Effect of Phage on Survival of Salmonella Enteritidis during Manufacture and Storage of Cheddar Cheese Made from Raw and Pasteurized Milk

Abstract

The ability of Salmonella Enteritidis to survive in the presence of phage, SJ2, during manufacture, ripening, and storage of Cheddar cheese produced from raw and pasteurized milk was investigated. Raw milk and pasteurized milk were inoculated to contain 10(4) CFU/ml of a luminescent strain of Salmonella Enteritidis (lux) and 10(8) PFU/ml SJ2 phage. The milks were processed into Cheddar cheese following standard procedures. Cheese samples were examined for Salmonella Enteritidis (lux), lactic acid bacteria, molds and yeasts, coliforms, and total counts, while moisture, fat, salt, and pH values were also measured. Salmonella Enteritidis (lux) was enumerated in duplicate samples by surface plating on MacConkey novobiocin agar. Bioluminescent colonies of Salmonella Enteritidis were identified in the NightOwl molecular imager. Samples were taken over a period of 99 days. Counts of Salmonella Enteritidis (lux) decreased by 1 to 2 log cycles in raw and pasteurized milk cheeses made from milk containing phage. In cheeses made from milks to which phage was not added, there was an increase in Salmonella counts of about 1 log cycle. Lower counts of Salmonella Enteritidis (lux) were observed after 24 h in pasteurized milk cheese containing phage compared to Salmonella counts in raw milk cheese with phage. Salmonella Enteritidis (lux) survived in raw milk and pasteurized milk cheese without phage, reaching a final concentration of 10(3) CFU/g after 99 days of storage at 8 degrees C. Salmonella did not survive in pasteurized milk cheese after 89 days in the presence of phage. However, Salmonella counts of approximately 50 CFU/g were observed in raw milk cheese containing phage even after 99 days of storage. In conclusion, this study demonstrates that the addition of phage may be a useful adjunct to reduce the ability of Salmonella to survive in Cheddar cheese made from both raw and pasteurized milk.

Aspectos físico-químicos e microbiológicos do queijo tipo coalho comercializado em estados do nordeste do Brasil

“…Sabe-se que a Salmonella mantém-se viável em queijo contaminado por longo período de tempo (Modi et al, 2001), o que ressalta a importância do controle da qualidade microbiológica do produto, visto que a legislação brasileira estabelece a ausência desta bactéria em alimentos (Brasil, 2001b). A Salmonella é potencialmente capaz de provocar infecção alimentar, e a presença dessa bactéria classifica os queijos como produtos impróprios para consumo.…”

O comércio de queijo de coalho na orla de Salvador, Bahia: trabalho infantil e segurança de alimentos

“…Resultados semelhantes ou muitas vezes inferiores foram reportados por outros autores 7,8,35,36 que também analisaram queijo de coalho cru, o que indica condições de higiene bastante insatisfatórias. Em referência ao índice de amostras confirmadas com E. coli, o presente estudo mostra valores relativamente altos, embora inferiores aos referidos por Feitosa et al 8 , que confirmaram a presença desse micro-organismo em 93,1% de 43 amostras de queijo coalho prove-nientes de diferentes microrregiöes do estado do Ceará.…”

“…Sabe-se, também, que a Salmonella spp. mantém--se viável por longo período de tempo em queijo contaminado 36 , o que ressalta a importância do controle de qualidade microbiológica do produto, visto que a legislação brasileira 18 estabelece ausên-cia dessa bactéria em alimentos.…”

Salmonella Typhimurium, Infantis, Derby, and Enteritidis survival in pasty dulce de leche

“…Borges, Brandão and Pinheiro (1990), who inoculated Salmonella in raw milk prior to cheese-making and found that this enterobacteria can remain viable in this food for up to 45 days of maturation. Modi et al (2001) also reported that this organism survives for long periods in raw milk and standardized milk. These results, as well as the ones in the current study, indicate that some strains of Salmonella are adapted to environments provided by dairy foods.…”