Tuna mayo onigiri is a Japanese rice ball filled with canned tuna mixed with mayonnaise, then wrapped in crisp nori. It makes a practical lunch or snack, and this home-style version keeps the rice simple so the savory, creamy filling stands out.
Ingredients
- 2 cups (370 g) Japanese short-grain rice, uncooked
- 2 1/4 cups (530 ml) water, for cooking the rice
- 1 can (5 oz / 142 g) tuna in water or oil, drained; this is about 4 oz (113 g) drained tuna
- 1 tablespoon (15 g) Japanese mayonnaise; or use regular mayonnaise
- 1 teaspoon (5 ml) soy sauce
- 1 tablespoon (8 g) toasted sesame seeds
- 2 tablespoons (12 g) finely sliced scallion
- 1/8 teaspoon (0.3 g) ground black pepper
- 1/2 teaspoon (3 g) fine salt, for shaping
- 2 tablespoons (30 ml) water, for wetting your hands
- 2 sheets (about 5 g) roasted nori, cut into 8 strips
Instructions
- Rinse the rice. Put the rice in a bowl, cover it with cool water, and gently swirl it with your fingers. Pour off the cloudy water and repeat until it is much less milky, usually three or four rinses. Drain the rice well in a fine-mesh sieve for a few minutes. Rinsing removes loose surface starch and helps the cooked grains stay distinct while still sticky enough to shape.
- Cook the rice. Transfer the drained rice to a heavy saucepan with the measured 2 1/4 cups (530 ml) water. Cover with a tight-fitting lid and bring to a boil over medium-high heat, which takes about 4 to 5 minutes. As soon as it boils, turn the heat to low and cook, covered, for 15 minutes. Avoid lifting the lid or stirring; either can interrupt the steaming and leave the rice unevenly cooked.
- Rest the rice and mix the filling. Take the pan off the heat and leave it covered for 10 minutes so the rice can finish steaming. While it rests, flake the drained tuna into a bowl and stir in the mayonnaise, soy sauce, sesame seeds, scallion, and black pepper. Break up large pieces but leave a little texture. The filling should hold together when spooned, not be runny; if the tuna was packed in oil, drain it especially well.
- Prepare a shaping station. Fluff the rice gently with a rice paddle or fork, lifting and turning rather than mashing it. Stir the salt into the small bowl of water. Set out the tuna filling and nori strips. The rice should be warm enough to shape comfortably, not so hot that handling it is difficult. Keep the bowl covered between portions so the rice does not dry out.
- Shape the onigiri. Wet your hands with the salted water, shake off excess, and take about 3/4 cup (roughly 120 g) cooked rice. Cup it in one palm and make a shallow hollow in the center. Add about 1 tablespoon of tuna filling, then cover it with rice from the edges. Press and turn gently into a triangle, using enough pressure to make it hold but not enough to crush the grains. Repeat to make eight rice balls, rewetting your hands whenever rice begins to stick. If shaping by hand feels awkward, use a lightly moistened onigiri mold or shape the rice into rounds.
- Wrap and serve. Place one strip of nori around the base or across one side of each rice ball, with the rough side facing the rice. For the crispest nori, add it just before serving. Serve warm or at room temperature, and do not leave the tuna-filled rice balls out for more than 2 hours.
Tips
- Use the right rice. Japanese short-grain rice is stickier than long-grain rice and makes the balls easier to shape. Sushi rice is a suitable short-grain choice, but do not season it with sushi vinegar for this recipe; plain rice is the usual base for onigiri. Medium-grain rice can work in a pinch, though the shapes may be more fragile.
- Drain the tuna thoroughly. Excess liquid or oil can make the filling seep into the rice and weaken the shape. Press it gently with a fork against the side of a sieve. If the mixture still seems loose, add a little more flaked tuna rather than piling in extra mayonnaise.
- Keep your hands damp, not soaking wet. A little salted water keeps rice from sticking and seasons the outside lightly. Too much water makes the rice slippery and can make the onigiri fall apart. A small bowl of water beside the work area is easier than repeatedly washing your hands.
- Choose a mayonnaise that suits you. Japanese mayonnaise is often tangier and richer than standard American-style mayonnaise. Regular mayonnaise is a practical substitute; the filling will taste a little less tangy. Add a few drops of rice vinegar only if you want that extra brightness, and avoid adding enough to make the filling wet.
