Cornstarch Slurry (Starch to Cold Water)

1

Cornstarch (dry) — Heaped teaspoon ≈ 2.5 g; tablespoon ≈ 8 g

2

Cold water — Must be cold — hot water causes premature lump formation

Measure dry cornstarch into a small bowl or cup. Add exactly double the volume of cold (room temperature or below) water. Stir or whisk until no dry lumps remain — the mixture will look opaque white and settle quickly. Bring the target sauce or liquid to a full simmer. Re-stir the slurry immediately before use (the starch settles within seconds). Pour the slurry in a thin, steady stream while stirring the hot liquid constantly. Within 30–60 seconds the sauce will thicken and turn from opaque to glossy-clear. Simmer for 1–2 minutes to cook out any raw starch flavour, but do not overcook — prolonged boiling degrades the amylose network and thins the sauce again.

• Always re-stir the slurry immediately before pouring — starch settles out within 10 seconds and a partially mixed slurry causes lumps.
• Add the slurry off the direct centre of heat while stirring; this gives a few extra seconds before gelatinisation locks lumps in place.
• Acidic liquids (tomato, citrus, vinegar) weaken cornstarch gels by up to 30% — use slightly more starch or switch to arrowroot.
• Sauces thickened with cornstarch thin again if held at above 90 °C for more than a few minutes; thicken just before service.
• Frozen sauces thickened with cornstarch often weep on thawing (syneresis) — use waxy maize starch or a modified food starch for freeze-thaw stability.

• Potato starch slurry

  Ratio stays 1:2; gelatinises at a slightly lower temperature (58–65 °C) and produces an even glossier, more translucent set — preferred in Japanese and Korean cooking

• Arrowroot slurry

  1:2 ratio; gelatinises at 60–70 °C; stays clear when cooled; breaks down if boiled or held too long, so add at the very end

• Tapioca starch slurry

  1:2 ratio; very glossy; used in dim sum sauces and some pie fillings; thicker gel than cornstarch at the same concentration

• Light glaze (sauce application)

  1 tsp cornstarch per 240 ml liquid — thin, shiny glaze that coats without gelling

• Medium sauce

  1 Tbsp cornstarch per 240 ml liquid — spooning consistency for stir-fries and braises

• Firm pie filling

  2–3 Tbsp cornstarch per 240 ml liquid — sets to sliceable consistency on cooling

• Roux (Flour to Butter)

  Slower-acting starch thickener that must be cooked before adding liquid; longer hold stability than a cornstarch slurry

• Beurre Manié

  Raw flour kneaded with butter — a 'cold roux' dropped into simmering liquid; coarser than a slurry but needs no pre-cooking

• Gelatin Bloom (Percentage by Liquid Weight)

  Protein-based gelling at room temperature vs. starch-based thickening at serving temperature

1. 1.McGee, Harold. On Food and Cooking. Scribner, 2004
2. 2.Ruhlman, Michael. Ratio: The Simple Codes Behind the Craft of Everyday Cooking. Scribner, 2009
3. 3.Belitz, H.-D., Grosch, W., Schieberle, P. Food Chemistry. 4th ed. Springer, 2009

Confidence: high