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portuguesOs queijos com media e alta umidade sao alimentos prontos para o consumo, que tem sido descritos como veiculadores de patogenos em diversos surtos de doencas transmitidas por alimentos. A contaminacao microbiana pode ter origem na materia prima, ou ocorrer durante as etapas de elaboracao do produto, atraves de praticas inadequadas de higiene. Dessa forma, o objetivo deste estudo foi avaliar a qualidade e a seguranca microbiologica na producao de queijos de media umidade. Amostras da materia prima, dos manipuladores e do produto final foram coletadas em tres laticinios situados na regiao sul do Rio Grande do Sul, com diferentes niveis de inspecao sanitaria. A eficiencia da pasteurizacao do leite tambem foi avaliada. Coliformes termotolerantes, estafilococos coagulase-positivos (ECP), Salmonella spp. e Listeria monocytogenes foram avaliados. As amostras de leite cru foram as que apresentaram os maiores niveis de contaminacao, com enumeracao de 1,1x105 numero mais provavel (NMP) mL-1 para coliformes termotolerantes, 4x105 unidades formadoras de colonia (UFC) mL-1 para ECP e a presenca de Salmonella spp.. Contudo, apenas uma amostra de produto final estava em desacordo com o padrao regulamentar vigente, excedendo o limite permitido para ECP. A pasteurizacao do leite utilizado no preparo dos queijos foi eficiente em todos os laticinios, independentemente do nivel de inspecao sanitaria dos estabelecimentos. No entanto, houve contaminacao pre e pos-pasteurizacao, demonstrando a necessidade de melhores praticas higienicas, tanto na obtencao da materia-prima, quanto na manipulacao durante as diversas etapas de fabricacao dos queijos. Palavras-chave: Listeria monocytogenes; Salmonella spp.; coliformes termotolerantes; estafilococos coagulase positiva; seguranca alimentar. EnglishModerate and high humidity cheeses are described as important vehicles of pathogens in many foodborne diseases outbreaks. Microbial contamination can occur in raw material or in the different steps of the product processing due to inadequate hygiene practices. Thus, the aim of this study was to evaluate the microbiological quality and safety in the production of moderate and high humidity cheese. Samples from raw milk, handlers’ hands surface, final product were collected in three cheese manufacturing plants located in southern Brazil, with different levels of sanitary control. Effectiveness of milk pasteurization was also evaluated. Thermotolerant coliforms, coagulase-positive staphylococci (CPS), Salmonella spp., and Listeria monocytogenes were evaluated. Raw milk samples showed the highest contamination levels, with enumeration of 1.1x105 most probable number (MPN) mL-1 for thermotolerant coliforms, 4x105 colony-forming units (CFU) mL-1 for CPS and presence of Salmonella spp. CPS were also reported in one sample of handler’s hands surface. However, only one sample of the final product was out of Brazilian regulatory standards, exceeding the limit allowed for CPS. Milk pasteurization process used in cheese preparation was effective, regardless the level of sanitary control of the industries. Results highlighted the need for better hygiene practices, in obtaining the raw milk and in the handling during the cheese manufacturing steps. Key words: Listeria monocytogenes; Salmonella spp.; thermotolerant coliforms; coagulase-positive staphylococci; food safety.

In order to investigate the use of semi-synthetic antimicrobial compounds, the objective of this study was to evaluate the 3-(p-chlorophenyl)thio citronellal, a novel compound that is derived from the essential oil of Cymbopogon citratus, against spoilage and pathogenic bacteria in food. This study also evaluated the possible mechanisms of action and cellular targets. Qualitative and quantitative tests and scanning electron microscopy were used to compare 3-(p-chlorophenyl)thio citronellal with citral and (R)-citronellal. It was observed that 3-(p-chlorophenyl)thio citronellal is a potent antimicrobial agent with bactericidal activity against different pathogenic and spoilage bacteria, of which the Gram-positive species were the most sensitive. The minimal inhibitory concentration for 3-(p-chlorophenyl)thio citronellal was approximately 100 times lower than that of citral, and this was corroborated by the kinetic curve of action, demonstrating that cell death was faster when the bacterial cells were treated with 3-(p-chlorophenyl)thio citronellal. This finding showed that the addition of thiol enhances the bioactivity of citral. In vitro testing showed that the compound does not show toxicity. The SEM images showed cell damage with the formation of pores in the cell wall and membrane, which are possibly the cellular targets of the compound.

Streptococcus mutans is the primary bacteria involved in caries. To prevent this disease, fluoride compounds are used; however, these compounds can become toxic at certain concentrations. The purpose of this study was to evaluate the antimicrobial activity of essential oils (Eos) from two eucalyptus species (Eucalyptus globulus and Eucalyptus urograndis) against planktonic and biofilm cells of S. mutans using the agar diffusion assay and by determining the minimum inhibitory concentrations, kinetic of action and ability to inhibit biofilm formation. The synergistic effect of the combined oils was also tested (1:1). Films constructed of biodegradable starch with the EOs were prepared, and their bioactivity was tested using the macrodilution technique. These essential oils were active against S. mutans, and they presented inhibition zones between 14.7 ± 1.2 mm and 35.3 ± 0.34 mm in diameter. It was observed that when the oils were used together, there was an increase in bioactivity. The kinetics of loss of cell viability test showed a reduction of 1 log cycle in the microorganism counts within less than 5 min of contact time. The essential oil from E. globulus gave the best results, requiring only 15 min of contact to cause microbial death; E. urograndis oil required 50 min to induce the same bactericidal effect. These results can be explained by the larger concentration of 1,8-cineole in the EO of E. globulus. Biofilm formation by S. mutans was also inhibited in the presence of the tested oils, which yielded more effective results when compared to 0.1% commercial NaF (sodium fluoride). The increased bioactivity of these oils suggests their technological potential.

This work aimed to evaluate the bioactivity of 3-(p-chlorophenyl)thio citronellal against planktonic and biofilm cells of S. aureus and its use in biodegradable films. 3-(p-chlorophenyl)thio citronellal demonstrated antimicrobial activity against planktonic (MIC = 62.5 ± 0.5 μg.mL−1) and biofilm cells of S. aureus. Regarding barley starch films containing 3-(p-chlorophenyl)thio citronellal, after 4 h of contact there was a difference of 5 log CFU.mL−1 in relation to control film (without additives). The films prepared with 3-(p-chlorophenyl)thio citronellal and citral (its precursor) were more opaque and had lower tensile strength than the control film. However, the addition of the 3-(p-chlorophenyl)thio citronellal in the film had lower effect on the water solubility and tensile strength than the addition of citral. 3-(p-chlorophenyl)thio citronellal have activity against planktonic and biofilm cells of S. aureus and could be applied in biodegradable films as an alternative to inhibit the microbial growth on the surface of food, enhancing food safety.