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- Evaluation of a bacteriocinogenic Lactobacillus plantarum strain on the microbiological characteristics of “Alheira de Vitela”Publication . Macieira, Ariana; Albano, Helena; Pinto, Miguel; Linheiro, Raquel; Barbosa, Joana; Teixeira, PaulaLactic Acid Bacteria (LAB) and their bacteriocins can be successfully used as natural preservatives in meat products. This work aimed to investigate the effect of fresh and lyophilized starter cultures of an autochthonous bacteriocinogenic LAB strain (Lactobacillus plantarum ST153Ch: bac + culture) on the microbiological characteristics of “Alheira”, a traditional Portuguese smoked product. “Alheira” with the addition of fresh or lyophilized culture (ca. 108 cfu/g) and “Alheira” control (no bacteriocinogenic culture added) were produced by an industrial meat company. The antilisterial activity of this culture in this food matrix was investigated, with some samples being inoculated with Listeria monocytogenes (ca. 105 cfu/g). Detection of L. monocytogenes, Salmonella spp., sulphite reducing clostridia, Yersinia enterocolitica and enumeration of L. monocytogenes, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Enterobacteriaceae, lactic acid bacteria, yeasts and moulds were performed immediately after production and at 3, 7, 15, 21, 28, 60 and 90 days of storage at 4 ℃, according to ISO methodologies. Also, a 16S rRNA Gene Analysis was performed of the microbial communities of “Alheira” with and without the lyophilized bacteriocinogenic culture. Pathogenic and indicator organisms were not detected or were below acceptable levels in all samples. LAB counts increased during storage and reached similar values after 15 days (ca. 1010 cfu/g) in all samples. There was a clear trend for a higher reduction of L. monocytogenes in the presence of the bioprotective culture, more pronounced during the initial 15 days of storage. From the analysis of the microbial communities of samples of “Alheiras” at different stages of fermentation, Leuconostocaceae and Lactobacillaceae predominated in all the samples and Lactobacillus was the genus more prevalent in “Alheiras” after 60 days of storage with the addition of bacteriocinogenic culture.
- Characterization of a lactiplantibacillus plantarum r23 isolated from arugula by whole-genome sequencing and its bacteriocin production abilityPublication . Barbosa, Joana; Albano, Helena; Silva, Beatriz; Almeida, Maria Helena; Nogueira, Teresa; Teixeira, PaulaLactiplantibacillus plantarum is one of the lactic acid bacteria species most used as probiotics and starter cultures in food production. Bacteriocin-producers Lpb. plantarum are also promising natural food preservatives. This study aimed to characterize Lpb. plantarum R23 and its bacteriocins (R23 bacteriocins). The genome sequence of Lpb. plantarum R23 was obtained by whole-genome sequencing (WGS) in an Illumina NovaSeq platform. The activity of Lpb. plantarum R23-produced bacteriocin against two Listeria monocytogenes strains (L7946 and L7947) was evaluated, and its molecular size was determined by tricine-SDS-PAGE. No virulence or antibiotic resistance genes were detected. Four 100% identical proteins to the class II bacteriocins (Plantaricin E, Plantaricin F, Pedi-ocin PA-1 (Pediocin AcH), and Coagulin A) were found by WGS analysis. The small (<6.5 kDa) R23 bacteriocins were stable at different pH values (ranging from 2 to 8), temperatures (between 4 and 100 °C), detergents (all, except Triton X-100 and Triton X-114 at 0.01 g/mL), and enzymes (catalase and α-amylase), did not adsorb to the producer cells, had a bacteriostatic mode of action and their maximum activity (AU/mL = 12,800) against two L. monocytogenes strains occurred between 15 and 21 h of Lpb. plantarum R23 growth. Lactiplantibacillus plantarum R23 showed to be a promising bio-preservative culture because, besides being safe, it produces a stable bacteriocin or bacteriocins (har-bors genes encoding for the production of four) inhibiting pathogens as L. monocytogenes. Further studies in different food matrices are required to confirm this hypothesis and its suitability as a future starter culture.
- Effects of lactobacillus plantarum bacteriocinogenic culture on physicochemical, microbiological, and sensorial characteristics of "Chouriço Vinha d'Alhos", a traditional Portuguese sausagePublication . Macieira, A.; Barros, D.; Vaz Velho, Manuela; Pinheiro, R.; Fonseca, S.; Albano, H.; Teixeira, P.Background: “Chouriço Vinha d’Alhos” is a traditional fermented dry meat sausage from North of Portugal. The aim of this work was to evaluate the effects of a fresh and a lyophilized bioprotective Lactobacillus plantarum ST153Ch culture, on an industrial scale, on the physicochemical, microbiological, and sensorial characteristics of “Chouriço Vinha d’Alhos”. Methods: “Chouriço Vinha d’Alhos” added with Lb. plantarum ST153Ch (fresh or lyophilized) were analyzed for the physicochemical, microbiological, and sensorial characteristics, over 90 days of storage at 4 ºC. All data were statistically analyzed using an ANOVA procedure by IBM SPSS Statistics v. 25. Results: The results showed that there was no difference in the reduction of L. monocytogenes, without or with the addition of Lb. plantarum either fresh or lyophilized. There were no significant differences (p>0.05) in some analyzed physicochemical parameters of products added with fresh or lyophilized Lb. plantarum cultures over the 90 days of storage; but both, fresh and lyophilized cultures, influenced some of the tested physicochemical parameters. Conclusion: Considering no significant differences between application methodologies (fresh or lyophilized Lb. plantarum), industry might be able to choose the most suitable method according to their manufacturing process.
