Browsing by Author "Carvalho, Teresa Bento de"
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- Antimicrobial activity of in-situ bacterial nanocellulose-zinc oxide composites for food packagingPublication . Silva, Francisco A. G. Soares; Carvalho, Marta; Carvalho, Teresa Bento de; Gama, Miguel; Poças, Fátima; Teixeira, PaulaActive substances such as zinc oxide nanoparticles (ZnO) have been extensively explored due to their antimicrobial properties, low cost and scalability. Yet, their effectiveness is highly dependent on their morphology and specific surface area. Bacterial nanocellulose (BNC) is a suitable carrier due to its ability to transport and deliver active substances. In the case of nanocellulose-ZnO composites, conclusions drawn from antimicrobial studies are often based on only a few representatives of Gram-positive and Gram-negative bacteria. A more comprehensive study using different species and strains, and different methods to assess antimicrobial activity is required. Therefore, in this work, the antimicrobial activity of ZnO suspensions and BNCZnO films was assessed against a wide range of Gram-negative and Gram-positive bacteria using disc diffusion and viable cell count assays. Regarding the results of the disc diffusion assay, the increase of ZnO content (21–27% mZn/mBNCZnO) (in both ZnO suspensions and BNCZnO films), increased antimicrobial activity against all Gram-negative bacteria tested and some Gram-positive bacteria. In the viable cell count assay, BNCZnO films were effective against Escherichia coli (3 log reduction) and Listeria monocytogenes (1–3 log reduction) after 24 h. Low temperatures reduced the antimicrobial activity of BNCZnO.
- Assessing antimicrobial efficacy on plastics and other non-porous surfaces: a closer look at studies using the ISO 22196:2011 standardPublication . Carvalho, Teresa Bento de; Barbosa, Joana Bastos; Teixeira, PaulaThe survival and spread of foodborne and nosocomial-associated bacteria through hightouch surfaces or contamination-prone sites, in either healthcare, domestic or food industry settings, are not always prevented by the employment of sanitary hygiene protocols. Antimicrobial surface coatings have emerged as a solution to eradicate pathogenic bacteria and prevent future infections and even outbreaks. Standardised antimicrobial testing methods play a crucial role in validating the effectiveness of these materials and enabling their application in real-life settings, providing reliable results that allow for comparison between antimicrobial surfaces while assuring end-use product safety. This review provides an insight into the studies using ISO 22196, which is considered the gold standard for antimicrobial surface coatings and examines the current state of the art in antimicrobial testing methods. It primarily focuses on identifying pitfalls and how even small variations in methods can lead to different results, affecting the assessment of the antimicrobial activity of a particular product.
- Development of alternative "clean label" proposal to the use of preservatives and other additives in meat productsPublication . Carvalho, Teresa Bento de; Komora, Norton; Barbosa, Joana Bastos; Teixeira, Paula
- Evaluation of the antimicrobial activity of a surface coating against different pathogensPublication . Carvalho, Teresa Bento de; Barbosa, Joana; Teixeira, PaulaThe survival and spread of resistant foodborne and nosocomial-associatedbacteria through high-touch surfaces is not always prevented by theemployment of cleaning protocols. Antimicrobial surface coatings surge fromthe need to eradicate pathogenic bacteria and prevent future infections and evenoutbreaks.
