Science Fair Projects on the Effect of Temperature
on the Growth Rate of Bacteria in Meat

Purpose

The first purpose of this experiment was to determine the effect of temperature on the growth rate of bacteria in meat.

The second purpose of this experiment was to determine the effect of temperature on the types of bacteria that grow in meat.

I became interested in this idea when my mom would thaw out the meat in the sink then leave it there until we cooked it. I wondered how long it took the meat to spoil in different temperatures.

The information gained from this experiment could help homemakers and the food service industry protect people from food poisoning. Hospitals, schools, and restaurants would all benefit.

Hypothesis

My first hypothesis was that the most bacteria would grow in the temperatures between 21° and 37° Celsius.

I based my first hypothesis on a statement made my the U.S Department of Agriculture's Meat and Poultry Hotline that said “Bacteria grow most rapidly in the range of temperatures between 21° and 37°C. If the temperature is above 32°C, food should not be left out more than one hour.”

My second hypothesis was that the four main types of bacteria that would grow were Staphylococcus aureus, Salmonella enteriditis, Escherichia coli O157:H7, and Campylobacter.

I based my second hypothesis on another statement made by the U.S. Department of Agriculture’s Meat and Poultry Hotline which said “leaving food out too long at room temperature can cause bacteria (such as Staphylococcus aureus, Salmonella enteriditis, Escherichia coli O157:H7, and Campylobacter) to grow to dangerous levels that can cause illness.”

Experiment Design

The constants in this study were:

•  Amount of Meat
•  Temperatures Used
• Sterile knives and grinder
•  Autoclave
•  Incubator and incubation temperature
•  Petri Dishes
•  General test method

•  Freezing (0ºC)
•  Refrigeration (4ºC)
•  Room Temperature (20ºC)
•   Body Temperature (36ºC)

•  Hamburger
•  Sausage
•  Steak
•  Chicken

Materials