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Salmonella in Chicken Fillets Inactivated by Pressure

by 5m Editor
23 June 2009, at 9:46a.m.

SPAIN - P. Morales and colleagues at the Department of Food Technology, INIA, in Madrid have published a report into the inactivation of <em>Salmonella enteritidis</em> in chicken breast fillets by single-cycle and multiple-cycle high pressure treatments in the latest issue of <em>Foodborne Pathogens and Disease</em>.

The effect of single-cycle and multiple-cycle high hydrostatic pressure (HHP) treatments on the survival of three Salmonella Enteritidis strains in chicken breast fillets was investigated by the group based at INIA. They achieved reductions of up to five log in colony-forming units (CFU) of Salmonella per gramme.

The surface of fillets was inoculated with a cocktail of three Salmonella strains at approximately 107 colony-forming units (CFU) per gramme, and held at 4°C for 20 hours before HHP treatments.

Reduction of Salmonella counts on tryptic soy agar (TSA) by single-cycle treatments at 300MPa and 12°C ranged from 0.58 log CFU/g for a 0-minute (no dwell time) cycle to 3.35 log CFU/g for a 20-minute cycle, whereas with 400MPa treatments the decline ranged from 0.93 log CFU/g to more than five log CFU/g, respectively. The 4.8 log unit reduction in Salmonella counts on TSA achieved by a 15-minute treatment at 400MPa should suffice to eliminate the pathogen naturally present in contaminated chicken meat.

When plated on Salmonella Shigella agar (SSA), the reduction of Salmonella counts by single-cycle treatments at 300MPa and 12°C ranged from 0.69 log CFU/g for a 0-minute cycle to 4.21 log CFU/g for a 20-minute cycle, and with 400MPa treatments from 1.25 log CFU/g to more than five log CFU/g, respectively.

From the comparison of Salmonella counts on SSA and TSA, Morales and colleagues concluded that not only the lethality but also the proportion of injured Salmonella cells increased with the length of HHP treatments.

The use of multiple-cycle treatments instead of single-cycle treatments of the same HHP time for the inactivation of Salmonella Enteritidis inoculated on chicken breast fillets showed to be more advantageous at 400MPa than at 300MPa.

No recovery of injured Salmonella cells was observed when fillets treated at 300 or 400MPa for five minutes were held for 72 hours at 4°C.

Reference

Morales P., J. Calzada, B. Rodríguez, M. De Paz and M. Nuñez. 2009. Inactivation of Salmonella enteritidis in chicken breast fillets by single-cycle and multiple-cycle high pressure treatments. Foodborne Pathogens and Disease. June 2009, 6(5): 577-581. doi:10.1089/fpd.2008.0218.