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The Food Lab: The Best Guacamole (and the Science of Avocados)
Guacamole and I have come a long way together. It's one of the earliest foods I remember eating. My mother would make a batch heavy with tomato and onion every time we had a potluck event at my school. I'd hit it first knowing that it'd soon be too brown for me to eat without grossing myself (or friends) out.
I remember eating guacamole on the back porch of a Cape Cod vacation home. We were each quietly browning in our own ways—me from the afternoon rays of New England sunshine filtering through the scrub oaks, the avocado-dip through the effects of the oxygen rich breeze gently rolling in off the Cape Cod surf.
Guacamole was the very first dish I learned how to make—unless you count heating up a frozen chicken pot pie or pouring hot water into a Cup of Noodles—and as a consequence, was ground zero for my kitchen experimentations. It stuck with me through my awkward formative years in the kitchen, a gentle, creamy backdrop for my foibles and the follies I foisted upon it, the silent recipient of the short end of countless kitchen adventures gone wrong.
Ever try pouring fancy balsamic vinegar into your guacamole? Or how about roasting your avocado before mashing it? These are things I strongly advise against trying, and certainly not in mixed company.
I've come to realize in my 25-odd year relationship with the dip that the best guacamole is the simplest. Which is not to say there's no stone left unturned as of yet.
It's really no wonder that guacamole was the first thing I learned how to make. It wouldn't surprise me if that's not true of a lot of you Serious Eaters. I mean, I know people who can't make anything but guacamole. As foods go, it's about as simple as it comes.
The word comes from the Aztec Nahuatl words for avocado (ahuacatl) and sauce (molli), and at its most basic, all it requires is an avocado—traditionally mashed in the large basalt mortar and pestle—and some salt. The Aztecs were preparing it this way 500 years ago, making guacamole one of the oldest (if not the oldest) traditional American food still made in America.
These days, it's more often than not upgraded with onions, lime juice, cilantro, perhaps a bit of tomato or garlic, but at its heart, it's the same old sauce. And damn if we don't love the stuff. Over 50 million pounds of the stuff, some sources say, will be consumed on Superbowl Sunday. That's a 2 1/2 ounce serving for every man, woman, and child in the United States!
With this much collective experience, you'd think we'd know all there is to know about it, but there are a number of questions that still don't seem to have a clear answer.
What's the best way to incorporate aromatics? Does the seed really prevent it from browning? What's the best way to mash your 'cados?
We'll answer all of those questions today and once we've perfected our basic guacamole, we'll go on and come up with a dozen or so variations on the theme.
Let's get two things straight right off the bat. First, avocados are freaking delicious. Depending on the variety they can range from moist and semi-firm, like the big, fat, smooth-skinned Fuerte avocados that my wife likes to eat with crunchy sea salt, to rich and creamy, like the familiar pebble-skinned Hass variety. It's the latter you want for the best guacamole.
Second, perfectly ripe avocados are a pain in the ass to find. The window of time in which they are absolutely perfect—soft and tender with no brown spots or streaks—is notoriously short. It can make planning an avocado-based party a harrowing experience. Will my avocados ripen in time for game day? What if they turn brown?
Fortunately, there are a few ways to moderate the rate at which they ripen. Ripening in fruits is regulated by a gas called ethylene. It's produced naturally by the fruit itself and is intended to make sure that all the fruit in one area ripens at the same time. The higher the concentration of ethylene, the faster your fruit ripens. That's why you'll see instructions to leave underripe avocados or bananas in paper bags—it concentrates ethylene and causes fast ripening.
In my tests, avocados from the supermarket showing no softness at all take between 3 to 5 days to ripen in a brown paper bag. Throw a banana in there (an ethylene powerhouse), and you can bring that range down to 2 to 3 days.
Once ripened, an avocado will start to produce brown spots and streaks within about 2 days. However, refrigerating a ripened avocado can increase that window up to around 5 days. Best way to guarantee perfect avocados for a Sunday night game? Buy them the Monday before, ripen them at room temperature in a brown paper bag and refrigerate them as soon as they soften.
Of course, we've all seen those avocados that seem perfect on the outside, but once you cut into them, a series of deep brown stripes and striations appear. What's up with that?
Unfortunately, it's not something that can be predicted or prevented. It's caused by uneven enzymatic action inside the avocado as its developing and is exacerbated by extreme weather conditions as the fruit develops.
For Hass avocados, you can expect the likelihood of this phenomenon to increase starting in December and maxing out around February (ack, Superbowl season!).
What about leftover avocado? Any way to keep it from browning? Oxygen is the enemy of avocados—it's what causes them to turn that unsightly brown. Plastic wrap works alright, but even plastic wrap is oxygen-permeable. My avocados didn't last more than about 8 hours wrapped in plastic before visible browning occurred.
