A difference in minimum temperature for development between P. glabrum (29/12 NGT) and P. polonicum (33/12 NGT) was observed, both in culture medium and on the surface of the nuggets. There was no difference between the brands of nuggets assessed.
P. polonicum (33/12 NGT) was able to germinate forming micro-colonies (about 1 mm) in 2 of 5 (40%) of the plates of culture media incubated at 0 °C, whereas P. glabrum (29/12 NGT) did not germinate in this temperature. Both species formed colonies in the first week when incubated at 5 °C.
Moreover, the minimum temperatures at which growth was observed in both species in the nuggets were lower than those observed in the culture medium (Fig. 1A and 1B). It was observed that an approximate count of 105 CFU/g was necessary for visualization of the colonies on the nuggets.