[Thermoresistance of acid producing psychrotrophic bacteria isolated from milk]

An acidificant psychrotrophic bacteria was isolated from raw milk from Bromocresol Purple Agar medium, after incubation at 7 degrees C, for 10 days. Cells from the culture, at the beginning of the stationary phase, were inoculated sterilized in powder milk, reconstituted at 12% of total solids, resulting in approximately 10(8) cells per milliliter. Portions of 3 ml of inoculated milk were transferred to borosilicate tubes and were submitted to cells resistance determination at 62, 70, 75 and 80 degrees C, by the TDT tube method. The survival curves at the respective temperatures and the curve of thermal death were drawn. The bacteria presented a D75 degrees C value of 0.15 minutes and z = 8.7 degrees C. Treatments LTLT and HTST of pasteurization promoted 5.27 and 0.53 decimal reductions in the number of available bacteria cells, respectively. The conclusion of this study was that the isolated bacteria is destroyed only by the treatment LTLT of pasteurization.