In class, we did a lab testing substances for four different macromolecules (Protein, glucose, starch and lipids). These substances included egg whites, egg yolks, potatoes, apples, onions, strawberries and lemons. My substance was onion, which tested positive for protein and glucose and negative for starch and lipids.
This plant website explaining starch has an excerpt that says "Bulbs like garlic and onion store food in the form of sugar rather than starch."
Through this lab, we were able to find out what substances had what in them. This lab was extremely interesting because we could test things that we eat in our everyday lives.