, conditions simulating cold-smoked fish,were inoculated onto salmon fillets, in co-culturewith Listeria innocua 2030c, and cold-smoked processed (dry salted for 6h; drying for 6h; smoke for 2h).The finished product was then packed under vacuum and stored at 5 °C. Enumeration of LAB and L. innocua was performed during storage. Results showed that strain E. faecium ET05 was the best biopreservative candidate for controlling L. innocua growth in vacuum-packaged cold-smoked salmon (CSS) processed under the salting/drying/smoking parameters referred above. L. curvatus ET30 and L. delbrueckii ET32 also showed a good biopreservation potential for CSS although they were less effective than the former. L. curvatus ET06 and P. acidilactici ET34 showed a bacteriostatic mode of action against the target bacteria in vitro as well as when inoculated into the salmon fillets. This study describes a potential application of five different LAB in the biopreservation of Listeria in CSS.
- In vitro tests of suitability of bacteriocin-producing lactic acid bacteria, as potential biopreservation cultures in vacuum-packaged cold-smoked salmonPublication . Tomé, Elisabetta; Pereira, Vera L.; Lopes, Carla I.; Gibbs, Paul A.; Teixeira, Paula C.The objectives of this study were to ascertain the in vitro potential of nine bacteriocin-producing lactic acid bacteria (LAB) strains, isolated from vacuum-packaged cold-smoked salmon (CSS), for possible use as biopreservative cultures against Listeria monocytogenes. The antilisterial activity of cultures’ supernatants was assessed at 0.5%, 3.0% and 5.0% w/v of salt, at 5ºC, 10ºC and 25ºC both in aerobic and anaerobic atmospheres, simulating the conditions pertaining in vacuum-packaged CSS. The kinetics of growth, bacteriocin biosynthesis, the minimum inhibitory concentrations (MICs) of ten antibiotics, histamine and tyramine production of LAB strains, were determined jointly with the haemolytic activity for the enterococci. Only five strains were able to secrete active bacteriocins into the culture medium, at high salt concentrations and low temperatures, both in aerobic and anaerobic atmospheres. Enterococci showed neither haemolyt ic activity nor vancomycin resistance. The production of histamine was not observed for any of the bacteriocin-producing strains.
- Listeriosis in Portugal: an existing but under reported infectionPublication . Almeida, Gonçalo N.; Gibbs, Paul A.; Hogg, Tim; Teixeira, Paula C.Listeriosis is a rare disease caused by the bacterium Listeria monocytogenes, the normal vehicle of which is food. The disease, which is largely confined to its risk groups of pregnant women, the elderly and immunocompromised individuals, has increased in incidence in recent years. In Portugal, listeriosis is not a notifiable infection and available data are scarce. The objective of this work was to collate the available information concerning listeriosis in Portugal by compiling a retrospective study of cases recorded over a decade. Methods: Requests for case data on clinically confirmed listeriosis, recorded over the previous decade, were replied to by 23 hospitals and a National Institute of Health delegation. Results: 35 cases of listeriosis were identified for the period between 1994 and 2003 inclusive, the mortality rate being greater than 17%. According to the data collected in this study for the year 2003, the incidence of this disease in Portugal was at least 1.4 cases per million inhabitants in that year. Conclusion: The study demonstrates, for the first time in the widely available literature, that despite their being no cases of listeriosis in Portugal recorded in official reports, the threat of L. monocytogenes to public health is of a similar dimension to that in other countries.
- Numeric taxonomy approaches for lytic evaluation of Salmonella specific bacteriophagesPublication . Amorim, Lara R.P.; Tamames, Juan A.C.; Silva, Joana G.L.; Gibbs, Paul A.; Teixeira, Paula C.This study explored the lytic ability of bacteriophages as a future tool for reducing the Salmonella spp. loads in food animals. It investigated (a) the concept of a phage cocktail resulting from an exploratory analysis of the 13 phages which were examined, and (b) the possibility of using them in phage typing techniques for a broad range of serotypes. By using the conventional plaque assay method and cluster analysis, it was possible to select the 2/2, N5, 2a, 135KP and 120 phages, as potential elements of a cocktail as a means of efficiently eliminating the greatest number of several types of Salmonella. The 2/2 and N5 phages were also the most efficacious infective elements against the Typhimurium and Enteritidis serovars, respectively.
- Partial characterization of nine bacteriocins produced by lactic acid bacteria isolated from cold-smoked salmon with activity against listeria monocytogenesPublication . Tomé, Elisabetta; Todorov, Svetoslav D.; Gibbs, Paul A.; Teixeira, Paula C.Nine LAB bacteriocin-producers, isolated from vacuum-packaged cold-smoked salmon (CSS), were phenotypically and genotypically identified as Lactobacillus curvatus, Lactobacillus delbrueckii, Lactobacillus fermentum, Enterococcus faecium, and Pediococcus acidilactici. Their bacteriocins were partially characterized. The antimicrobial spectrum was determined against Listeria monocytogenes, E. faecalis, E. faecium, and Staphylococcus aureus. The molecular size of bacteriocins ranged from 2.8 to 4.5 kDa. They were inactivated by treatment with proteolytic enzymes but not by lipolytic or glycolytic enzymes. Maximal activity against L. monocytogenes ranged between 800 and 10000 AU/mL at pH 6.5. Most of the bacteriocins maintained full activity in a pH range of 2.0 to 8.0 but were partially or completely inactivated at pH 10.0. After heating at 60°C and 100°C, only two bacteriocins from Lb. curvatus strains partially lost activity. All bacteriocins showed a narrow spectrum of activity and a high anti-listerial activity, which is characteristic of the class IIa bacteriocins. Isolated bacteriocinproducing LAB could be used successfully in the bio-preservation of CSS and development of new potential bio-preservatives for CSS active against L. monocytogenes.