The sporadic occurrence of C. zeylanoides in the production
environment and its frequent isolation from meat samples at the
early stage of the production suggests external sources of contamination.
It is very likely that both fresh and frozen meat delivered tothe production facility were already contaminated with C. zeylanoides.
Earlier studies showed that the yeast composition of fresh
and frozen meat was generally dominated by C. zeylanoides (Hsieh
and Jay, 1984; Johannsen et al., 1984; Deak and Beuchat, 1996). On
the other hand, it looks like that house cultures of D. hansenii exist in
the production facility, which serves as internal sources of
contamination. The similar pattern of the isolation frequency curves
for meat and environmental isolates of D. hansenii supports this
hypothesis (Figs. 4 and 5). The isolation frequency of D. hansenii
from meat samples was higher in processing stages where it was
isolated frequently from the environmental samples. None of the air
samples contained D. hansenii and hence the sources of contamination
for the species are believed to be room installations and
production materials. It was isolated frequently from sticks on which
the meat were hanged during brining, drying and ripening
processes, nets that were used to hold the meat firm, the truck,
towel and brushes used for cleaning.