There are over 1,500 foods in the app's food database, with over 246,000 extra foods (worldwide) available through the scan function. Foods which are not in either of these two databases must be added manually but, once this is done, they are stored in your app for future use.
The scan function is powered by OpenFoodFacts.org. This is a communal database. You can therefore log into their website and add the new food. As such, you and the whole community can benefit from this new food in the scan function.