The fate of Salmonella during the preparation and storage of salpicon, a cold shredded beef salad commonly consumed in Mexico, was evaluated. Salmonella contamination was introduced by a person shredding the cooked beef, who previously had handled raw pork containing several native serotypes of Salmonella at 9,000 salmonellae per g. The salad was prepared with 0, 2, or 4% vinegar and was held for 48 h (8 at 24–26°C and 40 at 5–7°C). The optimal concentration of vinegar for acceptable salad flavor was 4%. The initial number of salmonellae in salads prepared with 0 or 4% vinegar was 20/g. Salmonella populations increased to 5,000 after 48 h. Salmonella did not grow in salad containing 4% vinegar (pH 5.3); however, the organism was isolated at levels of 7 cells per g at 48 h of incubation. Fourteen different serovars of Salmonella were isolated from the salads. Critical control points in the preparation and storage of salpicon are shredding the beef, the concentration of vinegar, and rapid cooling of salad before serving.
1Facultad de Química, Universidad Autonóma de Querétaro. Centro Universitario. Apartado postal 494, Querétaro 76010, México.