Lab: Salmon Gravlax

Salmon Gravlax

Salt curing has been used for centuries to preserve fish caught at sea. It’s also easy to do at home! Surrounding fish with a sufficient quantity of salt draws out the moisture; this is called dry brining. But salt doesn’t just dry out the food (along with any bacteria and parasites). At sufficient concentration, dry brining actively disrupts a cell’s ability to function and kills it, rendering bacteria and parasites nonviable.

In a bowl, mix together:
     5 teaspoons (30g) kosher salt
     1 tablespoon (12g) sugar
     3 tablespoons (12g) finely chopped fresh dill
     1 teaspoon (5 mL) vodka
     1 teaspoon (2g) crushed peppercorns (ideally, use a mortar and pestle)
On a large piece of plastic wrap, place:
     1 pound (450g) salmon, washed and bones removed; preferably a center cut so that its shape is rectangular
Sprinkle the salt mixture over the fish and massage it in. Wrap the fish in plastic and store it in the fridge, flipping and massaging it twice a day for a day or two.
Store it in the fridge and consume within a week.
Remove the skin from your salmon fillet.
Remove the skin by placing the fish skin-side-down on a cutting board and carefully running a knife along the surface between the skin and flesh while using your hand to keep the fish from sliding around.
     • Vodka is used here as a solvent to dissolve some of the non-water-soluble aromatic compounds. You can substitute other spirits, such as cognac or whiskey, to bring additional flavors in. And in place of dill, try using coriander seed, loose tea leaves (e.g., Earl Grey or Lapsang Souchong), shallots, or lemon zest. The Scandinavians traditionally serve salmon gravlax on top of bread with a mustard dill sauce.
      • You can substitute other fatty fish, such as tuna, for the salmon and obtain a similar texture.
     • This recipe is a bit heavy on the salt—6% by weight—to err on the side of safety. You can reduce the saltiness before eating the fish by rinsing the finished product in fresh water. Curing above 3.5% salt prevents most common bacterial growth, but not all. Modest concentrations of salt prevent Gram-negative bacteria—which are the most common ones found in food—from growing, but won’t handle the few that are Gram-positive, such as Listeria.
     • Salt curing—as is done in salmon gravlax— is the first step in making lox. After curing, lox is also cold-smoked, which is the process of exposing a food to smoke vapors that have been cooled down. You can approximate the flavor of lox by adding liquid smoke to the rub.

Traditional Preservatives: Salt & Sugar

Ahh, salt: responsible for the salvation of many a food (or is that salivation?). The oldest chemical in use, salt was used in prehistoric times and there are records of its use for drycuring hams in the third century BC by the Roman Cato the Elder. The use of sugar as a preservative wasn’t far behind; the Romans used honey to preserve foods as well. And another historical preservative is vinegar, used as an acidity regulator (sounds delicious when I put it that way, no?).
Chemical preservation has the fundamental purpose of preventing microbial growth. While there are plenty of other ways to preserve food, like smoking or drying, using chemicals doesn’t necessarily change flavors as much. Sausages, vinegar pickles, and fruit preserves all rely on chemicals to keep them safe for eating. Chemicals prevent microbial growth by either disrupting cells’ abilities to function, as nitrite does to sausage, or by changing any of the FAT TOM variables to be inhospitable, such as increasing acidity with vinegar or reducing moisture with sugar in fruit preserves.
Salt’s ability to kill pathogens and preserve things isn’t limited to foods. For an adult human, the lethal dose of table salt is about 80 grams—about the amount in the saltshaker on your typical restaurant table. Overdosing on salt is reportedly a really painful way to go, as your brain swells up and ruptures. Plus, it’s unlikely the emergency room physicians will correctly diagnose the cause before it’s too late.
While the chemistry of preservatives may not seem important to everyday cooking, it’s revealing to understand how these ingredients work, and the basics of preservation apply to how most other food additives work. First, a quick refresher on a few definitions that’ll pop up throughout this post:
Basic building block of matter. By definition, atoms have the same number of electrons and protons. Some atoms are stable in this arrangement (e.g., helium), making them less likely to form bonds with other compounds (which is why you don’t see any compounds made of helium). Other atoms (e.g., sodium) are extremely unstable and readily react. A sodium atom (Na) will react violently with water (don’t try licking a sample of pure sodium—it’d ignite due to the water on your tongue), but when an electron is removed it turns into a delicious salty sodium ion (Na+).
Two or more atoms bonded together. H = hydrogen atom; H2 = two hydrogen atoms, making it a molecule. When it’s two or more different atoms, it becomes a compound (e.g., H2O). Sucrose (a.k.a. sugar) is a compound with the composition C12H22O11—12 carbon, 22 hydrogen, and 11 oxygen atoms per molecule. Note that the composition doesn’t tell you what the arrangement of the atoms is, but that arrangement is part of what defines a molecule.
Any atom or molecule that’s charged—that is, where the numbers of electrons and protons aren’t equal. Because of the imbalance, ions can bond with other ions by transferring electrons to (or from) each other.
An atom or molecule that’s positively charged. Pronounced “cat-ion”—meow!—a cation is any atom or molecule that has more protons than electrons; it’s paw-sitively charged. For example, Na+ is a cation—an atom of sodium that has lost an electron, giving it more protons than electrons and thus a net positive charge. Ca2+ is a cation—a cation of calcium—that has lost two electrons.
An atom or molecule that’s negatively charged (i.e., one that has more electrons than protons). Cl– is an atomic anion—in this case an atom of chlorine that has gained an extra electron, giving it a net negative charge.
From these definitions, you’ll hopefully deduce that a lot of chemistry is about ions interacting with each other based on differences in electrical charges. Sodium chloride, common table salt, is a classic example: it’s an ionic compound composed of a cation and an anion. In solid form, though—the stuff in your salt shaker—salt is more complicated than one anion plus one cation. It takes the solid form of a crystal of atoms arranged in an alternating pattern (like a 3D checkerboard) based on charge: cation, anion, cation, anion. In water, the salt crystals dissolve and the individual ions are freed (disassociated). The anions and the cations separate out into individual ions, which can then react and form bonds with other atoms and molecules. That’s why salt is so amazing! Sucrose doesn’t do this. Sodium chloride is one particular type of salt, made up of sodium (a metal, and one that in its pure form happens to react violently when dropped in water) and chloride (chlorine with an extra electron, making it an anion). There are many other types of salts, created with different metals and anions, and they don’t always taste salty. Monosodium glutamate, for example, is a salt that tastes savory and boosts the sensation of other flavors. Epsom salt— magnesium sulfate—tastes bitter.
Multiple types of salts are used to preserve foods. Salmon gravlax is cured with a large amount of sodium chloride, which preserves the fish by increasing osmotic pressure, dehydrating and starving living microbial cells of critical water as well as creating an electrolytic imbalance that poisons them. Many sausages, hams, prosciutto, and corned beef are cured using small quantities of sodium nitrite, which also gives these foods a distinctive flavor and pinkish color. Unlike gravlax, in which the sodium does the preserving, sodium nitrite works because of nitrite; the sodium is merely an escort for the nitrite molecule. Nitrites inhibit bacterial growth by preventing cells from being able to transport an amino acid, meaning they can’t reproduce. (Incidentally, nitrites are also toxic to us at high levels, for presumably the same reason; but without the nitrites, microbial growth would be toxic to us too—dosage matters!)
Sugar can also be used as a preservative. It works like sodium chloride, by changing the osmotic pressure of the environment (see page 386 for more on osmosis in food). With less available water, sugary foods such as candies and jams don’t require refrigeration to prevent bacterial spoilage. Think back to the M in the FAT TOM rule: bacteria need moisture for growth, and adding sugar reduces their ability to drink.
Sugar’s osmotic properties can be used for more than just preserving food. Researchers in the UK have found that sugar can be used as a dressing for wounds, essentially as a cheap bactericidal. The researchers used sugar (sterilized, please), polyethylene glycol, and hydrogen peroxide (0.15% final concentration) to make a paste with high osmotic pressure and low water activity, creating something that dries out the wound while preventing bacteria from being able to grow. Whoever thought of rubbing salt in a wound should’ve tried sugar!
Besides salts and sugar starving microbes of vital water, enzymatic inhibitors and acids are used to prevent their growth. Benzoate is one of the most commonly used modern preservatives, often used in breads to prevent mold growth. (Fans of The Simpsons may recall potassium benzoate as part of the curse of frogurt—see Like nitrite, benzoate interferes with a cell’s ability to function (in the case of bread, by decreasing fungi’s ability to convert glucose to adenosine triphosphate, thus cutting off the energy supply).
Compounds that lower a food’s pH also preserve the food, and are so critical that acidity regulators get an entire section in the E numbers list. Many of these compounds don’t have uses interesting to the home cook, who already has citric acid (thanks, lemon juice!) and acetic acid (from vinegar) on hand. For industry, the other acidity regulators give a wider range of flavoring options and functional properties, but for home use, there isn’t much re-purposing to be explored beyond a few baking tricks like using a pinch of vitamin C (ascorbic acid) to give yeast a boost during fermentation.
Check back next week for my recipe for Salmon Gravlax.

