Unconventional Cooking: The Power of Acid, Salt, and Freezing

When I contemplate the definition of “cooking,” I invariably associate it with the use of heat. But what actually is cooking? Whether it’s simmering a hearty vegetable stew, whipping up a demi-glace or béchamel sauce, or searing a steak over high heat. All of those things definitely count as “cooking”.

What about instances where heat isn’t required? If we aren’t simmering, stewing, or braising anything, can what we’re doing still be considered “cooking”?

In other words, can you cook without heat?

Yes. You absolutely can cook without heat.

And I don’t mean just mixing together ingredients to make a salad or a sandwich. No — what I mean is taking one or more ingredients and permanently changing them. Like searing a steak, for example. Once you cook a steak, well, that’s it. It can’t be uncooked, right? The proteins have been changed forever.

Well, as it turns out, heat isn’t the only way to permanently change food.

There exist certain microorganisms that can eat carbohydrates and convert them into other things, like alcohol or acid. This process, which we call fermentation, is how loads of common foodstuffs are made.

For example, cabbage is fermented to make sauerkraut or kimchi. Soybeans are fermented to make soy sauce, miso, or tempeh. And milk is fermented to make yoghurt, which is one of the most popular fermented foods on the market.

Yogurt is easy to make, too. Milk contains a specific sugar called lactose. Sugar is a type of carbohydrate. When specific strains of bacteria are added to milk, they consume this lactose and convert it into lactic acid. And that’s basically it. After about 8 hours, once the bacteria has converted all of the lactose into lactic acid, the yogurt is ready.

In any case, to make fermentation happen, you don’t need the sort of “heat” you’d use to, say, cook a steak. But most foods do need some temperature control for fermentation to happen. Foods, such as kimchi, need cool conditions to ferment while others, such as yogurt, only ferment in warm temperatures.

But there are other ways you can “cook” where the temperature isn’t a factor.

A while ago, I was chatting with a friend who was at the time traveling around South America. He told me about a Peruvian dish he tried called ceviche. Ceviche is kinda like a fish salad. But what makes it special is that the fish is “cooked” using the acid from lemon or lime juice.

Let me explain. When you cook meat or fish, it turns opaque and the texture firms up. This is how that works: raw proteins are complex 3-dimensional shapes. We call these raw proteins “folded”. Folded proteins are difficult for our bodies to consume. Our digestive systems have to work extra hard to unfold raw proteins so that we can actually absorb the nutrients from them.

But if we apply heat to the folded proteins, they unfold before we eat them. Our bodies can digest these unfolded proteins more efficiently, meaning we absorb more nutrients with less effort. Many believe this ability to use heat to unfold proteins partly helped us evolve into the humans we are today.

This process of unfolding proteins is called denaturing. You can see when a protein has been denatured because it will have turned opaque and firm.

And heat isn’t the only way to denature protein. Acid can denature protein, too.

In the case of ceviche, citrus acid, such as lemon or lime juice, is used to cook the fish instead of heat.

All proteins can be denatured, whether the protein is from fish, egg, meat, or even plants. You might wonder, then, whether you can use lemon juice to cook, say, a steak?

Technically, yes. Lemon juice can denature a steak’s protein. But cooking with heat does more than just denature protein.

Unlike heat, lemon juice can’t kill off harmful bacteria. And not only will acid-cooked steak be dangerous, it probably won’t taste great, either. Lemon juice can’t trigger chemical reactions, like caramelisation or the Maillard Reaction. Obviously lemon juice isn’t going to brown your steak. And this browning is the reason a perfectly-seared steak is so delicious.

So yes, you could technically cook a steak with lemon juice, but it wouldn’t be a steak you’d want to eat. (You’ll probably have your head in the toilet bowl for a while, too).

But there is another way to cook meat and fish without heat. All you need is time and a bucket load of salt. The process is called curing.

The process is pretty straightforward. Big chunks of meat or fish are coated in ridiculous amounts of salt and then left in a cool place to age. (And when I say ridiculous, I mean ridiculous).

The curing process is how loads of meat products, like beef jerky, ham, and salami, are made. Sometimes cured meat is heated with smoke, which helps to kill off bacteria and give a smoky flavour. But other than that, nothing is “cooked” during the curing process.

Conversely, salt undertakes the main role. Similar to acid, salt denatures proteins, resulting in meat that is opaque and firm. But the main purpose of salt is to dry the meat. Salt draws moisture from the meat in a process called osmosis.

Osmosis has two major benefits.

First, unlike acid, salt (through osmosis) can produce meat that is safe to eat. Bacteria needs a moisture environment to develop and survive. So as the salt dehydrates the meat, it also kills any harmful bacteria.

And therein lies the second benefit of osmosis: it also preserves the meat. Bacteria struggles to grow in the dry meat, and so cured meat generally lasts a lot longer than fresh meat. Not all cured meats are safe to eat without cooking, though. It depends on how long they’re cured for. Bacon, for example, is usually only cured briefly and still needs to be cooked over heat.

But why limit yourself to cool temperatures? You can go a step further and use the freezer as a cooking tool.

When food is frozen, ice crystals form inside of it and damage the food’s cells. This often permanently changes the texture.

If you’ve ever frozen a banana and tried to defrost it, you’ll know exactly what I mean. Fresh bananas are quite firm, but after a few days in the freezer, the texture turns smudgy. This can be used to your advantage, though. You can freeze vegetables before you cook them to soften their texture so that they cook faster. This works great for starchy vegetables, like sweet potatoes. Though in this case, you’re not completely cooking the food in the freezer. You still need heat to finish the job.

But in Northeast China, people do use just the freezer to “cook” food. One example is pears.

Normally, they use proper Chinese winter pears, but I couldn’t find any. Thankfully, the process works the same with these normal pears, too. I defrosted and thawed the pear on the right 3 or 4 times.

I suppose as it froze, and ice crystals formed, it burst the fruit’s cells. It kinda looks like a burst water balloon. The texture has been utterly and permanently transformed. It’s more of a puree than a fruit. It might not look that appealing, but the thawed pear would blend much better into, say, ice cream or smoothies. And it tasted pretty good on its own, too, believe it or not.

Speaking of the freezer, what about dishes that are meant to be prepared and served cold?

Can we really only call food preparation “cooking” if heat is involved? If, say, a so-called “master sushi chef” spends their entire day elegantly preparing raw fish and vegetables, do they only get the title of “chef” because they cooked the sushi rice in a rice cooker? And what about straight-up raw dishes, like beef tartare, gazpacho, or even salads and sandwiches? Does the chef who made these dishes not qualify as a proper “cook” simply because they didn’t use heat? No, that’s ridiculous.

But let’s not get bogged down in semantics. There’s many definitions of cooking. Some mention heat, others don’t. Let’s be honest, it doesn’t matter in real life. You’re not gonna go in a restaurant kitchen and be like, “look guys, this ‘chef’ isn’t even using the hob.”

No, come on. Cooking is about a lot more than just heat, right? Sure, heat and temperature control are important in the kitchen. But there are loads of situations where you don’t need either. Between veg prep, fermentation, curing, and everything else I’ve mentioned, heat and temperature control are just another two tools in your cooking arsenal.