Calcium fortification kills salmonella

Orange juice fortified with calcium lactate/tricalcium phosphate may affect the survival rate of salmonella whereas calcium citrate malate and calcium citrate fortifications have little effect, scientists report this week. This conclusion follows recent research carried out at the University of Georgia's Department of Food Science and Technology. Researchers set out to determine the survival of salmonellae in orange juice as affected by fortification with different types of calcium. Four brands of commercially pasteurised orange juice fortified with calcium (350 mg/240-ml serving) and nonfortified juice were inoculated separately with three types of inocula: strains of Salmonella Muenchen (inoculum 1), serotypes of human and animal origin (inoculum 2), and isolates from raw produce- and juice-associated outbreaks (inoculum 3). The juice inoculated with populations of 6.6 to 7.0 log10 CFU of Salmonella per ml was held at 4°C for up to 32 days. The number of cells of inoculum 1 that survived in juice fortified with calcium lactate/tricalcium phosphate (CaL/TCP) was significantly lower (P 0.05) (2.80 log10 CFU/ml) than in nonfortified juice (3.50 log10 CFU/ml) after 32 days' storage. Death of salmonellae in inocula 1 and 2 was less in juice fortified with TCP (3.21 and 3.33 log10 CFU/ml, respectively) than in the nonfortified juice (3.75 and 4.15 log10 CFU/ml, respectively). During the 32-day storage period, populations in inocula 1 and 3 showed significantly less inactivation (2.62 and 3.12 log10 CFU/ml, respectively) in juice fortified with calcium citrate (CC) than in nonfortified juice (3.14 and 3.60 log10 CFU/ml, respectively). There were no significant differences in the survival of Salmonella in juice fortified with calcium citrate malate (CCM) and nonfortified juice. Polymerase chain reaction (PCR) typing of randomly selected Salmonella colonies revealed that Salmonella Heidelberg in inoculum 2 and Salmonella Baildon and Salmonella Poona in inoculum 3 were the most prevalent at the end of the 32-day storage period at 4°C, suggesting that serotypes selected for use in inocula differed in tolerance to acidic environments. Full findings are published in the September 2001 issue of The Journal of Food Protection, Vol. 64, No. 9, pp. 1299-1304.