Aromatic bases & spice pastes
lemongrass-galangal paste
bumbu halus · A pounded aromatic base essential to Thai, Lao, Cambodian, and parts of Indonesian and Malaysian cooking. The paste combines the floral-citrus brightness of lemongrass with the sharp, camphoraceous heat of galangal, building the aromatic foundation for soups, curries, stir-fries, and marinades. Unlike a finished sauce, it is a working component added during cooking to perfume and structure the dish.
The formula
3 : 1 : 1 : 1 : 0.5 (lemongrass : galangal : shallots : garlic : salt by weight) + 10–15% liquid as needed
Measured by weight. Lemongrass is measured after trimming away woody tops and outer layers; only the pale inner stalk (5–8 cm from root end) is used. Galangal is peeled and diced. Shallots and garlic are peeled. The liquid bridges the fibrous aromatics into a smooth paste; oil also extends shelf life when the paste is briefly bloomed after pounding.
Identity
- Only fresh, never dried lemongrass — the fresh stalk provides the essential oil content and floral aldehydes (citronellol, geraniol) that dried cannot reconstitute
- True galangal (Alpinia galanga), never ginger — galangal's dominant note is eucalyptol and α-pinene, creating a sharp, almost pine-like heat distinctly different from ginger's zingiberene warmth
- Pounded, not merely chopped — mechanical cell-wall rupture releases volatile aromatics that blade-cooking partially destroys; a mortar and stone grinder yield superior fragrance
- No added fat required for raw paste — fat is introduced only when the paste is cooked in oil (as in curry paste base), where it serves as solvent for fat-soluble volatiles
- Salt added during pounding — salt's ionic strength denatures proteins in garlic, releasing more sulfur compounds and aiding paste cohesion
- Acidic ingredients (lime zest, tamarind) are added during the dish, not the paste — acid degrades volatile aromatics during storage
Ingredients
| Aromatics | lemongrass (Cymbopogon citratus) lower 5–8 cm of stalk, pale inner only | Trim woody tops and green upper leaves; peel away 1–2 outer layers. The white/yellow base is the only usable portion. Typical: 3 medium stalks for 250 g paste. |
| Aromatics | galangal (Alpinia galanga) root, peeled | Slice into thin coins before pounding. Skin must be completely removed. Ginger (Zingiber officinale) is not a true substitute — flavor profile diverges significantly; galangal's eucalyptol notes are absent in ginger. |
| Aromatics | shallots, peeled | Provide sweetness and sulfurous depth. Approximately 2–3 medium shallots per 250 g paste. May be halved and added to mortar in pieces. |
| Aromatics | garlic cloves | Approximately 4–5 cloves per 250 g paste. Adds alliaceous pungency and diallyl disulfide complexity. |
| Seasoning | fine salt | Added during pounding (0.5 part by weight to total aromatics). Facilitates extraction of water-soluble flavor compounds and acts as mild preservative. |
| Liquid | cold water or neutral vegetable oil | Water is used for raw pounding; oil (often coconut or peanut) is added when the paste is briefly cooked in fat after pounding, which dissolves fat-soluble aromatics and extends refrigerated shelf life to 10–14 days versus 5–7 days for water-based paste. |
Method
- 1Trim lemongrass: cut away the upper green stalks and any dried layers. Slice the lower 5–8 cm of each lemongrass stalk lengthwise, then lay flat and slice thinly on the bias.The upper stalk is too woody and fibrous to break down; only the pale, moist base contains usable essential oils. Slicing exposes more cell surface area for efficient pounding.
- 2Peel galangal with a spoon or paring knife. Slice into thin coins (3–5 mm) and add to the mortar alongside the prepared lemongrass.Galangal is denser and more fibrous than lemongrass; thin slices break down faster. Galangal's essential oils (eucalyptol, α-pinene) are heat-stable, unlike many in lemongrass, so slicing does not diminish their retention.
- 3Add shallots (halved) and garlic to the mortar. Add salt. Begin pounding with a heavy wooden or stone pestle using circular grinding motions, not blunt smashing.Salt denatures garlic proteins, releasing sulfur volatiles (alliin converts to allicin on cell disruption). Circular grinding tears cell walls more completely than straight pounding, maximizing extractable compounds from all three ingredients simultaneously.
- 4Once shallots and garlic form a rough paste, add lemongrass and galangal. Continue grinding until a smooth, homogeneous paste forms, adding liquid (water or oil) tablespoon by tablespoon as needed.Lemongrass contains harder, more fibrous bundles; it requires the prior paste as a grinding matrix. Adding liquid progressively reduces friction and prevents overheating, which would volatilize delicate citrus aldehydes (citronellal, geranial).
