Re: Can you please explain the process of enzymatic oxidation in apples?

Hi Bon,

You have made some interesting observations from your apple experiments. What you have seen is enzymatic browning. There are a number of substrates for polyphenol oxidase (referred to as phenolic acids). As you stated, oxygen is required for enzyme activity. In the intact apple (unpeeled) the enzyme and substrates are separated and browing doesn't take place. When you peel the apple the enzyme and phenolic acids can interact along with oxygen to cause browning. The brown color that occurs when fruit is bruised is a result of this enzyme system. for more detailed information on the enzyme reaction you can go to the following website. http://chemistry .about.com/science/chemistry/library/weekly/aao52499a.htm?iam=dpile&t erms=52Benzymatic+52Bbrowning

For an actual laboratroy experiment, you might visit the following website http:// class.fstohio-state.edu/FST605/Laboratories/Lab7.html

I don't believe you can make the generalization that all pale skined apples will demonstrate less browning. Browning will be influenced by the parents used to breed a particular variety, growing and storage conditions, etc. I have seen some newer varieties, which are fairly red skinned but demonstrate minimal brwoning.

I hope this information is of assistance.

Al Bushway
Professor of Food Science