25.4: Materials and Procedures

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Page ID: 40317

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Materials

One food sample/group, at least 20g
Sterile blender container
1 ml pipettes
1-180 ml sterile water blank
1-99 ml sterile water blank
Sterile spatula and weigh boats
3 Eugon Agar pours
3 sterile empty petri dishes
1 EMB plate

Procedures

Using the best aseptic technique possible, weigh out 20g of food and transfer to the sterile blender container.
Add the 180 ml of sterile water to the container and blend the food for 5 minutes.
Use the 99ml water blank for diluting, mix thoroughly, and then plate out the sample to the following dilutions: 1:100, 1:1000, 1:10,000.
Pour the Eugonpours into the plates, gently mix the plates using a slow figure-eight motion on the lab bench. Set aside the plates to harden.
From the food in the blender container, use a sterile loop to streak an EMB plate to look for coliforms.
Incubate plates at 35C for 24h.
After incubation, evaluate plates.
1. Count the colonies on the appropriate plate and report total #CFUs/ml.
2. Look for presence of coliforms on the EMB plate.

Results

Standard Plate Count

Food that you tested:____________________________________________________________

Plate Dilution	1:100	1:1,000	1:10,000
Colonies Counted

Calculate the SPC, the number of bacteria/g of food for your group:

EMB plate observations:

Class Results: Place all class results in the table below.

Group	Food tested	SPC	EMB +/- for coliforms
1
2
3
4
5
6

Contributors and Attributions

Kelly C. Burke (College of the Canyons)