freezing a bun or bread roll

We scientists do the strangest of things. We wanted to see the temperature changes when you freeze and thaw things. So we took a ‘bun’ (a bread roll), placed temperature sensors in and around it and eagerly awaited our results.
One probe was placed deep in the bun, one probe was placed its surface, and one was placed in the freezer itself.

What we did

We took a ‘bun’ (a bread roll), and placed one temperature sensor deep in the bun, one probe in its surface, and one in the freezer itself. We plugged the temperature sensors into a data logger and left it recording. After a few hours we removed the roll from the freezer to let it thaw.

Our results

This graph shows the temperatures in and around a bread roll as it froze and thawed.

You will find some of the questions easier if you put these results into your data logging software. Click here to get the results

Looking at the results

  • One probe was placed deep in the bun, one probe was placed its surface, and one was placed in the freezer itself. Look at the graph lines, and say or mark which line is which.
  • What is the normal temperature of the freezer?
  • After we opened the freezer door, how long does the air in the freezer take to get to get back to normal?
  • You’ll notice two kinks in the red line. What might be happening at those kinks?
  • There is water in the centre of the bun. What is its temperature and why doesn’t it freeze at zero degrees?
  • Why isn’t there a kink in the blue line?
  • What is the gradient of the red, blue and green graphs during the cooling?
  • What do these gradients tell you about freezing food for storage?

What you can do

Try this for yourself. You can choose the food, but do see how your results compare when you use fatty food.

This page was written by Roger Frost. Idea and experiment results by Laurence Rogers, Leicester University. Questions suggested by teachers Leeds.

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