Taste – Law Street

Foodie Flavor: The Science Behind Your Favorite Tastes

Ashley Bell — Fri, 06 Feb 2015 17:20:15 +0000

Image courtesy of [kawaiikiri via Flickr]

You just ordered a chargrilled pineapple steak with blue cheese ice cream. If the cost is any indication, it has to taste good. Right?

You take a tentative bite. The flavors mingle on your tongue in an explosion of taste bud pleasure. How do they come up with this stuff?

Some chefs use science to select ingredient pairs that lead to culinary bliss. The odd coupling of pineapple and blue cheese owes its delectable flavor to a compound found in both ingredients: methyl hexanoate. So if you don’t trust your imagination and instincts to prepare food with the reckless elegance of a chef, turn to matching aromatic compounds as a logical guide to selecting ingredients that complement instead of clash.

Here’s your science-based foodie flavor guide.

Getting to Yum

You have it pretty easy when it comes to flavor. You bring a fork to your mouth and experience a burst of flavor instantly. Yum. No thinking. No processing. Meanwhile, your senses work overtime to endow you with the gift of flavor.

When we talk about flavor, we’re talking about the overall sensation that combines smell, taste, temperature, texture, and appearance–the whole delicious bundle of qualities that food delivers to your ravenous senses. While texture and appearance deserve honorable mentions, taste and smell take the flavor trophy. Taste and smell (made possible by the olfactory dream team of nose, mouth, and brain) work together to bring you flavor.

Taste

Your mouth contains a hierarchy of structures that help you taste. You know those bumps you can see on your tongue? They’re not taste buds, they’re called papillae. The papillae contain taste buds, the taste buds contain taste cells, and the taste cells contain even smaller structures called microvilli. And it’s not over yet. The microvilli contain the receptor proteins that tell your brain when you’re tasting something. These little receptors send messages through a network of nerves that ends at the cerebral cortex, which then creates the perception of taste.

We all have about 5,000-10,000 taste buds, but we can only detect five flavors: sweet, salty, bitter, sour, and umami. As the central location for taste, the mouth hogs a lot of credit for flavor. But your underappreciated sense of smell deserves more glory than it receives.

Smell

Your sense of smell helps you perceive flavor more than your sense of taste. Smell works in two ways:

Orthonasal olfaction: This happens when you inhale and smell. Think of the aroma of fresh baked bread wafting through the cracks in the floorboards.
Retronasal olfaction: This happens when you already have food in your mouth. Once food gets to your mouth, its aroma vapors creep up the back of your throat and make it to your nose. Chewing food accelerates this process. Retronasal olfaction enables most flavor sensations. Imagine how your food tastes like cardboard when you have a cold. It’s because essential aroma vapors can’t reach your nasal passage.

Your nasal passage is home to millions of receptors. They’re standing at attention to attach to odor molecules and send scent signals to your olfactory bulb, the brain’s odor-processing hub. The olfactory bulb translates the scent signals and relays that information to the piriform cortex, which recognizes the odor and lets you know what it is. As complicated as it seems, this all happens in a flash, enabling you to recognize odors instantly.

Bonus fun fact: the olfactory bulb connects to the limbic system, the part of our brain that deals with emotions. That’s why certain scents spark vivid memories.

What makes a flavor?

Your favorite foods contain hundreds of compounds that work together to create flavor. Compounds in food are generally low per unit, but their synergies bring us the flavors we know and love. Some of the aroma molecules in cacao beans smell separately like cooked cabbage or beef. When they merge with the bean’s other molecules and a few key ingredients, they present the flavor of chocolate.

Aroma compounds and taste compounds work together to bring you the impression of flavor. Nonvolatile taste compounds only react with receptors when they dissolve in your mouth, so their range of detection is limited to the five kinds of taste. Volatile aroma compounds become gas at room temperature and reach nasal passage receptors via inhalation. Your nasal odor receptors help your brain detect thousands of different aromas–just one of the ways aroma compounds and our sense of smell bring flavors to life.

Are compounds the key to perfect flavor?

With the number of ingredients at our disposal, our recipes could be infinite. Yet we always return to the same key ingredients and steadfast combinations. Researchers Yong-Yeol Ahn and Sebastian E. Ahnert set out to discover a scientific reason for this inclination.

They explored the world of taste and aromatic compounds to find out why some foods taste wonderful together and end up in recipes while others fade to obscurity. They based their research around a long-standing culinary hypothesis: ingredients that share flavor compounds will taste the best together.

The researchers created a flavor network of ingredients that share compounds. They used over 50,000 recipes to perform their analysis and split cuisines into geographic subgroups to account for cultural disparity.

