I hypothesize that no bacteria will grow at 74°C because it kills all the bacteria that were on it because it is too hot.

Background

According to the Centers for Disease Control and Prevention (CDC) foodborne illnesses cause about 48 million people to get sick, 128,000 people to be hospitalized, and 3,000 people to die in the United States per year.

Campylobacter, Salmonella, and Eschericia coli (E-coli) are the three most common bacteria that cause foodborne illness. Salmonella can be found on raw meat including poultry and causes more hospitalizations and deaths than any other foodborne illness. E-coli comes from cows and can be found in beef.

On August 29, 2023 there was a major E-coli outbreak in Calgary's daycare systems causing 446 E. coli cases from food that was contaminated as well 32 secondary cases. Thirty-nine people were hospitalized, 38 children and 1 adult. Eight of the 39 people who were hospitalized had to get dialysis (a treatment that removes extra fluid and waste from your blood) because their kidneys failed. https://calgary.ctvnews.ca/e-coli-outbreak-at-calgary-daycares-declared-over-by-ahs-1.6625206 

Health Canada and the CDC recommend washing your hands thoroughly, separating cooked and uncooked food, cooking meat to the recommended temperature (below), and storing your food at 4°C or below. The CDC and Health Canada both recommend thoroughly cooking meats to prevent foodborne illnesses by cooking meat to 74°C.

Controlled Varibles

•  Kitchen 
•  Petri dishes 
•  Agar Powder 
• Sterile environment
• Same Thermometer 
• Same places temperature taken
• Same pizza
• Swabbing tecnique

Manipulated variables 

• Temperature of the food
• Types of food: Beef Cheese Dough (Not testing effect of different types of bacteria on different foods I am using it to back up my hypothesis)

Responding variables

• The amount of bacteria colonies that grow

Materials:

• Agar Agar Powder
• Bleach
• Beef broth 
• Sugar
• Filtered water
• Isopropyl alcohol
• Paper towel 
•  Cheese and beef uncooked Pizza
•  40 petri dishes (You actually only need 39, but I would get 40 just in case 1 breaks)
• Stove
• Pot
• Pan
• Q-tips^r
• Soap
• Thermometer 
• Measuring Cups
• 2 big bowls (or 2 other big things) to hold the bleach and Isopropyl alcohol 
• Tongs
• Cup
• Plastic Wrap
• Microwave
• Glass cup
• Sharpee^r

Procedure:

1. Wash your hands
2. Saturate a paper towel with Isopropyl alcohol and sterilize your counter
3. Fill your sink with soapy water
4. Put the petri dishes in the sink full of soapy water (make sure they are all completely submerged in the water)
5. While you let the petri dishes soak in the soapy water fill 1 of the bowls with 9 cups of water for every cup of bleach and the 2nd bowl with 1-2 cups of Isopropyl alcohol
6. Take the saturated paper towel and sterilize the glass cup with it
7. Submerge all the Q-tips^r in isopropyl alcohol and put them in the cup and cover it with plastic wrap 
8. Take 1 one petri dish rinse it with water then shake the petri dish lightly making sure the petri dish is somewhat dry and put it into the bowl with the bleach then repeat with the other 39 petri dishes. If you run out of space in the bowl for all the petri dishes to be submerged do steps 9 and 10 (below this one) then repeat this step again.
9. Then dip the tongs into the bowl with Isopropyl alcohol
10. Place one of the Q-tips^r down on the counter, then take one of the petri dishes with the tongs and gently dip it in the isopropyl alcohol then place on top of the Q-tips^r to dry (make sure that it is at an angle not completely covering the Q-tip^r), do the same with all the others except instead of putting them on the Q-tip^r put them on top of each other
11. While the Petri dishes are drying mix water sugar and beef broth wait for it to boil then add the agar powder and bring mixture to a simmer
12. Then take the mixture off the heat and cool for about an hour or until cool enough to touch
13. Then poor the mixture into the petri dishes (put the lid at a pack man shape to reduce bacteria from the air from settling on the agar)
14. Then put lid back on petri dish and wait about an hour for it to set
15. Label the petri dishes with a felt marker
16. Take one of the sterile Q-tips^r and gently rub it against the agar making sure that every side eventually touches the agar on the conrol dish reapeat for the second control
17. Then take the uncooked (23^oC) pizza and gently roll one Q-tip^r on each ingredient (Beef Cheese dough) and gently roll (making sure that all sides of the Q-tip^r touch the agar) the Q-tip^{​​​​​​​r} on the agar in the petri dish labeled with the same lable then reapeat 2 more times so that you have 3 samples for each ingredient
18. Put the pizza in the oven checking occasionally, to see what temperature it’s at
19. Repeat step 17 for each temperature 50°C (122°F), 60°C (140°F) and 74°C (165.2°F) 
20. Now wait about 3 days for the bacteria to grow then count how many colonies grew!

