The good news is . . . . . you won't need to practice on 20 bananas! But you might plan on using more than what you want to make because there is a trick to getting it right. I will try and walk you through my experiments so you won't make the same mistakes that I did.
I used store bought flavored jell-0 for the jello filled banana because it worked better.Ingredients:
Fruit juice (I am not sure about pineapple juice though)
Knox unflavored gelatin or Agar Agar.
Greenish firm Bananas
Lemon juice approximately 2 Tablespoons, used to help prevent browning on the bananas
Sweetener if desired
Funnel, ladle or spoon
Tiny heart shaped cookie cutter
Tooth pick is helpful
A bowl or something to prop the banana up as well as the banana end as shown in the pictures.
I made some banana jello that was made using apple juice, Knox unflavored gelatin and the banana. I blended the juice together with the banana and followed the recipe. It tasted very good. The color was off unfortunately, so I did not use it. I thought it would be awesome to make a banana jello filled banana! It tasted just like a banana only it had a different texture!