They found that North American and Western European palettes favor ingredients that share compounds–the more shared compounds, the better. One of the most common compound-sharing triads in North American and Western European cuisine is butter, egg, and vanilla.

In contrast, East Asian and Southern European recipes prefer ingredients without matching compounds. East Asian recipes often feature scallions, sesame oil, and soy sauce–ingredients with no matching compounds.

What does that mean for your cooking?

If you’re really serious about compound-based food pairing and don’t happen to have the equipment to detect aromatic matches in your ingredients, you have other options. You could use the flavor network we already discussed or a website like foodpairing.com, which helps you find ingredients with aromatic-compound matches. According to the site, these ingredients have compound matches:

Bacon, cranberries, olive oil, chicken, buffalo mozzarella, and strawberries
Peanuts and Cointreau
Avocado, tomato, banana, carrot, and rosemary
Werthers hard candy and beef (seriously)
Carrot, cilantro, rosemary, and raspberry
Graham cracker, strawberry, and beef (this might make an interesting pie if you’re feeling adventurous)

When someone doesn’t like your food…

Sadly, you can’t win them all. Some people might not be able to handle your culinary food pairing prowess. Even if you follow compound matching, human preferences remain tenuous, unpredictable, and far from universal.

Here are some reasons why people have different flavor preferences (a.k.a why they’re wrong):

Many flavor preferences form in infancy: In the first months of life, what the mother eats will be passed through breast milk and influence preferences for life. Bottle feeding takes some of this sensory learning away. If babies are repetitively exposed to the same boring flavors, they might learn to love bland food.
Some people have more sensitive flavor receptors: Some people have a receptor gene, 6-n-Propylthiouracil (PROP), that makes them especially sensitive to bitter flavors. They’re often called supertasters. Supertasters typically have more papillae on the tongue and feel everything on the tongue more strongly, including pain. The discovery of the receptor gene confirms that flavor preference cannot be universal.
They might be fooled by appearances: What a food looks like has a huge impact on the flavor you’re expecting. If you’re always taking a gulp of root beer and expecting Coke, you might learn to hate root beer on account of unpleasant surprise.

Beyond all of this, food preferences can be environmental and psychological as well. Positive scent associations, childhood memories, and more can stack the cards for or against different foods. But just remember, it’s not you, it’s them.

True Flavor Appreciation

Going out to dinner in the near future? Keep an eye out for ingredients in your favorite dishes and look them up to see if they have any compound matches. There might be a science behind your preferences.

But mostly remember that even the simplest bite of food is a magical experience. The minute it hits your lips, thousands of compounds trigger a frenzy of processes that course through your nerves on their way to the brain. Thousands of compounds and thousands of internal reactions enable you to say yum or yuck. Even if you don’t like what you’re eating, you can appreciate the process that allowed you to experience its flavor. Now that’s appreciating food.

Bon appetit!

Resources

Primary

American Chemical Society: Flavor Chemistry Research at the USDA Western Regional Research Center

Additional

Nature: Flavor Network and the Principles of Food Pairing

Prepared Foods: Altered Senses

Food Processing: Fighting Palate Fatigue

Prepared Foods: Focus on Flavor

Brain Facts: Taste and Smell

Accidental Scientist: Experiencing Flavor

Science of Cooking: What is Flavor?

Food Navigator: The Science Behind Food Pairing

Food Pairing: Home

Bon Appetit: The Science Behind Our Seemingly Weird Food Combinations

Science of Cooking: The Molecular Basis For Taste

Bon Appetit: The Senses – A Primer

Ashley Bell

Ashley Bell communicates about health and wellness every day as a non-profit Program Manager. She has a Bachelor’s degree in Business and Economics from the College of William and Mary, and loves to investigate what changes in healthy policy and research might mean for the future. Contact Ashley at staff@LawStreetMedia.com.

The post Foodie Flavor: The Science Behind Your Favorite Tastes appeared first on Law Street.

The Science of Wine Tasting

Ashley Bell — Thu, 15 Jan 2015 18:46:25 +0000

Image courtesy of [Greg Pye via Flickr]

Wine tasting can be an abstract art. As the pourer dribbles a tragically small amount of wine into your glass, you glance at the tasting notes. You definitely taste the dark cherries. After another sip you detect leather and possibly a hint of dirt.

Your friends think you’re a wine tasting genius. But truthfully, you kind of just made all of that up. In fact, while drinking the same wine alone later on, you start to wonder if it ever tasted like leather at all. Maybe you were just carried away by a tide of wine snobbery. It’s been known to happen.

