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The Food Lab: Ceviche And The Science Of Marinades
It's time for another round of The Food Lab. Got a suggestion for an upcoming topic? Email Kenji here, and he'll do his best to answer your queries in a future post. Become a fan of The Food Lab on Facebook for play-by-plays on future kitchen tests and recipe experiments.
Sashimi and crudo may be the John and Paul of the raw seafood band, but ceviche is the George. A little less popular, a little less flashy, but altogether more complex, sharper, with a bit of acid. It differs from George in one key way though: It's really easy to get into.
It comes in on the upper half of the Top 100 Easiest Dishes to Make Of All Time, and I'd bet good money that it's #1 for Most Impressive Return For Your Time Investment. It's a dish that looks and tastes elegant, yet is quite literally thrown together in a matter of moments.
Though the origins of the dish are not precisely known, with folks citing everything from Polynesia to Spain, the mostly likely true origins are Peru. Indeed, El Pais reports that archaeological evidence shows native Peruvians were eating a dish very similar to modern ceviche as far back as 2,000 year ago. Peru remains the country most closely tied with ceviche, though you'll find it and its variants all along the South and Central American coasts.
Even the word itself is shrouded in mystery. It bears resemblances to escabeche, Spanish for pickle (as does the dish), as well as sakbaj, Arabic for vinegar-cooked meat, and even with siwichi, the original name for the dish spoken in Quechua one of the native languages of the region.
But I think I'm getting a bit ahead of myself here.
First off, what exactly is ceviche? At its most basic, it consists of slices or chunks of raw fish (or sometimes shellfish) tossed with an acidic marinade, most commonly plain citrus juice. As the pieces of fish sit in the marinade, the citric acid from the juice slowly causes the flesh's proteins to denature, in very much the same way that heating will. The result is raw fish with the opaque appearance and firmed texture of cooked fish.
Tart, bright, and refreshing, the fish should be firm on the exterior, but with a tender, translucent center that gives as you bite into it. Flavorings run the gamut from passionfruit juice and mint to fried shallots and coconut milk to just plain lime juice, but the most traditional Peruvian version is made with sea bass marinated in bitter orange or lime juice and flavored with thinly sliced red onion, hot chiles, and perhaps some herbs. It all comes on a big platter along with chunks of corn on the cob (or perhaps large nuggets of fried Cuzco corn—A.K.A. Corn Nuts), and sweet potatoes.
It's an exceedingly simple dish to make once you understand a few of the principles involved, and there's only a couple of small difficulties involved. Getting perfectly fresh fish (and it must be perfectly fresh), and knowing exactly how long to let it marinate. Eat it too soon, and you end up with fish that's nearly raw. Let it sit too long, and your fish turns dry and chalky as the acid works its way into the flesh. So what's the best way to make sure your ceviche has perfect texture? Let's see if we can figure it out.
First and foremost, ceviche must be made with the absolute freshest seafood available. Fish is traditional, but shrimp, scallops, even squid will work just fine. Just make sure it's fresh.
Because seafood lives in, well, the sea, the bacteria and enzymes naturally present in it are used to operating at much much colder temperatures than those in, say, a cow. Because of this, even at regular fridge temperatures, they multiply much faster than bacteria from land-dwelling animals, which is what causes seafood to spoil so much faster than its terrestrial counterparts. With perfect care, fish can be stored for several days before it starts to go over the peak, but still, the fresher the better.
Here's how to buy select the best fresh fish.
- Go to a trusted source. The best is obviously to catch it yourself, or if you're lucky, have a dad who likes to go fishing for stripers three or four times a week (thanks, Dad). Next best is a dedicated fishmonger. Look for shops that are clean, busy, and scrupulous about their fish. If you see fish hanging out in pools of melted ice, chances are, the fishmonger doesn't care much about freshness. Fish should always be stored on top of and under crushed ice, or in refrigerated display cases on top of ice. If the fish is treated roughly, folded in half, stacked haphazardly, you might want to think twice.
- Follow your nose. Fresh fish should not have a fishy smell at all, at most giving off a faintly briny, ocean-like aroma. The same rules apply for shrimp, scallops, squid, and other shellfish. If your fishmonger won't let you smell his fish, find a new fishmonger, or eat burgers instead.
- Look for firm flesh. Fresh fish flesh should have a clean, slightly translucent appearance that doesn't give when you push. If you poke it with your finger and leave a permanent dent, the flesh has most likely started to decompose.
- Look it in the eye. Fresh fish should have bright, clear, moist looking eyes. Avoid fish with dark eyes or eyes that have a cloudy film over them.
- Check the gills. They should be bright red and distinct. If they are brownish or have begun to stick together, the fish has been out of the water for far too long.
Virtually any fish will work for ceviche, but I prefer to use semi-firm, white-fleshed ocean fish such as sea bass, striped bass, grouper, or flat fishes like sole or flounder. The key is not to get locked into one fish before you get to the market—whatever is freshest is what you should go with, even if it's not what you originally planned. The exception are certain types of fishes in the mackerel family, such as mackerel, sardines, or tuna. Other oily fishes like bluefish or jack don't make the best ceviche either, nor do freshwater fish like trout or catfish.
