In the Northern Hemisphere, when October arrives, the fruit at the tips of yuja branches slowly turns from green to yellow. (Yuja is the citrus many people know by its Japanese name, yuzu.) Reach between the thorns, rub one, and a rich fragrance stays on your fingertips. Most of that scent comes from the peel. If you've ever had yuja tea, you may remember the bits of rind at the bottom of the cup. In Korea, people slice the whole fruit thin, peel and all, and pack it in sugar to make yuja-cheong, a chunky citrus syrup somewhere between marmalade and tea concentrate. A spoonful stirred into hot water makes the tea. So how did an early 17th-century medical text describe a fruit valued mostly for its peel?
Yuja (柚子) in the Fruit Section of the Donguibogam
The Donguibogam is a medical encyclopedia compiled in the early 17th century by Heo Jun, a royal physician of Korea's Joseon Dynasty. It gives yuja (柚子) its own entry in the Gwabu (果部), the section on fruits. The text says the small fruit is called gyul (mandarin) and the large one yuja. It adds that yuja looks like the deungja (橙子, another kind of citrus) but is bigger than a mandarin. In other words, the book used the name yuja for the fruit that was larger than a mandarin and had a thicker rind. The entry focuses mainly on the fragrant peel.
The yuja in the original text is the fruit of a tree in the rue family (Rutaceae). It's the same fruit people enjoy today as yuja-cheong and yuja tea. Keep in mind, though, that this is what a historical medical text recorded. It is not the view of modern medicine. You can read the original entry heading and its explanation in the yuja entry of Homiclub's Donguibogam.
What's in Yuja, According to Modern Research
The main compounds in the juice and peel of yuja (Citrus junos) are:
- Vitamin C: yuja has more than most citrus fruits.
- Hesperidin: a compound commonly found in citrus peel.
- Limonene: the source of yuja's distinctive aroma.
- Pectin: what makes yuja-cheong thick and syrupy.
The old record and modern science overlap at the peel. The Donguibogam focused on the fragrant rind, and modern researchers have also studied yuja peel extracts, measuring antioxidant markers and aroma compounds.
They also differ. The old text identified yuja by the size of the fruit and the thickness of its rind, while today we describe it by its chemical compounds. The research so far has looked at peel extracts, and there are still few studies in people. That makes it hard to claim yuja prevents or cures any particular disease. For now, the evidence supports eating it as a winter fruit rich in vitamin C, and not much more.
Growing Yuja in Your Garden
Yuja is native to China and widely grown in Korea and Japan. It handles cold better than most citrus trees, so it can get through winter in cooler places than mandarins can. Still, if your winters are long and the ground freezes deep, it's safer to grow it in a large container and move it indoors to a frost-free spot in the coldest months.
Plant in March to April (Northern Hemisphere). Trees grown from seed take a long time to bear fruit, so buy a grafted nursery tree and plant it in full sun, in soil that drains well. Harvest in October to November (Northern Hemisphere). The branches have thorns, so wear thick gloves. Once the peel turns yellow, cut each fruit off at the stem with pruners. For planting times and key nutrients at a glance, keep the yuja entry in our Crop Guide open as you read.
Bringing Yuja to the Table
Along with its fragrance, yuja peel has some bitterness. Because you eat the peel, scrub the fruit well under running water before using it. The right pairings tone down the bitterness and keep the aroma.
- Ginger and honey: when you make yuja-cheong, try adding thin slices of ginger to the jar. Ginger's sharp, spicy aroma makes the peel taste less bitter. You can also replace some of the sugar with honey and use less sugar overall.
- Radish and Asian pear saengchae (a raw salad of shredded vegetables tossed with seasonings): a little yuja juice softens the sharp bite of Korean radish. Toss in some very finely shredded peel and let the salad sit about 10 minutes before serving so the fragrance spreads through it.
- White fish and seafood: a sprinkle of yuja juice and zest cuts fishy smells. Long cooking dulls the aroma, so add it once the dish is done. Use only the yellow outer peel and remove the white pith.
Tonight, try finely shredding the outer peel of one yuja and scattering a little over a radish salad or grilled fish at dinner.
Source: Heo Jun, Donguibogam, Tangaek-pyeon (Materia Medica), Fruit Section (果部), "Yuja" (柚子).
