Comparison of methods for research of Salmonella sp. e Listeria sp. and microbial and physical-chemistry evaluation in artisanal Minas cheese / Comparação de métodos para pesquisa de Salmonella sp. e Listeria sp. e avaliação microbiana e físico-química em queijo Minas artesanal

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The objectives of this research had been to compare the conventional method of detention of Salmonella sp., Listeria monocytogenes and Listeria sp. with fast methods for analysis of artisanal Minas cheese and to verify the survival of Listeria innocua to the maturation. Moreover, it was objectified to evaluate the product in relation to the counting of lactic bacteria, the contamination by bacterias from the coliform group and to determine physical and physical-chemistries characteristics. Forty eight sample units of artisanal Minas cheese had been collected of the region of Serro-MG, amongst these: 12 proceeding ones from six producers whose properties were registered in Instituto Mineiro de Agropecuária-IMA, that had been matured under refrigeration in the original packing to the vacuum and evaluated with 37 and 69 days; 20 proceeding from two properties not registered in IMA and 16 proceeding ones from a registered property, that had been matured at ambient temperature and analyzed before and after 60 days. Raw milk artificially contaminated with L. innocua, in the concentration of 10 UFC/mL, was used for the manufacture of 15 sample units of artisanal Minas cheese. The survival of this bacteria during the maturation for 5, 15, 30, 45 and 60 days was verified. The sample units artificially contaminated or not (n = 63) had been analyzed by the conventional method, immunoanalytical VIDAS-SLM and molecular PCR-BAX in relation to the presence of Salmonella sp. Sample units not contaminated (n = 48) had been evaluated by the conventional method and immunoanalytical VIDAS-LMO in relation to the presence of L. monocytogenes, while sample units artificially contaminated (n = 15) had been analyzed by the conventional method and immunoanalytical Lateral Flow SystemTM in relation to the presence of Listeria sp. The performance of the fast methods was determined based on the Kappa agreement index and in the values of sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV). The results of lactic microbiota, total and thermotolerant coliform population and physical and physical-chemistries analyses of the 63 sample units had been submitted to the analysis of variance or linear regression with 5 % of significance. It was not evidenced Salmonella sp. by the conventional method and the method of PCR-BAX, but it was verified in 3,17 % of the sample units evaluated by VIDAS-SLM. The Kappa agreement index zero and the sensitivity were not determined, the specificity and accuracy of 96,83 %, the PPV of 0 % and NPV equal 100 % when comparing VIDAS-SLM method with the conventional method. The presence of L. monocytogenes was not detected by the evaluated methods. L. innocua was detected in 13 of the 15 sample units analyzed in the evaluated times of maturation. The Lateral Flow SystemTM method presented Kappa of 0,30, sensitivity of 61,54 %, specificity of 100 %, accuracy of 66,67 %, PPV of 100 % and NPV of 28.57 % compared with the conventional method. Reduction of the population of total and thermotolerant coliforms was observed at acceptable values for the legislation and average reduction of 2 cycles log in the counting of lactic bacteria to the end of 60 days of maturation under ambient temperature. The physical and physical-chemistries characteristics of matured cheeses in vacuum packages and under refrigeration, in general, had been kept what it was not observed in the matured cheeses out of the packages and to the ambient temperature. The PCR-BAX method for the research of Salmonella sp. e VIDAS-LMO for the research of L. monocytogenes had presented similar results to the presented ones for the conventional methodology. Salmonella sp. e L. monocytogenes had not been recovered in the sample units evaluated. The minimum period of maturation of 60 days for the artisanal Minas cheese, demanded for State Law 14,185, was not enough to guarantee microbiological security when cheeses had been produced with raw milk artificially contaminated with L. innocua.

ASSUNTO(S)

artisanal minas cheese salmonella sp. listeria sp. salmonella sp. listeria sp. queijo minas artesanal microbiologia

ACESSO AO ARTIGO

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