Cooking for Geeks: Real Science, Great Hacks, and Good Food

by Jeff Potter

  Note

  Where it says "not homogenized," it really means not homogenized. (The milk can, and probably should, be pasteurized, though.) If you use homogenized milk, you’ll end up with a squeaky mess that vaguely resembles cottage cheese but doesn’t melt together. The homogenization process disrupts the protein structures such that they can no longer bind together.

  Once the liquid is at 88°F / 31°C, add the calcium chloride and rennet mixtures and continue to slowly heat to 105°F / 40.5°C, stirring every few minutes. At this point, you should begin to see curds separating from whey.

  Once the liquid is at 105°F / 40.5°C, remove from heat, cover the pot, and wait 20 minutes. At this point, the curds should be fully separated from the whey; if not, wait a while longer.

  Transfer the curds to a microwave-safe bowl using a slotted spoon, or strain out the whey and transfer it from your strainer. Squeeze as much of the whey out of the curd as possible, tipping the bowl to drain the liquid. Microwave on high for one minute. Squeeze more of the whey out. The cheese should now be sticky; if not, continue to microwave in 15-second increments until it is warm and sticky (but not too hot to handle).

  Add ½ teaspoon flaked salt to the cheese and knead. Microwave for one more minute on high until the cheese is around 130°F / 54.4°C. Remove and stretch, working it just like playing with silly putty: stretch, fold in half, twist, and stretch again, over and over, until you’ve achieved a stringy texture.

  Notes

  The addition of acid denatures proteins in the milk, helping curd formation. Citric acid is commonly used. For similar reasons, many cheeses use rennet—traditionally derived from calf stomach—because it has a number of enzymes that break down proteins in the milk.

  The lipase powder is not chemically required, especially given that animal-based rennet contains lipase. Your rennet source might not contain it, however, and the lipase enzyme is responsible for the characteristic flavor of mozzarella because of the way it cleaves the fats in milk. For a lacto-vegetarian mozzarella cheese, use vegetable-based rennet and skip the lipase powder, but note that the cheese will not have the traditional flavor. For a source of lipase, try http://www.dairyconnection.com or http://thecheesemaker.com/cultures.htm.

  For a good writeup on making mozzarella following a more traditional, more authentic, and much more involved approach, see http://fiascofarm.com/dairy/mozzarella.htm.

  Green Olives

  If you are lucky enough to have access to an olive tree during the fall, when the unripe fruit is available, try your hand at making green olives.

  Unlike the mature black fruit of the olive tree, olives in their green form can be soaked in lye (sodium hydroxide, a.k.a. caustic soda) to remove the bitter compound oleuropein that is present in the unripe flesh.

  Obtaining food-grade sodium hydroxide might require some searching online; http://www.lyedepot.com carries food-grade micro beads. Do not use industrial products such as Drano, because they contain other chemicals! Also, because lye is extremely corrosive, take great care not to come into direct contact with it. Use rubber gloves and eye protection, and consider finding an outdoor space that is more forgiving of accidental spills than your kitchen.

  In a large plastic bucket or glass jar, place:

  Green olives of a consistent size, with any of the fruit that is bruised or soft discarded

  Room-temperature water (add enough to completely cover olives)

  Transfer the water to a second plastic bucket or glass jar, and measure how much water you used. (Adding it to the first container was just to determine the amount needed.) Add to the water:

  1 tablespoon of lye per quart of water for a 1.5% solution

  Stir carefully to combine, and gently pour over olives into the first container. Soak for one day.

  After a day, discard the lye/water solution and refresh with a new batch of water and lye. Soak for an additional day.

  After the second day, take an olive out and cut into it, exposing the pit. If there is any whiteness near the center, discard the lye/water solution again and refresh with a new batch. Repeat until the entire olive flesh is a consistent color.

