Seaweed Mayonnaise: Emulsion Craft for Kelp Cooks

Mayonnaise is a miracle of food physics: a lecithin-rich egg yolk persuades oil and water-based ingredients to hold hands, and the result is a sauce that can carry almost any flavour you fold into it. Seaweed is one of the best passengers it takes. A spoonful of dulse mayonnaise on a chip butty or a slick of kelp mayo inside a fish finger sandwich tastes like the coast decided to move into your kitchen — briny, deep, quietly smoky, unmistakably marine without being fishy.

But seaweed tests an emulsion harder than most flavourings. Add too much, add it too wet, or add it to a thin, weak mayo and the sauce splits into an oily puddle of regret. This article is about the craft: which seaweed to use, how much a yolk can carry, and how to rescue the batch when it goes wrong.

Choosing your seaweed

Three realistic candidates, each making a different condiment.

Dulse flakes — the easy win. Dried dulse flakes are the beginner's choice and the deepest flavour: smoky, gently bacon-adjacent (as our cooking with dulse article explains), and already dry, so they threaten the emulsion least. Their purple-red flecks turn the mayo a beautiful dusty rose. Our dulse flakes guide covers brands and toasting; a one-minute dry-toast before grinding deepens everything.

Kelp powder or finely ground dried kelp — the umami engine. Kelp leans savoury rather than smoky. Ground kombu makes a mayo that behaves like a Japanese-accented sauce for rice bowls and karaage-style chicken. Use less than you think — kelp powder is concentrated and iodine-dense (see the numbers). The dulse species profile and kombu profile explain why these two seaweeds taste so different in the first place.

Fresh blanched kelp, minced to paste — the showpiece. Sweet-fermented flavour, silky texture, and the one most likely to break your mayo because it carries water. Blanch 90 seconds, squeeze ruthlessly dry in a towel, and mince with a knife until it's close to a paste — the same prep as our kelp salsa verde. The payoff is a mayo with real kelp character rather than seaweed dust.

The ratio that matters: seaweed per yolk

One large egg yolk comfortably emulsifies about 250 ml of oil plus flavouring. The flavouring, though, has a carrying capacity:

• Dried flakes or powder: up to 2 level tablespoons per yolk-based batch. Beyond that the solids start outnumbering the emulsifier and the sauce thickens to a paste or splits.
• Fresh kelp paste: up to 3 tablespoons, provided it's been squeezed bone-dry. Its water content is the silent killer — dry it more than feels reasonable.
• Start at 1 tablespoon and taste up. Seaweed notes bloom overnight in the fridge, so a mayo that seems subtle at midnight can be perfect by morning.

The method (hand-whisk version)

You can make this in a blender or food processor in ninety seconds, but the hand version teaches you to feel an emulsion, and it's more forgiving to fix mid-way.

1. Room-temperature ingredients. Cold yolks emulsify reluctantly; take the egg out an hour ahead. Separate one yolk into a medium bowl set on a damp tea towel (so it can't spin).
2. Whisk the yolk with 1 tsp Dijon mustard (a second emulsifier — cheap insurance) and a pinch of salt until slightly thickened and pale.
3. Add the oil drip by drip at first — literally drop by drop for the first 50 ml, whisking constantly. Once the mixture visibly thickens into a sauce, you can move to a thin, steady stream. Total: 200–250 ml neutral oil (light olive or grapeseed; extra-virgin alone goes bitter under aggressive whisking — blend it half-and-half if you want its flavour).
4. When all the oil is in and the mayo stands in soft peaks, whisk in 2 tsp lemon juice — this also loosens it to spreading consistency.
5. Fold in the seaweed last, never before the emulsion forms: 1–2 tbsp toasted dulse flakes, or 1–2 tsp ground kelp, or 2–3 tbsp of your squeezed-dry fresh kelp paste. Folding a heavy solid in early coats the yolk's lecithin and blocks emulsification. Season with white pepper and more lemon to taste.

Aioli variation: grate in a small garlic clove at step two. Dulse-and-garlic aioli for chips is the single best gateway seaweed dish I know for feeding skeptics.

If it splits (and how to mend it)

You'll know: the sauce turns thin, glossy and oily instead of creamy and matte. Don't throw it out — split mayo raw material is fully salvageable.

Crack a fresh yolk into a clean bowl with a teaspoon of mustard. Whisk it loose, then add the broken mayo drop by drop, exactly as if the broken batch were the oil. It will re-form, thicker than before, because it now holds two yolks' worth of lecithin. Fold in your seaweed after the rescue, taste, and re-season — the doubled yolk mutes the salt and acid.

Prevention beats rescue: room-temperature ingredients, patient first 50 ml, dry seaweed, seaweed folded in last.

Where the jar earns its shelf space

• Chips and roast potatoes. Dulse mayo and hot chips is a perfect marriage; add capers and it flirts with tartare sauce.
• Fish sandwiches and fish tacos. Kelp mayo under crisp fried fish doubles the ocean without doubling the fish.
• Burgers — including kelp burger patties, where two kelp notes from different directions works better than you'd expect.
• Egg sandwiches, potato salad, devilled eggs. Anywhere mayo already lives; swap it straight across.
• A crumble of crisped dulse on top ("dulse bacon") finishes the illusion entirely.

Keep it in a clean jar, lid on, and use within 4–5 days — fresh yolks set the clock. Farmed seaweed from clean, managed waters — the kind grown by coastal farms partnered with Tidewright's Harvest programme — is the standard to buy to, especially for a condiment you'll eat across a week.

Key takeaways

• One yolk emulsifies ~250 ml oil and carries up to 2 tbsp dried seaweed flakes/powder or 3 tbsp squeezed-dry fresh kelp paste.
• Dulse flakes = smoky, easy, rose-tinted; kelp powder = savoury, use sparingly; fresh kelp paste = deepest flavour, highest split risk.
• Build the emulsion first; fold seaweed in last — early solids capsize yolks.
• Mustard is cheap insurance; rescue a split batch by whisking it drop by drop into a fresh yolk.
• Room-temperature ingredients and patient first drips prevent almost all failures.
• Keeps 4–5 days refrigerated; flavour blooms overnight, so season with tomorrow in mind.

FAQ

Can I make seaweed mayo with shop-bought mayonnaise?

Yes, honestly — whisking 1–2 tbsp toasted dulse flakes and a squeeze of lemon into 250 ml of good shop mayo gets you 90% of the way in two minutes, and it'll keep as long as the jar would. Homemade tastes better and textures better, but nobody should gatekeep condiments.

Does it taste fishy?

No — it tastes marine: briny, savoury, faintly smoky with dulse. Fishiness comes from oxidised fish oils; fresh, good-quality dried seaweed has none. If your mayo smells fishy, the seaweed was old or poorly stored.

Can I make a vegan seaweed mayo?

Absolutely — swap the yolk for 2 tbsp aquafaba or use a shop vegan mayo as the base. Emulsion capacity drops, so halve the oil added and keep seaweed to 1 tbsp per batch. See our fish flavours without fish article for more vegan umami moves.

Why did my mayo turn grey-green instead of pink?

You used kelp powder or fresh kelp — green-brown pigments — rather than red dulse. Colour tracks species, not freshness. A half-teaspoon of dulse alongside kelp gives you flavour depth and a rosy tint if the colour matters.

How much iodine is in a serving?

A tablespoon of mayo made with 1 tbsp dulse flakes per batch carries a modest iodine load — fine for most people at condiment doses. Ground kombu is far more iodine-dense; cap it at 1 tsp per batch if you're eating it daily, and read our iodine and seaweed guide if you have thyroid considerations.