Pizza Dough—No-Knead Method

Christine reaches for a slice of pizza.

This makes enough dough for one medium-sized pizza with the crust rolled thin. You’ll probably want to multiply these quantities by the number of people you’re cooking for.
Weigh into a large bowl or container:
1 1/3 cups (185g) flour
1 teaspoon (6g) salt
1 tablespoon (9g) instant yeast
Using a spoon, mix together so that the salt and yeast are thoroughly distributed. Add:
½ cup (120 mL) water
Mix in the water using the spoon so that the flour and water are incorporated. Cover the bowl or container with plastic wrap and let it rest on the counter for six hours, preferably longer. When ready, transfer the dough to a floured cutting board and gently stretch the dough out, pushing it into either a rectangular or circular pizza shape from the center. For a more rustic crust, leave the edge thicker and handle it minimally to leave more air pockets in the dough. For a thinner crust, roll the dough out. Follow standard pizza making instructions from this point on.
You can mix the ingredients together at breakfast time, before running off to your day job or wherever, and the dough will be ready by the time you get home. The glutenin and gliadin proteins will slowly crosslink on their own.
Note: If you want to experiment, order some sourdough yeast culture (which is actually a culture of both the well-known sourdough strain of yeast and the bacteria Lactobacillus). The ratio of yeast to bacteria in the dough will impact the flavor. You can control that ratio by letting the dough mature for some amount of time in the fridge, where yeast will multiply but bacteria won’t, and some amount of time at room temperature, where the bacteria will contribute flavors.

How to Cook a High-Heat Pizza

A serious examination of pizza is clearly a must-have for a book called Cooking for Geeks. Pizza covers so many variables: flavor combinations, Maillard reactions, gluten, fermentation, moisture levels, and temperature. We’ve covered most of these elsewhere in the book, but we haven’t yet talked about temperature, which is key to a good crust.

Great thick-crust pizzas have a great interior that comes from good dough that’s baked at moderate temperatures. My local delicious thick-crust pizza place runs its oven at 450°F / 230°C in the winter, 350°F / 180ºC in the summer. (The oven can’t be run any hotter in summer without the kitchen becoming unbearable; they just bake the pizzas longer.) Easy enough.

