Fruit of the Month: Cas
When I first moved to Costa Rica, the backyard behind my rental house had a towering tree that was called "cas." It was January, and small, spherical green fruits covered the ground. My friendly landlady indicated that I could collect as many as I wanted to make a fruit drink, and so I gladly gathered up a bunch to throw in the blender.
Several weeks later, as my landlady and I were sipping a particularly delicious batch of the tart nectar, she asked me about my preparation process. I painstakingly explained how I collected the smaller, softer fruits (they're a little sweeter), blended them with sugar and water, and then strained everything in a colander to achieve the perfect consistency. Cool as a cucumber – and still drinking her juice, I might add – she asked if I bothered to remove the worms. The what?
That was the day I learned that almost every cas fruit has at least one small, white worm inside – like good tequila or a cartoon apple. Most people don't bother to remove them, although some do cut the fruits into small pieces in order to weed out the little creatures. By the time I made my discovery, I can honestly say I was too hooked on the juice to worry about a little extra protein. Cas is that delicious!
This small, green fruit (Psidium friedrichsthalianum) is known as Costa Rican guava or sour guava. A staple on Costa Rican tables, ripe cas is almost exclusively used for drinks, since its tart flavor, like a mix between lemon juice and white grapefruit, is usually too strong to eat plain. Green, or unripe cas, are also delicious, and sold on the street as a crunchy treat topped with a sprinkling of salt.
Cas is available year-round, but is most common from December-February and again from June-August. You can pick some up at the farmers' market or grocery store for about $2 a pound. Look for yellow fruits with no major bruising; brown spots on the skin are normal and do not affect flavor. Tastes vary, so be sure to check out different levels of ripeness – greener fruits are crunchy and less tart, and very yellow fruits are a little bit sweeter – to see which best suits your palate.
1-2 liters water
Sugar, to taste
Blend cas fruits, water and sugar. Add sugar slowly and taste as you go, since overly sweet cas juice will not be refreshing. If you're worried about fruit flies or worms, cut the fruits open to remove the worms. Alternatively, you can boil the fruits for a few minutes to sterilize the skin.