Your wine tasting experience can be more than just an effusive bubbling of wine poetry. While wine tasting is an art, science explains everything you see, smell, and taste. Here’s what you need to know about the science of wine tasting to back up your assertions.

How to Taste Wine

Before we get into the science behind wine tasting, let’s review how to do it. Winefolly.com has an excellent infographic with some basic steps to keep in mind when wine tasting: look, smell, taste, and conclude.

Now let’s find out what scientific factors contribute to each step.

Look

When you look in your glass, your wine should be red, white, or something in between. Step one complete. Now, why the different colors when all grape juice is essentially clear? The answer lies in grape skin.

Grape skins contain little compounds called anthocyanins. During winemaking, acids in the wine react with anthocyanins to produce velvety red hues. The acid level of the wine is especially important in achieving this red color; when anthocyanins meet an alkaline solution, they’ll produce completely different colors like blue and green. Anthocyanins are highly reactive, they’re even responsible for the changing colors of autumn leaves.

Anthocyanins continue their complex reactions during aging, forming complexes that create subtle differences in wine color. While anthocyanins decrease over time, the complexes they’ve formed ensure the wine will stay a shade of red.

Many other subtle factors contribute to the range of red wine colors you see, including:

Variations in grape skin thickness and pigment;
How long the grape was on the vine;
How long the skins were soaked in the wine before and after fermentation; and
The handling of the grape skins. For example, macerating the skins brings out other pigment compounds, like carotenoids, that add even more color to the wine.

To make white wine, juice is pressed and separated from the skins very early on and no red pigmentation develops. For a rosé, winemakers leave skins in the grape juice for a short time.

What to remember? Grape skins, and the reactions among different compounds they contain, determine wine color.

Smell

Wine aroma stems from the complex interaction of volatile compounds present in the wine.

When you smell a glass of wine, odor-active volatiles travel through your nose and connect with odor-binding proteins in your olfactory epithelium, or the area in your nose that recognizes odors. From there, receptors pass the odors onto the brain for processing and interpretation.

But there’s more to the aromatic experience than the first smell. Much of the liquid’s perceived aroma releases after you swallow and exhale. The motion releases even more aroma compounds into your system.

Variations in the enzymes, microflora, and mucus in your mouth further complicate aroma, altering how different people perceive odors. So aroma might be relative after all. It’s one of the most abstract aspects of tasting wine.

You can make wine tasting more concrete by recognizing and articulating what you smell. Ann C. Noble’s wine wheel will help you do this. She took information from several wine descriptive analysis studies and picked concrete terms over abstract ones to create the wheel. Take a look at the video below for more information on the wheel.

Aroma judgement might also be clouded by other senses. Researchers from the National Institute for Agronomic Research in Montpellier, France found that perceived smell is highly influenced by appearance. They noticed that wine critics frequently used red or dark objects to describe the smell of red wine, like raspberries or tobacco. The critics similarly used golden hues as descriptors when tasting white wine, like honey and apricots. When they asked students with little wine-drinking experience to describe wine, they saw similar results.

Then the researchers gave subjects two white wines, one of which had been colored with unobtrusive red dye. The subjects still described the disguised white wine in terms of red-hued objects, proving that our noses might be highly influenced by our eyes.

What to remember? Just because the person next to you smells asparagus doesn’t mean you have to. If they try to argue with you, tell them that wine aromas are subject to complex interactions of volatile compounds that people perceive differently. You could both be right.

Taste

Now it’s time for the best part–the tasting. But how did the wine in your glass end up tasting so much different from the grape juice it once was? Wine is made through an intricate series of interactions between different compounds in grapes. These compounds are released and heightened during various winemaking processes like crushing, fermentation, and aging.

Since many compounds are released and intermingle in the process of making wine, it’s hard to pinpoint a flavor or aroma to its chemical cause. But knowing some of the basic compounds is step one. The chemical classes of compounds found in wine include esters, alcohols, acids, lactones, carbonyl compounds, acetals, phenols, sulfur-containing volatiles, nitrogen-containing volatiles as well as other miscellaneous substances. Below are some examples of how different substances affect the flavor of wine. (Please note that aroma and flavor are closely linked. Many of the compounds below contribute to both the flavor and aroma of wine.)

