Passion fruits grow on vines, and are native to South America. There are purple and yellow varieties, and the fruits vary in size from about the size of a plum to the size of a grapefruit. They have a taut shiny skin when freshly picked, and their skin becomes shriveled and wrinkled as they ripen. Their flavor is very astringent and refreshingly tart when the fruit is fresh. Their flavor becomes sweeter and more complex as the fruit ripens. Some people like to wait until the fruits are overripe and the pulp has an almost fermented taste.
Passion fruits have a gelatinous seed-filled pulp which can be easily scooped out with a spoon. Gently heating the pulp in the microwave or on the stove makes the pulp more liquid and easier to strain. Strain the warm pulp through a fine sieve to remove the seeds. The seeds are sometimes reserved to use as a decoration. You can find frozen passion fruit pulp in many grocery stores and latin markets. Bottled passion fruit juice is often contains sweeteners and other ingredients.