What is this vial for in this package of grass jelly?

Question

Recently I bought a package of grass jelly. My understanding of the instructions is that I should mix the powder in the package with a liter of cold water and 100g of sugar and then heat on a stove until it thickens. However, there is also a little vial of liquid in the package labelled "dầu chuối" which google translate tells me is "banana oil" and I don't see anything about it in the instructions. Is this something optional to add at the end for flavoring? Should I add it at the beginning? Or should I just not be consuming it at all?

Answer 1

Ok, did a little more hunting and found this link which says:

Some packages contain a sugar packet and a small tube of banana essence. The banana essence can be a bit strong, but if you enjoy it, add during the last minute of cooking.

Answer 2

In most (or all) sweet soups or jelly-like cakes like this, we use banana oil when the soup is being served. Just drop 2 or 3 drops to give aroma to the sweet soup bowl.

Don't put it when you are cooking, the oil will evaporate.