This study was developed in order to evaluate two alternatives for the control of Listeria monocytogenes in raw bovine meat pieces, both based on the use of Thymus vulgaris and Rosmarinus officinalis essential oils (EOs). The antilisterial activity of different concentrations of the EOs was tested in vitro using agar dilution and disk volatilization techniques. In addition, L. monocytogenes was inoculated in meat pieces, which were submerged in edible gelatin coatings containing 2% (v/v) EOs or submitted to the vapor of EOs (0.74 μL.cm-3). L. monocytogenes was quantified after one, 48 and 96 hours of storage (7 °C). In the in vitro tests, the EO of T. vulgaris presented higher activity. The two options used (edible gelatin coating and vapor activity), in spite of exercising effects with differentiated behaviors, presented antibacterial activity against L. monocytogenes inoculated in raw bovine meat (p < 0.05). Greatest antibacterial activity were obtained in the experiment that used edible coatings containing EOs, at 48 hours of storage reductions in bacterial counts between 1.09 and 1.25 Log CFU.g-1 were obtained. In the vapor effect experiment, the EO of T. vulgaris caused the highest reduction in the population of bacteria inoculated in raw bovine meat (p < 0.05), 0.40 Log CFU.g-1 at 96 hours of storage. This study supplied important information regarding new and promising natural alternatives, based on the concept of active packaging, for the control of L. monocytogenes in the meat industry.

A capacidade de adesão e formação de biofilme por Pseudomonas aeruginosa e Pseudomonas fluorescens em aço inoxidável AISI 304, na presença de leite desnatado resconstituído sobre diferentes temperaturas foi conduzido e o potencial de três sanificantes químicos na remoção de biofilmes monoespécies foi comparado. Pseudomonas aeruginosa cultivada em leite desnatado a 28 °C apresentou melhor crescimento (10,4 log UFC.mL-1) quando comparado com 3,7 and 4,2 log UFC.mL-1 para P. aeruginosa e P. fluorescens cultivadas a 7 °C, respectivamente. Pseudomonas aeruginosa formou biofilme quando cultivada a 28 °C. Contudo foi observado somente adesão de P. aeruginosa e P. fluorescens quando incubada a 7 °C. O dicloroisocianurato de sódio foi o sanificante mais eficiente na redução de células aderidas e em biofilme de P. aeruginosa a 7 e 28 °C, respectivamente. O peróxido de hidrogênio foi o mais eficiente na redução de células aderidas de P. fluorescens a 7 °C.

The biofilm formation of Pseudomonas aeruginosa and Pseudomonas fluorescens on AISI 304 stainless steel in the presence of reconstituted skim milk under different temperatures was conducted, and the potential of three chemical sanitizers in removing the mono-species biofilms formed was compared. Pseudomonas aeruginosa cultivated in skim milk at 28 °C presented better growth rate (10.4 log CFU.mL-1) when compared with 3.7 and 4.2 log CFU.mL-1 for P. aeruginosa and P. fluorescens cultivated at 7 °C, respectively. Pseudomonas aeruginosa formed biofilm when cultivated at 28 °C. However, only the adhesion of P. aeruginosa and P. fluorescens was observed when incubated at 7 °C. The sodium dichloroisocyanurate was the most efficient sanitizer in the reduction of the adhered P. aeruginosa cells at 7 and 28 °C and those on the biofilm, respectively. The hydrogen peroxide was more effective in the reduction of adhered cells of P. fluorescens at 7 °C.

An experimental model was proposed to study biofilm formation by Listeria monocytogenes ATCC 19117 on AISI 304 (#4) stainless steel surface and biotransfer potential during this process. In this model, biofilm formation was conducted on the surface of stainless steel coupons, set on a stainless steel base with 4 divisions, each one supporting 21 coupons. Trypic Soy Broth was used as bacterial growth substrate, with incubation at 37 ºC and stirring of 50 rpm. The number of adhered cells was determined after 3, 48, 96, 144, 192 and 240 hours of biofilm formation and biotransfer potential from 96 hours. Stainless steel coupons were submitted to Scanning Electron Microscopy (SEM) after 3, 144 and 240 hours. Based on the number of adhered cells and SEM, it was observed that L. monocytogenes adhered rapidly to the stainless steel surface, with mature biofilm being formed after 240 hours. The biotransfer potential of bacterium to substrate occurred at all the stages analyzed. The rapid capacity of adhesion to surface, combined with biotransfer potential throughout the biofilm formation stages, make L. monocytogenes a potential risk to the food industry. Both the experimental model developed and the methodology used were efficient in the study of biofilm formation by L. monocytogenes on stainless steel surface and biotransfer potential.

Foram avaliadas condições higiênico-sanitárias de máquinas de moer carne e mãos de manipuladores e observou-se a interferência na qualidade microbiológica da carne moída. Nas máquinas de moer carne e mãos de manipuladores, realizaram-se análises de microrganismos aeróbios mesófilos, fungos filamentosos e leveduras, coliformes totais e termotolerantes, Escherichia coli e estafilococos coagulase positiva. Nenhuma das máquinas enquadrou-se nos padrões da APHA. Para manipuladores, as contagens de aeróbios mesófilos, estafilococos coagulase positiva, fungos filamentosos e leveduras, coliformes totais e termotolerantes apresentaram-se elevadas. Nas amostras de carne inteira e moída, realizaram-se, além das citadas acima, análises de Salmonella sp. aeróbios psicrotróficos e clostrídios sulfito-redutores. Comparando-se os resultados das análises microbiológicas das carnes antes e após a moagem e manipulação, constatou-se aumento da contagem microbiana na maioria das amostras analisadas, indicando higienização inadequada das máquinas de moer e mão dos manipuladores.

Hygienic-sanitary conditions of meat grinding-machines and handlers' hands were evaluated and the interference on the microbiologic quality of the ground meat was observed. In the meat-ground machines and handlers' hands analyses of mesophyllic aerobic microorganisms, filamentous fungi and yeasts, total and heat-tolerant coliforms, Escherichia coli and positive coagulase staphylococcus were accomplished. None of the machines fitted in the APHA standards. For the handlers, the counts of mesophyllic aerobes, positive coagulase staphylococcus, filamentous fungi and yeasts, total and heat-tolerant coliforms proved elevated. In the samples of whole and ground meat, in addition to those above-cited, analyses of Salmonella sp. psychotrophic aerobes and sulfite-reducing clostridia were performed. By comparing the results of the microbiological analyses of the meats before and after grinding and handling, an increase of the microbial count in most of the samples analyzed was found, denoting inadequate cleaning of the grinding-machines and handlers' hands.