But if you want to make a crispy thin-crust pizza, high heat is critical for creating a great crust. The lower temperature bound I’ve found acceptable for great flat-crust pizza was 600°F / 315°C. At 700°F / 370°C, the crust becomes noticeably better. The best thin-crust pizzas I’ve had were cooked in wood-fired brick ovens or on a grill over wood charcoal with temperatures running between 750°F / 400°C and 900°F / 480°C. Sadly, most ovens max out at 550°F / 290°C, making great thin-crust pizza hard to do in the oven. What’s a thin-crust pizza-loving geek to do? If only there were a flow chart for this…

Wood Grill Method
This is by far the easiest method. Grills fueled by charcoal or wood get hot, easily up into the 800°F / 425°C temperature range. (Propane grills tend to run cooler, even though propane itself technically burns hotter.)
Wood charcoal grill temperature: 742°F/ 394°C.
Cooking with a Lot of Heat 371
Place a pizza stone on top of the grill and light the fire. Once the grill is hot, transfer the pizza with toppings onto the grill. Depending upon the size of your grill, you may be able to cook the pizza directly on top of the grill, sans stone—give both a try!
Super-hot Cast Iron Pan Method


Grill-lusting apartment dwellers have to get creative to create high-heat pizza. While most ovens limit the temperature to 550°F / 290°C, both the oven’s broiler and the stovetop reach higher temperatures. Preheat the oven to 550°F / 290°C, or as hot as it goes. Heat up an empty cast iron pan on the stovetop at maximum heat for at least 5 minutes. Switch the oven to broiler mode, transfer the hot cast iron pan to the oven, flipping it upside down and setting under the broiler set to high. Parbake the pizza dough until it just begins to brown, about 1–2 minutes. Transfer the dough to a cutting board and add sauce and toppings. Transfer the pizza back to the cast iron pan and bake until toppings are melted and browned as desired.
Cleaning Cycle Method (a.k.a. “oven overclocking”)


While consumer ovens top out at 550°F / 290°C, that doesn’t mean they can’t get hotter. It’s just dangerous, voids your warranty, and, given that the alternative ways of getting this kind of heat are far easier, is really not worth doing. Still, in the name of science…


Ovens get a lot hotter—a lot, lot hotter—when they run in the cleaning cycle. The problem is that ovens mechanically lock the door, preventing you from slipping a pizza in and out, and leaving a pizza in for the entire cleaning cycle will result in less-than-tasty charcoal.


Cut or remove the lock, however, and ta-da! You’ve got access to a superheated oven. After some fiddling, I took my oven to over 1,000°F / 540°C. The first pizza we tried took a blistering 45 seconds to cook, with the bottom of the crust perfectly crisped and the toppings bubbling and melted.
However, the center of the pizza never had a chance to heat up, so the 1,000°F / 540°C pizza wasn’t quite right. Another attempt at around 600°F / 315°C was remarkably good but didn’t capture the magic of the crispy thin crust and toasty-brown toppings. At around 750–800°F / 400–425°C, however, we started getting pizzas that were just right.
Ovens aren’t designed to have their doors opened when running in the cleaning cycle. Honestly, I don’t recommend this approach. I broke the glass in my oven door and had to “upgrade” it, although it is cool to have bragging rights to an oven sporting a piece of PyroCeram, the same stuff the military used for missile nose cones in the 1950s. Given that an upside-down cast iron pan under a broiler or a wood-fired grill turns out delicious flat-crust pizzas, I’d recommend skipping the oven overclocking, as much fun as it is.
Check back next week for my Recipe: No-Knead Pizza Dough.


The Sweet Way To Calibrate Your Oven

What if you don’t have a digital thermometer and need to check an oven? It’s common practice to calibrate thermometers with ice water and boiling water because those have temperatures based on the physical properties of water. Water isn’t the only chemical in the kitchen with known temperature dependent properties, though: you can also calibrate your oven’s thermometer using sugar!
Mankind has been harvesting sugar for millennia, but only in the past few hundred years have we industrialized it. The sugar you buy most likely comes from either the sugarcane or sugar beet plant, which is soaked in hot water to dissolve out its sugar into a syrup that’s then crystallized. The white table sugar that you’re familiar with is ~99% sucrose—a pure substance (C12H22O11)—with the rest being water and a tiny percentage of stuff like trace minerals and ash that come along for the ride.
First, grab these supplies:
• Aluminum foil
• Sugar
• A timer
• A plate (for hot sugar samples)
• And, obviously, an oven!
Here’s what to do:
The sucrose in table sugar melts at 367°F / 186°C. It turns from the familiar white granulated substance to something resembling glass. (Sucrose undergoes a chemical breakdown at low temperatures; see page 221.) A properly calibrated oven won’t melt sugar when set to 350°F / 180°C but it will when set to 375°F / 190°C.
We’re going to bake two different samples of sugar at two different temperatures, one hopefully below and the other above sugar’s melting point, to check your oven’s temperature.
1. Preheat your oven to 350°F / 180°C.
2. Make two aluminum foil “sample containers”:
     a) Tear the aluminum foil into 5” × 5” (12 cm × 12 cm) squares.
     b) Fold the edges of each piece up, making a miniature pan that’s about 4” / 10      cm square and ½”/ 1 cm high.
3. Add a spoonful of sugar into each sample container.
4. Put the first sample container in the preheated oven (350°F / 180°C). Set a timer for 20 minutes and wait.
5. After 20 minutes, remove the first sample and transfer it to your plate. Remember, the sugar is hot, even if it doesn’t look it!
6. Set your oven to 375°F / 190°C and wait 10 minutes for it to adjust.
7. Put the second sample container in the oven. Set a timer for 20 minutes and wait.
8. After 20 minutes, remove the second sample and transfer it to your plate.
Investigation time!
What differences do you see between the two samples? Why do you think that happened? Compare the 350°F / 177°C sample with some uncooked sugar; what do you notice? Why might that be happening? And the best part of the investigation: once the samples have cooled down, taste them! What does the 375°F / 190°C sample remind you of?
Sugar at 350°F / 177°C. Sugar at 375°F / 190°C.
Check back soon for my next post: How To Cook A High Heat Pizza

The Two Things You Should Do to Your Oven RIGHT NOW

One piece of equipment that you’re probably stuck with is your oven. What makes an oven “good” is its ability to accurately measure and regulate heat. Since so much of cooking is about controlling the rate of chemical reactions using heat, an oven that keeps a steady temperature and isn’t too cold or too hot can make a huge difference in your cooking and baking. There are two things you can do to make sure you get the best results with what you have:

Calibrate your oven. Get a digital probe thermometer and check that setting your oven to 350°F / 180°C actually lines up with the thermometer, placing the thermometer in the same location in the oven as your baked goods are going to go. If the temperature is way off, check to see if your oven has either an adjustment knob or a calibration offset setting. Otherwise, keep in mind the offset when setting temperatures. Your oven will cycle a bit above and below the target temperature—the oven will overshoot its target temperature, then turn off, cool down, turn back on, and so on. It’s possible that your oven could be correctly calibrated but measure too hot or too cool, so check the thermometer several times over a span of 10 minutes.

