Thai Herb and Aromatic Preparation
Thompson's *Thai Food* opens its ingredient section with extraordinary depth on these aromatics — treating each one as its own study. The approach reflects the Thai cook's view of these ingredients not as flavourings but as structural elements, each performing a specific function in the four-taste balance and the aromatic architecture of the dish.
The preparation and understanding of the five primary aromatics of Thai cooking — lemongrass, galangal, kaffir lime, coriander root, and Thai basil — as distinct ingredients with specific preparation methods, specific applications, and specific flavour functions. These are not interchangeable and are not substitutable within their respective applications. Understanding each one's character is understanding Thai cooking at the level below the recipe.
The five aromatics of Thai cookery represent five distinct aromatic compound families that interact synergistically in combination. As Segnit notes, lemongrass and kaffir lime are both terpene-based aromatics that share citral as a common compound — when used together, they amplify each other's character rather than competing. Galangal's ACA compound is in a different chemical family and provides the sharp, medicinal counterpoint that prevents the citrus-floral compounds from dominating. Coriander root's resinous compounds serve as a bridge between the volatile citrus aromatics and the more stable umami compounds of the shrimp paste. This is not arbitrary combination — it is the cumulative wisdom of centuries of refinement.
**Lemongrass (takrai — Cymbopogon citratus):** - Character: citral-dominated, bright, lemon-adjacent but not lemon — warmer, slightly floral. - Preparation for paste: outer leaves removed, white portion only (the bottom 10cm), thinly sliced before mortar pounding. - Preparation for broth/soup: bruised with the back of a knife — releases citral into the liquid. Not sliced. Remove before serving. - Preparation for salads: tender inner stalk only, extremely thinly sliced on the diagonal — almost translucent. - Storage: refrigerate wrapped in plastic for 2 weeks; freeze whole for 6 months. **Galangal (kha — Alpinia galanga):** - Character: sharp, medicinal, pine-citrus, slightly camphor — quite different from ginger despite visual similarity. They are not interchangeable. - Preparation for paste: peeled, very finely sliced, then pounded — fibrous and requires thorough mortar work. - Preparation for broth: sliced into coins, lightly bruised. Remove before serving — not eaten. - Storage: refrigerate in a plastic bag for 1 week; freeze sliced for 3 months. **Kaffir lime (makrut lime — Citrus hystrix):** - Leaves: used whole (bruised, in broth) or with the central stem removed and finely shredded (in salads) or very finely chiffonade (in pastes). The two-lobed leaf shape is distinctive. The leaves must be fresh — dried kaffir lime leaves have almost no aromatic value. - Zest: for paste only — never the juice, which is too bitter. Use a fine grater; avoid the white pith entirely. - Storage: freeze whole leaves — they keep their aromatic character for 3 months frozen; refrigerated leaves deteriorate within days. **Coriander root (rak pak chee):** - Character: more intense and more complex than the leaves — earthier, with a resinous aromatic depth. - Preparation: scraped clean with a knife (not peeled), roughly chopped before mortar pounding. - Note: bunches sold with roots intact in Southeast Asian markets. In standard Western markets, coriander roots are rarely available — the lower stems used in larger quantities are an imperfect substitute. **Thai basils (three varieties — not interchangeable):** - Thai sweet basil (bai horapa): anise-forward, clove-adjacent. Used in curries (added last), in salads. - Thai holy basil (bai kra pao): clove-dominant, peppery. Used in wok dishes — the specific basil of pad kra pao. - Lemon basil (bai manglak): lemon-forward, lighter than sweet basil. Used in certain soups and noodle dishes. Decisive moment: For all aromatics: using them at the correct stage of cooking. Aromatics added too early to a broth give their compounds to the liquid and then lose their character. Aromatics added at the correct stage develop progressively. Understanding which aromatics are for infusion (lemongrass, galangal in soup — removed before eating), which are for paste (all — pounded), and which are for finishing (fresh herb — added last) is the entire decision tree. Sensory tests: **Lemongrass — freshness test:** Snap a piece of lemongrass. A fresh stalk makes a clean, crisp snap and immediately releases a burst of citral — detectable from 30cm away. Old lemongrass bends rather than snapping and produces almost no smell. **Galangal — freshness test:** Slice a thin round. The cut surface should be crisp, slightly moist, and pale tan — not dried or fibrous. The smell: sharp, medicinal, immediately distinctive. Old galangal smells flat or of nothing. **Kaffir lime leaves:** Hold the leaf up to light. Fresh: vivid green, flexible, slightly glossy. Old: yellowing, rigid, dull. Tear a small piece and smell — a correctly fresh leaf releases a floral-citrus aroma immediately. Old or dried leaves: minimal smell.
David Thompson — *Thai Food*
Common Questions
Why does Thai Herb and Aromatic Preparation taste the way it does?
The five aromatics of Thai cookery represent five distinct aromatic compound families that interact synergistically in combination. As Segnit notes, lemongrass and kaffir lime are both terpene-based aromatics that share citral as a common compound — when used together, they amplify each other's character rather than competing. Galangal's ACA compound is in a different chemical family and provides the sharp, medicinal counterpoint that prevents the citrus-floral compounds from dominating. Coriander root's resinous compounds serve as a bridge between the volatile citrus aromatics and the more stable umami compounds of the shrimp paste. This is not arbitrary combination — it is the cumulative wisdom of centuries of refinement.