We conducted a very interesting experiment in our Undergrad Research class two weeks ago. We were divided into three groups to determine the number of bacteria on sample of raw salmon, raw chicken and cooked chicken. Both salmon and chicken were bought just one day before the lab day. I will not detail how the experiment was conducted but the results obtained. There was 2506 CFUs/mL counted on raw salmon sample while 470 CFUs/mL on raw chicken and only 330 CFUs/ on cooked chicken. Please be noted that CFU is Colony Forming Unit or a chain of bacteria. We did not count single bacteria because they are too tiny and too many to be counted. CFUs are like “small islands” where a lot of bacteria are growing (See pictures).
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| CFUs of raw salmon sample (One spot is one CFU) |
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| CFUs of raw chicken sample |
Also, we found that the bacteria of raw salmon are more diverse than that of chicken; you can see from the pictures, CFUs on salmon sample have more colors than chicken. To write the formal lab report for this experiment, I did a lot of research about raw meat and bacteria. It is said that the shelf – life of seafood is very short (O. Mejlholm and P. Dalgaard, 2002) as compared with other meats. That is the reason of quick spoilage of seafood. Right after taking the salmon out of the pack for the test, there were 1400 CFUs/mL counted on the sample for run 1, after about 10 minutes we conducted run 2 and got 3800 CFUs/mL, the salmon was re-contaminated so quickly. I am thinking about the salmon we eat at a sushi restaurant, that piece of salmon takes a certain time from the moment of being made, travelling around on the chain, to arriving at our table, how long is it? Is such time enough for it to be re-contaminated? So scary!!!
Reference
O. Mejlholm and P. Dalgaard, “Antimicrobial effect of essential oils on the seafood
spoilage micro-organism Photobacterium phosphoreum in liquid media and fish products”, The Society for Applied Microbiology, 2002: p1
Wow. That does not make any of fish and chicken sound to tasty. I am not sure if you know this but I am curious about where you sourced the fish and chicken? I wonder if a mass produced brand chicken and a local butcher chicken would create different results.
ReplyDelete:) The chicken was bought at Safeway , prepacked by Draper Farm, and salmon at QFC. That's why we should eat cooked meat. As your concern about a mass produced brand chicken and a local butcher chicken, I think that could be a great idea for our next experiment.
ReplyDeleteThat is pretty nasty to say the least. And to imagine that I actually enjoy eating sushi occasionally. Haha I will never look at sushi the same ever again ;p. Anyway, I agree with Rebecca, It would be interesting to see the end results created from examining chicken from a local butcher and to that done on chicken which is mass produced.
ReplyDeleteI was actually craving sushi a few minutes ago, not so much anymore. Being that they are raw we know the risks of eating uncooked food, but to actually see the bacteria just shows are serious the warnings are. I guess I will be eating cooked food for a while. Thank you for this post!
ReplyDeleteThanks for your post this week! It's an eye opener for people who loves to eat raw. Some people may not know the risks of eating raw food. Personally, I do not eat anything raw . I cannot eat a steak without having any pink on it or I will simply will get sick right away.
ReplyDeleteI knew there was a reason I do not like sushi...something about eating raw fish just seems wrong. But hey, millions of people love it, and as a chef, I sort of feel I'm not very suave because I don't eat sushi. Thanks for a great experiment!
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