Salmonella response to heat and pH in meat juice (#364)
Salmonella enterica is a major cause of bacterial gastrointestinal food-borne infection. Survival of, and cross-contamination by, Salmonella in red meat processing facilities may lead to human disease. Interventions such as application of hot water during processing may reduce this risk. This study examined the effect of gradual heat treatment to 70°C and heat shock treatment at 70°C for 5 min on S. Anatum (2), S. Heidelberg (1), S. Saintpaul (1) and S. Typhimurium (1) in beef, in lamb and in goat meat juice and phosphate buffered saline (PBS).The effect of pH on heat treatment was also examined by altering the pH of the respective meat juices (beef pH 5.9, lamb pH 5.6 and goat pH 5.6) to match that of PBS (pH 7.4) and vice versa. Untreated controls were included in all experiments. Bacterial numbers in all meat juices and PBS were determined on thin layer xylose lysine deoxycholate agar. In lamb juice, all treatments significantly (p<0.05) reduced numbers of Salmonella (~2.84 – 6.49 log cfu/ml). In goat meat juice most treatments reduced numbers of Salmonella below the limit of detection (>7.24 log cfu/ml), except for gradual heat treatment which significantly (p<0.05) reduced numbers of S. Anatum (~3.31 log cfu/ml) at pH 5.6. In beef juice gradual heat treatment significantly (p<0.05) reduced numbers of Salmonella (~3.07 – 7.08 log cfu/ml) except for both S. Anatum strains at pH 7.4 where numbers were reduced to below the limit of detection (>6.62 log cfu/ml). Salmonella numbers were reduced to be less than the limit of detection after heat shock in all meat juices at pH 7.4 and in beef juice at pH 5.9. By contrast Salmonella numbers after heat shock were reduced to less than the limit of detection (>7.22 log cfu/ml) for all treatments in PBS irrespective of its pH. Meat juice constituents and pH may play a role in protecting Salmonella against the effect of heat treatment.