Re: Can a colorimeter be used to determine the change in colour of cut apple?

Hi Alyssa,

This sounds like an interesting experiment. I think that you could use a colorimeter for this kind of measurement. You would first have to mash up your apples in some sort of solvent. I would suggest that you try water first, but you may find that other liquids work as well (or better) - there's another variable for your experiment! Then you would need to remove all of the solid matter so that you were left only with the brown colour in solution. You could try filtration or low-speed centrifugation, if you have access to a centrifuge. Finally, you prepare a "blank" (containing only solvent, no apple colour), use that to zero the colorimeter and take your measurement. You might have to play around to get a good reading by making the solution more concentrated (if the reading is too low) or diluting it (if the reading is off the scale).

An important factor in your experiment will be reproducibility. You should use the same amount of apple each time, extract the brown colour in the same way and ensure that other factors (such as temperature) are constant. You might want to do your experiment several times and do some simple statistics when you get the readings (such as finding the mean, standard deviation and standard error of your values). You will also want to determine whether the rate of browning is linear or not, by plotting your values over time to see if you get a straight line. Finally, you will want to express the values correctly - something like "units of brown colour per gram of apple per minute".

It may be difficult to get reproducible results using a colorimeter. Another idea might be to use a slice of apple and take a digital photograph of the slice over time. You could probably use some computer program to measure the area of the slice and the coloration of the image.

I hope that these ideas help you plan your experiments. Try searching the web for some of the words in italics to learn more about planning and analysing experiments. The Google search apple browning measure will help you too - a few people have thought about this before!