- Impact of different diets and starvation periods on microbial load of Tenebrio molitor larvaePublication . Pereira, Inês; Carvalho, Teresa Bento de; Soares, Luís; Ribeiro, Tiago; Esteves, Vasco; Barbosa, Joana Bastos; Teixeira, PaulaIntroduction: In a world facing an environmental crisis, the growth of the world's population coupled with an increasing demand for natural resources emphasizes the importance of adopting new dietary patterns based on health and sustainability (1). The consumption of edible insects (e.g. Tenebrio molitor) offers an alternative to animal protein sources, providing a sustainable food production cycle that ensures food security with minimal environmental impact (2). The main challenges in the T. molitor production industry are the selection of an appropriate feeding regime, as this affects the growth performance, nutritional profile and microbiota of the insect, and the processing steps required to commercialize mealworm larvae for human consumption. These steps have a direct impact on safety by allowing the gut contents to be discarded, thereby reducing the microbiological load and the presence of pathogenic microorganisms (3, 4). Typically, mealworm larvae are reared in a dry, starchy substrate supplemented by a water source, such as slices of vegetables or fruit. After being reared under optimal growth conditions, the larvae are sifted and then subjected to a fasting period of at least 24 hours, as required by law. This fasting process allows the intestinal contents to be discarded and limits the microbiological load, with the fasting period being a legal requirement of at least 24 hours (3, 4). Objective: This study aimed to analyze the microbiology of Tenebrio molitor larvae subjected to various feeding regimes (substrate with water, potato, carrot, or a fresh vegetable mix) and subsequently subjected to different starvations periods (0 hours, 24 hours, 48 hours and 72 hours). Discussion and conclusions: In general, the performance of starvation is dependent on the diet to which the larvae were subjected for each microbiological parameter evaluated. A positive result is considered when, for larvae subjected to the same diet, the counts of a given parameter at a given starvation period (24 h, 48 h, 72 h) are lower than those observed in the control without starvation (0h). This was observed only for: larvae A, for anaerobic Bacillus spores after 48h, and for yeasts after 72h; larvae B, for aerobic Bacillus spores and anaerobic Bacillus spores after 24 h ,48 h and 72 h and for molds after 24 h and 72h; larvae C, for Enterobacteria and yeasts after 24h and 72h; for aerobic Bacillus spores after 24h, 48h and 72h; and for anaerobic Bacillus spores after 24 h and 48h; larvae D, for TVC, LAB and anaerobic Bacillus spores after 24, 48h, 72h; for Enterococcus after 48 h and 72 h; for Enterococcus after 48h and 72h; for aerobic Bacillus spores after 24 h and 72 h; and for yeasts after 48h. Salmonella spp. and Listeria spp. were not detected in 10 g of each sample analysed. In conclusion, these results call into question the efficacy of fasting periods in reducing the microbial load of T. molitor larvae, as previously reported in other studies, and highlight the importance of heat treatments following fasting to ensure the food safety of the final product.
- Impact of novel clean label ham formulations on the human gut microbiotaPublication . Carvalho, Teresa Bento de; Barbosa, Joana Bastos; Carvalho, Nelson Mota de; Souza, Carla; Costa, Célia; Komora, Norton; Azevedo, Alexandra; Madureira, Ana Raquel; Teixeira, PaulaIntroduction: The influence of diet on the human gut microbiota has been the subject of much debate, particularly in relation to innovative products that are still considered novel. Dietary habits have a fundamental impact on the human gut microbiota, which explains the variations observed between individuals and over the course of a lifetime. The aim of this study was to evaluate the effect of four clean label ham formulations (Table 1) (without sodium nitrite and with natural nitrate sources combined with the addition of nitrate reducing cultures) on the human gut microbiota of potential consumers after in vitro digestion, according to the INFOGEST protocol, and colonic fermentation. Methods: DNA extraction from the stored pellets was carried out using the Invitrogen PureLink™ Microbiome DNA Purification Kit. 16S rRNA gene sequence data was processed with QIIME2 by Novogene UK; Quantification of fermentation metabolites, short-chained fatty acids and branched- chained fatty acids, by high-performance liquid chromatography (HPLC) from supernatant. The impact of each novel formulation and for a faecal inoculum control (Inoc) on the gut microbiota profile and fermentation metabolites (i.e., SCFAs) was assessed by next-generation sequencing (NGS) and high-performance liquid chromatography (HPLC), respectively. Results and discussion: Higher concentration of SCFA (Acetate + Butyrate + Propionate) after 48 h colonic fermentation were found for: D (65.96 mM) > A (63.36 mM) > E (59.35 mM) > C (58.64 mM) > B (57.22 mM) > Inoc (16.20 mM); Lowest SCFA concentrations were found for the inoculum control (Inoc), as expected, due to the lack of nutrients to promote bacterial fermentation over time. The most abundant phylum present were Bacillota and Pseudomonadota for all samples (A, B, C, D, E and Inoc) and all time points (0h, 24h and 48h); Higher relative abundance of Pseudomonadota was observed for all samples when compared to the inoculum control (Inoc); After fermentation, relative abundance of Bacteroidota is higher for the ham control sample (added sodium nitrite) than for the samples that are formulated with natural plant nitrate coupled with starter cultures. Conclusions: There were no discernible variations in SCFA levels or microbial populations during colonic fermentation between the new formulations and the conventional ham, indicating that the suggested clean label approach produced encouraging outcomes; Additional investigation should provide light on the endogenous production of volatile and non-volatile chemicals (nitrosamines) in vitro, their effects on the microbiota in the human gut, and any potential toxicity to human intestinal epithelial cells.
