Adesão de esporos de Bacillus sporothermodurans ao aço inoxidável e sua resistência a sanificantes químicos em condições de uso simulado
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2001-05-21
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Universidade Federal de Viçosa
Resumo
Esporos de Bacillus sporothermodurans CCT6247 foram avaliados quanto à adesão em cupons de aço inoxidável e resistência a sanificantes químicos, em condições de uso simulado, utilizando um modelo de linha de circulação de leite, em aço inoxidável AISI 304. Seis cupons de prova, sendo dois em formato de cotovelo 90º, dois cilíndricos e dois em T, foram inoculados com uma suspensão, em tampão fosfato, de 0,31 M em pH 7,0±0,1, contendo cerca de 10^5 esporos/mL por 12 horas a 30°C. A quantificação dos esporos foi feita em três dos seis cupons após rinsagem com tampão fosfato, durante 15 minutos, plaqueando diluições adequadas por espalhamento superficial em ágar BHI e incubação a 37°C/24h. Depois, os seis cupons foram conectados, em pontos específicos, no modelo utilizado. Simulou-se um processo de sanificação, circulando-se 15 L dos sanificantes por 15 minutos a uma velocidade de 1,5 m/s, à temperatura ambiente (20-25°C), pelas tubulações. Verificou-se que não houve diferença (P ≥0,05) na adesão entre os cupons cotovelo 90º, cilíndrico e T. O log10 do número de esporos aderidos por cm² nesses cupons foi, respectivamente, de 4,01, 3,88 e 4,03, correspondentes a 3,93, 2,55 e 4,46% de adesão. Nenhum dos sanificantes obteve três reduções decimais (RD) na população de esporos, valor sugerido na aprovação de sanificantes, atuando sobre microrganismos aderidos. Não houve diferença (P≥0,05) entre os sanificantes, com exceção do hipoclorito de sódio a 100 mg/L de CRT, em pH 9,45, que apresentou a menor eficiência (1,57 RD), e também não se observou influência do tipo de cupom na ação dos sanificantes. Os números de reduções decimais obtidos, em ordem descrescente, foram 2,84; 2,77; 2,67; 2,47; 2,43; e 2,26 RD para as soluções de hipoclorito contendo 100 mg/L em pH 7,0; de cloramina orgânica contendo 100 mg/L em pH 7,18; de hipoclorito contendo 100 mg/L em pH 8,0; de cloramina orgânica contendo 60 mg/L, em pH 7,18; de ácido peracético a 60 mg/L em pH 3,4; e de ácido peracético a 30 mg/L em pH 3,7, respectivamente. Portanto, os resultados sugerem que o uso de hipoclorito corrigido para pH 8,0 ou 7,0 pode ser escolhido sem prejuízo da eficiência do processo de higienização, além de apresentar menor custo. Avaliando a higienização dos cupons pela técnica de ATP bioluminescência, verificou-se inconsistência entre os resultados desta técnica e do método tradicional de contagem em placa na detecção de esporos aderidos ao aço inoxidável, em razão, provavelmente, do baixo nível de ATP detectável desses esporos.