  Once the olives are cured to the center, drain the liquid and soak in fresh water. A day later, replace the fresh water with salt water, using 1 tablespoon of salt per quart. Replace the salt water daily for three to five days. Transfer to a jar, fill with salt water, and store in the fridge.

  Notes

  As with the scallops in ceviche, you can see the flesh of the olive change over time as the sodium hydroxide penetrates to the center of the olive.

  Try adding vinegar and spices (e.g., bay leaves, rosemary) to the final saltwater brine to impart those flavors into the olives. For suggestions on further variations, including other curing techniques, see UC Davis’s excellent writeup at http://anrcatalog.ucdavis.edu/pdf/8267.pdf.

  Be careful with the lye! No, really, I mean it. Pretend that it’s oil at 400°F / 200°C. Also, avoid metal containers or utensils, because lye reacts with metal, especially aluminum. Wood, plastic, stainless steel, and glass are okay.

  If any of the olives float above the surface, you can place a glass or plate on top of the bowl to immerse them fully. (Floating olives will oxidize.)

  Alcohol

  A number of organic compounds that provide aromas in food are readily dissolved in ethanol but not in water. You will invariably encounter dishes where alcohol is used for its chemical properties, either as a medium to carry flavors or as a tool for making flavors in the food available in sufficient quantity for your olfactory system to notice.

  Note

  Ethanol can react with carboxylic acids in acid-catalyzed conditions, forming compounds that then react with more ethanol to generate water and the ester compounds that help carry aromas up into the nasal cavity.

  Alcohol is often added to sauces or stews to aid in releasing aromatic compounds "locked up" in the ingredients. Try adding red wine to a tomato sauce or dribbling a bit of Pernod (anise liqueur) on top of a piece of pan-seared cod served with roasted fennel and rice.

  You can also make your own flavor-infused vodkas by adding diced fruit, berries, herbs, or other spices to straight vodka. And since your concoction doesn’t have to be shelf-stable like commercial varieties, you can generate better-tasting infusions. Don’t limit yourself to just vodkas, either; try adding mint and a small quantity of sugar syrup to bourbon whiskey and storing it in the freezer.

  Does Alcohol "Burn Off" in Cooking?

  No, not entirely. Even though the boiling point of pure ethanol (C2H5OH) is lower than that of water at atmospheric pressure (173°F / 78°C), the intermolecular bonding between ethanol and other compounds in the food is strong enough that its boiling point varies based on the concentration of ethanol in the food and how the other chemicals in the food hold on to it.

  The table to the right shows the percentage of alcohol remaining after various cooking methods according to a paper published by researchers at the University of Idaho.

  Cooking method

  % remaining

  Alcohol added to boiling liquid and removed from heat

  85%

  Alcohol flamed

  75%

  No heat, stored overnight

  70%

  Baked, 25 minutes, alcohol not stirred into mixture

  45%

  Baked/simmered, alcohol stirred into mixture:

  ...for 15 minutes

  40%

  ...for 30 minutes

  35%

  ...for 1 hour

  25%

  ...for 2 hours

  10%

  Fat-Washing Alcohols: Butter-Infused Rum, Bacon-Infused Bourbon

  The term "fat washing" comes from the process of using fat to "wash out" undesirable molecules, but it is more useful in the home kitchen (and in molecular mixology) as a way of infusing oil-soluble compounds into alcohol. If you use a non-neutral flavored fat—a fat that has other molecules mixed in—some of the flavorfu
l molecules will bind with the alcohol molecules (it is a solvent, after all) and remain behind in the drink.

  Why do this? Because you can create infused alcohols with flavors that might not come out in traditional infusing. The flavors can either be native to the fat (butter, bacon) or fat-soluble compounds bloomed in the fat before fat washing.

  Create an infusion of 3–5% fat and 95–97% alcohol. Try 2 teaspoons (10g) of melted butter with 1 cup (200g) of rum or 2 teaspoons (10g) of bacon fat (filtered!) with 1 cup (200g) of bourbon. Let rest at room temperature for 12+ hours. Longer times and higher temperatures will yield a stronger infusion, so you’ll want to experiment.

