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Utilização de agentes antimicrobianos naturais como alternativas na conservação e melhoria da qualidade microbiológica de produtos de charcutaria
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Abstract(s)
A qualidade microbiológica dos alimentos é um aspeto preocupante para a indústria alimentar visto
que a ação de microrganismos pode causar a deterioração dos alimentos e afetar a saúde dos
consumidores. O uso de aditivos alimentares, a aplicação de um tratamento térmico adequado e de
Boas Práticas de Fabrico são essenciais para a redução microbiana nos alimentos.
O presente trabalho foi desenvolvido nos laboratórios do Centro de Biotecnologia e Química Fina
(CBQF) e na empresa Primor. O estudo em laboratório teve como objetivos testar a atividade
antimicrobiana de três compostos naturais – quitosano, extrato etanólico de propólis e nisina – contra
vários microrganismos, 21 Gram-positivo, 15 Gram-negativo e dois fungos e, ainda, comparar com a
ação antimicrobiana do composto químico nitrito de sódio, isoladamente e em combinação com
cloreto de sódio. A concentração mínima inibitória foi determinada através dos métodos da diluição
em agar e da difusão da gota em agar, de modo a verificar a diferença entre os métodos. Também foi
testada a atividade antimicrobiana com diferentes valores de pH do meio de cultura (5, 6 e 7) e
diferentes temperaturas de incubação (4, 12, 20 e 37 ºC), com os objetivos de verificar a influência do
pH e temperatura na inibição dos microrganismos e simular a presença dos patogénicos em
diferentes produtos alimentares e diferentes condições de armazenamento. Os compostos naturais
testados tiveram maior efeito inibitório contra os vários microrganismos comparativamente com o
nitrito de sódio sozinho e em combinação com cloreto de sódio, nas diferentes condições de pH e
temperatura. Com a concentração de 0,65% (m/v) de quitosano foi possível inibir a maioria dos
microrganismos testados. Com a concentração de 10 mg/mL de propólis foram inibidos os fungos, a
maioria das bactérias Gram-positivo e algumas Gram-negativo. Com a concentração de 25 μg/mL de
nisina foi possível inibir a maioria das bactérias Gram-positivo.
O trabalho desenvolvido na empresa alimentar Primor teve como objetivos o desenvolvimento de um
novo tratamento térmico para o chouriço corrente e a implementação de melhorias nas Boas Práticas
no seu processo de produção para reduzir a quantidade de bactérias do ácido lático, principal
contaminante do produto. De modo a reduzir o número destes microrganismos de deterioração e de
microrganismos totais, para melhorar a qualidade e segurança microbiológica do chouriço, também
se aplicou quitosano a este produto de charcutaria. Após i) a aplicação de uma cozedura de 77 ºC
durante 40 minutos no chouriço corrente, com 100% humidade e a chaminé da estufa semi-aberta, e
ii) a aplicação de metodologias de monitorização de Boas Práticas mais eficazes, incluindo maior
controlo do processo de produção do chouriço, as quantidades de bactérias do ácido lático obtidas
nas amostras, após embalamento, foram inferiores às das amostras do processo de cozedura
standard e também das amostras obtidas por um processo não monitorizado. Com a adição de 0,15%
(m/v) de quitosano ao chouriço, as quantidades de bactérias do ácido lático e de microrganismos
totais obtidas foram inferiores comparativamente com o chouriço com nitrito, ao fim de 14 dias de
armazenamento. Por isso, a aplicação de um tratamento térmico alternativo ao do chouriço corrente
standard e a implementação de melhorias nas Boas Práticas de Fabrico permitiram a melhoria da
qualidade microbiológica do enchido após embalamento. Além disso, o quitosano parece ser uma
alternativa natural com características interessantes para aplicação num produto alimentar.
