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Avaliação do potencial tecnológico de bactérias ácido láticas isoladas de queijos artesanais portugueses
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Os queijos artesanais portugueses, produzidos com leite cru, representam uma importante herança cultural de Portugal. Estes produtos possuem uma elevada riqueza e características distintas, que advêm da microbiota autóctone, nomeadamente das bactérias ácido láticas-(BAL), sendo essa a razão pela qual os queijos artesanais foram atribuídos os rótulos de Denominação de Origem Protegida (DOP). A manufatura destes queijos conta com a participação das BAL nos processos de fermentação e de cura. Além disso, estas bactérias contribuem significativamente para as características organoléticas e a segurança dos queijos. Nesse contexto, o presente estudo teve como objetivo avaliar o potencial tecnológico, das bactérias ácido láticas isoladas de Queijos de Azeitão e de Nisa, com selo (DOP). A coleção microbiana pré-existentes de um conjunto de 81 isolados, foram submetidas a uma serie de testes de caraterização fenotípica, para avaliar o potencial tecnológico e o potencial patogénico. Os resultados indicaram que todos os isolados tiveram a capacidade de acidificação do leite de ovelha. A maioria de isolados demonstraram a capacidade de multiplicação em diferentes concentrações salinas, temperaturas, e a diferentes valores de pH. Relativamente a atividade antimicrobiana, dos 81 isolados foram verificadas pelo método spot on lawn, contra as bactérias Gram-positivas (Bacillus cereus e Enterococcus faecalis) e Gram-negativas (Escherichia coli e Pseudomonas fluorescens). Relativamente ao potencial de patogenicidade, foram avaliadas a capacidade hemolítica e os perfis de resistência aos antibióticos. Nenhum dos isolados apresentou atividade β-hemolítica, enquanto 45 apresentaram atividade γ-hemolítica e 34 atividade α hemolítica. Os 29 isolados mais promissores foram selecionados para a avaliação da resistência aos antibióticos. Verificou-se, no entanto, um número elevado de isolados resistentes, nomeadamente: 28 à Canamicina, 27 à Vancomicina, 27 à Estreptomicina e 26 à Gentamicina. Com base de vários ensaios realizados, foi possível selecionar oito isolados mais promissores com caraterísticas relevante, para utilização como cultura starter e não starter para o fabrico de queijos artesanais e para possível aplicação na indústria alimentar. Neste estudo conclui-se que, cada queijo avaliado, possui efetivamente microbiota autóctone com potencial tecnológico. Contudo, são necessários a realização de estudos complementares
Evaluation of the Technological Potential of Lactic Acid Bacteria Isolated from Portuguese Artisanal Cheeses - Portuguese artisanal cheeses, produced from raw milk, represent an important part of the country’s cultural heritage. These products possess great diversity and unique characteristics, mainly due to their native microbiota, particularly lactic acid bacteria (LAB), which is one of the main reasons why many of these cheeses have been granted Protected Designation of Origin (PDO) status. The manufacturing process of these cheeses involves LAB in both fermentation and ripening stages. Furthermore, these bacteria contribute significantly to the sensory qualities and safety of the final products. In this context, the aim of the present study was to assess the technological and pathogenic potential of LAB isolated from Azeitão and Nisa PDO cheeses. A pre-existing microbial collection of 81 isolates was subjected to a series of phenotypic characterization tests to evaluate both their technological attributes and pathogenic potential. The results indicated that all isolates were capable of acidifying sheep’s milk. Most of them were able to grow under various salt concentrations, temperature conditions, and pH values. Regarding antimicrobial activity, all 81 isolates were evaluated using the spot-on-lawn method against Gram-positive bacteria (Bacillus cereus and Enterococcus faecalis) and Gram negative bacteria (Escherichia coli and Pseudomonas fluorescens). To evaluate pathogenic potential, hemolytic activity and antibiotic resistance profiles were assessed. None of the isolates showed β-hemolytic activity, while 45 showed γ-hemolytic activity and 34 α-hemolytic activity. However, a high number of resistant isolates were found, namely: 28 to kanamycin, 27 to Vancomycin, 27 to Streptomycin and 26 to Gentamicin. Based on the results of various tests, eight promising isolates were identified with relevant characteristics for potential use as starter or non-starter cultures in artisanal cheese production, and possibly for broader application in the food industry. This study concludes that each cheese analyzed harbors an autochthonous microbiota with technological potential. However, further complementary studies are required
Evaluation of the Technological Potential of Lactic Acid Bacteria Isolated from Portuguese Artisanal Cheeses - Portuguese artisanal cheeses, produced from raw milk, represent an important part of the country’s cultural heritage. These products possess great diversity and unique characteristics, mainly due to their native microbiota, particularly lactic acid bacteria (LAB), which is one of the main reasons why many of these cheeses have been granted Protected Designation of Origin (PDO) status. The manufacturing process of these cheeses involves LAB in both fermentation and ripening stages. Furthermore, these bacteria contribute significantly to the sensory qualities and safety of the final products. In this context, the aim of the present study was to assess the technological and pathogenic potential of LAB isolated from Azeitão and Nisa PDO cheeses. A pre-existing microbial collection of 81 isolates was subjected to a series of phenotypic characterization tests to evaluate both their technological attributes and pathogenic potential. The results indicated that all isolates were capable of acidifying sheep’s milk. Most of them were able to grow under various salt concentrations, temperature conditions, and pH values. Regarding antimicrobial activity, all 81 isolates were evaluated using the spot-on-lawn method against Gram-positive bacteria (Bacillus cereus and Enterococcus faecalis) and Gram negative bacteria (Escherichia coli and Pseudomonas fluorescens). To evaluate pathogenic potential, hemolytic activity and antibiotic resistance profiles were assessed. None of the isolates showed β-hemolytic activity, while 45 showed γ-hemolytic activity and 34 α-hemolytic activity. However, a high number of resistant isolates were found, namely: 28 to kanamycin, 27 to Vancomycin, 27 to Streptomycin and 26 to Gentamicin. Based on the results of various tests, eight promising isolates were identified with relevant characteristics for potential use as starter or non-starter cultures in artisanal cheese production, and possibly for broader application in the food industry. This study concludes that each cheese analyzed harbors an autochthonous microbiota with technological potential. However, further complementary studies are required
Descrição
Dissertação de Mestrado em Segurança Alimentar, área científica de Produção Animal e Segurança Alimentar
Palavras-chave
Queijo artesanais Denominação de Origem Protegida Bactérias ácidas láticas Potencial tecnológico Potencial patogénico Artisanal cheeses Protected Designation of Origin Lactic acid bacteria Technological potential Pathogenic potential assessment