Sodium alginate
A gelling powder from brown seaweed that sets the moment it meets calcium. It's what makes spherification work: a skin of gel forms wherever alginate and calcium touch, trapping liquid inside.
neutral · sets on contact with calcium
Kinds
- Direct spherification
- About 0.5% alginate in the flavoured liquid, dropped into a bath of 0.5–1% calcium chloride or lactate. A thin skin that keeps setting inward — serve within minutes.
- Reverse spherification
- Calcium in the flavoured liquid (1–2% calcium lactate, or none for yoghurt or cream), spooned into a 0.5% alginate bath. The skin stops growing once rinsed, so spheres can be bigger and made ahead.
Knowing it
- Where to buy
- Modernist suppliers, often in kits with a calcium salt.
- A little history
- Industry used it for decades — it holds the pimento in a stuffed olive — before elBulli made liquid olives and 'caviar' famous in the 2000s.
- Worth knowing
- Blend the alginate in with a stick blender, then rest it in the fridge for a few hours, or overnight, until the bubbles have gone. Direct spherification fails in acidic liquids (below about pH 4) and calcium-rich ones — use reverse, or buffer with a little sodium citrate. Hard tap water can set the alginate early; use low-mineral bottled water.