- Influence of oregano essential oil on the inhibition of selected pathogens in “alheira” during storagePublication . Carvalho, Marta I. P.; Albano, Helena C. P.; Teixeira, Paula C. M.Background. Plant-derived essential oils (EOs) have shown remarkable antimicrobial potential against spoilage and pathogenic microorganisms in meat and meat products. The aim of this study was to investigate the influence of oregano EO on the inhibition of Salmonella Enteritidis, Listeria monocytogenes and Staphylococcus aureus in an internal mixture of "Alheira" during storage. Material and methods. Different concentrations of oregano EO (4%, 1.5%, 0.5%, 0.195% and 0.0975%) were evaluated against the selected pathogens during 21 days of storage at 4 degrees C. The pH and water activity values and lactic acid bacteria (LAB) counts were also evaluated. Finally, sensory assessment was performed. Results. The antibacterial effect varied according to the oregano EO concentration used, and target pathogen. Oregano EO at 4% demonstrated the highest antimicrobial activity against all the pathogens tested. The lowest concentrations used (0.195% and 0.0975%) resulted in similar to 2-3 log reduction, but only for L. monocytogenes after 21 days of storage. Counts of LAB were similar to 10(9) CFU/ml for all samples and no differences in the pH and a(w) values were detected between samples. However, at a concentration of 0.195%, Oregano EO had a negative impact on consumer acceptance of "Alheira". Conclusion. These results could be interesting for the meat industry, as a starting point for other studies that have now to concentrate on strategies to "mask" unpleasant sensorial alterations caused by EOs in "Alheira" and helping the industry to ensure the microbiological safety of its products.
- Non meat-based alheiras - a safer novel trend?Publication . Azevedo, Inês; Barbosa, Joana; Albano, Helena; Teixeira, PaulaIn response to nutritional and health concerns, the food industry has begun to offer a wider variety of products that reflect changing consumer preferences. In addition to traditional alheiras, made with pork and/or poultry meats, other varieties of alheiras (“innovative”) made from codfish, mushrooms, tofu, soy and vegetables were launched on the Portuguese market. The objective of this study was the characterisation of these products, giving particular attention to their microbiological and chemical safety. Therefore, fourteen different products were analysed. Enterobacteriaceae, Enterococcus, lactic acid bacteria, yeasts and moulds, were the prevalent microbiota of “innovative” alheiras. Sulphite reducing Clostridium spores, Escherichia coli, Listeria monocytogenes, Salmonella spp. or Staphylococcus aureus were not detected in any sample. No differences were observed between traditional and “innovative” alheiras concerning pH and water activity values while nitrites, nitrates and biogenic amines were found to be within accepted limits for these kinds of products. In terms of organic acids, lactic acid was found in all analysed samples while malic and succinic acid seemed to be predominant only in “innovative” alheiras. In conclusion, unlike traditional alheiras which often contain pathogenic agents, no harmful organisms nor chemical hazards were found in these new products, even though produced by the same companies.
- Antibiotic resistance of Enterobacteriaceae isolated from the domestic food related environmentsPublication . Azevedo, I.; Albano, H.; Silva, J.; Teixeira, P.Background: Multidrug resistant Enterobacteriaceae which was confined to the hospital environments is now emerging in the domestic food related environments as well. The main objective of the present study was to investigate the prevalence of antibiotic re-sistant Enterobacteriaceae in the domestic food related environments. Methods: Resistance to ampicillin, chloramphenicol, ciprofloxacin, gentamicin, tetracy-cline, nalidixic acid, nitrofurantoin, and trimethoprim was evaluated in 125 isolates; col-lected in domestic food related environments using agar micro dilution method. Results: Results indicated that 49.6% of the isolates were resistant to at least one antibi-otic (32.8% to ampicillin, 6.4% to nitrofurantoin, 4% to tetracycline, 3.2% to nalidixic acid, 2.4% to chloramphenicol and 1.7% to trimethoprim). Resistance to multiple antibi-otics was observed in 6.4% of the isolates. Conclusion: This study implicates existence of antibiotic resistant Enterobactericeae in the domestic food related environments. This resistance phenomenon requires continual vigilance; and further studies are required to evaluate the role of domestic surfaces in the transmission of resistant pathogens and spread of infectious diseases.
- Food safety in the domestic environmentPublication . Azevedo, Inês; Albano, Helena; Silva, Joana; Teixeira, PaulaThe main purpose of this work was to evaluate the significance of food safety in domestic environments. In this study, several points in 15 houses (handles of doors, refrigerators and dishwashers, cooking stove knobs, surfaces of preparation of foods, taps and kitchen towels, as well as from domestic animals' feet that usually have access to the kitchen area, and WC knobs and taps) were sampled and tested for detection and quantification of Enterobacteriaceae, Staphylococcus coagulase-positive, Escherichia coli, Listeria spp. and Campylobacter spp. A questionnaire was also prepared and administered to the person responsible for domestic tasks in order to evaluate their experience of hygienic practices. The results showed a total of 125 Enterobacteriaceae spp. isolates, 86 Staphylococcus coagulase-positive isolates, 5 Listeria spp., 13 E. coli isolates and no Campylobacter spp. was found. Most of the isolates were found distributed by the entire house, with handles, knobs and domestic animals' feet being the points more contaminated. Also, there was no relation between the answers to the questionnaires administered and the microbiological results obtained. These results revealed the need to develop some education campaigns designed to educate consumers in good hygiene practices at home.