Cooking for Geeks: Real Science, Great Hacks, and Good Food
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You’ll need a standard ice cream mixer, or you can go all-out geek and either make your own (see DIY Lego Ice Cream Maker in Chapter 3) or use liquid nitrogen or dry ice. For the latter options, see the instructions in Making ice cream in Chapter 7.
To create the base, combine in a mixing bowl:
2 cups (475g) whole milk
1 cup (238g) heavy cream
⅓ cup (75g) sugar
¼ cup (75g) chocolate syrup
¾ cup (25g) medium-sized marshmallows
15 drops (0.75g) liquid smoke
Proceed with the directions for your chosen method of making ice cream. Once the ice cream has set, stir in:
1 cup (60g) graham crackers, toasted and chopped into pieces
Serve with hot fudge or chocolate syrup—whipped cream, cherries, and nuts optional.
Oven-Cooked Barbeque Ribs
In a large baking pan (9″ × 13″ / 23 cm × 33 cm), place:
2 pounds (1kg) pork baby back ribs, excess fat trimmed off
In a small bowl, create a dry rub by mixing:
1 tablespoon (15g) salt
1 tablespoon (15g) brown sugar
1 tablespoon (9g) cumin seed
1 tablespoon (9g) mustard seed
20 drops (1g) liquid smoke
Cover ribs with spice mix. Cover baking pan with foil and bake at 300°F / 150°C for two hours.
In a small bowl, create a sauce by mixing:
4 tablespoons (60g) ketchup
1 tablespoon (15g) soy sauce
1 tablespoon (15g) brown sugar
1 teaspoon (5g) Worcestershire sauce
Remove foil from baking pan and coat ribs with sauce. Bake for 45 minutes, or until done.
Note
Experiment with other savory spices in the dry rub, such as chilies, garlic, or paprika. Also, try adding items such as onions, garlic, or Tabasco to the sauce.
Making Liquid Smoke
The smells that we associate with that smoky, barbeque goodness result solely from the chemical reactions that occur during pyrolyzation (burning) of wood. The flavor that you think of as "smoky" does not come from a chemical interaction between the food and the smoke. This lucky quirk means that the chemicals in smoke can be isolated, so the stage of generating smoke flavor can be separated from the step of applying that flavor to food.
You can make your own liquid smoke for about $20 worth of supplies and a few hours of your time. For day-to-day uses, you’re way better off buying liquid smoke from the grocery store, but it’s rewarding to see how straightforward it is to make, and the process touches on some elementary chemistry techniques as well.
Liquid smoke is made by heating wood chips to a temperature high enough for the lignins in wood to burn, condensing the resulting smoke, and then dissolving it in water. The water-soluble components of smoke remain dissolved in the water, while the non-water-soluble components either precipitate out or form an oil layer that is then discarded. The resulting product is an amber-tinted liquid that you can brush onto meats or mix in with your ingredients.
What actually happens when you burn wood? Wood is primarily made of cellulose, hemicellulose, and lignin, which during burning convert to several hundred different chemical compounds. The aromatic molecules that provide smoke flavoring are generated by the lignin, which breaks down at around 752°F / 400°C. Cellulose and hemicellulose break down at lower temperatures (480–570°F / 250–300°C), but they generate compounds that both detract from the flavor and are mutagenic. This is why, when grilling, you should make sure you have a hot fire, which will guarantee that the lignins, and not just the celluloses, break down.
Making your own liquid smoke can be a little tricky because of the high heat required to properly burn the lignins and the difficulty in correctly capturing the resulting lignin-based compounds, not to mention the need for proper chemistry lab equipment for creating a closed system and heating it safely.
Kent Kirshenbaum demonstrates making liquid smoke during a talk at NYU’s Experimental Cuisine Collective (see http://www.experimentalcuisine.org). Here, he burns hickory chips using a propane blowtorch. The smoke is then piped through a water flask (on right), which traps the water-soluble particulate in suspension.
