Mezzo ESP-7501 User Manual

Petrifilm
™
Yeast and Mould Count Plate
Interpretation
Guide
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)
Figure 1
Yeast count = 44
Mold count = 27
Figure 2
3

Mezzo ESP-7501 Specifications

General

Type	Espresso Machine
Voltage	220-240V
Frequency	50/60Hz
Weight	4.5 kg
Capacity	2 Cups
Color	Black

Summary

Yeast and Mould Count Plate Interpretation

Differentiating Yeast vs. Mould

Explains how to distinguish yeast from mould colonies based on typical characteristics like size, color, and edges.

Yeast Colony Characteristics

Defines typical traits of yeast colonies: small size, defined edges, pink-tan to blue-green color, and no focus.

Mould Colony Characteristics

Defines typical traits of mould colonies: large size, diffuse edges, variable color, and a focus in the center.

Advanced Yeast Counting and TNTC

Mould Counting and Identification

Mould Colony Examples and Features

Illustrates mould colonies with variable pigmentation, diffuse edges, and centre foci, as shown in figures.

Estimating High Mould Counts

Explains how to estimate mould counts when numbers are high or TNTC, focusing on foci.

Phosphatase Reaction Analysis

Identifying Natural Phosphatase

Explains how phosphatase causes blue colour reactions and how to distinguish it from true colonies.

Distinguishing Phosphatase Methods

Outlines techniques like dilution, supernate use, temperature, and checking for product colour changes.

Incubation Time and Temperature

Impact on Yeast and Mould Growth

Details the importance of incubation time and temperature for accurate yeast and mould growth.

Microscopic Differentiation

Microscopic Identification Methods

Describes methods for microscopic examination to differentiate yeast and mould morphology.

Procedural Guidelines

Storage and Sample Preparation

Covers proper storage of plates and preparation of food product samples for testing.

Inoculation and Incubation Steps

Details the steps for inoculating plates, including spreader use, and recommended incubation.

Reading and Interpretation

Explains how to read plates using a colony counter and refer to the interpretation guide for results.