The best way to tell if a passion fruit is ripe is by looking at the fruit's skin color; a purple-skinned passion fruit is considered to be ripe. If the passion fruit's skin has any green tint to it, it is not ripe yet. For the best-tasting passion fruit, wait until the skin wrinkles a bit, as the fruit will have a sweeter flavor.
As a native fruit of Brazil, passion fruit is similar to a pomegranate in that it has pulp on the inside that features edible seeds. The inside of a passion fruit is yellow, and its seeds are black. On average, the fruit grows to be about the size of a large egg, but it can grow to be three times that size.