Mezzo ESP-7501 User Manual

3
Petrifilm
Yeast and Mould Count Plate
Yeast count = 44
Mold count = 27
™
Figure 1
Figure 2
Interpretation
It is easy to count yeast and mould colonies on Petrifilm
Yeast and Mould count plates. An indicator
dye stains yeast and mould colonies to provide contrast
and facilitate counting.
To differentiate yeast and mould colonies on Petrifilm
Yeast and Mould count plates, look for one or more of
the following typical characteristics:
YEAST
- Small colonies
- Colony has defined edges
- Pink-tan to blue-green in colour
- Colony may appear raised ("3D")
- Usually no focus (dark centre) in middle of colony
MOULD
- Large colonies
- Colony has diffuse edges
- Variable colour (moulds may produce their own pigments)
- Colonies appear flat
- Usually a focus in centre of colony
The colonies in figure 1 are characteristic examples of
yeasts: small, blue-green colonies, with defined edges, and
no foci. (Yeast count = 44)
The colonies in figure 2 are characteristic examples of
moulds: large, variable coloured colonies, with diffuse
edges, and centre foci. (Mould count = 27)
Guide