The microbiological quality of food is of considerable concern to the food industry since the activity of microorganisms can result in food spoilage and, more seriously, affect the health of consumers. The use of food additives, the application of a suitable heat treatment and Good Manufacturing Practices are essential to reducing microbial loads in foods. The present work was developed in the Microbiology laboratory of Centro de Biotecnologia e Química Fina (CBQF) and at the food company Primor. In the laboratory, the objectives of the study were to test the antimicrobial activity of 3 natural compounds – chitosan, ethanolic extract of propolis, and nisin – against various microorganisms, 21 Gram-positive, 15 Gram-negative bacteria and 2 fungi and, also, to compare with the antimicrobial action of the chemical compound sodium nitrite, alone and in combination with sodium chloride. The minimal inhibitory concentration was determined through the agar dilution and the drop agar diffusion methods, to examine any differences between both methods. Antimicrobial activity was also tested at different pH values of the culture medium at 5, 6 and 7 and different temperatures of incubation at 4, 12, 20 and 37 °C, with the objectives of determining the influences of pH and temperature on the inhibition of microorganisms and simulating the presence of the pathogens in different food products and different storage conditions. The natural compounds tested had greater inhibitory effect against the various microorganisms compared with sodium nitrite alone and in combination with sodium chloride, in the different conditions of pH and temperature. With the concentration of 0.65% (w/v) of chitosan it was possible to inhibit most of the tested microorganisms. With a concentration of 10 mg/mL of propolis, fungi, most of the Gram-positive microorganisms and some of the Gram-negatives were inhibited. With a concentration of 25 μg/mL of nisin it was possible to inhibit most of the Grampositive microorganisms. The work developed in Primor had as objectives the development of a new heat treatment for chouriço corrente and implementation of improvements in Good Practices in its production process to reduce the number of lactic acid bacteria, the major contaminant of the product. To reduce the number of such spoilage microorganisms and also total microorganisms, and to improve the microbiological safety of chouriço, chitosan was added to this charcuterie product. After i) the application of baking at 77 °C for 40 minutes on the chouriço corrente, with 100% humidity and with the stove chimney semiopen, and ii) the application of Good Practices monitoring methodologies with greater effectiveness, including greater control of the chouriço production process, the number of lactic acid bacteria in the samples after packing was lower than in the samples produced by the standard baking process and also lower than in samples obtained through a non-monitored process. With the addition of 0.15% (w/v) of chitosan to the chouriço, the number of lactic acid bacteria and total microorganisms was lower compared with the chouriço with nitrite, after 14 days of storage. Therefore, the application of an alternative heat treatment to the one used in the standard chouriço corrente and the implementation of improvements in Good Manufacturing Practices resulted in an improvement in the microbiological safety and shelf-life of the food product after packing. Additionally, chitosan appears to be a natural alternative with interesting characteristics for application in a food product.
The microbiological quality of food is of considerable concern to the food industry since the activity of microorganisms can result in food spoilage and, more seriously, affect the health of consumers. The use of food additives, the application of a suitable heat treatment and Good Manufacturing Practices are essential to reducing microbial loads in foods. The present work was developed in the Microbiology laboratory of Centro de Biotecnologia e Química Fina (CBQF) and at the food company Primor. In the laboratory, the objectives of the study were to test the antimicrobial activity of 3 natural compounds – chitosan, ethanolic extract of propolis, and nisin – against various microorganisms, 21 Gram-positive, 15 Gram-negative bacteria and 2 fungi and, also, to compare with the antimicrobial action of the chemical compound sodium nitrite, alone and in combination with sodium chloride. The minimal inhibitory concentration was determined through the agar dilution and the drop agar diffusion methods, to examine any differences between both methods. Antimicrobial activity was also tested at different pH values of the culture medium at 5, 6 and 7 and different temperatures of incubation at 4, 12, 20 and 37 °C, with the objectives of determining the influences of pH and temperature on the inhibition of microorganisms and simulating the presence of the pathogens in different food products and different storage conditions. The natural compounds tested had greater inhibitory effect against the various microorganisms compared with sodium nitrite alone and in combination with sodium chloride, in the different conditions of pH and temperature. With the concentration of 0.65% (w/v) of chitosan it was possible to inhibit most of the tested microorganisms. With a concentration of 10 mg/mL of propolis, fungi, most of the Gram-positive microorganisms and some of the Gram-negatives were inhibited. With a concentration of 25 μg/mL of nisin it was possible to inhibit most of the Grampositive microorganisms. The work developed in Primor had as objectives the development of a new heat treatment for chouriço corrente and implementation of improvements in Good Practices in its production process to reduce the number of lactic acid bacteria, the major contaminant of the product. To reduce the number of such spoilage microorganisms and also total microorganisms, and to improve the microbiological safety of chouriço, chitosan was added to this charcuterie product. After i) the application of baking at 77 °C for 40 minutes on the chouriço corrente, with 100% humidity and with the stove chimney semiopen, and ii) the application of Good Practices monitoring methodologies with greater effectiveness, including greater control of the chouriço production process, the number of lactic acid bacteria in the samples after packing was lower than in the samples produced by the standard baking process and also lower than in samples obtained through a non-monitored process. With the addition of 0.15% (w/v) of chitosan to the chouriço, the number of lactic acid bacteria and total microorganisms was lower compared with the chouriço with nitrite, after 14 days of storage. Therefore, the application of an alternative heat treatment to the one used in the standard chouriço corrente and the implementation of improvements in Good Manufacturing Practices resulted in an improvement in the microbiological safety and shelf-life of the food product after packing. Additionally, chitosan appears to be a natural alternative with interesting characteristics for application in a food product.