Improve your oven’s recovery time and even out the heat: always keep a baking or pizza stone in your oven. Say you’re baking cookies: oven set to 375°F / 190°C, cookies on pan, ready to go. In an empty oven, the only thing hot is the air and the oven walls, and opening the door to pop the cookies in leaves you with just hot oven walls. You’ll get much better results by keeping a baking or pizza stone on the very bottom rack in your oven. (Don’t place the cookie sheet directly on the pizza stone!)

The baking stone does two things. First, it acts as a thermal mass, meaning faster recovery times for the hot air lost when you open the door to put your cookies in. Second, if you have an electric oven, the stone serves as a diffuser between the heating element and the bottom of your baking tray. The heating element emits a hefty kick of thermal radiation, which normally hits the bottom side of whatever bakeware you put in the oven. By interposing between the heating element and the tray, the stone blocks the direct thermal radiation and evens out the temperature, leading to a more uniform heat. Buy the thickest, heaviest stone you can. Like any thermal mass, a stone will add lag to heating up the oven (and cooling it down— that’s the point!), so make sure to allow extra time to preheat your oven.

Check back next week for the Lab: The Sweet Way To Calibrate Your Oven.

Winter White Bean and Garlic Soup

In a bowl, soak for several hours or overnight: 2 cups (400g) dry white beans, such as cannellini beans. After soaking them, drain the beans, place them in a pot, and fill it with water (try adding a few bay leaves or a sprig of rosemary). Bring the water to a boil and simmer the beans for at least 15 minutes. Strain out the water and put the beans back in a pot (if using an immersion blender) or in the bowl of a food processor. Add to the pot or bowl with the beans and then purée until blended:

  • 2 cups (480 mL) chicken or vegetable stock
  • 1 medium (100g) yellow onion, diced and sautéed
  • 3 slices (50g) French bread, coated in olive oil and toasted on both sides
  • ½ head (25g) garlic, peeled, crushed, and sautéed or roasted
  • Salt and pepper, to taste


• Don’t skip boiling the beans. Really. One type of protein present in beans— phytohaemagglutinin—causes extreme intestinal distress. The beans need to be boiled to denature this protein; cooking them at lower temperatures (e.g., in a slow cooker) will not denature the protein and actually makes things worse. If you’re in a rush, use canned white beans; they’ll have already been cooked.

Variations: try blending some fresh oregano into the soup. Toss some bacon chunks on top or grate on some Parmesan cheese as well. As with many soups, how chunky versus how creamy to blend the soup is a personal preference.

What is Flavor – A lesson in Orthonasal Olfaction

Flavor is a Jedi trick of the mind, a combination of the gustatory sense of taste and the olfactory sense of smell that your brain fuses into a new sensation. To give you an idea of just how clever your brain is about flavor, consider this: your brain detects odors differently based on whether you are breathing in or out. This is crazy! It’s like saying swiping your hand left to right on a cold countertop causes you to feel temperatures differently than swiping right to left. Our brains are wired to process smell signals in two different ways; flavor uses the second way.

Some definitions will make this easier to discuss. Orthonasal olfaction is defined as what your nose detects from sniffing something that exists in the world. Sniffing a rose, unless you’re also chewing it, uses the orthonasal route for smell. Retronasal olfaction is what your nose detects in the foods you eat when air is taken in from the mouth and circulated up to your nasal cavity. Even if you don’t notice it happening, it is! Try chewing food with your nose pinched: cut off the airflow, and poof, the flavor sensation’s gone.

To unravel this trick of the brain, a researcher, Paul Rozin, gave subjects unfamiliar fruit juices and soups via the orthonasal route—“Here, sniff this; remember this odor”—and then gave the foods to the subjects again via the retronasal route (through a plastic tube), asking them to identify the previously remembered odor. They did horribly. Same compound, same sensory apparatus, completely different experience. As I promised, smell is simple in the abstract but complicated in the details, so it follows that flavor is no different.

From a practical perspective, which flavors you’ll like or dislike is a matter of exposure and preference. Rozin started studying the orthonasal and retronasal issue when stumped by stinky cheeses—how is it that we have a different experience of flavor for something that smells disgusting? There’s a lot that psychologists and physiologists are still exploring. Fortunately, you needn’t be one to cook a good meal. When working with food, keep in mind that flavor is a specific combination of the two senses of taste and smell, but not a straightforward summation of the two. Taste the food to adjust its flavor before serving it! Smelling alone isn’t enough.

Here are some tips for great flavor when cooking:

