How can i test sugar or protein levels in food?

Question

I need to conduct an experiment in chemistry to test either sugar levels or protein levels in commercially produced food. I'm thinking of testing the sugar levels in apple juice and I'm wondering how to go about this. I need to obtain a quantitative result.

Thanks in advance.

Answer 1

The sugar in apple juice is a mixture of glucose an fructose at a ratio of about 1 to 4.

The easiest way is a photometric enzyme test. It allows to measure the both sugars in a single run. In the course of the reaction, an coenzyme NAD is reduced to NADH and the extinction change at a wavelenth of 340 nm can be followed in a photometer.

A second way is to use the reducing properties of the sugars. You will find an experimental setup under the keyword "Luff Schorl".