A whipping siphon will aerate almost any liquid with enough structure to trap gas — not just cream. Replace dairy fat with a stabiliser such as gelatine or agar, strain the base until no solids remain, then charge with nitrous oxide. The result is an espuma: the flavour concentration of a sauce with the texture of air.
The same canister will hold a parmesan espuma, an aerated beurre blanc, or a basil oil infused in minutes.
How is an espuma different from whipped cream?
An espuma is held together by a gelling agent or protein rather than by butterfat, which is why it can be built from stock, juice, purée or infused oil. In cream, fat globules partially coalesce around each air bubble and form the wall that stops it collapsing. A stock has nothing to build that wall with, so you supply one: a gel soft enough to pass the valve, firm enough to hold shape.
Which stabiliser should you use — gelatine, agar or lecithin?
Choose by service temperature first: gelatine for cold, agar for warm and hot, lecithin only for thin, short-lived airs.
| Stabiliser | Starting ratio | Behaviour with heat | Notes |
|---|---|---|---|
| Gelatine | About 2–3 g per 500 ml | Sets when chilled; softens near body temperature | Cold espumas and fruit foams; slumps on a warm pass |
| Agar | About 1–2 g per 500 ml | Needs a boil to hydrate; stays firm well above fridge temperature | Hot foams and fluid gels; blend the set gel smooth, then strain |
| Lecithin | Roughly 0.3–0.6% of liquid weight | No gel; acts as a surfactant | Light airs on watery liquids; fragile, plate immediately |
| Cream (36%+ fat) | None needed | Must stay cold | Over-shaking churns the fat to butter |
Treat those as starting points: acid, alcohol, salt and fat all change how a gel sets, so test a small batch first.
Why must you strain the base before charging?
Because a single seed, fibre or herb fragment can lodge in the valve and hold it open, venting the whole canister across your bench. Pass every base through a fine chinois, then through muslin, and blend purées before straining rather than after. Powdered stabilisers must be fully dissolved: a lump of hydrated agar is both a blockage and a sandy patch in the foam.
How many charges does a siphon base need?
One charge per 0.5 L canister and two per 1 L canister covers most work, with stabilised bases wanting the higher end because they are denser than cream.
| Canister | Fill volume | Cream | Stabilised espuma |
|---|---|---|---|
| 0.5 L | 250–350 ml | 1 × 8 g equivalent | 1–2 × 8 g equivalent |
| 1 L | 500–700 ml | 2 × 8 g equivalent | 2 × 8 g equivalent |
Never fill past the manufacturer's maximum line: the headspace is where the gas expands, and without it output turns dense and spitting. Shake to dissolve the gas, then stop — continued agitation on a cream base destabilises the fat globules and churns them toward butter. Rest gelatine bases cold for an hour after charging so the gel sets around the dissolved gas.
Can you make hot foams in a whipping siphon?
Yes, provided the siphon is rated by its manufacturer for hot use and the stabiliser survives the temperature. Gelatine is out, since it softens near body temperature; agar holds well when warm, and methylcellulose behaves in reverse, gelling as it heats. Hold hot canisters in a temperature-controlled bain-marie, not on direct heat. Pressure inside a sealed canister rises as the contents warm, because the gas expands — which makes that rating a mechanical limit, not a suggestion. Cold espumas serve straight from the fridge; hot foams are plated as they leave the nozzle, since foam drains as soon as it is dispensed.
How does rapid infusion with nitrous oxide work?
Under pressure, nitrous oxide dissolves into the liquid and is forced into the cells of whatever solid sits in the canister; venting quickly makes that trapped gas expand and rupture the cell walls, releasing aromatics in minutes rather than days.
- Fill no more than halfway with spirit, oil, vinegar or syrup.
- Add the aromatic — citrus zest, toasted spice, chilli, soft herbs, cacao nibs.
- Seal, charge, shake about 30 seconds, then rest one to two minutes.
- Vent rapidly in one continuous release and strain straight away.
Strain immediately — solids left in contact after venting pull bitterness from pith and tannin from woody stems.
How much gas does foam-heavy service use?
A kitchen running espumas across several courses charges far more often than one finishing desserts with cream, and a larger cylinder means fewer changeovers mid-service.
| Cylinder | N₂O fill | 8 g cartridge equivalent |
|---|---|---|
| 660 g (1.1 L vessel) | 660 g | About 83 |
| 3.3 L | 2000 g | 250 |
| 4.4 L | 3000 g | 375 |
660 g and 1.1 L describe the same cylinder: 660 g is the gas fill, 1.1 L the water capacity of that vessel. The 4.4 L holds 50% more gas than the 3.3 L. These are gas-content equivalents, not guaranteed serves — no cylinder empties completely through a regulator.
Adelaide Whip, a culinary supply business in Salisbury East, South Australia, stocks cream chargers in all three sizes alongside cream dispensers and the regulator hose that connects a cylinder to a siphon head. Kitchens working through volume can look at bulk quantities or the wholesale page.
Why won't my foam hold?
Collapse has three usual causes: too little structure, gas that never dissolved, or a base worked too hard.
- Thin and watery. Under-gelled, or dispensed before the gel set.
- Spitting or bursting. Overfilled, or the canister was not inverted.
- Grainy or split. Over-shaking a cream base; undissolved stabiliser in a gel base.
Frequently asked questions
Can you make savoury foams in the same siphon you use for cream?
Yes, but strip and wash the head, gasket and valve between uses — fat and aromatic oils cling to the seals and carry into the next base.
Do hot foams need a different siphon?
They need one the manufacturer rates for hot use. Pressure inside the canister rises as the contents warm, so that rating is a mechanical limit.
How long does a rapid infusion take?
A few minutes: shake, rest one to two minutes, vent fast, strain. Strain immediately, because extraction continues after venting and tips into bitterness.
Can you re-charge a siphon that has gone flat?
Yes. Add a charge, shake briefly and re-test. If it still dispenses poorly the fault is usually a blocked valve, not a shortage of gas.
Which stabiliser is most forgiving for a first attempt?
Gelatine in a cold base. It doses easily, sets predictably, and signals an overdose clearly: the foam sets firm in the canister instead of dispensing.
