I am currently a high school student doing their Biology IB IA. For those who don't know, an IA is, in simple terms, an experiment that you design and execute yourself. My topic is "The effect of temperature on lactase activity in milk".
However, to determine the effectiveness of lactase, I need a reliable method to measure how much lactose will remain in a sample of milk (or some other dairy product if milk doesn't work). So far, what I've seen online calls for some highly advanced equipment that a high school lab does not exist. I am open to all methods (titration, measuring mass, chemical reactions, etc).
What can I do to measure this?