With the help of a couple of mentors, Sam designed an experiment using a technique called Presence/Absence testing -- it's a protocol that can be used for testing of water and food contamination. There were many, many test tubes and swabs and lots of learning. It turns out that when the HDPE bags are used once, there are microbes living on them. But after a week's time, most of the microbes didn't find the environment good for growing and multiplying, and died. This is important research because it supports our idea that it's pretty safe to reuse your plastic grocery bags for food. Now, if there was a bad spill in one of the bags (with meat or something else), you might not want to reuse that for food. And to make the bags even more sanitary, simply exposing them to air will most likely take care of things -- microbes mostly like wet, dark and moist places with a food source. HDPE plastic bags don't really do it for them -- they kind of don't like it.
How about that for science detectives?
Here is the link to the video he created to explain the story:
And some charts and a graph with data ...
Whoo go Sam! When I saw Sam doing this, he looked like a real scientist in a lab, with his plastic gloves on and test tubes. Trying to be as clean as possible, it was so cool!
ReplyDeleteVery interesting, indeed. Do you think that there is a difference in safety between using a bag for a second round of groceries and using the bag to store raw food or mix salad or that kind of thing? I had a friend who always tossed salad in a "single use" grocery bag and I thought that seemed a bit risky. But if you're placing mostly wrapped food into it anyway, I don't see a problem... Comments?
ReplyDeleteSince there are microbes present on the bag surface immediately after they've been used once, it would seem that your friend should let the bags sort of "die down" before using them for that kind of thing. But here's the thing: The experiment didn't show specifically what kind of bacteria was growing there. Most bacteria/microbes won't hurt us in the least and some of them are beneficial actually. Your friend is obviously still with us and probably has been doing this for years right? People have all different comfort levels when it comes to bacteria, as we found out through the survey. Thanks for the comment, Johanna!
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