For ceviche, you don't need skin, so ask your fishmonger to remove it for you, or if you've got the skills, do it yourself at home.
Once You've Got It Home
Like disagreeing with your wife, the absolute best way to store fish is to not do it at all. Catch it or buy it, then cook it immediately. If you've absolutely got to hold it, you might think that tossing it in the refrigerator is good enough. Think again. At normal fridge temperatures (around 38°F), fish will decompose noticeably even overnight. So how do you keep it even cooler? With ice.
Here's what you do: Line a shallow plastic tray or a plate with a couple of frozen ice packs or a layer of ice cubes, then place a layer of plastic wrap directly over them to cover. Lay your fish straight onto the plastic in a thin, even layer (be gentle!), cover with another piece of plastic, then top them off with a couple more ice packs. Store this whole get up on the bottom shelf of your fridge, right at the back. This should keep your fish down to at least 32 degrees. Ultra fresh fish can be kept like this for up to two or three days, but any longer is pushing it.
I like to keep my fish on ice the same way while working with it, placing the tray with the ice packs directly on my counter. That way, your fish will stay cold even at room temperature for several hours.
There are a few theories as to how to cut fish for ceviche. Some like to cut it into paper thin slices, others into corn-kernel sized nuggets. I prefer my slices slightly thicker. One of the joys of really great ceviche is the contrast between the exterior and the center of the fish.
Consider each slice of fish to be like a little steak. You want a well-cooked exterior layer, but plenty of rare to medium-rare meat in the center. Quarter-inch slices are just about perfect for me—any thinner and they cook too fast, any thicker, and the outer layers get completely overcooked before they've cooked deep enough.
But what exactly is the ideal marinating time? I decided to find out, marinating slices of fish everywhere from one minute and up to two hours.
The photo above shows slices of fish marinated in straight lime juice (pH of about 2.5) for various amounts of time. From left to right, we've got:
- 0 minutes: Fish is completely raw. Slippery texture, like sashimi (I mean, it is sashimi).
- 1 minute: Fish is strongly flavored, but still essentially raw. No noticeable difference in texture yet.
- 2 minutes: Very exterior of fish is starting to show some textural changes.
- 5 minutes: Definite textural changes in fish, with a pleasing firmness to the exterior. Not ideal yet.
- 10 minutes: For my taste, this is where it begins to become ideal. Niceley firm on the outside, but still tender and moist in the interior.
- 15 minutes: Even better.
- 30 minutes: Still good, bordering on too cooked.
- 1 hour: Overcooked. The acid has begun breaking down the connective tissue in between the layers of the flesh, which causes it to start falling apart.
- 1 1/2 hours: The fish breaks into distinct chunks with even the slightest poke from a finger or fork.
- 2 hours: Completely gone. Fish has spontaneously started to break apart even without touching it. It's cooked through to nearly the center, with a chalky, dry texture.
So as you can see, ceviche has got a pretty limited lifespan. Anywhere from the 5 minute to 30 minutes range is in edible-to-great territorty. Below that is fine if you're into the slipperier texture of sashimi, but you don't want to go for any longer, lest your fish turn dry and chalky.
There are, of course, those who prefer their fish this way, sometimes even letting their fish marinate overnight. I can accept that, about as much as I can accept those who prefer to have their meat cooked well-done. Just don't do it to my fish. I've been to restaurants that do this, though one would assume that in those situations it's more about ease of storage and expedience of service than the ultimate in taste.
There's not all that much reason for having this photo in here, other than the fact that it illustrates just how much like cooking with heat the "cooking" with acid in a marinade is really doing. Just like cooking a steak over a high flame, the cooked zone slowly works its way into the fish. I like my steaks medium to medium-rare, and I feel the same way about my ceviche—the core should still be translucent.
Here's where the fun begins. Your imagination, or more realistically, your palate are the only things stopping you here. I usually like to go the traditional route, with super-thin sliced onions (you can use a mandoline to help if you want), and jalapeño peppers from which I've removed the seeds and ribs so that I can add a ton of them. See, the heat in a pepper comes from capsaicin, a chemical that's mostly stored in the ribs and seeds. Remove them, and you can add a ton of pepper, giving you real jalapeño flavor in each bite, instead of just blinding heat.
Some times I'll use sour orange juice along with some smoked paprika and chopped olives. For these days, a can of good Spanish octopus might find its way alongside my fish as well. Other times, I prefer to take a Southeast Asian route, adding fish sauce, coconut milk, and perhaps a bit of chopped lemongrass, galangal, or kaffir lime leaf. Or if my wife is around, I'll add some passionfruit juice and sub out the cilantro for another herb—perhaps chives or just sliced scallions (my wife is one of the strange ones who can't stand cilantro).
You get the picture.
If any of you've got some great flavoring ideas for ceviches, I'd love to hear them in the comments. Oh, also, if anyone can think of who Ringo'd be in the raw seafood band, I'm all ears.