25.4: Materials and Procedures
- 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.
- Count the colonies on the appropriate plate and report total #CFUs/ml.
- 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 |
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Colonies Counted |
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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 |
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1 |
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2 |
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3 |
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4 |
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5 |
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6 |
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Contributors and Attributions
Kelly C. Burke (College of the Canyons)