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

by Jeff Potter

  More recent research by Dr. Linda Bartoshuk has shown that those of us of who can sense PTC can be broken down into two groups: a supertaster group that detects these compounds as unbearably bitter (~25% of the general population of European heritage) and a second group of medium tasters who find the compounds bitter, but not overwhelmingly so (50%).

  If you’re looking at the percentages and thinking "Mendelian trait?," you’re right: you’re a supertaster if you’ve inherited both dominant alleles from your parents. As with other Mendelian traits, the percentage breakdowns do differ by ethnicity and gender. For example, white females have a 35% chance of being supertasters, while white males have only a 10% chance. Asians, SubSaharan Africans, and indigenous Americans have a much higher chance of being supertasters.

  If you’re wondering if you’re a supertaster, there are a couple of ways to tell.

  Method #1: PTC or PROP test strips

  The best way to tell if you’re a supertaster is to see if you can taste the chemical directly. Two chemical compounds are commonly used to test for taste differences: phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP). You’ll need to order paper strips impregnated with either chemical (search online for "supertaster test paper" or see http://www.cookingforgeeks.com/book/supertaster/ for up-to-date sources).

  Place the test strip on your tongue and let it rest there for 10 seconds. You’ll know if you’re a supertaster if you experience an extremely bitter taste. Supertasters will generally yank the piece of paper out of their mouths really fast. Medium tasters (individuals with only one dominant allele) will sense a mild but tolerable bitter taste, and nontasters will enjoy the pleasant sensation of, well, wet paper.

  Method #2: Taste bud count

  If you don’t have test strips, you’ll have to stick your tongue out (all in the name of science, of course). Because supertasters generally have more taste buds on their tongues than medium tasters, the low-tech (and low-accuracy, unfortunately) way of checking to see if you’re a supertaster is to count the fungiform papillae, which contain taste buds and are correlated to the number of taste buds you have. You’ll need blue food coloring, a cotton swab or spoon, and a sheet of binder paper (i.e., three-hole punched paper that has a / 8mm–diameter hole).

  Place a drop of the food coloring on the cotton swab, and then stain your tongue with it. Place the paper on top of your tongue such that you or a partner can see the tongue through one of the holes. Choose the area that is densest with spots, usually the front portion of the tongue. Count the number of pink dots visible (fungiform papillae aren’t stained by the food coloring). If you count more than 30 papillae, you’re probably a supertaster. Normal tasters tend to have between 15 and 30 papillae, while nontasters have fewer than 15, on average. These numbers are only broad generalizations, so it’s hard to say for sure which group you fall into based on the counts.

  Counting the number of fungiform papillae visible in a three-hole-punch-sized area of the tongue takes a bit of dexterity and good lighting. Look for the densest area, the location of which varies among people. Count the lighter dots in the circle. This image shows approximately 12.

  Being a supertaster or a nontaster isn’t necessarily good or bad. Supertasters might find some foods—especially dark-green leafy vegetables such as kale, cabbage, broccoli, and Brussels sprouts—to be overly bitter, because of phenylthiourea-like compounds that their tongues can sense. Supertasters generally also find astringent, acidic, and spicy foods to be stronger, due to the higher number of taste buds and thus larger number of cells experiencing oral irritation. Researchers have found that in addition to bitter tastes (tested using quinine), supertasters also experience sweet (sucrose), sour (citric acid), and salty (sodium chloride) tastes as being more intense. Nicotine is more bitter to supertasters, and sure enough, supertasters are less likely to smoke. Caffeine also tastes more bitter, and researchers have found that supertasters are more likely to add milk/cream or sugar to coffee and tea.

  Keep in mind that supertasting is just one of many factors that impact our sense of taste and our food habits. Physiological factors and disease can affect our sense of taste, as can our experiences. Stress leads to an increase in the hormone cortisol, which, among other things, dampens the stimuli strength of taste buds. Our environment can also impact our taste buds. For example, drier conditions change the amount of saliva in the mouth, resulting in a decrease of taste sensitivity.