- Impact of red wine vinegar-based solution on bacterial communities of squid and shrimp skewers: a classic and genomic approachPublication . Rezende, Lourenço Pinto de; Barbosa, Joana Bastos; Carvalho, Teresa Bento de; Vaz-Moreira, Ivone; Monteiro, Maria João P.; Teixeira, PaulaSeafood is an essential component of a balanced and healthy diet, which increases its demand. However, its biological composition and high moisture content make these products extremely perishable. To prevent spoilage, and the consequent food waste and fnancial expenses throughout the seafood supply chain, new technologies have been successfully developed to inhibit bacterial growth, the main cause of seafood spoilage. This work aimed to test a shelf life extension technique for seafood skewers whilst maintaining an all-natural label using a fnancially feasible red wine vinegar treatment applied by immersion or pulverisation. Bacterial growth was monitored by classical methods and by 16S rRNA gene amplicon sequencing during the 5 days of storage. Immersion of samples in a vinegar-based solution efectively reduced Pseudomonas and Enterobacterales counts (by 2 log cfu/g), immediately after application and throughout storage. The overall structure and diversity of the bacterial community were analysed, and a strong reduction in bacterial diversity and impact on bacterial composition was observed immediately after immersion in the red wine vinegar solution. In untreated samples, Pseudomonadota (especially the Gammaproteobacteria class) was the principal phylum, whereas the microbiota of the treated samples was dominated by Bacillota (mainly the Bacilli class). Sensory analysis revealed a mild vinegar or vinaigrette favour in treated samples; however, these characteristics were not unpleasant. Although applying a vinegar-based solution by immersion promoted a signifcant reduction in the growth of spoilage bacteria during the frst days of storage, further tests are required to confrm the shelf life extension.
- Impact of salt reduction on lactic acid bacteria and total viable counts in chouriçãoPublication . Barbosa, Joana; Carvalho, Teresa Bento de; Komora, Norton; Azevedo, Maria A.; Silva, Beatriz Nunes; Teixeira, PaulaIntroduction: Salt has been used as a food additive and preservative in meat products for many centuries. As excessive sodium intake can lead to cardiovascular and cerebrovascular diseases, primary liver cancer, and atrial fibrillation, low-salt reformulations of traditional meat products have been developed. Nevertheless, while salt reduction may address the issue of excessive sodium intake, the effects of using reduced amounts of salt must be carefully considered and raise questions regarding the microbiological stability and shelf-life of the products. Purpose: This study aimed to assess the impact of reducing the salt content in the formulation of sliced chourição on the growth of Total Viable Counts (TVC) and Lactic Acid Bacteria (LAB) during the shelf-life of the product. Discussion: An increase in the number of TVC (Figure 1) and LAB (Figure 2) was observed over the 60 days of storage at the two temperatures tested, although this increase was more pronounced at 10 °C (abuse temperature). Regarding TVC (Figure 1), an increase in the bacterial levels was observed in the salt-reduced prototypes compared to the standard samples, particularly in samples stored at 10 °C (4 and 6-log cycle increase for the traditional formulation (chourição standard), and 6 and 7-log cycle increase for salt-reduced prototypes, at 4 °C and 10 °C, respectively. Regarding LAB (Figure 2), an increase of 4 and 5-log cycles was observed at 4 °C and 10 °C, respectively, for the traditional chourição, while an increase of 5-log cycles was observed at both temperatures for the salt-reduced salt formulation. Conclusions: Salt plays a critical role in the preservation of meat products. Therefore, product reformulation that involves salt reduction must ensure the same degree of economic and technological feasibility, and, most importantly, maintain the microbiological quality of the final product. New reduced-salt formulations must be further studied, such as physico-chemical characteristics, sensory analysis and challenge tests with target foodborne pathogens, and new hurdles should be introduced or improved in chourição production to achieve the same microbiological stability and shelf-life.