  Try using an immersion blender to kick-start the infusion.

  After infusing, place infusion in freezer until fats have solidified, and then filter through a coffee filter or other ~20-micron filter (see the filtration section in Filtration in Chapter 7).

  Unfiltered.

  100 micron filter.

  ~10–20 micron filter.

  Notes

  Try this with blue cheese, nut butters, and other fats.

  A key step in refining alcohol is the removal of undesirable compounds. It’s impossible to remove every last "bad" molecule, but the more that are removed, the better tasting the beverage will be. This is why "the good stuff" costs more: refiners are able to remove more of the off-tasting compounds by increasing the number of steps in processing or giving the alcohol longer to age, which allows for better yield of the chemical reactions that remove the compounds. Fat washing can be used as a DIY way to further refine an alcohol: the compounds will bind with some of the fat molecules, which can then be removed by simple filtration. Try using a neutral-flavored fat, such as lard, for refining without altering the flavor.

  Incidental advice if you ever find yourself writing a book involving alcoholic drinks: don’t write after drinking your experiments.

  Vanilla Extract

  In a small glass jar with a tight-fitting lid, put:

  1 vanilla bean, sliced open lengthwise and chopped into strips to fit jar

  1 oz (30g) vodka (use enough to cover vanilla bean)

  Screw lid on jar or place plastic wrap over top and store in a cool, dark place (e.g., pantry) for at least a few days. Give the extract at least several weeks to steep.

  Notes

  The vanilla bean can be left over from some other recipe. If you cook with vanilla frequently, consider keeping the jar of vanilla constantly topped off. Whenever you use a vanilla bean, add it to the jar, removing an old one when space requires it. And as you use the extract, occasionally top off the jar with a bit more vodka or other liquor such as rum.

  Play with other variations: instead of vodka, which is used for its high ethanol content and general lack of flavor, you can use other spirits such as rum, brandy, or a blend of these.

  The ethanol dissolves a number of compounds present in the vanilla bean, including the compound vanillin, which gives vanilla its characteristic flavor.

  Instead of vanilla beans, try using star anise, cloves, or cinnamon sticks. Or try varying both solvent and substance (e.g., orange rind with Grand Marnier).

  Flavored alcoholic drinks can be made with this same technique. Instead of a large quantity of the solute (e.g., vanilla bean) and a minor amount of solvent (e.g., vodka), place a small bit of the solute into a bottle of the solvent. For an example, search online for nocino, an Italian walnut liqueur made with unripe walnuts, aromatic spices, and ethanol.

  Sage Rush: Gin, Sage, and Grapefruit Juice

  This is a simple cocktail and a darn good one. And having a simple, darn-good cocktail in your repertoire can be handy. It only takes knowing one good drink to impress that romantic potential.

  Put two or three sage leaves (fresh!) in a shaker and muddle with the back side of a spoon. Add 1 part gin and 1 part pink grapefruit juice—say, 2 oz (50 ml) of each—and add several ice cubes. Shake vigorously. Strain into a martini glass.

  Note

  If you have fresh pink grapefruit, use that. Squeeze the juice from half a grapefruit and add gin to taste. You can muddle the sage leaf post-shaker directly in the glass as well.

  When a Molecule Meets a Molecule...

  Alcohol isn’t the only solvent in the kitchen. The same chemical interactions that give alcohol its magic apply to oil and water, which is why recipes call for steps such as toasting caraway seeds in oil: the oil captures the molecules responsible for the characteristic nutty flavors developed and released by heating the seeds.

  But how does a solvent work? What happens when one molecule bumps into another molecule? Will they form a bond (called an intermolecular bond) or repel each other? It depends on a number of forces that stem from differences in the electrical charges and charge distributions of the two molecules.

