Inativação termoquímica de Escherichia coli, Staphylococcus aureus e Salmonella enterica Enteritidis por óleos essenciais / Thermochemical inactivation of Escherichia coli, Staphylococcus aureus and Salmonella enterica Enteritidis by essencial oils

O controle do crescimento microbiano tanto na indústria de alimentos quanto em ambientes hospitalares é de extrema importância. Entretanto, observa-se aumento da resistência dos microrganismos aos desinfetantes mais empregados, observando-se a necessidade de estudos com novos antimicrobianos. Assim, o objetivo desse trabalho foi avaliar a atividade antimicrobiana e a curva de morte termoquímica de soluções desinfetantes de óleos essenciais sobre Escherichia coli, Staphylococcus aureus e Salmonella Enteritidis. Foram utilizados os óleos essenciais de Thymus vulgaris (tomilho), Elettaria cardamomum (cardamomo), Eugenia caryophyllus (cravo botão) e Foeniculum vulgare dulce (funcho doce). As concentrações mínimas inibitórias foram determinadas utilizando-se a técnica de diluição em placas. As concentrações testadas foram de (%): 0,00; 0,25; 0,5; 1,0; 2,0; 2,5; 3,0; 3,5; 4,0; 4,5; e 5,0. Escherichia coli foi a única bactéria sensível a todos os óleos em concentrações abaixo de 5%. Cravo da índia não inibiu o crescimento de S. aureus nas concentrações testadas. Somente o óleo essencial de tomilho inibiu o crescimento de Salmonella Enteritidis. Observando-se as curvas de morte termoquímica de S. aureus, nota-se que a solução desinfetante contendo óleo essencial de tomilho foi a mais eficiente, tanto a 25 quanto a 40°C, sendo necessário apenas 10min. de contato para não serem mais detectadas células viáveis. A solução desinfetante contendo 0,25% de óleo essencial de tomilho, tanto a 25 quanto a 40°C, eliminou as células de S. Enteritidis após10min. de contato. Já pra E. coli , os melhores resultados foram obtidos com as soluções desinfetantes contendo óleos essenciais de funcho doce e cravo da índia ...

The control of microbial growth in the food industry and in hospital environments is extremely important. However there is increasing resistance of microorganisms to disinfectants normally applied, which leads to the need for new antimicrobial studies. The aim of this study was to evaluate the antimicrobial activity and thermochemical death curve of disinfectant solutions from essential oils on Escherichia coli, Staphylococcus aureus and Salmonella Enteritidis. The essential oils of Thymus vulgaris (thyme), Elettaria cardamomum (cardamom), Eugenia caryophyllus (clove bud) and Foeniculum vulgare dulce (sweet fennel) were used. The minimum inhibitory concentrations were determined using dilution technique in Petridish. The concentrations tested were (%): 0.00 , 0.25, 0.5, 1.0 , 2.0, 2.5 , 3.0, 3.5, 4.0 , 4.5, and 5.0. Escherichia coli were the only bacteria sensitive to all oils at concentrations below 5%. Cloves did not inhibit the growth of S. aureus at the concentrations tested. Only the thyme essential oil inhibited the growth of Salmonella Enteritidis. Observing the thermochemical death curves of S. aureus one can see that the disinfectant solution containing thyme essential oil was the most effective, both at 25 and 40°C, requiring only 10min contact to no longer detecte viable cells. The disinfectant solution containing 0.25% thyme essential oil, both at 25 and 40°C removed S. Enteritidis cells after 10min. contact. For E. coli the best results were obtained with disinfectant solutions containing fennel and sweet clove essential oils at 25 and 40°C and thyme at 40°C. All treatments, except that containing cardamom essential oil, reduce the number of viable bacteria cells tested in at least 5log cycles, being considered suitable for use as disinfectants.

Essential oils of thyme and Rosemary in the control of Listeria monocytogenes in raw beef

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.

Biofilmes microbianos na indústria de alimentos: uma revisão / Microbial biofilms in the food industry: a review

Biofilmes podem ser definidos como comunidades microbianas envoltas por uma matriz de polímeros extracelulares e aderidas a superfícies. Na indústria de alimentos, os microrganismos podem se aderir a resíduos orgânicos e inorgânicos presentes na superfície de equipamentos e utensílios, caso o processo de higienização seja aplicado incorretamente. Células sésseis, presentes no biofilme, além de reduzir a eficiência e vida útil de equipamentos, em função do fenômeno denominado corrosão microbiologicamente induzida, são mais resistentes ao processo de desinfecção. As células podem se desprender e contaminar os alimentos que passam pelo local, que causam prejuízos econômicos e risco de ocorrência de toxinfecções alimentares. A compreensão do conceito de biofilmes microbianos e de aspectos inerentes a sua estrutura e composição, bem como de seu processo de formação, são fundamentais para efetuar o desenvolvimento de estratégias de controle efetivas e entendimento do risco que estes representam para as indústrias de alimentos. Na presente revisão bibliográfica, estão descritos os principais aspectos de biofilmes microbianos de importância na indústria de alimentos: i) definição, estrutura e composição; ii) etapas envolvidas na formação; iii) mecanismos de resistência a antimicrobianos; iv) riscos; v) microrganismos envolvidos; vi)importância da higienização como ferramenta de controle.

Bacterial biofilms are defined as microbial communities surrounded by an extracellular matrix of polymers and adhered to surfaces. In food industry, the microorganisms can adhere to organic and inorganic waste occurring on the equipment and utensils surfaces, if the cleaning and sanitization procedures are done incorrectly. The presence of sessile cells in the biofilm reduces the efficiency and durability of equipments through the phenomenon called microbiologically induced corrosion. Additionally, they show muchgreater resistance to the sanitization process; the cells can be loosen and contaminate foods that pass through the place, causing economic losses and risk of occurrence of food borne diseases. Understanding the concept, the structure and composition inherent aspects, and also the producing process of microbial biofilms, are fundamental for establishing effective control strategies and being assured on the risks that they represent to the food industry. This article reviews the crucial aspects concerned with microbialbiofilms in the food industry i) definition, structure and composition; ii) steps involved in the formation; iii) mechanisms of resistance to antimicrobials; iv) risks; v) involved microorganisms; and vi) importance of hygienization as a control strategy.

Biofilm formation by Listeria monocytogenes on stainless steel surface and biotransfer potential

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.

Condições higiênico-sanitárias de máquinas de moer carne, mãos de manipuladores e qualidade microbiológica da carne moída / Hygienic-sanitary conditions of meat-grinding machines, handlers' hands and microbiologic quality of ground meat

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.