If you’ve ever cut open an avocado, you know it’s only a matter of time before it starts to turn brown. Even your homemade guac will discolor after a while. Why is that? Oxidation. In the same way sun exposure ages our skin, oxygen is the enemy of fruit that doesn’t want to brown.
Specifically, avocados and other fruits have an enzyme called polyphenol oxidase. When it consorts with oxygen, brown pigments form in the green flesh. Hence, when you leave out freshly made guacamole or a cut-up avocado, it turns brown pretty quickly. But packaged guacamole always seems to be bright green upon purchase, despite having sat on the shelf for countless days. What’s up with that?
Tricks of the Trade
Manufacturers have to make sure there’s no oxygen present in their packaging if they want the product to stay green, says Ardy Haerizadeh, the CEO of guacamole manufacturer Yucatan Foods. They can do this by vacuuming the oxygen from packages, having plastic film in contact with the top of the guacamole, or filling the headspace of tubs with nitrogen gas.
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If you end up with an avocado half left over, keep it fresh with this case.
The polyphenol oxidase enzyme is also sensitive to temperature and acid, so manufacturers can maintain the green color of their guacamole by refrigerating the product and by adding citric acid and/or ascorbic acid, says Diane M. Barrett, director of the Center for Fruit & Vegetable Quality at the University of California–Davis. Acids lower the pH “to the point that the enzyme is not that active,” explains Barrett, who adds that enzymes are also “less active at cold temperatures.”
While not a concern with packaged guac (that we know of), it may even be possible that there are no avocados in the mix: read more about mock guacamole.
Refrigeration, adding lemon or lime juice, and limiting exposure to oxygen can also help keep homemade guacamole from turning brown; the simplest way to keep it looking fresh is just to press a layer of plastic wrap fully onto the surface of the guac before you pop it in the fridge. Chowhounds offer a helpful guacamole timetable for a seven-layer dip. Once it’s unveiled, just eat fast and it won’t have time to oxidize—but if it does, it’s still good; scrape off the discolored areas and re-seal with plastic wrap before storing any leftovers.
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An alternative to plastic, but be sure to still press it into the surface of the guac.
On a related note, if you do buy commercially prepared guacamole, read the ingredients carefully. Haerizadeh says the FDA hasn’t created a standard of identity for the dish, so manufacturers can label pretty much anything they want as guacamole, whether it’s 95 percent avocado, or a “guacamole flavor” dip that contains less than 2 percent avocado.
As long as you have a ripe (slightly soft to the touch, and if it’s a Haas avocado, black on the outside) avocado, guacamole is simple to make yourself. Try some of our recipes, from classic to quite alternative.
And you know what’s great to wash down all that guacamole? Something a little sour, a little sweet, and a little salty, like a margarita (bet you couldn’t see that one coming).
Homemade guacamole is as easy as chopping and peeling a few ingredients and then mashing it all up. Here, you’ll need a tomato, lime juice, chiles, cilantro, scallions, and salt—in addition to the avocados, of course. Get our Guacamole recipe.
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This Mexican mortar and pestle is the traditional way to grind avocados into guacamole, and doubles as a serving vessel too.
The only other ingredient that could possibly make guacamole more decadent than it already is with all that creamy goodness, is bacon. Yeah, there’s tomato in there too, and that’s nice, but you know why you’re making this one. Get our Bacon and Tomato Guacamole recipe.
Garlic is roasted until it’s sweet and jalapeños are all blistery-good in this recipe that’s quite an indulgent appetizer when you’re entertaining guests. Two of everyone’s favorite flavors—crab and guac—combine for a terrific start to a special meal. Get our Dungeness Crab Guacamole with Endive recipe.
On the other end of the guac spectrum, there’s this sweet, fresh, creamy, crisp (thanks to the cucumber), and acidic version. Diced instead of smashed or blended, it’s more salsa-like than the others. Get our Pineapple and Cucumber Guacamole recipe.
Now here’s a guacamole with not one, but two unexpected twists. Celebrated Chef Rick Bayless came up with this nutty, sweet incarnation. Get our Toasted Almond Guacamole with Apricots recipe.
Not quite guacamole, this blend of avocado, sour cream, cilantro, and lime juice (made in a food processor) is nonetheless good anywhere you would use traditional guac, but also works as a sauce. Get our Avocado Crema recipe.
Related Video: Beware Avocado Hand
— Original article by Roxanne Webber on May 8, 2009; updated article by Amy Sowder.
Header image by Chowhound.