- In vitro colonic fermentation of clean label ham formulations: gut microbiota modulation and metabolite productionPublication . Carvalho, Teresa Bento de; Barbosa, Joana Bastos; Carvalho, Nelson Mota de; Komora, Norton; Carvalho, Fátima; Madureira, Ana Raquel; Teixeira, PaulaConsumer wishes for “clean label” products have prompted the rise of these products available in the market. With dietary choices directly influencing market trends, developing novel meat products with natural nitrate and nitrite alternatives is a sought-after premise. Cured meats like ham have been under scrutiny due to their potential harm to human health, having sodium nitrite been theorised to trigger dysbiosis of the gut microbiota and impair faecal short-chain fatty acids (SCFAs) production. Four novel ham formulations with a natural nitrate source coupled with nitrate-reducing starter cultures were subjected to an in vitro gastrointestinal digestion simulation (INFOGEST) and followed by in vitro colonic fermentation. The impact of each novel ham formulation on the gut microbiota and their fermentation metabolites, namely SCFAs, was assessed by quantitative Next Generation Sequencing and High-Performance Liquid Chromatography, respectively. No significant differences have been found for SCFAs levels or microbial communities throughout colonic fermentation. Further research should provide insight into how these alternatives can be associated with nitrosamine formation. The potential benefits of "clean label" alternatives need to be thoroughly demonstrated. While these solutions are often considered preferable to traditional nitrite-containing products, their implementation should be approached with caution. In addition to their antimicrobial efficacy and consumer acceptance, it is essential to assess their impact on product cost and compare their performance and health impact (positive or negative) with that of traditional nitrite formulations. Extensive research is needed to ensure that any move to "clean label" formulations is based on solid evidence rather than market trends.
- Microbiological characterization of Tenebrio molitor after different feeding regimesPublication . Pereira, Inês; Carvalho, Teresa Bento de; Soares, Luís; Ribeiro, Tiago; Esteves, Vasco; Barbosa, Joana Bastos; Teixeira, PaulaIntroduction: In a world facing an environmental crisis, the increase in world population coupled with a growing demand for natural resources emphasizes the importance of adopting new dietary patterns based on health and sustainability. The consumption of edible insects (e.g. Tenebrio molitor) offers an alternative to livestock consumption, providing a sustainable food production cycle that ensures food security with minimal environmental impact. One of the major challenges in the insect production industry is the selection of its feeding regime, since it has a direct impact on the growth performance and in nutritional profile of T. molitor, as well as on its safety, since it may lead to changes in the insect's microbiota and the presence of pathogenic microorganisms. Purpose: This study aimed to analyze the microbiology of Tenebrio molitor larvae subjected to different feeding regimes (substrate with water, potato, carrot, or a fresh vegetable mix). Results: In general, the original substrate had a lower microbial load, while initial larvae (two-weeks old) had a higher microbial load for TVC, LAB, Enterococcus, Enterobacteriaceae and yeasts. Larvae fed with potatoes had slightly higher microbial loads, especially for TVC, LAB, and Enterobacteriaceae. On the contrary larvae fed with carrot had the lower loads for TVC, LAB, aerobic and anaerobic bacillus spores and molds. Escherichia coli was only found at low levels in the substrate (1.0 log CFU/g) and B. cereus in the frass of larvae fed with potato (4.7 log CFU/g). The microbial load of the larvae and respective frass was compared. It was found that only in the potato substrate regime the microbial load was not higher in the frass. Salmonella spp. and Listeria spp. were not detected. Conclusion: This preliminary study indicates apparent differences in the microbial loads of larvae fed with different regimes. An initial substrate with potato seems to increase the microbial load of both larvae and frass. Further studies of the microbial community using culture-independent methods are an alternative to expand knowledge of the microbiota of T. molitor and to overcome the detection limits of of this technique. Although untreated larvae are not fit for human consumption, it is important to further analyze the effect of different treatments on the quality of the final product.
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