Expert: Paul Wagner - 5/23/2007

Question
I am trying to make a mango iced tea. I am using green tea leaves, and a clarified but not clear mango juice concentrate.  The mango is added after the tea is brewed, temperature is approx 70C, but a few days later the mango sediment turns quite a dark brown. How can I prevent the discolouration? Is it something to do with the temperature when mango is added (ie it starts getting cooked) or the pH?

Answer
Hi Daphne

This is a classic case of the mango oxidizing.  There are a couple of ways to prevent oxidation, including lowering the pH--but that would change the flavor a lot, or using sulfur dioxide ( not always a good idea for consumers).  

Think of the Mango as a apple that you have cut open--the more it is exposed to air, the more it turns brown.  So the other possible solution is to bottle this stuff under an inert gas ( nitrogen, or CO2) to protect it from oxygen.  Oxygen is what turns it brown.

Paul Wagner