sour lime

Sour lime (Citrus aurantifolia), also known as key lime or Mexican lime, is a small, round citrus fruit native to Southeast Asia and the Malay Archipelago, with subsequent cultivation throughout tropical and subtropical regions. The fruit is characterized by its small size (1–1.5 inches in diameter), thin yellowish-green or greenish skin, and high acidity content (typically 4–5% citric acid by weight). The juice is intensely acidic and aromatic, with a distinctive tart, slightly floral flavor profile that differs from the sweeter, less acidic Persian lime. Sour limes are harvested when immature and green, retaining their tartness and vigor—they are occasionally allowed to ripen yellow, though this diminishes their signature acidity and appeal in traditional cuisines.

Sour lime juice is foundational to Southeast Asian, Caribbean, and Latin American cuisines, where its concentrated acidity and aromatic quality make it indispensable for marinating fish and seafood, acidulating ceviche preparations, and brightening curries and soups. The juice is a primary ingredient in Thai som tam (green papaya salad), Vietnamese fish sauce dipping sauces, and Mexican ceviche. Whole sour limes are fermented in salt to create preserved limes (loomi or black lime), which contribute umami depth to Middle Eastern and Persian stews. The thinness of the peel allows for easy hand-squeezing, and the superior juice yield and flavor intensity compared to Persian limes make it the preferred choice for applications requiring assertive acidity without diluting other flavors.