Bacillus sporothermodurans CCT 6247 spores were evaluated for attachment on stainless steel coupons and resistance to chemical sanitizing agents, under simulated conditions, using a milk circulation AISI 304 stainless steel pipe system. Six coupon tests (two 90° elbow, two cylindrical and two T- piece) were inoculated in a phosphate buffer, 0.31M, pH 7.0 ± 0.1 suspension, containing around 10^5 spores/ mL during 12 h at 30°C. Spore quantification was performed in 3 of 6 coupons following phosphate buffer rinsing for 15 min., plating adequate dilutions on BHI agar plate and incubation at 37°C/24h. The six coupons were then connected at specific points in the model. A sanitizing process was simulated by circulating 15 L of the sanitizing agents for 15 min. at a speed of 1.5 m/s at room temperature (20-25°C) through the tubes. No difference (P≥0.05) was verified in the attachment among the 90º elbow, the cylindrical and the T-piece coupons. The spore number log10 attached per cm² on these coupons were, respectively, 4.01, 3.88 and 4.03, which correspond to 3.93, 2.55 and 4.46%. None of the sanitizing agents obtained 3 decimal reductions (DR) within the spore population, a value suggested for the sanitizing agents approval, when acting on the attached microorganisms. No difference was found (P≥0.05) among the sanitizing agents, except for sodium hypochlorite at 100 mg/L of CRT, pH 9.45, which showed the least efficiency (1.57 DR) nor any influence of the type of coupon was observed on the sanitizing agents’ action. The decimal reductions number reached, in decreasing order, 2.84, 2.77, 2.67, 2.47, 2.43 and 2.26 DR for the hypochlorite solution containing 100 mg/L, pH 7.0; the organic chloramine solutions containing 100 mg/L, pH 7.18; hypochlorite containing 100 mg/L, pH 8.0; organic chloramine containing 60 mg/L, pH 7.18; peracetic acid at 60 mg/L in pH 3.4; and of peracetic acid at 30 mg/L in pH3.7, respectively. Thus, the results suggest that the use of hypochlorite corrected for 8.0 or 7.0 can be chosen without compromising the process of hygienization, besides presenting lower cost. When evaluating the coupons higienization by bioluminescence ATP technique, inconsistency between the results of this technique and those of the traditional method of plate counting was observed in detecting spores attached to the stainless steel, this being probably due to these spores low detectable ATP levels.
Bacillus sporothermodurans CCT 6247 spores were evaluated for attachment on stainless steel coupons and resistance to chemical sanitizing agents, under simulated conditions, using a milk circulation AISI 304 stainless steel pipe system. Six coupon tests (two 90° elbow, two cylindrical and two T- piece) were inoculated in a phosphate buffer, 0.31M, pH 7.0 ± 0.1 suspension, containing around 10^5 spores/ mL during 12 h at 30°C. Spore quantification was performed in 3 of 6 coupons following phosphate buffer rinsing for 15 min., plating adequate dilutions on BHI agar plate and incubation at 37°C/24h. The six coupons were then connected at specific points in the model. A sanitizing process was simulated by circulating 15 L of the sanitizing agents for 15 min. at a speed of 1.5 m/s at room temperature (20-25°C) through the tubes. No difference (P≥0.05) was verified in the attachment among the 90º elbow, the cylindrical and the T-piece coupons. The spore number log10 attached per cm² on these coupons were, respectively, 4.01, 3.88 and 4.03, which correspond to 3.93, 2.55 and 4.46%. None of the sanitizing agents obtained 3 decimal reductions (DR) within the spore population, a value suggested for the sanitizing agents approval, when acting on the attached microorganisms. No difference was found (P≥0.05) among the sanitizing agents, except for sodium hypochlorite at 100 mg/L of CRT, pH 9.45, which showed the least efficiency (1.57 DR) nor any influence of the type of coupon was observed on the sanitizing agents’ action. The decimal reductions number reached, in decreasing order, 2.84, 2.77, 2.67, 2.47, 2.43 and 2.26 DR for the hypochlorite solution containing 100 mg/L, pH 7.0; the organic chloramine solutions containing 100 mg/L, pH 7.18; hypochlorite containing 100 mg/L, pH 8.0; organic chloramine containing 60 mg/L, pH 7.18; peracetic acid at 60 mg/L in pH 3.4; and of peracetic acid at 30 mg/L in pH3.7, respectively. Thus, the results suggest that the use of hypochlorite corrected for 8.0 or 7.0 can be chosen without compromising the process of hygienization, besides presenting lower cost. When evaluating the coupons higienization by bioluminescence ATP technique, inconsistency between the results of this technique and those of the traditional method of plate counting was observed in detecting spores attached to the stainless steel, this being probably due to these spores low detectable ATP levels.
Descrição
Palavras-chave
Adesão de esporos, Bacillus sporothermodurans, Aço inoxidável, Resistência a sanificantes químicos
Citação
AKUTSU, Cleusa Kiyomi. Adesão de esporos de Bacillus sporothermodurans ao aço inoxidável e sua resistência a sanificantes químicos em condições de uso simulado. 2001. 83 f. Dissertação (Mestrado em Ciência e Tecnologia de Alimentos) - Universidade Federal de Viçosa, Viçosa. 2001.