Serving Suggestions
Serve the onigiri as a light lunch, a portable picnic food, or one part of a Japanese-style meal. Miso soup, sliced cucumber, quick-pickled vegetables, or a small salad make useful accompaniments without competing with the tuna filling. For a lunch box, pack the rice balls snugly so they do not roll around, and keep them chilled until it is time to eat if they will be carried for a while.
The nori is at its best when crisp, so pack the strips separately and wrap them around the rice shortly before eating. If you prefer soft, slightly chewy nori that adheres to the rice, wrap the onigiri as soon as they are shaped. A little extra sesame seed on the outside is optional, but the filling already has a toasted sesame flavor.
Variations
For a sharper, saltier filling, stir in 1 teaspoon (5 g) of finely chopped pickled Japanese plum, or umeboshi, after removing its pit. Umeboshi is sold in Japanese and many international grocery stores; if it is difficult to find, use a small amount of chopped dill pickle for a different but pleasantly tart result. Start with less than a teaspoon because both options can be quite salty.
For gentle heat, add 1 teaspoon (5 g) of Japanese chili mayonnaise or a pinch of shichimi togarashi, a Japanese seven-spice blend. If neither is available, a small pinch of red pepper flakes works, though it gives a simpler heat rather than the citrus and spice notes of shichimi. You can also replace the scallion with 1 teaspoon of finely chopped chives.
To make a crisp-edged version, shape the rice balls first and pan-sear them in a lightly oiled nonstick skillet over medium heat, turning until the outsides are golden. Brush each side sparingly with soy sauce near the end so it does not burn. This is a variation rather than the basic method: the exterior becomes crisp and savory, while the nori is best added after searing.
For a less creamy filling, reduce the mayonnaise to 2 teaspoons (10 g) and add a little more tuna. A small amount of finely chopped cucumber can add crunch, but remove watery seeds and use it just before shaping so it does not release moisture into the mixture. Keep additions modest; an overfilled center makes the rice balls harder to seal.
Storage and Reheating
Onigiri are best soon after shaping, when the rice is soft and the nori can still be crisp. Because these contain tuna and mayonnaise, do not keep them at room temperature for more than 2 hours; refrigerate them sooner if the room is warm. Place leftovers in an airtight container and refrigerate promptly. For best texture, eat them within 1 to 2 days, although cooked leftovers are generally kept refrigerated for 3 to 4 days.
Rice firms up in the refrigerator, so reheating can improve its texture. Remove the nori, wrap an onigiri loosely in a damp paper towel, and microwave it until steaming hot throughout. USDA FSIS guidance is to reheat leftovers to 165°F (74°C); check the center with a food thermometer if you need to verify the temperature. Add fresh nori after heating. You can freeze individually wrapped onigiri for up to about one month for better quality; thaw in the refrigerator and reheat until steaming hot. The filling may be a little less creamy after freezing.
Frequently Asked Questions
Can I use tuna packed in oil?
Yes. Drain it well before mixing, then taste the filling before adding anything extra. Oil-packed tuna tends to taste richer, so you may want to use 2 teaspoons of mayonnaise instead of the full tablespoon. The recipe works with either tuna packed in water or oil.
Can I make tuna mayo onigiri ahead?
Yes, but they have the best rice texture on the day they are made. Shape them, store them covered in the refrigerator, and keep the nori separate if you want it crisp. Do not leave them out for a long stretch while preparing lunch; refrigerate within 2 hours, or sooner in a warm setting.
Why are my rice balls falling apart?
The rice may be too dry, the tuna filling may be too wet, or the rice may not be short-grain. Make sure the rice is cooked and still warm, drain the tuna well, and press the rice gently but firmly around the filling. If a ball splits, add a little rice over the opening and reshape with damp hands.
Do I need to season the rice with vinegar?
No. Onigiri are commonly made with plain rice, unlike sushi rice, which is seasoned with vinegar, sugar, and salt. This recipe uses a small amount of salt on damp hands, while the mayonnaise and soy sauce season the tuna center. You can add vinegar if you like, but it changes the flavor and can make the rice harder to shape if you add too much.
Can I use a rice cooker?
Yes. Rinse and drain the rice as directed, then add it and the water to your cooker and use its regular white-rice setting. Let the rice rest for 10 minutes after the cycle ends if your cooker does not include a resting period. Rice cookers differ, so follow the cooker’s water guidance if it specifies a different amount for short-grain rice.
What can I use instead of nori?
Nori is traditional and gives the rice ball its familiar roasted-seaweed flavor, but it can be omitted. You can roll the outside in sesame seeds or leave it plain. For a different flavor, a shiso leaf can wrap part of an onigiri, though it tastes herbal rather than sea-like and may be less readily available.
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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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