Ceviche 'cooks' raw seafood through acid denaturation rather than heat. Citrus juice (primarily lime) denatures the surface proteins of fish, turning it opaque and firm — the same structural change that heat causes, achieved through pH instead of temperature. Peruvian ceviche is defined by its leche de tigre (tiger's milk) — the citrus-based curing liquid that becomes a flavoured sauce. Ecuadorian, Mexican, and other Latin American ceviches each follow distinct traditions.
Fresh, sashimi-quality fish is essential — acid does not kill parasites the way heat does. Fish is cut into uniform pieces (1-2cm cubes for Peruvian style). Lime juice must be freshly squeezed — bottled has different acidity and flavour. Classic Peruvian: fish 'cooks' in lime juice for only 5-15 minutes, then is served immediately with red onion, ají amarillo (Peruvian yellow chilli), cilantro, and the leche de tigre. The fish should be opaque on the outside but still slightly translucent in the centre.
For Peruvian-style leche de tigre: blend lime juice with a small piece of fish, garlic, aji amarillo, celery, ginger, cilantro stems, salt, and ice. Strain. This concentrated curing liquid is served alongside the ceviche and is considered a hangover cure. The fish goes INTO the leche de tigre only 5-10 minutes before serving. Time it to the table. The best ceviche in Lima is served within minutes of preparation — it's a dish that exists in a window.
Marinating too long — after 30 minutes the texture becomes chalky and rubbery. Using anything less than impeccably fresh fish. Cutting pieces too large — they won't cure evenly. Using lemon instead of lime — different acid profile. Adding salt too early — it draws moisture and changes texture before the acid can work. Treating it as a marinade rather than a flash cure.