Wednesday, July 8, 2009

Gratawn, Santol

Here's an amazingly delicious fruit that's difficult to find outside Southeast Asia.

The closest thing to an English name for the fruit would be "Santol", from Tagalog. The Thais call them "gra-tawn". You gotta say the first syllable staccato-like.

How does it taste? That's a difficult question. No other fruits come to mind as a reference. Looking at its lineage, you can see why:

Species: Santol Tree (Sandoricum Koetjape)
Genus: Sandoricum
Family: Meliaceae
Order: Sapindales

The Meliaceae family contains about 575 different shrubs and trees, but the Santol is one of the few that produces a fruit of distinction. So, unless genomics proves otherwise in the future, it seems that the Santol is somewhat evolutionarily removed from run-of-the-mill fruits in your supermarket. Moving to the broader category of "order", you do find that Sapindales include ordinary citrus fruits, lychees, and more.

Another Meliaceae that produces edible fruit would be the Lansium Domesticum. The Thais call these fruits "longkang" and the Philipinos "langsat". This is a source for eternal confusion, since "langsat" in Thai refers to a particular variety of longkang. What's more, there's another fruit that we call "longan", but Thais call "lomyai". Not to be confused with loganberries. Longkang and longan look similar, but belong to different botanical families. Longkang are tasty. Somewhat woody. On occasions when I have the will to peel and de-seed the little fruits, I mix lime, longkang, sugar, and gin in a blender. I don't see the appeal of longan, though...they're kind of radishy.

You can see a few similarities between longkang and gratawn. They both have yellow, leathery skin, and a handful of seeds inside. In Thailand, the two fruits come into season in the same brief period...usually June and July. But gratawn are much bigger and taste different. Longkang resin will stick to your hands even after you soap them off, and the pulp will occasionally squirt in your eye. If you let a gratawn ripen fully, however, the flesh is custardy. The seeds are big and tough, so you cut a circle around them, twist the two hemispheres apart, and dig into the flesh with a spoon. The sweetest pulp surrounds the seeds, so you suck on the seeds.

The flavor is...still difficult to describe. Bear in mind that Meliaceae includes frankincense and myrhh and mahogany. There's something spicy going on. I'm guessing that the pulp is loaded with interesting terpenes like linalool, the distinctive fragrance of Froot Loops. When I worked as a chemist at a winery, we had bottle of linalool in the refrigerator. I'm not sure why, actually. Perhaps because the winemaker desired to make illegal midnight flavor adjustments, dripping a few drops into the tanks. Opening a bottle of pure linalool was something like finding yourself in the midst of an exploding Froot Loops factory.

A couple papers suggest the presence of catechins and proanthocyanidins in gratawn...these are more typically found in teas, fruit skins, cinnamon, cocoa, and tree bark.

I just cut a gratawn open...there's something banana-ish in there too.

Unfortunately, I haven't been able to dig up a full profile of the flavor components of gratawn in the academic literature. There are plenty of papers focusing on possible medicinal qualities of the bark and leaves, but no in-depth analysis of the qualities that make the fruit distinctive from an olfactory/gustatory perspective. Sounds like a decent Masters or Ph.D. thesis for someone interested in natural products chemistry.

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