- 5Taste and adjust salt. If preparing the oil-enriched version, heat neutral oil in a wok or pan to just shimmering, remove from heat, and stir in the freshly pounded paste. Cool completely before storing.Briefly cooking the paste in fat (called blooming) dissolves fat-soluble aroma compounds (the galangal's sesquiterpenes, the lemongrass's geraniol fraction) that water alone cannot extract, intensifying flavor and adding a protective oil layer that slows microbial growth.
Techniques that matter
Pounding (mortar work)
Mortar grinding ruptures cell walls mechanically without generating significant heat, preserving thermolabile volatiles (citronellal, myrcene) that blade-processing or heat-cooking destroys. The shearing action creates a true colloidal paste rather than a rough chop.
Component sequencing
Pounding the densest, most fibrous ingredients last, after a paste matrix forms, prevents uneven texture. Garlic and shallots create the initial paste body; galangal and lemongrass are progressively worked in, requiring more mechanical energy.
Fat blooming
The lipophilic volatiles in galangal (1,8-cineole, α-pinene) and the higher-boiling terpenes in lemongrass (geraniol, citronellol) are more fully extracted into oil at temperatures between 120–160°C without degradation, creating a more aromatic finished paste.
Variations & derivatives
Thai red curry paste baseThailand
Dried red chilies (prik haeng) and fresh red birds-eye chilies are added to the base, along with kaffir lime zest and coriander root. The resulting paste becomes the foundation for red curries; the lemongrass-galangal relationship remains constant.
Tom yum nam khon baseThailand
For the iconic sour-spicy soup, the paste includes additional lemon zest and is made slightly coarser. Often includes makhuea plee (fingerroot/Boon Niem) in southern Thai versions.
Sambal belacan foundationMalaysia / Indonesia
Galangal dominates, with lemongrass as secondary. Dried shrimp paste (belacan) and candlenuts are added. The galangal:lemongrass ratio inverts to approximately 2:1 for this umami-forward application.
Laab/larb pasteLaos / Northern Thailand
Toasted rice powder and shallots are blended into the paste, with galangal and lemongrass providing the aromatic lift for this minced-meat salad. Often includes fresh mint and saw-leaf herb.
Used in these dishes
Substitutions
- galangal → ginger (Zingiber officinale) — Ginger lacks galangal's eucalyptol and camphor notes. The result will be sweeter and more pungently spicy (gingerols), missing galangal's essential pine-sharp character. Acceptable in a pinch for non-traditional preparations; not acceptable for authentic Thai or Indonesian results.changes result
- fresh lemongrass → lemongrass paste (commercially bottled) — Commercial pastes contain citric acid and preservatives that alter flavor. Acceptable for convenience; the fresh brightness degrades significantly. Dilution with a little fresh zest may partially compensate.changes result
- shallots → red onion — Red onion is a valid substitute in non-traditional contexts, providing sweetness and sulfur compounds. It introduces a slightly more aggressive sharpness; shallots' subtlety is lost.
- mortar and pestle → food processor — Blade processing generates heat through friction, partially volatilizing delicate aromatics. The texture is also coarser and less colloidal. Functional but inferior for flavor retention.
Troubleshooting
Paste turns brownish and loses bright citrus aroma after storage
Oxidation of chlorophyll and degradation of citronellal and geranial; caused by insufficient oil layer when storing or improper sealing allowing air exposure → Press a thin layer of neutral oil over the surface before sealing. Use an airtight container with minimal headspace. Freeze in ice cube trays for portioned storage.
Gritty, stringy texture when used in soup
Galangal was not sliced thin enough before pounding, leaving fibrous strands; or paste was added too late in cooking without blooming first → Slice galangal into 3mm pieces maximum. Always bloom in fat (coconut cream or oil) for 60–90 seconds before adding liquid; this softens the fiber and disperses it.
Bitter, medicinal flavor in the finished dish
Galangal pieces were overheated during blooming (oil above 180°C causes charring and bitter compound formation); or galangal skin was not fully removed → Bloom paste over medium heat in oil that shimmers but does not smoke (160–170°C). Ensure complete peeling of galangal; the skin contains tannins.
Paste separates into liquid and solids when stored
Insufficient binding; water-based paste was not homogenized properly or was stored too long without stirring → Stir thoroughly before each use. For water-based paste, use within 5 days refrigerated. For longer storage, add 1 tbsp oil per 100g paste and mix thoroughly before refrigerating.