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Food Science Science Fair Project

Investigating Baby Food Contamination

Investigating Baby Food Contamination | Science Fair Projects | STEM Projects
We're going to explore what happens when baby food is left out of the fridge for different amounts of time. We'll measure the rate of bacteria growth in the food and see if it changes depending on how long it's been left out.


The hypothesis is that baby food will become more contaminated when it is left out for a longer period of time.

Method & Materials

You will label three bottles of each type of baby food (chicken, pumpkin, and apple) with A, B, and C. Bottle A will be placed in the fridge for 24 hours, bottle B will be left out for 30 minutes before being placed in the fridge, and bottle C will be left out for 24 hours. After 24 hours, you will take a sample from each bottle and place it in a petri dish. You will then measure the size of the bacteria colony after 3 days.
You will need 9 petri dishes prepared with blood agar, 3 bottles of chicken baby food, 3 bottles of pumpkin baby food, 3 bottles of apple baby food, a refrigerator, 9 sterile cotton buds, and a permanent marker pen.


The results showed that the specimen that was left outside for 24 hours had the highest rate of bacteria growth. The chicken specimen had a larger bacteria colony than the pumpkin and apple specimens.

Why do this project?

This science project is interesting because it shows how quickly bacteria can grow on food that has been left out of the fridge. It also shows the difference between different types of food in terms of how quickly they become contaminated.

Also Consider

Variations of this experiment could include using different brands of baby food, or repeating the experiment using milk, porridge, and soup. Another variation could be to dip a used spoon (containing baby saliva) into the bottles of food and observe the results.

Full project details

You can find additional information and details for this science fair project here. Have fun exploring!

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