  Of the four types of bonds defined in chemistry, two are of culinary interest: polar and nonpolar.

  A molecule that has an uneven electrical field around it or that has an uneven arrangement of electrons is polar. The simplest arrangement, where two sides of a molecule have opposite electrical charges, is called a dipole. Water is polar because the two hydrogen atoms attach themselves to the oxygen atom such that the molecule as a whole has a negatively charged side. When two polar molecules bump into each other, a strong bond forms between the first molecule’s positive side and the second molecule’s negative side, just like when two magnets are lined up. On the atomic level, the side of the first molecule that has a negative charge is balancing out the side of the second molecule that has a positive charge.

  A water molecule is polar because the electrostatic field around the molecule is asymmetric, due to the oxygen atom being more electronegative than the hydrogen atoms and the resulting differences in how the two hydrogen atoms share their electrons with the oxygen atom. (Electron sharing is another type of bond, a covalent bond.)

  A molecule that has a spherically symmetric electrostatic field—that is, there is no dipole, and the molecule doesn’t have a "side" that has a different electrical charge—is nonpolar. Oil is nonpolar because of the shape in which the carbon, oxygen, and hydrogen atoms arrange themselves.

  In most cases, when a polar molecule bumps into a nonpolar molecule, the polar molecule is unlikely to find an electron to balance out its electrical field. It’s a bit like trying to stick a magnet to a piece of wood: the magnet and wood aren’t actively repelled by each other, but they’re also not actually attracted. It’s the same for polar-nonpolar interaction: the molecules might bounce into each other, but they won’t stick and will end up drifting off and continuing to bounce around into other molecules.

  This is why oil and water do not mix. The water molecules are polar and form strong intermolecular bonds with other polar molecules, which are able to balance out their electrical charges. At an atomic level, the oil doesn’t provide a sufficiently strong bonding opportunity for the negatively charged side of the water molecule.

  Water and sugar (sucrose), however, get along fine. Sucrose is also polar, so the electrical fields of the two molecules are able to line up to some degree. The strength of the intermolecular bond depends on how well the two different compounds line up, which is why some things dissolve together well while others only dissolve together to a certain point.

  Extracts for drinks

  Bitters are to bartenders what extracts and spices are to chefs: they provide flavor with minimal impact on texture, volume, or other variables. Bitters refers to any extract that includes a bittering agent, such as gentian, quinine, or citrus rind. Angostura bitters is the "generic" bitter—one of the few to have survived through the Prohibition era—and is what most people think of when a recipe calls for bitters. Campari is also a bitter, although not commonly described this way. Bitters come in a range of flavors: from the complex and spicy (clove, anise, cinnamon) to the bright and clean (orange, grapefruit, mint).

  This collection of bitters shows just a small selection of the flavors available.

/>   Bitters can be used as flavorings in things besides alcoholic drinks. Try a dash of bitters in soda water, along with a slice of lime. Since they are a subset of extracts, you can use them in any place where a bitter extract would work. You can balance out bitterness with the addition of sugar, just as is done in an old-fashioned cocktail. Bitters as an accent flavor in a chocolate truffle? As part of a dressing? Try it!

  Bitters recipes can be quite complicated, requiring exotic ingredients and involving dozens of steps taking upward of a month. If you want to try your hand at one of the more involved recipes, try the one that follows here. For additional recipes, pick up Gary Regan’s book, The Joy of Mixology (Clarkson Potter), from which the recipe on the following page is adapted with permission. His recipe uses both ethanol and water as solvents. The ethanol at the beginning dissolves one set of organic compounds present in the spices. Later, the water dissolves a different set. Notice that the ethanol that contains the first set of alcohol-solvent organic compounds is never subjected to heat!

  Regan’s Orange Bitters No. 5

  Combine in a large jar:

  2 cups (450g) grain alcohol such as Everclear or vodka

  ½ cup (160g) water