Subject: How can we test for acids in foods, expecially those that cause reflux?

We are trying to plan a project on the testing of the level of acids in foods.  
My daughter would like to do this as a science project but we can not find a 
way to test the foods for the acids levels.  Is there a way that would be 
easily understandable for a middle school student (without a chemistry or 
molecular studies background)?  she is very curious about this topic because 
her brother has acid reflux and would like to help him identify the foods that 
are can cause problems and then we would be able to make some informed 
decisions about how to modify the diet and offer better alternatives.

Re: How can we test for acids in foods, expecially those that cause reflux?