Start by placing wood chips—either hickory or cedar—into a vessel that can be sealed (to create a closed system) and heated with a burner or blow torch. Run a line from the closed system into a container of water, so as to filter the smoke vapor through the water. Heat the vessel, making sure to get it hot enough for the lignins to burn. Because the "tasty molecules" of the smoke are water soluble, the water will end up capturing those flavors, becoming your liquid smoke. Discard any solids that precipitate out or oils that separate and float to the top. Theoretically, something like this could be done with a pipe on a charcoal grill, with the pipe sealed on one end and copper tubing running from the other end into a water container, but it’s definitely not up to lab safety protocols.
If you do manage to make your own liquid smoke—it does make for a fun experiment—you’ll probably find that it’s a lot more work than it’s worth. Still, understanding that liquid smoke is nothing more than smoke particles captured in water removes most of the mystery about what’s in the bottle at your grocery store.
Chapter 7. Fun with Hardware
IF YOU’RE ANYTHING LIKE ME, THIS IS THE FIRST CHAPTER YOU’LL FLIP TO WHILE PERUSING THIS BOOK IN THE BOOKSTORE. And, might I add, you have excellent taste.
While this chapter is designed such that a foodie-geek can jump right in, really, it does assume that you’re up to speed with pairing flavors, that you understand various cooking and baking techniques, and that you’re familiar with some of the chemistry concepts covered in earlier chapters. So, don’t judge this book solely by this chapter.
Modern commercial kitchens, probably including the high-end ones in your town, use many tools that consumers rarely encounter but that can help create some absolutely stellar meals. We’ll cover a few of the commercial and industrial tools used in preparing foods, and throw in a few, uh, "crazy" (and fun!) things that you can do as well.
Time and temperature really are the two key variables in cooking (see Chapter 4). Under normal circumstances, cooking is performed with these variables at moderate values: roasting potatoes for half an hour at around 350°F / 177°C, baking pizza at 450°F / 230°C for 10 minutes, or churning ice cream at –20°F / –29°C for an hour or so. But what happens when you move one of these variables to an extreme?
Cooking at extreme temperatures isn’t as uncommon as it might sound at first. Potatoes, for example, wrapped in foil and roasted in the coals of a campfire are in an environment that reaches well above 800°F / 425°C. With this in mind, it shouldn’t be too much of a stretch to imagine baking thin-crust pizza in 45 seconds at 900°F / 480°C (the result is amazingly good!). And making ice cream in 30 seconds with liquid nitrogen isn’t just fun; this technique actually makes great ice cream because the water crystals don’t have time to form large aggregates, resulting in a smoother texture.
It’s also possible to move cooking times to extreme values. Sous vide cooking, the topic of the first half of this chapter, enables this by precisely controlling the temperature of the cooking environment, a water bath, so that it is equal to the target temperature of the cooked food. This allows time to run to extreme values without any risk of overcooking (at least in the conventional sense).
Beyond sous vide, other techniques can be used to produce new culinary creations—or at least, to return an iota of sanity to the life of the commercial chef by making some preparations vastly easier than they are with traditional methods. Filtration makes easy work of creating stocks, clear juices, and consommés. Cream whippers can "whip" air into liquids, allowing for the quick creation of not just whipped creams, but also mousses, foams, and even cakes. And for extreme temperature variations, we’ll take a look at blowtorches and high-heat ovens on the hot side and liquid nitrogen and dry ice on the cold side. We’ll talk a
bout all of this in the second half of this chapter.
Unfortunately, many of these techniques involve tools that you’re unlikely to find at your nearest shopping mall. Expect to do some online sleuthing or to break out the wire cutters and soldering iron, and be willing to try, try, and try again. This chapter is all about experimentation. As with the modern food additives section in Chapter 6, the "recipes" here are really only simple examples to give you a sense of where to start with your experiments. Use your creativity and imagination to create your own dishes!
Brownies in an Orange
Using food as a serving bowl is nothing new: stew in a bread bowl, sliced fruit in half a cantaloupe, and now, brownies in an orange.
