Kapi — Shrimp Paste Grades & Application / กะปิ

Overview

Kapi is fermented shrimp paste made from small krill or shrimp (Acetes species) mixed with salt and sun-dried over several days before being pounded and aged. It is the backbone of almost every Thai curry paste and many nam prik, providing umami depth, salinity, and a characteristic fermented complexity that cannot be replicated by fish sauce alone. Quality grades range from pale purple-grey, freshly made kapi (moist, strong) to deep purple-brown aged kapi (drier, more complex, less pungent when raw) to the almost-black kapi from Rayong and Klong Kone (prized for paste work). Kapi is always cooked before service — either roasted, fried in the curry paste, or wrapped in banana leaf and grilled.

Flavour Context

Kapi anchors the umami foundation of paste-based dishes — it is the reason a Thai curry tastes categorically different from an Indian one despite sharing spice profiles.

Key Principles

{"Never use raw kapi in finished dishes — cooking neutralises harsh ammonia notes and develops sweetness","For pastes: kapi is added to the mortar and pounded with the other aromatics — it acts as a binder","For nam prik kapi: wrap in banana leaf and grill until fragrant before pounding","Grade selection: pale, fresh kapi for green curry pastes; darker, aged kapi for massaman and red","Storage: refrigerated in airtight container; a white salt crust on surface is normal and correct"}

Pro Tips

The best kapi smells intensely of the sea — pungent, fishy, and fermented — but after cooking, that funk transforms into a deeply savoury, almost miso-like sweetness. A kapi that is merely salty and not particularly aromatic will produce flat, one-dimensional pastes.

Common Mistakes

{"Adding kapi too early in paste-making before other aromatics are broken down — it sticks to the mortar","Using Chinese shrimp paste (darker, wetter, different fermentation) as a direct substitute","Under-cooking kapi in the wok — it must fry in the oil phase of coconut fat before liquid is added","Over-salting the finished dish because the kapi's sodium contribution was not accounted for"}

Cross-Cuisine Parallels

• Belacan (Malaysian/Indonesian) is the closest direct parallel; Cambodian prahok is a fermented fish paste serving a similar function; Vietnamese mam tom is wetter and sharper.