When we include sliced bananas in desserts, they tend to turn brown very quickly. And the riper the banana, the faster it will seems to turn brown.So if you need attractive slices of banana for your desserts, choose those that are not too ripe and always use a stainless steel knife to cut them. When decorating a dessert or gateau, simply brush the banana slices with freshly squeezed lemon juice. Do not dip them in a bowl of lemon juice as this can make them slimy.
However, if you are mashing bananas, turning those slices in a bowl of lemon juice first not only keeps the flesh white but also encourages the slices to soften into a creamy paste. This would make the job of mashing easier.
** Asian Recipes