What citrus juice is commonly added to guacamole to prevent browning?

Lime juice is the citrus juice commonly added to guacamole to help prevent browning.

When an avocado is cut or mashed, its flesh comes into contact with oxygen. An enzyme called polyphenol oxidase then helps trigger a chemical reaction that produces brown pigments. The same process affects prepared guacamole, especially on its exposed surface.

Lime juice helps in two ways. Its acidity slows the browning reaction, while its bright, tart flavor complements the creamy avocado and other traditional ingredients such as salt, onion, cilantro, and jalapeño. For best results, cooks usually mix it into the guacamole soon after mashing the avocados.

Lemon juice can also slow browning and appears in some recipes, but lime is the classic and most characteristic choice for guacamole. Citrus juice does not stop browning forever: airtight storage or tightly covering the surface can further reduce contact with oxygen. Browning usually affects appearance more than safety, provided the guacamole has been stored properly.