The old rub-with-oil-and-place-face-down-on-an-oiled-plate works fine if you've got a perfect half of an avocado with a smooth face, but it doesn't help if you've got, say, 3/4 or 1/4 of an avocado.
The better solution in that situation? Just submerge the sucker in water. I store my unused avocado pieces in a plastic container filled with water in the fridge for up to overnight. Perfect, oxygen-free seal for any shape, and because an avocado is so dense and high in fat, water is slow to penetrate it (it'll eventually become softer).
Once you've got your perfectly ripe fruit, the next question is what's the ideal way to treat it? Getting at the tender inner flesh is simple—I like to cut around the circumference of the avocado the long way then twist gently to separate the two halves. The pit is easily dispatched with a quick strike-and-twist with the heel of your knife.
Some recipes have you cut your avocado flesh into cubes with a paring knife before spooning them out. Others ask you to mash the avocado with a fork. Traditionalists will use a heavy stone molcajete to pound them into submission. After trying out nearly every utensil in my kitchen I've discovered that the ideal instrument is actually this one:
A whisk is great precisely because it mashes so unevenly. You end up with a guacamole with great textural contrast. Plenty of smooth and creamy avocado to bind your dip, but still plenty of big chunks to go around. And if The Goonies taught me anything at all, it's that we could always do with a bit more Chunk.
Once you've got your avocado mashed, you've got to move relatively fast. Oxygen and enzymes don't go on vacation and immediately jump to work turning that flesh a nasty shade of brown. Though there are more than a few old-wives tales claiming that throwing the pit into the bowl will help prevent this from happening, it's a trivial task to prove that this isn't true.
Harold McGee did it in his great book The Curious Cook by leaving two bowls of mashed avocado sit side-by-side, one with the seed placed in it, the other with a seed-sized light bulb stuck into it. Both browned at exactly the same rate.
What about acid? Many books claim that lime or lemon juice will prevent avocados from browning. That's not what my tests said. In fact, depending on how much I added, some batches of guacamole actually browned faster in the presence of citrus juice—significantly so. By the time I added enough acid to slow the browning down to a reasonable degree, the guacamole was inedibly sour.
The only way to prevent it from happening? Prevent contact with oxygen. You can't submerge mashed avocado in water the way you can with sliced avocado, but a double layer of plastic wrap pressed directly onto the surface of the mash will give it a couple extra hours of shelf life.
On Adding Aromatics
Aromatics are just about the only place in a guacamole recipe where there's real room for technique to come into play. For the purposes of my testing. I'm sticking with a very basic combination of onions, cilantro, and serrano pepper.
In the halcyon days of my youth, back when I'd whip out batch after batch of guacamole without a care in the world, I was content to simply finely chop and fold in my aromatics, resulting in a guac that was nicely chunky, but not particularly flavorful. See, vegetables pack their flavor inside their cells. In order to access that flavor, you've got to break down cell walls either by cooking, grinding, or chewing.
With some aromatics—say, onions—even after you release the contents of its cells, chemical reactions must take place between various components before characteristic onion aromas can develop. By chopping and incorporating the aromatics directly into the guacamole, you're doing yourself a disservice flavorwise as many of the flavorful compounds won't get released until you start chewing—some may not even get released at all.
The key is to give those flavors a bit of a pre-release by masticating them before they ever meet the avocado. Now you could chew up the onions, cilantro, and chilies in your mouth, but a mortar and pestle (or even a good food processor) will do the job in a much more sanitary manner.
By mashing my aromatics into a paste before adding them to the avocado, not only did I end up with a guacamole that was far more evenly flavored, but it was more deeply flavored as well. But, I wondered to myself, could I do even better?
I thought back to a very similar vegetable project I had last summer: Andalusian gazpacho. When developing that recipe, I discovered that I could effectively boost the flavor of my soup by using the salt to draw flavorful liquid out from inside vegetable cells through the power of osmosis. As I explained then:
Water is a fickle lover. Given the opportunity, it likes to spread itself around evenly. Normally, it sits around safely inside the vegetables' cells, keeping all those flavor compounds company. With no competition from the outside, it's content. But once we add a few salt molecules to the outside of the cell membrane, the water feels compelled to share itself with the salt as well. Water migrates out from inside the cell walls, bringing along some of those flavorful compounds for a salt-water-flavor threesome.
My guacamole tests showed similar results: combining the aromatics with salt before pounding them resulted in a finished guac that was noticeably more flavorful.
Of course, if you're the type who likes garlic, tomato, scallions, or what have you in your guac, the method works just as well. Want your guacamole chunkier? Try pounding half of the aromatics with salt and leaving the other half in larger chunks to get the best of both worlds.