  • Chew! Admittedly an odd suggestion for good flavor, chewing food crushes, mixes, and kicks up a bunch of compounds for your olfactory system to detect, adding smells that fold into flavor sensation. Remember, for a compound to activate an odor receptor, it has to be present at the point of detection. This raises the question: does chewing food with your mouth open lead to a different flavor experience? (If animals always chew with their mouths open…)
  • Use fresh herbs. Most dried herbs have weaker flavor because the volatile oils that are responsible for the aromas oxidize and break down, meaning that the dry herbs are a pale substitute. Dried herbs have their place, though; it makes sense to use them in the dead of winter when annual plants like basil aren’t in season. Store dry herbs in a cool, dark place (not above the stove!) to limit their exposure to heat and light, which contribute to the breakdown of organic compounds in spices. Grind your own spices. Don’t used preground black pepper; it loses much of its flavor over time as many of the volatile compounds change. Fresh-grated nutmeg is also much stronger than preground nutmeg. The aromatics in a preground spice will have had time to either hydrate or oxidize and disperse, resulting in flavor changes. Most dried spices also benefit from being bloomed—cooked in oil or a dry skillet under moderate but not scorching heat—as a way of releasing their volatile chemicals without breaking them down.
  • Don’t discount frozen ingredients. Commercially frozen vegetables and fruits are convenient and work fine in some dishes. Freezing produce right when it is harvested has advantages: nutritional breakdown is halted, and the frozen item is from the peak of the season with maximal flavor (whereas the fresh version in your store may have been harvested early or late). Frozen produce is especially useful if you’re cooking for just yourself: you can pull out a single portion as needed. Want to freeze your own crop or a surplus from a CSA (community-supported agriculture) food share? See page 365 of my cookbook (you can buy it here) for how to use dry ice. (Freezing in your home freezer takes too long and leads to mushy veggies.)
  • Use alcohol in cooking. My favorite restaurant in San Francisco uses kirschwasser in its fruit soufflés, and adding a splash of wine in sauces or to deglaze a pan to make a quick sauce is standard practice. Using alcohol changes flavors because of its chemistry: it takes the place of water molecules normally attached to compounds, resulting in lighter molecules that are more likely to evaporate, and with higher evaporation rates there are more volatiles for your nose to detect.

*See Also: Taste Aversions


Gluten Free Diets: Fad or Science?

Interest in eating gluten free has seen a major uptick in the past few years, but how much does the science back up the claims?

First, some numbers. I spoke with Darren Seifer at the NPD Group earlier this summer. During our conversation he shared some numbers with me from their annual research of consumer behavior around food and beverage:

“Most people who are trying to avoid gluten don’t need to. They don’t have celiac; less than 1% of Americans have celiac. It’s estimated that another 6-7% of people have some kind of sensitivity to gluten. There’s only about 8% who have some kind of sensitivity to gluten. At the same time, 30% of people are telling us that they are trying to avoid gluten. Most of the people are avoiding gluten for reasons other than some need. The reasons that they are telling us is that they feel better, or that they feel it’s healthier even when isn’t necessarily. But that’s the predominant reasons that we’re getting: they just feel better when they avoid it.

That 8% of a population is sensitive to gluten is huge. Having more food options for these individuals is fantastic. We’ll all benefit from a better understanding of what causes these health issues and new processes created for making gluten-free food won’t be limited to just the gluten-free eater. (Side note: 8% may be high—I’ve seen 0.5%—but there will be a difference if one study is looking at gluten in isolation and another is looking at it in context. It may be that for 8% of us, gluten triggers a response to something else we’re eating—see this study.)

But what about everyone else? Depending upon the report*, somewhere between 24% (30%-8%) and 39% of Americans claim gluten sensitivity. (*Another report, mentioned by NPR’s The Salt, claims 47% of Americans identify as gluten-sensitive, so that 24% “self-report but not diagnosed” might be more like 39%.)

I suspect that 24-39% (can we just call it “one third?”) of the American population who incorrectly claim gluten sensitivity—excluding those who have a measurable physiological response—fall into one of the following categories:

  • Placebo effect—believing that the food is better for you may in fact make the food better for you. There are plenty of anecdotes of this; I’d be grateful for readers aware of good stories and studies that relate to food (please contact me with them!).
  • Perceptions around health—related to placebo effect, but more of a “health halo.” Ironically, eating gluten-free can cause long-term deficits in trace nutrients normally obtained from flour (iron, thiamin, folate, vitamin A, etc.); fortified gluten-free foods may be in order.
  • Distrust of the food system—i.e. who controls our food system, corporate monopolies on patents, monocultures / non-suistanable farming. There are very important issues here, but they’re outside my domain of knowledge. In conversation with readers, people bring up fears that “modern wheat” has been genetically altered and is unhealthy, or that modern baking practices use shorter ferment times for yeast to “fully convert” the wheat. I’ve seen this pattern before in conversations about GMOs; I have found that the science–based fears are generally masking concerns around food policy issues.
  • Sense of community—there must be a New Yorker cartoon out there with a college student showing up to a protest with a blank sign and a pen, asking “What are we protesting this time?” Being part of a tribe is empowering. From weight loss to smoking, the behaviors you perform are shaped by your peers. I’d be fascinated to see a study on correlation of when individuals start claiming gluten sensitivity based on when their friends did.

What I find fascinating is the perception around gluten-free. Why do we eat the way we do? Where do we get our beliefs about our food from? (The placebo effect fascinates me.) How can we learn to set aside personal beliefs so we can correctly apply the science? Let me know your thoughts.

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Comments of Note that I’ve Received:

  • There’s also a known effect that *any* food restriction will make most people eat better, because they have to pay attention. e.g. people who eat a lot of junk will legitimately feel better gf, because they can’t just grab a doughnut today. It’s essentially the same as the “any diet works” trick for non-calorie counting stuff. —@MagpieChristine
  • Open Question: differences between FODMAP and gluten sensitivity. See this study for more about FODMAPs. Some individuals may be sensitive to FODMAPs (short chain carbs & co.) but think it’s gluten causing the problem.
  • One reader calls into question the 8% figure — the paper I link to has a very small sample size (37 subjects), but Darren’s figure is also in that same range. His data was based on the NPD Group’s annual report, I believe, but I’d like to find more data on this stat!

Two Fun DIY Projects: Vanilla Extract and Liquid Smoke

Last Friday, I was on Science Friday chatting with Ira Flatow about some fun do-it-yourself things you can do at home from the second edition of Cooking for Geeks.

I already wrote up instructions for my DIY Bittersweet Chocolate Bar; in this post I’ll share details for how to make homemade vanilla extract as well as DIY liquid smoke. Spoiler: vanilla extract is super easy; liquid smoke is super hard. These two projects are great examples of solvency, and liquid smoke demonstrates how to do what chemists call dry distillation. Science! Bam!

First, here’s the interview, courtesy Soundcloud. Scroll down for the geeky science details.