  As we touched on earlier, temperature also impacts taste sensation, just as it impacts our sense of smell: foods served warmer (by some accounts, above 86°F / 30°C) will be detected as stronger by the taste buds than colder dishes, due to the heat sensitivity of at least one of the receptors (TRPM5) responsible for taste. Foods served below body temperature won’t register as warm, so if you want a dish—say, a spinach and bacon salad—to taste stronger, serve it on the warmer side (but below body temp). If you want a dish to carry milder tastes—e.g., to moderate the bitterness of beer or sweetness of ice cream—serve it colder.

  Finally, if you’re a cilantro hater—if it tastes like dish soap and you can’t stand it—you’re not alone; even Julia Child hated cilantro. While there’s no known scientific mechanism or genetic marker for determining this reaction, preliminary research based on differences between identical and fraternal twins does suggest that a distaste for cilantro is genetic.

  In some recipes, salt is used for its chemical properties, such as the osmosis of cellular fluids for food preservation. We’ll cover more uses for salt in Chapter 7.

  As described in the sidebar Differences in Taste and Supertasting, there are known genetic differences in the way people taste some bitter compounds. Because salt masks bitterness, those of us who taste things like broccoli, Brussels sprouts, and kale as being bitter tend to add more salt to compensate.

  Sour

  Sour tastes are caused by acids in foods. The sensation of sourness is detected by part of the taste bud (ion channels) interacting with the hydrogen ions in the acids. Quite literally, your sour taste buds are a primitive chemical pH tester. In cooking, lemon juice and vinegar are commonly used to make dishes more sour, sometimes for effect but more often to bring balance. When cooking, taste the food and think about the balance of both saltiness and sourness, adding an ingredient such as vinegar to "brighten up" the flavors.

  Note

  In Latin American and Asian cuisines, tamarind paste is often used to adjust the sourness of a dish.

  From an evolutionary perspective, we appear to have evolved to taste sourness as one method of determining spoilage, because a number of acids are produced by bacteria during the breakdown of food. This isn’t to say that sourness in food is always due to bacterial breakdown or that the fermentation caused by bacterial breakdown necessarily results in bad food. Lemon juice is sour due to citric acid, and yogurt (pH of 3.8–4.2) acquires a sour taste because of the lactic acid created by the bacteria breaking down the lactose in the milk (pH of 6.0–6.8).

  To get a better understanding of how bacteria make the taste of a food more sour, try making your own yogurt using the recipe in Yogurt, tasting the liquid before and after fermentation.

  Sweet

  We’re hardwired to like sweet foods—no surprise here. Sweet tastes signal quickly digestible calories (and thus fast energy), which would have been more important in the days when picking up the groceries also involved picking up a spear.

  Our desire for sweetness changes over our lifespan. Researchers have found that our preference for sweetness decreases as we mature. A child’s preference for sweet things is biologically related to the physical process of bone growth. (Quick, kids, run and tell your parents that your sweet tooth is because of biology!) And the infamous sweet tooth isn’t unique to American kids either; this finding holds up in other cultures.

  Sugar is good at simultaneously promoting other flavors while masking sour and bitter tastes. Take ginger, which has a strong, pungent, and slightly sour taste. With
a bit of sugar, it becomes enjoyable on its own; sugared and dipped in chocolate, it becomes irresistible. Try making a simple ginger-flavored syrup (recipe at right).

  Simple Ginger Syrup

  In a pot, bring to a boil and then simmer on low heat:

  2 cups (470g) water

  ½ cup (100g) sugar

  6 oz (65g) ginger (raw), finely chopped or minced

  Simmer for 30 minutes, let cool, and then strain the mix into a bottle or container, discarding the strained-out ginger pieces.

  Besides adding it to club soda for a simple ginger soda, try using this syrup on top of pancakes or waffles or in mixed drinks (ginger mojitos!). You can also add a vanilla bean, split lengthwise, to the mix while boiling to impart a richer flavor. And if the idea of chocolate-covered candied ginger is still bouncing around your head, take a look at the Sugar section of Chapter 6 and use ginger instead of citrus rind.

