SUMMARY
Thermoresistence of acid producing psychrotrophic bacteria isolated from milk
An acidificant psychrotrophic bacterial was isolated from raw milk from Bromocresol Purple Agar medium, after incubation at 7°C, for 10 days. Cells from the culture at begining of the stationary phase, were inoculated sterilized in power milk, reconstituded at 12% of total solids, resulting in approximately 108 cells per mililiter. Portions of 3 mi of inoculated milk were transfered to borosilicate tubes and were submited to cells resistance determination at 62, 70, 75 and 80°C, by the TDT tube method. The survival curves at the respective temperatures and the cuve thermal death were drawn. The bacteria presented a D75ºC value of 0.15 minutes and z = 8,7°C. Treatments LTLT and HTST of pasteurization promoted 5,27 and 0,53 decimal reductions in the number of available bacteria cells. respectively. The concuision of this study was that the isolated bacteria is destroyed only by treatment LTLT of pasteurization.

Key words: Acidificant psychrotrophic bacteria, thermoresistance, survival curves, curve of thermal death.



Recibido: 14/05/1998
Aceptado: 04/11/1998

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