Science Buddies: "Ask an Expert"

Hi experts,

I'm a student in grade 11 and as a part of my science research paper, I need to do an experimental investigation.
I was interested in doing something related to chemicals found in the skin of apples, and whether or not reacting the skin with strong acids would remove the toxins present. After some research, I found out that diphenylamine is usually applied to prevent the skin from turning brown. I also found out that reacting diphenylamine with acids would form salts.
I wanted to know if I can actually find diphenylamine in local store bought apples? Would the experiment really work, if I peel the skin and react it with acids?

If not, please let me know about alternative investigations that can be done relating to this topic.

Thank you so much!

Hi Priyanka,

You have a great idea for a project--unfortunately it would require a university chemistry lab to do it.

Yes, diphenylamine could react with an acid, but then how would you measure it? Apple trees are sprayed with pesticides, fungicides and probably other chemicals, but detecting residues of these chemicals in the fruit requires some very complex and expensive apparatus such as would be only found in a university research lab.

I don't know of a project where you can neutralize a chemical such as diphenylamine in the skin of an apple. Other experts--any ideas?

You could compare an organically grown apple that has presumably not been exposed to any pesticides, fungicides, stabilizers, dyes or whatever, to a non-organic apple. The problem is what to use as your dependent variable. One thing I thought of was to just cut a piece of apple of both types, leave it out at room temperature on a plate inside a cupboard and photograph the two pieces every day for a couple of weeks. Your hypothesis might be--an organic fruit will rot quicker than a non-organic one.

For a more elaborate project you would need some organism that you could use to test an extract of the fruit on. This could be bakers yeast because you can measure its activity by how much carbon dioxide (CO2) it produces. You could core apples of both organic and non-organic types and puree them in a food processor with a little distilled water (DW). Filter the resulting puree through a coffee filter (rinsed with DW first) to get an apple extract.

Scibuddies has a project using bakers yeast in which the activity is determined by measuring the amount of CO2 produced: https://www.sciencebuddies.org/science- ... #procedure

You can use this method to compare an extract from an organic apple to one from a non-organic. My guess is that the organic apple extract will result in more active yeast.

Let us know if you like any of these ideas and if you need more help.

Sybee