  Umami (a.k.a. Savory)

  Umami (a Japanese word that roughly translates to "savory") generates a meaty, broth-like, lip-smacking sensation typically triggered by some amino acids and nucleotides (glutamate is the poster child; inosinate, guanylate, and aspartate are also not uncommon). Glutamate is naturally present in a number of foods, especially mushrooms. To an average American palate, umami is more subtle than the four primary tastes. It tends to amplify our other senses of taste. For example, in dishes with salt, umami "brings out" the salty taste, meaning that you can cut the amount of salt in a dish by adding umami-tasting ingredients.

  If you’re unable to imagine the taste of umami, make a simple broth by rehydrating a tablespoon of dried shiitake mushrooms in 1 cup (240g) of boiling water. Let the mushrooms steep for at least 15 minutes, and then remove them and save them for something else (mmm, stir-fry). Taste the liquid; it will have a high glutamate content dissolved out from the mushrooms. (If this is too much work for you, I suppose you could just snag a container of MSG from your local Asian grocery store and dissolve a small amount in a glass of water.)

  Why we’ve evolved to have taste sensors for umami isn’t fully clear. Sweetness and saltiness are both associated with positive attributes of food (quick energy in the case of sweets and an element essential for regulating blood pressure in the case of saltiness), while sourness and bitterness indicate potential danger. Perhaps umami is a more subtle indicator of protein content, as a way of ensuring we ingest enough amino acids to maintain muscle function. Regardless, umami is worth understanding for the hedonistic value alone. MSG (monosodium glutamate) is to umami what sugar is to sweetness: as a chemical, it’s relatively odorless (still full of taste!), but it triggers the umami receptors on the tongue. MSG has gotten a bit of a bad rap in the United States, but so have salt and sugar at various times.

  Yogurt

  In a pan (or, preferably, a double-boiler), gently heat:

  1 cup (240ml) milk (any type other than lactose-free)

  Bring the milk up to 200°F / 93.3°C and hold at that temperature for 10 minutes using a candy or IR thermometer. Do not boil, because that will affect the yogurt’s flavor.

  After 10 minutes at temperature, transfer the milk to an open thermos, and wait until it cools to 115°F / 46°C.

  Add and stir to combine:

  1 tablespoon (14g) yogurt

  Screw the lid onto the thermos and incubate for four hours. Transfer the liquid to a storage container and put it in the fridge immediately.

  Notes

  The small addition of yogurt acts as a starter because it contains the proper types of bacteria for "good" yogurt. Make sure you use yogurt that states it has "active cultures."

  This recipe sterilizes the milk (pasteurized milk can still have a low level of bacteria) and keeps the incubation period to four hours to reduce the chance of growth of foodborne illness-related bacteria. Longer incubation times lead to a stronger, more developed flavor. As with anything you eat, keep in mind that if it tastes bad, smells off, or looks up at you and cracks a joke, you probably shouldn’t eat it. (The inverse is, of course, not true: just because something smells fine doesn’t mean it’s necessarily safe.)

  Try adding honey to the hot milk to take the sour edge off the finished product (sweet helps mask sour). For "Greek-style" thick yogurt, place the yogurt in a strainer over a bowl and let it drip-strain overnight in the fridge. For additional yogurt-making tips, see http://extension.missouri.edu/publications/DisplayPub.aspx?P=GH1183.

  There are plenty of natural sources of glutamate. Many traditional Japanese dishes call for dashi, a stock made from ingredients high in natural glutamate such as kombu seaweed (2.2% glutamate by weight). Making dashi is super easy: in a pot, place 3 cups (700g) cold water and a 6″ / 15 cm strip of kombu (dried kelp), and let rest for 10 minutes. Bring to a boil slowly on low heat. Remove the kombu just before the water begins to boil and add 10g of bonito flakes (flakes of dried and smoked bonito fish). Bring to a boil, remove from heat, and strain out the bonito flakes. This liquid is dashi. To make miso soup, add miso paste, diced tofu, and (optionally) sliced green onions, nori, or wakame (an edible seaweed).