Cut the top off and trim out the center.
Fill with brownie mix (guilty pleasure).
Bake until a toothpick inserted 1″ / 2.5 cm deep comes out clean. Dust with powdered sugar.
Sous Vide Cooking
With a name like "sous vide," this cooking technique sounds foreign, and for good reason: the French chef George Pralus introduced it to the culinary world in the 1970s. While foreign in origin, it is certainly not complicated or mysterious. At its simplest, sous vide cooking is about immersing a food item into a precisely temperature-controlled water bath, where the temperature is the same as the target temperature of the food being cooked. Translation? Ultra-low-temperature poaching. And since the temperature of the water bath isn’t hotter than the final target temperature, the food can’t overcook. Sous vide cooking essentially locks the variable of temperature in the "time * temperature" formula.
The temperature of the water bath is chosen to trigger chemical reactions (e.g., denaturing, hydrolysis) in some compounds in the food while leaving other compounds in their native state. It is one of the biggest culinary revolutions to hit the commercial cooking scene in the past few decades, but has appeared in the U.S. only recently. If I could pick only one new cooking method out of this entire book for you to try, sous vide would be it, hands down. The reason sous vide is so, well, amazing is that foods cooked this way have no gradient of doneness and the associated overcooked outer portion. Instead, the entire piece of food has a uniform temperature and uniform doneness.
Foods cooked sous vide have no temperature gradient, meaning that the entire portion of food is cooked to a consistent level of doneness.
The name sous vide (meaning "under vacuum") refers to the step in the cooking process where foods are placed in a vacuum-pack plastic bag and sealed. Using a vacuum bag—a plastic bag that is sealed after all the air in it has been removed—allows the water in the bath to transfer heat into the food while preventing the water from coming into direct contact with it. This means the water does not chemically interact with the food: the flavors of the food remain stronger, because the water is unable to dissolve and carry away any compounds in the food. (Sous vide is a funny name; I think it should have been called "water bath cooking," because the actual heat source is usually a bath of water. Bain-marie was already taken, I suppose. Still, as with the name "molecular gastronomy," once something gets popularized, it tends to stick.)
The steak tip on the left was cooked sous vide at 140°F / 60°C; the one on the right was pan-seared. Note that the sous vide steak has no "bull’s eye" shape—that is, it’s consistently medium-rare, center to edge, while the seared steak is well-done on the outside and rare in the middle.
Sous vide cooking doesn’t have to be done with a sealed bag in water. A few items don’t need to be packed at all. Eggs, for example, are already sealed (ignoring the microscopic pores), and when using this technique for secondary applications like preheating vegetables such as bok choy for steaming, there’s no benefit to sealing the food in plastic.
You can also use other fluids instead of water: oil, for example, or even melted butter. And because meats don’t absorb fat the same way that they can water, when using one of these as the liquid medium some applications can skip sealing. This can be extremely useful for those foods that might be difficult to seal. Chef Thomas Keller, for example, has a recipe for poaching lobster tails in a bath of butter and water (beurre monte, melted butter with water whisked in, which has a higher burning temperature than butter alone).
Temperature-controlled air would technically work as well, but the rate of heat transfer is much, much slower than for water—roughly 23 times slower. Given the low temperatures involved, something like chicken in a 140°F / 60°C "air bath" would take so long to come up to temperature that bacterial growth would be a serious concern. Using a liquid such as water ensures that heat can penetrate the food via conduction—liquid touching plastic touching food—rather quickly. Water is cheap and easy to use, so you’ll almost always see it called for, but some chefs do occasionally use other liquids.
The classic example given to explain how sous vide cooking works is cooking an egg. Since different egg proteins denature and coagulate at slightly different temperatures (most are in the range of 144–158°F / 62–70°C), holding an egg at various temperatures within that range will result in varying consistency of egg white and yolk. (Refer back to the discussion of egg proteins setting at different temperatures in 144°F / 62°C: Eggs Begin to Set in Chapter 4.)
