Why Avocado Turns Brown

Browning is caused by oxidation — the enzyme polyphenol oxidase in avocado flesh reacts with oxygen in the air, producing brown melanin compounds. The fix is simple: reduce contact with oxygen.

Method 1: Plastic Wrap Directly on the Flesh (Best)

Press a piece of cling wrap directly onto the cut surface of the avocado with no air gap between the wrap and the flesh. Every part of the flesh should be in direct contact with the wrap. Refrigerate. This prevents oxygen reaching the surface and keeps avocado green for 1–2 days.

Method 2: Citrus Juice

Brush or squeeze lemon or lime juice over the cut surface. Acid inhibits the oxidation enzyme. This slows browning noticeably but does not stop it completely as plastic wrap does. Good for guacamole — the lime juice is already in the recipe.

Method 3: Store with Onion (for Halved Avocados)

Place the avocado half cut-side up in an airtight container with a few slices of red onion. The sulphur compounds released by the onion inhibit oxidation. The avocado does not taste like onion but stays green for significantly longer than without. This works particularly well for halved avocados you want to use the next day.

Method 4: Keep the Pit In

Keeping the pit in the unused half reduces the surface area exposed to air. It only protects the area directly under the pit — not the whole half. Combine with plastic wrap for best results.

Method 5: Water Submersion (for Short Term)

Submerge the avocado half cut-side down in a container of cold water. The water creates an oxygen barrier. Replace the water daily. Works for 1–2 days but can affect texture slightly.

For guacamole specificallyPress plastic wrap directly onto the surface of the guacamole (not just over the bowl) before refrigerating. Or pour a thin layer of water or lime juice over the top and pour it off before serving. The green colour is preserved under the water layer even if the surface browns slightly.

Frequently Asked Questions

Both work equally well — the acid content is what matters, not which citrus. Lime is traditional in guacamole and avocado dishes, so it is the natural choice there. Lemon has a stronger flavour that may be noticeable on plain avocado slices. A very light coating is sufficient — you do not need to drench the avocado, which would make it soggy.
At room temperature: begins browning within 30–60 minutes. Refrigerated with plastic wrap on flesh: 1–2 days. Refrigerated with lime juice and plastic wrap: 2–3 days. Brown avocado is not dangerous to eat — it has just oxidised. Scrape off the brown layer to find still-green flesh underneath for use in guacamole or cooking where appearance is less important.