  Glutamate occurs naturally in many other foods—for example, beef (0.1%) and cabbage (0.1%). And if you’re like most geeks and pizza makes your mouth water, it might be because of the glutamate in the ingredients: Parmesan cheese (1.2%), tomatoes (0.14%), and mushrooms (0.07%).

  Glutamate content of common ingredients.

  Others

  In addition to the primary sensations of taste, our taste buds also respond to oral irritation brought about by hot peppers (typically from the chemical capsaicin), cooling sensations (typically menthol from plants like peppermint), and carbonation. The reaction to hot peppers is governed by a neurotransmitter called substance P (P is for pain; go figure). In one of nature’s more subtle moves, substance P can be depleted slowly and takes time—many days, possibly weeks—to replenish, meaning that if you eat hot foods often, you literally build up a tolerance for hotter and hotter foods as your ability to detect their presence goes down. Because of this, asking someone else if a dish is spicy won’t always tell you if it’s safe to jump in. Carbonation in soft drinks also irritates the taste buds, but in a different way that stimulates the somatosensory system. Carbonation also interacts with an enzyme (carbonic anhydrase 4) to trigger our sour taste receptors, but for now it’s unclear as to why it doesn’t actually taste sour to us.

  Our mouths also capture data for a few chemical families present in some foods, along with noticing texture and "mouthfeel." Some of the sensations picked up by our mouths include pungency, astringency, and cooling. Pungency is commonly described as being like some strong, stinky French cheeses: a sharp, caustic quality. Astringency results when certain compounds literally bind to taste receptors and causes a drying, puckering reaction. Astringent foods include persimmon, some teas, and lower-quality pomegranate juices (the bark and pulp are astringent). Cooling is the easiest to understand: the chemical menthol, which occurs naturally in mint oils from plants such as peppermint, triggers the same nerve pathways as cold. Menthol is commonly used in chewing gum and mint candies.

  Different cultures give different weights to some of the sensations listed here. Ayurvedic practices on the Indian subcontinent include food recommendations as part of their prescriptions, defining six types of taste: sweet, sour, salty, warm (like "hot" but not the same kind of kick), bitter, and astringent. No umami, but two additional variables: warm and astringent. Thai cooking also defines hot as a primary taste. For most European cuisines, these additional variables are of lesser importance, possibly due to genetic differences in taste receptors related to supertasting between Europeans and Asians.

  Taste Aversions

  Your reaction to a particular taste is based in part on your prior experiences with similar flavors. Have prior exposures been pleasant, or revolting? Taste aversions—a strong dislike for a food, but not one based on an innate biological preference—typically stem from prior bad experiences with food. Sometimes
only a single exposure that results in foodborne illness (and usually an unpleasant night near the bathroom) is all that it takes for your brain to create the negative association.

  The food that triggers the illness is correctly identified only part of the time. Typically, the blame is pinned on the most unfamiliar thing in a meal (this is known as sauce béarnaise syndrome). Sometimes the illness isn’t even food-related, but a negative association is still learned and becomes tied to the suspected culprit. This type of conditioned taste aversion is known as "the Garcia Effect." As further proof that we’re at the mercy of our subconscious, consider this: even when we know we’ve misidentified the cause of an illness ("It couldn’t be Tim’s mayonnaise salad, because everyone else had it and they’re fine!"), an incorrectly associated food aversion will still stick.

  One of the cleverest examinations of taste aversion was done by Carl Gustavson as a grad student stuck at the ABD (all but dissertation) point of his PhD. Reasoning that taste aversion could be artificially induced, he trained free-ranging coyotes to avoid sheep by leaving (nonlethally) poisoned chunks of lamb around for the coyotes to eat. They soon learned that the meat made them ill, and thus "learned" to avoid the sheep. I don’t recommend this method for kicking a junk food habit or keeping your coworkers from stealing unmarked food from the company fridge, as tempting as it might be.

  Combinations of Tastes and Smells

  Most dishes involve a combination of ingredients that contain at least two different primary tastes, because the combination brings balance and adds depth and complexity. Whether the dish is a French classic or a simple item of produce, the taste will be simple ("one note") unless it’s paired with at least one other.