Prevalence of Salmonella in chorizo and its survival under different storage temperatures

The prevalence of Salmonella in chorizo, a raw pork sausage, was studied in two locations in Mexico. Sixty samples were collected from butcher shops a nd retail markets in Guadalajara city, and an other 80 samples were collect ed from butcher shops (40 samples) and grocery stores (40 samples) in Quere taro city. Samples obtained from butcher shops had been produced at the sam e butchery whereas those obtained from grocery stores in Queretaro had been processed at national meat processing plants, in Guadalajara, 88% of the s amples tested positive to Salmonella. In Queretaro, 78% of the samples coll ected from butcher shops and 5% of the samples collected from grocery store s tested positive to Salmonella. The ability to isolate Salmonella from cho rizo was affected by the method of analysis and was best achieved by preenr ichment of 20 g of sample in buffered peptone water for 24 h, followed by e nrichment in tetrathionate brilliant green and selenite cystine broths. The five most frequent serovars isolated were S. derby (26%), S. anatum (14%) S. infantis (14%) S. typhimurium (12%) and S. branden burg (6%) Five select ed samples that tested positive for Salmonella were selected for enumeratio n by most probable number (MPN) and subsequent survival studies during stor age of chorizo at refrigeration (4-6 degrees C) and at room temperature (18 -22 degrees C) initial numbers of Salmonella varied from 900 to 0.04 MPN g( -1) and with the exception of the sample containing 900 Salmonella MPN g(-1 ) all other samples were cleared from this pathogen after 21 days of refrig eration or 5-10 days at room temperature. Salmonella contamination in chori zo can be prevented by improving the bacteriological qualify and safety of the raw materials and by controlling the natural aging process of this prod uct (C) 1999 Academic Press.