In the item-view, tap on the food-item you would like to update. I will use an apple in this example.
This will bring up a detailed food-item view. Change the values you would like to and than press the back button on your phone.
Tap on “yes” in the “Save changes” dialog that appears.
To remove an item, do a long-press on the item you would like to remove. This will bring up the remove dialog. Tap on “remove”
In the item-view, press the menu button on your phone.
Tap on “Add new Item”. This will bring up the detail-item view
Now, just fill in all fields and hit the back-button on your phone. (you may leave the unit field empty).