Are Your Clams Safe to Eat?
To determine if clams purchased fresh from local fish markets—as opposed to those that have gone through a depuration process at a purification plant—are safe to eat.
- masking tape
- marking pen
- 6 clams each from fish markets in about 10 different regions
- sterile steaming pan
- sterile knife
- blender (with sterile container)
- sterile applicators
- petri dishes: tryptic soy agar with 5% sheep blood
- photographed petri dishes of depured raw and steamed clams (as a control)
Clams from different geographical areas that have not been depured will be bacteria-tested in both a raw and a cooked state to observe and compare the fecal bacteria counts to those of photographed petri dishes of depured clams.
- Label the groups of clams as to the areas from which each group came.
- Take three clams of one group and steam them in the pan for 5 minutes. Then, open them with the knife and put their contents together in the blender; process for 90 seconds.
- Using a sterile applicator, streak the blend onto a petri dish and incubate for 24 hours.
- Repeat the blending and streaking procedure using the remaining three clams from the group. Do not steam them.
- Repeat steps 2 through 4 with clams from the other geographical groups.
- Compare the results from each group to the control petri dishes of both raw and steamed clams that have gone through the depuration process at a purification plant
- Identify the types and levels of bacteria present, and find out the levels at which they can be safely consumed.
- How does the bacteria count of the raw clams compare to that of the steamed clams? Did steaming in fact kill the bacteria? Are the raw clams safe to eat?
- How did the bacteria count of the clams compare from market to market? From market to control (depured)?
- Were all the bacteria that were found in the clams harmful?
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