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- Ocorrência de Listeria spp. e Listeria monocytogenes em pescado fumado a frio em PortugalPublication . Duarte, Gabriela; Velho, Manuela Vaz; Gibbs, Paul
- Effects of addition of sucrose and salt, and of starvation upon thermotolerance and survival during storage of freeze-dried Lactobacillus delbrueckii ssp bulgaricusPublication . Carvalho, A. S.; Silva, J.; Ho, P.; Teixeira, P.; Malcata, F. X.; Gibbs, P.Increased survival of freeze-dried cells of Lactobacillus bulgaricus was observed when the drying medium was supplemented with sucrose; however, the magnitude of such protection was dependent on the growth medium used. Supplementing the growth medium with NaCl markedly increased survival of dried cells, and only a small effect was exerted by the composition of the drying medium or prior to starvation of cells. The D57 values of Lactobacillus bulgaricus cells grown in MRS were about half of those of cells grown in MRS supplemented with sucrose, with sucrose plus NaCl, or with NaCl.
- Microbiological quality of Portuguese yogurtsPublication . Nogueira, C.; Albano, H.; Gibbs, P.; Teixeira, P.The microbiological quality of four brands of natural yogurts and two probiotic yogurts available in the Portuguese market, was evaluated during the shelf-life period. Although the specific flora decreased during storage it was always within the range of recommended values. No coliforms and an insignificant number of fungi were detected.
- Characterisation of alheiras, traditional sausages produced in the North of Portugal, with respect to their microbiological safetyPublication . Ferreira, Vânia; Barbosa, Joana; Silva, Joana; Felício, Maria Teresa; Mena, Cristina; Hogg, Tim; Gibbs, Paul; Teixeira, PaulaThe objective of this study was the characterisation of alheiras, traditional Portuguese sausages, with respect to their microbiological safety. Thirty-eight lots from 17 producers were analysed. The microbiological status of the analysed product can be considered of concern in terms of food safety. Although Campylobacter spp. and Escherichia coli O157 were not detected in any sample,and Clostridium perfringens when present was not at levels of concern with reference to public health, Salmonella spp. were detected in 2 lots of industrially produced alheiras, and more than 60% of the lots analysed were contaminated with Listeria monocytogenes in concentrations higher than 100 cfu/g.
- Effect of various growth media upon survival during storage of freeze-dried Enterococcus faecalis and Enterococcus duransPublication . Carvalho, A.S.; Silva, J.; Ho, P.; Teixeira, P.; Malcata, F. X.; Gibbs, P.The effects of three different growth media (MRS, M17 and Lee’s) on survival during freeze-drying and subsequent storage of six strains of Enterococcus faecalis and two strains of E. durans were investigated. Methods and Results: Distinct Enterococcus spp. strains were grown on M17, MRS and Lee’s broth, freeze-dried and stored at 20 C in air under darkness. At regular intervals throughout storage, freeze-dried samples were rehydrated and then plated on M17 agar. Conclusions: A higher survival rate during storage of dried E. durans was obtained when growth occurred in MRS. The same effect was not observed, however, for the majority of E. faecalis strains, which clearly survived better in the dried state when this organism had been grown in M17 or Lee’s medium. Significance and Impact of Study: The survival of the dried Enterococcus spp. tested during storage was shown to be strain-specific and dependent on the growth medium.
- Food Safety in the domestic environment: incidence of Listeria monocytogenes in domestic refrigeratorsPublication . Marujo, Daniela; Pereira, Isabel; Mena, Cristina; Carneiro, Luísa; Almeida, Gonçalo; Teixeira, Paula; Gibbs, Paul
- Protein extraction and comparison of stain protocols for analysis of two-dimensional electrophoresis gelsPublication . Silva, Joana; Carvalho, Ana Sofia; Votorino, Rui; Domingues, Pedro; Teixeira, Paula; Gibbs, paulProtein extraction and the proteome of Lactobacillus delbrueckii subsp. bulgaricus were studied using different stains. The reversible silver staining technique was shown to be more sensitive than the irreversible silver stain. Coomassie colloidal was demonstrated to be as sensitive as reversible silver stain; however, the Coomassie colloidal blue solution developed a higher background and for sample preparation was more time-consuming.
- Establishing a new pasteurization criterion based on Alicyclobacillus acidoterrestris spores for shelf-stable high-acidic fruit productsPublication . Silva, Filipa M.; Gibbs, Paul; Silva, Cristina L. M.
- Effect of various protecting compounds added to the growth medium upon survival of lactobacillus sakei to heating, freezing, freeze-drying and storage in the dried statePublication . Ferreira, Vânia; Soares, Vânia; Santos, Cristina; Silva, Joana; Gibbs, Paul A.; Teixeira, PaulaThe aim of the present study was to investigate if the presence of sorbitol, myoinositol, xylose, mannose and Tween 80 in the growth medium increased the survival of L. sakei during heating, freezing, freeze drying and storage of freeze dried cells. Survival during freezing was enhanced by ca. 8% when glycerol was present in the growth medium. Viability during freeze-drying and storage in the dried state was improved by the presence of xylose in the growth medium. In addition to xylose, the presence of mannose and myoinositol protected cells during storage but not during drying. Cells grown in the presence myoinositol presented the highest D value at 55?C, 1.4 folder higher than control cells. In comparison with cells grown in MRS, total amino acids concentrations were the same order of magnitude for cells grown in the presence of mannose and myoinositol but were lower for cells grown in the presence of the other compounds.
- Incidence of Listeria spp. in domestic refrigerators in PortugalPublication . Azevedo, Inês; Regalo, Mafalda; Mena, Cristina; Almeida, Gonçalo; Carneiro, Luísa; Teixeira, Paula; Hogg, Tim; Gibbs, Paul A.The main objectives of this study were to determine the incidence of Listeria spp. in Portuguese domestic refrigerators and to evaluate some of the hygienic practices in the domestic environment that might contribute to the persistence of the organisms. It was found that L. monocytogenes was present in 3 domestic refrigerators of the 86 investigated. L. grayi and L. innocua were also isolated from 4 and 1 refrigerators, respectively. Overall, the information obtained from our survey demonstrates the need for consumer education in Portugal regarding safe food handling practices. For the refrigerators investigated, ≈71% were operating at a temperature higher than 6.1ºC, 87% were cleaned only monthly or less frequently, and only 8% were cleaned with appropriate proprietary cleaning products available in supermarkets.