How to Make Vanilla Extract

Instructions: Slice open a few vanilla beans (shop online for the cheaper grade B ones), drop them into a small container, and top off with vodka. Wait a few weeks and you’ll have vanilla extract. The strength of the extract will depend on the vanillin levels, which will depend on the specifics of the vanilla beans and how many used. You’ll need to experiment and adjust quantities when using your DIY Vanilla Extract in cooking.

Why this works: Different compounds are soluble in different solutions. In cooking, we use three primary solvents: water, lipids, and alcohol. Each works on different types of compounds, so matching the chemistry of the solvent to the chemistry of the volatile compound is the key to making good extracts. The same chemical principle that allows water to dissolve compounds also applies to lipids and ethanol, so which solvent to use depends on the structure of the compounds being dissolved. In the case of vanilla, alcohol (a.k.a. ethanol) works the best. If you’re making extracts from other items, you may find water or lipids work better. This is why hot peppers are sometimes infused in oil—the capsaicin dissolves better with lipids (“like dissolves like”) due to the compound’s chemical structure.

One P.S. on my explanation: most compounds are more complicated than this abbreviated explanation implies. It’s not that vanillin or capsaicin can’t dissolve in water; but the solubility is much lower than in ethanol or fats. This is why capsaicin, without any lipids around, can still dissolve into water.

How to Make Liquid Smoke 

Instructions:  Download my lab for How to Make Liquid Smoke (PDF). Warning: it’s a long and complicated project. Liquid smoke involves similar concepts as vanilla extract—solubility of compounds in liquids—but is much more complicate.

Why this works: To make liquid smoke, you need to heat wood chips to a temperature high enough for the lignins in wood to burn (around 752°F / 400°C), pipe the resulting smoke through water, and do so without any oxygen. The water-soluble components of smoke remain dissolved in the water, while the non-water-soluble components either precipitate out and sink or form an oil layer that oats and is then discarded. The resulting product is an amber-tinted liquid that you can brush onto meats or mix in with your ingredients. I do NOT recommend using your own DIY Liquid Smoke, except perhaps once as a curiosity project.

Do NOT make liquid smoke by soaking “smoked” wood chips in water. Properly made liquid smoke filters out many mutagenic, cancer-causing compounds; the DIY instructions I typically see concentrates those compounds into what you’re eating.

Incidentally, the wood chips turn into charcoal in the process; they’re carbonized, but without oxygen present, they can’t combust. You can create your own charcoal by sealing up wood chips inside a container that will vent out smoke but not circulate air back in. You can also make charcoal from materials besides wood. I know one chef who uses leftover corn cobs and lobster shells to create “corn cob charcoal” and “lobster charcoal,” and because some of the flavor molecules from those items are extremely heat-stable, using the charcoal for cooking imparts a whiff of those flavors as well.

DIY Bittersweet Chocolate Bar

Psst… I’ll be on Science Friday today to talk about this and more — tune in at 3:40 pm Eastern Time! -Jeff

A bar of dark chocolate is amazing—but it wasn’t always this way. Back in 1879, a Swiss entrepreneur by the name of Rudolph Lindt invented a refining process call conching that took gritty, granular chocolate and turned it into the deliciously smooth bars that we enjoy today.

When working on the second edition of Cooking for Geeks, I wondered: what was chocolate like before Lindt’s discovery? And just how hard is it to conche your own chocolate?

Let’s start with fun trivia about the components of chocolate before digging into a simple do-it-yourself version:

  • Cacao Nibs are the dried, fermented seeds of the cacao plant.
    • Language geeks: Note the spelling: cacao vs cocoa. Cacao generally refers to parts of the plant and cocoa refers to edible food products. The letter transposition likely occurred in 1755 by dictionary maker Samuel Johnson on page 401 due to the Spanish spelling.
    • Old-fashioned Coca-Cola bottles, with their ribbed shape, are a reference to cacao pods—inspiration by proximity in the dictionary; the cacao tree has nothing to do with coca bush.
  • Cocoa butter, a.k.a. cocoa fat, is the fat from the cacao nibs. Sometimes we forget: plants have fats!
    • Fats are triglycerides; in the case of cocoa fat, the most prevalent triglycerides are myristic, oleic, and palmitic acid. Butter—as in cow, not cocoa—has a very similar fat composition, hence the similarities in melting temperatures.
    • The exact ratios of the triglycerides in cacao seeds will depend on the climate in which the plant lives. Cooler climates (i.e. higher elevations or geographic variations) will create a fat composition that has a lower melting point.
    • Cocoa butter tastes sorta like shortening. It’s not that delicious.
    • White chocolate is cocoa butter, sugar, and often flavorings like vanilla. Technically it is chocolate—it has parts of the cacao plant—but some may disagree.
  • Cocoa powder is the dried, dark solids of the cacao nibs—hence it’s sometimes call cocoa solids.
    • If you’re a baker and have wondered what Dutched cocoa powder is: it’s cocoa powder processed to improve solubility (it’ll mix better—it’s more hydrophilic) and alter its flavor. (The Dutching process raises the pH of cocoa powder, which is why Dutched cocoa powder shouldn’t be substituted for regular cocoa powder in baked goods that rely on it to react with baking soda.)
  • Bittersweet chocolate is the combination of cocoa fat, cocoa powder, and sugar. Sometimes flavorings like vanilla are added in; sometimes emulsifiers as well.
    • There’s no legal definition specific to bittersweet chocolate, but as a guideline, bittersweet chocolate is typically 30% cocoa fat, 40% cocoa powder, and 30% sugar.
    • When you see a bar of chocolate that says “70% bittersweet chocolate,” that’s the amount of cocoa fat and cocoa powder. One manufacturer’s 70% might be 30% fat, 40% powder; another’s could be 35% fat, 35% powder. Because cocoa powder is bitter and cocoa fat is not, a 70% bar made with more cocoa powder and less cocoa butter will taste more bitter, even though both bars are “70% bittersweet.”

Ok, so hopefully that clears up some common confusion around spellings, differences in ingredients, and other “base knowledge” parts of chocolate.

