Thermal Resistance of Listeria monocytogenes in Dairy Products

Abstract

The thermal resistance of Listeria monocytogenes strain Scott A that had been associated with a recent milkborne outbreak of listeriosis was determined in whole and skim milk, heavy cream, and ice cream mix. L. monocytogenes suspended at concentrations of approximately 1 × 105 cells/ml was heated at temperatures ranging from 52.2 to 79.4°C at various contact times. The D71.7°C values computed for milk samples ranged from 0.9 to 2.7 s. The D7.94°C value in ice cream mix was 0.5 s. The zD value for fluid products ranged from 5.8 to 7.1°C; the zF value for ice cream mix was 7.0°C. The L. monocytogenes suspensions would not survive a proper pasteurization process given to raw dairy products.

Evaluation of the heat resistance of pathogenic <i>Listeria monocytogenes</i> in milk and milk products in Sri Lanka

“…The z values of 6.5 (Bradshaw et al 1987), 7.3 (Bunning et al 1986), 8.0 (Bunning et al 1988, and 6.3 (Bradshaw et al 1985) were reported for L. monocytogenes in milk. The apparent difference of the z value of the present study from other reported studies could be attributed to the food system used in the experiments.…”

“…The differences, in the observed D value in the present study and reported D values, are once again due to the different milk food systems used in the respective experiments. Some scientists used skim milk (Bradshaw et al 1987), whereas other scientists used whole milk (Bunning et al 1988) in thermal resistance studies. Sterile whole milk was used in the present study as well.…”

“…The apparent difference of the z value of the present study from other reported studies could be attributed to the food system used in the experiments. Some scientists used skim milk (Bradshaw et al 1987), whereas other scientists used whole milk (Bunning et al 1988). The fat content is higher in whole milk thus giving protective effects to L. monocytogenes against heat processing.…”

“…4). Thermal Death Rate (TDR) curve was constructed using the survival number of L. (Bradshaw et al 1987), 3.1 and 5.0sec (Bunning et al 1988), and 1.9 sec (Bunning et al 1986). The differences, in the observed D value in the present study and reported D values, are once again due to the different milk food systems used in the respective experiments.…”

Kasaplarda Listeria Monocytogenes (O) Aglüti̇ni̇nleri̇ni̇n Dağilimi

“…monocytogenes bulunduğundan, besin maddelerinin bulaşı daima söz konusu olabilmektedir (6,10). Sığır, koyun ve kümes hayvanları ile kuşlardan elde edilen, L. monocytogenes, temel gıda maddeleri olan et ve et ürünlerinde kolaylıkla gelişebilmekte, gıda endüstrisi çalışan-larında problemler oluşturmaktadır (5,10,15,19,24,32).…”