To some, a "perfect" soft-cooked egg should have a slightly runny, custard-like yolk and a mostly set white. Cooking an egg in water brought to a boil can result in an overcooked end result, because the temperature of the egg ramps up to boiling point until it is pulled out. In sous vide, the temperature of the egg reaches only the ideal temperature of the cooked egg, so it cannot overcook.
By immersing the egg in a water bath held at that temperature you ensure that the egg cannot get any hotter, so in theory, those proteins that set at a higher temperature will remain in their native form. In reality, most chemical reactions in cooking aren’t specific to a particular temperature, but are dependent on time-at-temperature. In practice, though, this simple model is accurate enough to explain how sous vide cooking works.
For a "perfect" soft-cooked egg, try cooking it sous vide at 146°F / 63°C for one hour. Because eggs contain many proteins that set at slightly different temperatures, you can experiment by adjusting the temperature up or down a few degrees to suit your personal preferences.
Cooking eggs in a sous vide bath at 144.5°F / 62.5°C.
For other foods, consider the compounds they contain, determine the temperatures at which the compounds undergo their different transformations, and pick a temperature high enough to trigger the reactions you do want, yet low enough not to trigger the ones you don’t.
Note
Tip: after cooking an egg sous vide, crack open and drop the egg (without shell!) into a pot of just-boiled water. Then fetch the egg out immediately. The hot water will rapid-set the outside of the egg for better appearance and easier handling.
Sous vide cooking isn’t a magic bullet, though. For one thing, the textures of some foods break down when held at temperature for any extended period of time. Some types of fish will break down due to enzymatic reactions that normally occur at such a slow rate that they are not noticeable in traditional cooking methods. Sous vide also doesn’t reach the temperatures at which Maillard reactions or caramelization occur; meats cooked sous vide are commonly pan seared or even blowtorched briefly after cooking to introduce the flavors brought about by these browning reactions. The largest drawback, however, is the requirement to pay serious attention to food safety issues and pasteurization.
Note
Pasteurization reduces bacterial levels to a point where food can be considered reasonably safe. If it is stored improperly after pasteurization, bacteria can reproduce above safe levels.
Sterilization completely eliminates the target bacteria.
Foodborne Illness and Sous Vide Cooking
Sous vide cooking, when done properly, can safely create amazingly tender chicken, a perfect soft-cooked egg, or a succulent steak. However, it’s also possible to set up a perfect breeding ground f
or bacteria if the food is mishandled. The heat involved in sous vide cooking is very low, so if you start with, say, a very large piece of frozen meat, it will take a long time to come up to temperature and will spend too much time in the breeding ranges of common foodborne pathogens.
With sous vide cooking, it is possible to cook meats to a point where they are texturally done—proteins denatured—but have not had sufficient time at heat for bacteria and parasites to be rendered nonviable. For these reasons, sous vide cooking has run afoul of some restaurant health inspectors: without proper procedures and clear guidelines, pathogens such as listeria and botulism are valid concerns when the food is mishandled. These concerns can be addressed with a clear understanding of where the risks are and what factors mitigate them. With the popularity of sous vide cooking on the rise, health inspectors are creating new guidelines, and depending upon where you live, they might already be comfortable blessing restaurants that have demonstrated proper handling procedures.
With low-temperature cooking, it’s possible to violate the "40–140°F / 4–60°C danger zone" rule (see Foodborne Illness and Staying Safe in Chapter 4) and its derivative rule:
Thou shalt pasteurize all potentially contaminated foods.
In the FDA’s Bad Bug Book, the highest survival temperature listed for a foodborne pathogen at the time of this writing is 131°F / 55°C, for Bacillus cereus, which is relatively uncommon (you’re 50 times more likely to get ill from salmonella) and, while unpleasant, has caused no known fatalities. The next highest survival temperature listed by the FDA is 122°F / 50°C, which gives you an idea of how much of an outlier B. cereus is.