Ok, great—so how do I make a bar of delicious bittersweet chocolate?

  1. Take the cacao nibs, warm them, and slowly grind them for many hours. The fats in the seeds will melt, and the other parts of the seeds will get ground up and suspended in the fat. This, by the way, is called chocolate liquor. It’s bitter—no sugar yet.
  2. Add sugar and conche. Conching does a bunch of things: breaks up the sugar, thoroughly distributes the ground cocoa solids, and slowly aerates and oxidizes some compounds from the chocolate. Conching is a slow process—6 hours seems to be the shortest time I’ve read; some makers reportedly let chocolate conche for ~72 hours. Longer = smoother, but also more expensive.

But wait, Jeff, I don’t have a conching machine… there must be another way?!

There is, sort of. If you don’t mind skipping the conching, you can make a bar of chocolate that’s unconched. You won’t be rushing out to buy it, though—before Lindt’s improvements, chocolate was generally used as an ingredient in food and drinks, not as a consumable itself.

Still, it’s fun to see what chocolate would have been like before the modern improvements.

For a FULL do-it-yourself experience, you could start with cacao nibs and sugar, heat, grind, and labor away. But we can take a shortcut, albeit unfaithful: cacao nibs are processed into cocoa powder and cocoa fat, so we can use those instead.

Here’s how to make a sample of Unconched Bittersweet Chocolate:

  1. In a small bowl, melt 1 tablespoon (9g) of cocoa butter, either in a pan of simmering water or the microwave.
  2. Remove the butter from the heat or the microwave and add 2 teaspoons (10g) of sugar and 2 tablespoons (12g) of cocoa powder.
  3. Using a spoon, mix thoroughly, stirring for 1–2 minutes.
  4. Transfer the mixture to a flexible mold or parchment-paper- lined container and allow it to cool.

You’ll notice when tasting this chocolate that the initial flavor is astringent and bitter, followed
by a sweeter, possibly floral taste as the sugar dissolves in your mouth. Using superfine sugar instead will give a smoother texture, but the chocolate won’t have the same mouthfeel as the bars we are used to, which are conched and tempered.

Speaking of tempering: I’m skipping the details of that here, but for the curious, read pages 158-160 (PDF).

Happy Cooking!


P.S. Here’s what an industrial conching machine looks like:

Popcorn on a Cob

A cute video about popcorn, Pop On A Corn, has been exploding all over the internet, but it’s a hoax. But it’s so close to what can be done that… well, argggh!

The hoax video inspired me to attempt my own version, using REAL popping corn. With a time limit of 2 hours for shooting and 2 hours for editing, here’s a quick pass at a fun video on REAL pop corn on cob.

Appleless Apple Pie

This may look like an Apple pie — and it sure tasted like one — but no apples were harmed in the making. Mock Apple Pie, as it’s traditionally called, dates back to at least the 1850s and is a great example of how expectations play into our perceptions.

Mock apple pie relies on cream of tartar for the acidic kick normally provided by malic acid in apples. Crackers are soaked in sugar syrup for sweetness and texture (cooked apples and soggy crackers have similar texture). Lemon juice, vanilla, cinnamon, and nutmeg add enough of the flavors we associate with apple pie to fool an eater.

For more, see this Newsweek article that I’m feature in. For a recipe, check out page 96 of the second edition of Cooking for Geeks [pdf]. Let me know if you make it, and how it goes when foisting off on unsuspecting guests!

How They Printed Books in the 1940s

If you’re a book lover and a geek, spend ~10 minutes to watch this lovely video from the 1940s about how books were made.

Here I am, ~70 years later, marveling at how things have changed. So that’s where the phrase “put to bed” comes from!

Partway through the video, I wonder what book they’re printing. There’s a single clip of a person checking the page numbers are in sequence: 1… 3… 5…

Page 1 of 1940s book

I pause the video, go to, and type in the two phrases that I can see: “of Fair Luna” “with inimitable”

One match. From 1947.

Banner by the wayside

This is amazing. Isaac Asimov futuristic amazing. How would he have described what I just did? Sitting at home, pulling up a video from a digital archive, glancing at a few words and searching the vast databanks of human knowledge for an answer? I imagine Asimov would have written the scene with me making a cup of coffee while I wait for the digital systems to search for an answer. My wait? Under a second. Something to keep in mind when I swear at the computer for not being able to upload an image to Twitter…

P.S. The book that was printed in that video? On Amazon…

Awesome Food: UCSC Seed Library

I’m pleased to announce this month’s Awesome Food micro-grant! If you’re into gardening and near Santa Cruz, you should definitely stop by Andrew’s monthly seed exchange. -Jeff
UCSC Seed Library Receives February Awesome Food Grant

Awesome Food is happy to announce that its fifth micro-grant of $1,000 has been awarded to Andrew Whitman of the UCSC Seed Library, which is a seed repository and lending service based at the University of California at Santa Cruz. Whitman is among nearly 800 applicants from around the world who have applied for grants from Awesome Food, a chapter of the Awesome Foundation, which awarded its first micro-grant in October 2011.

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Dear Internet: I’m looking for a Food TV Co-Host…

Dear Internet,

Hi there, I’m Jeff Potter. And I’ve got this great idea for a TV show where we show viewers a new kind of cooking: one based on science. If you’re the type of cook who doesn’t like to follow a recipe, and if you’re curious about why we do things the way we do them, then my show American Food Geeks is going to rock your world.

But: I’m looking for a co-host. Maybe you know someone who’d be perfect? Head over to Jeff Potter’s American Food Geeks page to learn more.

Japanese Edition of Cooking for Geeks

I’m told that Asahi Newspaper is the most prestigious newspaper in Japan. They reviewed the Japanese edition of my book: Cooking for Geeks [著]ジェフ・ポッター/味わいの認知科学 [編]日下部裕子・和田有史 The writer of this article is YAMAGATA Hiroo (山形浩生), who is a famous critic and translator. Photo by MIZUHARA Bun; translation by TAMAGAWA Ryuji from Osaka, Japan.

