Yuja (Yuzu)

Health Benefits

What the old record says. Yuja appears in the Donguibogam's fruit section as yuja. The entry separates it from the mandarin by its larger size and thicker rind, and treats the fragrant peel as the part that matters. This is a record from a seventeenth-century medical text, not a modern medical judgement.

What studies have observed. Studies have reported on antioxidant markers and aroma compounds in yuja peel extract. Human trials are few, so this cannot be restated as an effect on any disease.

Nutrition

• Vitamin C (About 105 mg per 100 g of whole fruit, peel included) — High even among citrus
• Hesperidin (A flavonoid in the peel and white pith) — Commonly reported in citrus peel
• Limonene (The main aroma compound in the oil glands of the peel) — Gives yuja its distinctive scent
• Pectin (The soluble fibre of peel and membrane) — Why the syrup thickens

Vitamin C The national food composition table puts yuja at about 105 mg of vitamin C per 100 g, measured on the whole fruit with the peel included; as with the aroma, more of it sits in the peel. The preserve is a different story: it takes an equal weight of sugar, and a mug of yuja tea contains only a spoonful of actual fruit. Making it without heat and keeping the jar refrigerated limits the losses.

Flavonoids in the peel Hesperidin and naringin concentrate in the peel and the white pith. The bitterness comes from naringin and limonin; hesperidin itself is close to tasteless. Stripping all the pith reduces the bitterness but takes those compounds with it. Slicing finely so the bitterness spreads out is an easier balance to strike.

The sugar in the preserve Yuja preserve is normally one part fruit to one part sugar. Two spoonfuls in a mug means about 15 g of sugar. Several mugs across a day add up fast. Cutting the sugar invites mould, so instead of reducing it, refrigerate the jar and use it within two months.

Pairings

○ Ginger and honey — Thin slices of ginger layered into the preserve make a good winter drink. The heat of the ginger holds down the bitterness of the peel. Replacing part of the sugar with honey lowers the total sugar. Ginger

○ Radish or pear salad — A little yuja juice takes the sharp edge off raw radish. Shred the peel very finely into the mix and the aroma carries. Let it sit ten minutes after dressing so the scent spreads. Asian Pear · Korean Radish (Mu)

○ White fish and shellfish — Juice and grated peel cut the fishy note. Long cooking drives the aroma off, so add it at the end. Use only the coloured outer layer, not the pith.

△ The preserve if you are managing blood sugar — Half the weight of yuja preserve is sugar. Thinking of it as fruit and drinking it often adds up quickly. If you are managing blood sugar, cooking with the fresh fruit and peel is the better route. When you do drink it, one spoonful per mug with plenty of water.

△ Using unwashed peel — This is a fruit you use whole, so how you wash it matters. Scrub with coarse salt, rinse under running water, then dip in boiling water for ten seconds. Anything lodged in surface blemishes will not come off with water alone.

△ If you take regular medication — Grapefruit juice is well known for inhibiting liver enzymes involved in drug metabolism, and related compounds have been reported in yuja, a fellow citrus. The effect is described as weaker than grapefruit's, but check with your pharmacist before making a strong daily drink of it.

Varieties

• Native yuja (Sapling) — The long-grown Korean line. Thick peel, deep fragrance.
• Seedless yuja (Sapling) — Few seeds, so less work when making syrup.
• Green yuja (Sapling) — Picked unripe in September. A sharper, brighter scent.
• Yuja on trifoliate rootstock (a rootstock difference, not a cultivar) (Sapling) — Grafted onto trifoliate orange rootstock. Slightly hardier and stays smaller.