While I was counting how many bacteria colonies grew I noticed there were 6 main types of bacteria colonies. Those 6 main types were:

Colony A is bigger then colony B, is translucent, and is oddly shaped

Colony B is smaller then colony A, opaque, and circular

Colony C is brown, watery, and translucent

Colony D is orange, watery, and opaque 

Colony E is tiny. the further apart they got from each other, the bigger they got. The closer they got to each other the smaller they got

Colony F looks colony A but is less white and is more watery then A

All the samples at 23°C grew a lot of bacteria.The samples at 50°C and 60°C on the other hand had less colonies than 23°C so it was clear they had been cooked. The samples at 74°C had significantly less bacteria then 23°C, 50°C, and 60°C having no or very little bacteria that grew.   

+++ = too many colonies to count

I saw that lots of bacteria grew at 23°C. I also noticed that there were different types of bacteria for each food. Type A was the only type that actually appeared on all the samples ,and Type A was only on the edges where we didn’t swab. This lead me to believe that Type A was a contaminant. My suspicions were confirmed when I looked at the different temperatures each one had roughly the same amount of Type A around the edges without any big increases or decreases. I noticed that all the samples at 74°C had no bacteria (except Type A),  therefore cooking your food to 74°C must kill all the bacteria because it is too hot for the bacteria to survive.

According to Alberta Health Services (AHS) and Centre for Disease Control (CDC) you should cook your food to at least 74°C. I did 3 samples of each food at 74° (which makes 9 samples total) and none of them grew any bacteria. Therefore, my results prove that they are correct and you should cook your food to at least 74°C.

This experiment is important beacause it shows how important it is to cook foods to an internal temperature of at least 74^oC. It is important to cook your food to 74^oC because it can prevent people from getting sick, ending up in the hospital, or dieing. These things are especially important when thinking about public places, events and even at home! Think about the daycare outbreak if the food that had been cooked to 74^oC and stored it properly then that entire outbreak could have been avoided! At one of my moms community events this was also really important, they thought that precooked meat didn't need to cooked to 74C, but she told them  that it was important and backed it up with all my reasearch and experiments which probably stopped an outbreak in our neighbor hood! It is important to remeber these things at home because it isn't nice to get sick and again it can make you more then just sick, it can make you really sick, it can even make your kidneys fail and you would have to go through dialysis. That is why it is important to cook your food to 74^oC.

Sources of Error 

I kept forgetting to do the pacman method (which helps decrease the amount of contamination) if I had remembered this it probably would have helped me prove further that my results were accurate. This would have made my results more acurate because it would have been less likely that something fell into the agar and contaminated it.

• https://www.canada.ca/en/health-canada/services/general-food-safety-tips/safe-internal-cooking-temperatures.html
• https://www.cdc.gov/foodsafety/keep-food-safe.html
• https://www.cdc.gov/foodsafety/foodborne-germs.html
• https://teach.genetics.utah.edu/content/microbiology/media/
• https://www.wikihow.com/Create-Agar
• https://sciencing.com/make-nutrient-agar-home-6317533.html

I would like to acknowledge my dad for all his help throughout this project and my little brother for being so enthusiastic about helping me with this project.