Cook Like Science Experiments

It is quite popular to see stories in cooking comic books (mangas) where a gifted and passionate super-cook super-hero fights against a scientific cook who uses theorem and computers. Of course, the hero always wins and says, “Cold science never touches people’s soul!”

But a large part of cooking is done with chemical changes and it is obvious that chemical knowledge is useful. Though intuition and trial-and-error are important, scientific knowledge shows you the right direction to avoid mistakes. That is the reason why we have so many guide books.

“Cooking for Geeks” by Jeff Potter is outstanding in quality and quantity. It is truly a book for geeks, with rich contents such as how to adopt various cooking tools and surprising cooking methods. The book also covers related topics like organic foods and dishes that have less of an impact on the environment. In this book, recipes are demonstrations and experiments.

I do not recommend this book for cooking novices. There are no color pictures. The recipes look like science experiment manuals and do not seem delicious at the first glance. You should start with easy cooking guides. However, you will not understand the real fun in cooking until you start to make your own changes to recipes. Then, the explanations in this book come to the rescue.

“Cognitive science of Taste (Ajiwai No Ninchi Kagaku)” is more theoretical. It is a collection of papers which dives into the taste cognition system in the brain and completely an academic book. The contents are far beyond from being useful for cooking, but if you want to dive deep, you should read this.

The analytical approach of these books gives you strange feelings if you are used to popular recipe books. Some people will like this approach while others will not. But the process of institutional trials -> theoretical analysis -> reorganization is an essential process for any learning. These books will certainly help you in the process. And when you do, you’ll find that the dishes that result from the “cold science” aren’t bad. Give it a try!

Photo by TAMAGAWA Ryuji from Osaka, Japan

SNAP Gardens and Dinner Garden receive Awesome Food grant to promote food stamps for gardening

SNAP Gardens NYC Maker Faire by Glenn Wester
I’m delighted to announce this month’s Awesome Food grant has been awarded to a great project that helps get the word out about using food stamps to buy supplies for growing your own food. Here’s the press release! -Jeff

Awesome Food is delighted to announce its third microgrant of $1,000 has been awarded to SNAP Gardens and Dinner Garden to fund a collaboration to raise awareness that food stamps can be used gardening. The project is among the nearly 800 projects from around the world who have applied for grants from Awesome Food, a chapter of the Awesome Foundation which made its first micro-grant award in October.
Continue reading SNAP Gardens and Dinner Garden receive Awesome Food grant to promote food stamps for gardening

Looking for Single Cook for TV Show

My life continues to be full of unexpected surprises. A few days ago, I received an email asking if I was single and “would you be interested in being the star of a TV show where a bunch of beautiful women try to cook their way to your heart?”

It’s not a good fit for me (although it’d be fun to do!), but maybe someone out there reading this would be interested? Here are the details…
Continue reading Looking for Single Cook for TV Show

Wanted: Your Food Questions

Dear Internet: what questions do you have about food? Or food science? Ever wonder why certain foods cook the way they do? Or certain dishes call for the ingredients they do? Or maybe you have a recipe that you can’t get to turn our just the way you like. Please leave your questions in the comments below, or use the “contact me” option to email it.

And yes, I’ll give away a hint: this is for a project I’m working on. It’ll be fun! Can’t wait to see where this one goes… 😉

Continue reading Wanted: Your Food Questions

Awesome Food announces $1000 grant to CompostMobile

I’m delighted to announce that Awesome Food (of which I’m a trustee) has selected our first $1,000 micro-grant: CompostMobile. I had the great joy of calling Jennifer to tell her the good news, and let me just say that I could get used to calling people and telling them they’re awesome, doing awesome things, and that we’re giving them $1k to make the world a more awesome place.

(In case you missed my post about Awesome Food: Awesome Food helps the world realize awesome ideas that further food and culture by awarding a no-strings-attached $1,000 microgrant to people who want to pull off awesome ideas involving food. To learn more or to apply for a grant, visit

We had over 600 applicants, many of which were truly, well, awesome. (It’s a “rolling pool,” so we’ll still consider the other applications in future deliberations.) Perfect ice cubes? Random sandwiches? Gardens for schools? Lots of awesome ideas; enough to call someone every day instead of once a month!

Here’s the announcement we sent out—please help spread the word!

Continue reading Awesome Food announces $1000 grant to CompostMobile

Announcing “Awesome Food” – part of The Awesome Foundation

The Awesome Foundation now has a new chapter—Awesome Food—of which I’m a trustee. Details in the below press release!

July 20th, 2011

Awesome Food, a chapter of the worldwide Awesome Foundation, officially launched on Wednesday, July 20 and is now accepting grant applications from around the world to further food awesomeness in the universe. Visit to learn more and apply at The first round for application deadline is end-of-day, Friday, August 5th.

Each month, Awesome Food will give one applicant $1,000 to help pull off an awesome idea involving food. The ideas must relate to food in some form, and the definition will be more inclusive than exclusive. Examples could include educating the public about DIY-farming, creating an ad-hoc eatery in a subway car, or recording videos of immigrants’ recipes.

Anyone is eligible to apply: For profit, non-profit, individuals, companies, schools, adults, children. The $1,000 grants are not be loans or investments. They are not expected to be paid back. They are no-strings attached grants. The Awesome Foundation has a FAQ on how the grants work.

Continue reading Announcing “Awesome Food” – part of The Awesome Foundation

Cooking for Geeks Party

I’m sitting in a café in sunny LA with the goofiest of grins on my face, because of an email I just received:

I received your book as a present from my 12-year-old brother for Christmas last year and it was perfect for me! After reading the book, I decided to take your preface to heart and share it with others. Except instead of passing your book on, I hosted a party based on the book. We started out with the taste and smell experiments (had some trouble with counting our taste buds), Then I had everyone bring three ingredients and we all had to make a dish based on those random items using tips from your book. And dessert was made on an antigriddle. Overall we had a blast! I just wanted to thank you for writing this book and show you our party:
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