In September, clusters of purple flowers crowd the top of the trellis. The hyacinth bean is a short-day plant, so it only sets flowers once the days start to shorten. All summer long, the vine did nothing but put out leaves. Around now, the flat pods begin to appear. Pick a few and you'll notice some are still soft and pliable, while others are already lumpy where the seeds have filled out. That difference decides what you'll do with them at dinner tonight.
Soft Pods and Mature Seeds Need Different Treatment
The hyacinth bean is an annual climbing vine in the legume family. India grows more of it than anywhere else, and it's also widely planted in Bangladesh, Kenya, and Tanzania. It grows best between 22 and 30°C. It handles heat and drought well, but a single late frost will kill it. In the Northern Hemisphere, seeds go in the ground in May, and the harvest runs from August through October.
What you do with the harvest depends on how ripe it is. Young green pods, picked before the seeds mature, can be blanched and stir-fried the way you'd cook green beans. Fully mature seeds get soaked overnight and then cooked separately. Mature seeds should always be soaked and cooked thoroughly before eating. The seeds contain lectins and trypsin inhibitors, and how much of these survives depends heavily on soaking and heating. Studies have also found that a good deal remains when the seeds are cooked briefly at lower temperatures. For that reason, we don't recommend putting raw seeds in the pot with your rice and cooking them together.
Blanch the Young Pods Briefly, Then Stir-Fry
A young pod has smooth skin and still feels juicy when you press it. Snap off the stem end and pull the string down the length of the pod. Drop the pods into boiling water for just 3 to 4 minutes, then lift them out. A pinch of salt in the blanching water helps them keep their color. Next, give them a quick stir-fry in an oiled pan over high heat. If you blanch them too long, the pods go soft and lose their pleasant bite.
Deep purple pods and flowers contain anthocyanin pigments, and the amount reportedly varies a lot from one variety to another. Studies have also shown that these pigments leach into the water as the pods cook. A shorter blanch means less color lost. This is simply a note about the pigments, not a claim about health benefits.
Spoon the Mature Seeds Over Rice
In the evening, put the mature seeds in a bowl, cover them with plenty of water, and let them soak overnight. The next day, move just the soaked seeds to a pot and simmer them until they're tender all the way through. Cook your rice as usual, and during the final few minutes, while the rice rests and steams in the covered pot, scatter the cooked beans over the top. The beans mix evenly through the rice, and you won't have to worry about them coming out undercooked.
Hyacinth bean seeds contain plant protein and dietary fiber. Dietary fiber is made up of polysaccharides that pass through the gut undigested until they reach the large intestine, where they ferment. Stirring just a few spoonfuls of beans into a bowl of rice gives you more protein than eating the grain on its own.
Add a Slice of Ginger to the Pan
The Dongui Bogam, the classic 17th-century Korean medical text, lists the hyacinth bean as 藊豆 in its section on grains (穀部). It records the Korean folk name as byeondu-kong. The book also explains another name: because the seeds are black with a white stripe that looks like a magpie's plumage, they were called 鵲豆, the "magpie bean." It notes that the beans come in black and white forms. By its account, the white ones are warming, the black ones slightly cooling, and only the white ones are used in medicine. It describes their flavor as sweet and says they contain no toxins. The text gives preparation instructions, which are to skin the beans, toss them in ginger juice, and dry-roast them. Right next to that, it warns that people suffering from chills and fever should not eat them. These are the records of a historical medical text and do not reflect the views of modern medicine.
Of all this, the ginger is what has lasted in kitchens today. Slice a little ginger into the pan when you stir-fry, and it tames the beany flavor. You can also toss the cooked seeds with a spoonful of ginger juice ahead of time and then stir-fry them. Here's what pairs well with hyacinth beans:
- Ginger: Slice it into the pan before stir-frying to cut the beany taste.
- Salt: A pinch in the blanching water keeps the pods from fading.
- Rice: Scatter the cooked seeds on top while the rice rests and steams.
- Oil: Stir-fry the blanched pods quickly over high heat.
Today, start by picking the soft pods off the trellis. Put the ones with filled-out seeds in a separate bowl and cover them with water. Tomorrow morning, you can simmer them and spoon them over your rice.
Source: Dongui Bogam, Grains section (穀部), 藊豆
