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This is the final installment in our 3-part series on food science from the Modernist Cuisine team. We're giving away a copy of Modernist Cuisine at Home below, along with some handy equipment for your own Modernist kitchen. (We're selling copies in the Food52 Shop too, at an exclusive discount you won't find anywhere else.)
Water: Understanding Your Most Common Ingredient
By Nathan Myhrvold and Judy T. Oldfield
You have used a multitude of ingredients in your cooking, but nearly all of them share one thing in common: they contain water, and lots of it. From a chemical point of view, fresh foods are little more than water plus “impurities”: proteins, carbohydrates, fiber, and so on. A carrot, for example, is nearly 90% water; a pork loin, about 60%. So it should come as no surprise that much of cooking fundamentally comes down to manipulating water: adding it, removing it, using it as a solvent, or changing it from a liquid to a gas or a solid.
Many of the more challenging aspects of cooking can be traced to the counterintuitive behavior of water. H2O is a weird chemical. Boiling the stuff requires a tremendous amount of energy — but on the flip side, steam deposits a huge amount of heat when it condenses back into liquid form on the surface of food, speeding up the cooking. Water freezes in peculiar ways that can ruin ice cream — or can be exploited to concentrate fruit juices. And water is uncommonly good at dissolving certain kinds of ingredients — so much so that the inevitable impurities in our tap water can have dramatic effects on our cooking.
Let’s start with the proverbial watched pot. It takes so long to boil because the two hydrogen atoms (the Hs in H2O) in each water molecule have wandering eyes: sometimes instead of bonding faithfully with the oxygen atom (the O) in their own molecule, one of them will pair up with the oxygen in a neighboring molecule. It takes a lot of energy to sever those bonds and excite the water molecules enough that they fly away as steam. That’s why it takes so much longer to cook a pizza loaded up with wet toppings, such as tomatoes or pineapple, than it does to bake a plain cheese or pepperoni pie; much of the initial heat goes into boiling off the water in the toppings rather than melting the cheese and browning the crust.
It is possible to get foods hot enough to brown without drying them out, but only if you either dissolve lots of salt, sugar, or some other substance in the water to raise its boiling point or increase the air pressure over the water, which you can do by using a pressure cooker. Stocks in particular benefit from pressure-cooking, saving time and the amount of food needed.
Modernist chefs sometimes use the opposite technique — hooking up vacuum pumps to reduce the air pressure — to lower the boiling point of water. It’s a clever way to concentrate a juice or reduce a sauce without cooking away so much of the flavorful aromatics. The taste of the reduction remains wonderfully vibrant.
You can sometimes achieve similar effects by exploiting how ice crystals grow in water as it freezes. Seal fruit in a freezer bag and chill it at a temperature not far below 32°F. Slow-growing ice crystals become large and sharp, rupturing the cellular walls of the fruit and allowing you to extract more of the juice. (If preservation is your goal, you should instead freeze food fast and hard at the lowest temperatures you can, to keep the crystals as small as possible.)
The effect of dissolved sugar or salt on the boiling and freezing point of water can be dramatic, because water is a powerful solvent for these ingredients. Yet other substances, such as oils, don’t dissolve in water at all. The root of this behavior lies again in the molecular make-up of pure water. Hydrogen and oxygen atoms are differently charged. This imbalance is analogous to the north and south poles of a magnet. As a “polar” liquid, water readily dissolves large amounts of “polar” solids, such as sugar. But it resists intermingling with nonpolar foods, such as oils and fats.
As a cook, you should always keep this in mind: water comes out of the faucet already laden with dissolved minerals that affect your cooking. If your water is hard (rich in minerals), you may find that boiled vegetables turn out tough (and in particular, dried beans do not soften properly) because the minerals reinforce the natural mortar that holds plant cell walls together. In such cases, buy bottles of distilled or deionized water and cook with that instead. These purer alternatives are also handy when using Modernist ingredients such as hydrocolloid gelling and thickening agents, which are quite sensitive to calcium and some of the other minerals dissolved in tap water.
Water may be colorless, odorless, (nearly) tasteless, ubiquitous, and indispensable. But simple it is not.
Thanks to everyone who shared their brilliant modernist inventions with us -- we got together with the Modernist Cuisine team and picked a winner:
Congrats to Toni Kervina! The winning answer: "I would love there to be some sort of machine you could place over your food to see what's happening inside. Too long have I suffered from charred edges and uncooked middles!"
Us too! We loved Toni's simple but universal idea, and Judy Oldfield from the Modernist Cuisine team added, "The desire to see inside food is why we created cutaway photos."
And for those of you who didn't win, you still have time to pick up your copy (at a $40 discount) in the Food52 Shop.
Answer the question below in the comments section of this post by Monday, October 15th at 3pm EST*. Don't want to leave it up to chance? Get your copy now in the Food52 Shop (the first 10 orders get a signed bookplate!) with a discount you won't see anywhere else.
Sous-vide machines and pressure cookers have changed the way we cook. What's the not-yet-invented, life-changing kitchen gadget of your dreams?
*Sadly, the grand prize can only be shipped within the U.S., but if you don't live here (and don't know anyone here who could receive a sweet package on your behalf), we'll come up with something fun, but admittedly not as fabulous, to send you instead.
Photos: Book - Chris Hoover; Water - Ryan Matthew Smith / Modernist Cuisine, LLC; Pressure Cooker Cutaway - Tyson Stole / Modernist Cuisine, LLC
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