Ingredient Chemistry

When we talk about salt, we're really talking about tiny crystals of a mineral called sodium chloride. Our bodies naturally crave it – and more often than not, it's the key to amazing food.

Salt has its own distinct taste – 'salty' is one of the five main tastes that we talked about earlier in the pathway. But it also enhances other tastes, such as sweetness and umami, as well as suppressing less desirable flavors, like bitterness.

Salt also has other uses in cooking. It can dry out surfaces to make them crispier, it can be used as a preservative, and so on. As we said, salt is so often the key to an amazing piece of food.

So, salt has a taste of its own, but it's also a flavor enhancer.

When you add it to something rich in umami, like a beefy stew, it unlocks more complex flavors. Too much, and the stew will just taste like seawater. But if you can find the sweetspot, some salt will literally elevate a meal's taste.

Here's an experiment you can try. Take something meaty, like a chicken soup. Add a pinch of salt, and taste it. Add another pinch of salt, and taste it again. You'll notice how the flavors become deeper and more complex – then suddenly, you'll go one step too far, and the saltiness will ruin the soup.

If you're salting meat, you'll want to do it nice and early. Salt moves through food by diffusion, and diffusion takes a bit of time. Some chefs recommend rubbing salt on to the surface of a leg of meat a full 24 hours before cooking. That way, the salt can diffuse all the way through.

Interestingly, as salt diffuses through food, it actually pushes out water. Because of this, salt can also be used to dry out food. If you add it to a steak just an hour before frying, this 'drying' process will give that steak a crispier outer layer.

Of course, you don't always want to dry out food, so it’s important to get the balance right. With vegetables in particular, salting too early can make them dry and chewy. For best results, you should salt your vegetables about 15 minutes before cooking.

When you're cooking, the primary source of salt is those crystals of sodium chloride. This is what you find in a salt shaker; they're officially known as table salt.

However, salt can also be sourced from other ingredients, such as soy sauce. Certain fish, like anchovies, are salty too. Other options include seaweed, salted butter, and capers.

It’s important to remember, that while salt is totally amazing for cooking, it has been linked to health issues including high blood pressure. In other words, you should use it in moderation. Just a couple of pinches, here and there, should be enough to elevate a dish.

When we talk about acid, it refers to anything with a pH level under 7. That might sound like something from a chemistry class, but acid is actually super important in cooking.

Acids taste sour. For example, lemons are acidic. On its own, this sourness doesn't always taste great, but (just like salt) it enhances other flavors. The sour zing adds brightness, contrast, and complexity to dishes.

Acids also trigger your mouth to produce more saliva. This dilutes the acid, and is there to protect your teeth. But the added lubrication also improves the mouthfeel of food, improving the eating experience.

As a flavor enhancer, acids can be a massive help when flavors are overly sweet. For example, roasted carrots have a naturally sweet flavor, but a splash of vinegar will make them more complex and delicious. Acids also balance foods that are too umami, salty, or bitter.

Even if it’s not added directly to the food, an acid can work great on the side. For example, try pairing an umami-heavy meal with a side salad dressed in vinaigrette. The salad will provide a refreshing zing, which gives diners a change of pace.

Just like salt, acid should never be overused, but a splash here and there can work wonders. As with so much in cooking, it’s a balancing game that takes practice and experimentation.

Interestingly, fruit and vegetables will cook more slowly in the presence of acid. For example, if you boil them in red wine or tomato juice, they will soften much slower than they would if you boiled them in water.

Because of this, if you're cooking fruit or vegetables, it’s best to add acidic components towards the end of the cooking process. For instance, you might roast vegetables in the oven, then throw in a splash of balsamic vinegar with 5 minutes of cooking time left.

Acid also affects the color of vegetables, particularly greens, which can become duller or browner over time. This is another reason to add acids late on, even for something as simple as a dressing on a salad.

Acid also affects the texture of meat. It causes bundles of proteins to unwind, in a process known as denaturing. Cooking meat in red wine, or tomato sauce, will actually result in softer, more tender results.

There’s actually a technique called ceviche, which uses acid to "cook" fish. It’s surprising, but if you leave some pink chunks of salmon in lemon or lime juice, for about 20 minutes, they will come out looking (and tasting) cooked.

However, if you leave meat in acid for too long, the proteins will tighten up again. In many ways, the effect of acid on meat is similar to the effect of heat. Meat becomes more tender as you cook (or acid) it, but overcooking (or overaciding) makes it tough.

As a general rule, fats are animal-based and solid at room temperature, while oils are plant-based and liquid at room temperature.

Examples of fats include butter (derived from dairy), lard (derived from pork fat), and suet (derived from beef fat). Example of oils include olive oil, rapeseed oil, avocado oil, and coconut oil (you can guess what each of thoses is derived from).

So what can all these be used for? As we've already seen, oil is often used as a cooking medium, because it can reach higher temperatures than water. This is also the case for fats – their smoke point isn't usually as high as an oil, but something like butter can still get much hotter than water, which makes it an excellent choice for pan frying.

So, the first use of fats and oils is as a cooking medium. But these ingredients can be used in other ways too, to really bring a dish to life.

In particular, fats and oils make a massive difference to the texture of food. A simple example is a slice of toast – on its own, it’s relatively dry and bland, but add some melted butter, and suddenly it becomes moist and delicious.

Folding fat into pastry makes it flakier. Adding fat to a burger patty makes it juicier. If a dish ever feels like it’s lacking in texture, fats and oils will often be the solution.

Fats and oils also enhance taste. Each one has a distinctive flavor. Try taking that same slice of toast and drizzling one half with olive oil instead of butter. Does it taste different? Which one do you prefer?

Interestingly, many flavor molecules are repelled by water, but absorbed by fat. Because of this, beef fat, for example, actually contains more flavor molecules than the meat does.

To take advantage of this, a great skill to learn is rendering. Just take some solid animal fat, cut it into small pieces, and place it in a pot with some water. Cook it over a low heat until the water evaporates (this can take a few hours), leaving behind a clear liquid as the solid fat melts down.

Strain it through a sieve, then let it cool... and you'll end up with a liquid full of flavor. This liquid can be used as a cooking medium, just like oil. If you're frying vegetables or even a piece of meat, rendered fat will result in a stronger, meatier taste than you'd get with a plant-based oil.

Of course, you won't always want a meatier taste. Sometimes, the fruitiness of oil-fried food is preferable. It depends on the dish, and the experience you want to go for.

We've now learned the importance of fats and oils, as well as acid and salt. You can combine all of these to create some incredible dishes. For example, mixing red wine (acid), butter (fat), and a pinch of salt results in a delicious steak sauce. Combining balsamic vinegar (acid), olive oil (fat), and a pinch of salt makes an amazing salad dressing.

Mixing acids and fats/oils can be tricky, because they don't always readily combine. This is due to the molecular structure. Acids are polar, while fats are non-polar, meaning they repel each other instead of forming a stable mixture.

But this problem can be solved by adding an emulsifier – that's a third ingredient whose molecules act as a connective bridge between molecules of acid and molecules of fat/oil.

Popular emulsifiers include lecithin (found in egg yolk) and mucilage (found in mustard). If you're mixing vinegar and olive oil to make a vinaigrette, try adding a spoonful of mustard. Suddenly, you'll find that the acid and oil stop splitting.