Acids: Acid in wine comes from what is naturally present in the grape and what is produced as a byproduct of fermentation. Other than yielding tart flavors and balancing sweetness, acid’s role in wine is highly reactive. When acid meets substances like esters and alcohols, the subsequent reactions can produce a range of flavors from fruity to tart. Acid also plays a key role in fighting off microorganisms that cause wine spoilage.
Tannins: Tannins are the phenol polymers that are extracted from grape skins during fermentation. They’re more closely associated with “mouthfeel” than actual flavor. Tannins don’t react with olfactory receptors, but bind to the proteins on the surface of mouth cells and change their viscosity temporarily. This dries out the tongue and provides that familiar “puckery” sensation.
Sugars: Sugars do more than just determine the overall sweetness of wine. Sugar enables wine’s alcohol content. During fermentation, yeast converts the glucose and fructose in grape juice into alcohol and carbon dioxide. The exact sugar content of the grape can vary based on subtle differences in ripeness, making fermentation a very complicated process to perfect.
Esters: Esters are naturally occurring aromatic compounds in grapes that are heightened through fermentation and when exposed to acid. A multitude of esters are released during the winemaking process that interact to produce fruity and floral flavors and aromas along with other subtle variations. For example, lactones are the specific esters that impart creamy smells like vanilla, coconut, and butter.
Pyrazines: Pyrazines produce herbaceous smells in wine. Think green peppers and green beans. They’re found in extremely low quantities in grapes but they have such a low flavor threshold that even small amounts can emerge and alter the flavor of the wine.
Terpenes: Terpenes are organic compounds that can make wine smell and taste sweet, floral, resinous, or herbaceous. A specific example is pinene, the terpene that gives pine trees their familiar aroma.
Thiols: Thiols are organosulfur compounds that can taste and smell fruity or earthy when controlled. As these are the same compounds that give skunks their signature scents, too much thiol in wine produces an unpleasant odor.

That was just a sampling of the compounds that interact in a glass of wine to provide the symphony of aromas and flavors you experience. In addition to the interactions of compounds, tiny variations in fermentation and an individual’s unique flavor receptors further impact perceived flavor. That’s why two people can taste two different things in the same bottle of wine.

What to remember? Wine can contain a full range of robust flavors that taste like anything from vanilla to green beans. It’s not because wine is stuffed with additives, these flavors are a result of natural compounds interacting in the magic of wine making.

Why do we put wine in barrels?

Any wine tasting will inevitably include what sort of barrel or tank the wine was aged in, including where it came from. But what does it mean?

Even when wine is in a cask or a barrel, it’s changing chemically and absorbing qualities of the wood. The barrel’s wood contains compounds and tannins of its own that influence the wine. Barrel wood contains the following:

Vanillin, which imparts vanilla notes. It’s released when lignin in oak breaks down. Toasting the wood accelerates the degradation and release of vanillin and the developing of flavors.
Furfural, which is a byproduct of carbohydrate degradation. It gives wine a toasty-sweet aroma.
Lactones, which are esters that impart woody aromas.
Terpenes, which provide tea and tobacco flavors.
Hydrolysable tannins, which combine with tannins in grapes to affect the mouthfeel of the wine. The types of tannins in wood are heat sensitive, so winemakers can manipulate them through various barrel-making processes.
Hemicellulose, which are wood polymers that convert into sugars when heated. They add more toasty, caramelized aromas.

As no two trees are the same, no two wine barrels will be exactly the same. Different types of wood are know for different characteristics, such as those described below.

French oak contains the highest levels of tannins. French oak is more porous than other types of wood, providing more opportunity to impart elements of the wood into the wine. Caryophyllene and copaene are examples of compounds found in French oak that are responsible for some popular spice flavors.
American oak is a sturdier wood with more hemicellulose and lignin which typically results in warm vanilla flavors.
Eastern European oak is similar to French oak but is smaller and grows slowly. The hemicellulose in this wood breaks down easily to form more intense toasty aromas.

Apart from these reactions, wine slowly and slightly oxidizes in the barrel. This tames bitterness and can often change color. Aging wine in stainless steel doesn’t produce nearly as many reactions. That type of container is typically used to preserve the unique flavors of the fruit and keep all oxygen out.

How about terroir?

Terroir refers to the conditions that grapes were grown in including soil, sunlight, and water. Many believe the grapes’ milieu contributes to the final flavor of the wine. The word terroir originated as a name for soil, but it turns out wine terroir might be more dependent on climate than dirt.

Some experts argue that climate might have more impact than soil because it’s very difficult to prove that vines absorb minerals from the ground. Rocks and soil would have to undergo multiple reactions for their elemental particles to become soluble. From there, they would have to get to the vine’s roots and then to various parts of the grapevine. Fermentation and other winemaking processes could mask any small effect the minerals in soil had on the vine.

None of these speculation are conclusive and even geologists are getting into the terroir mystery. This would just be a fun tidbit to throw out if the subject comes up.

Whoa whoa whoa, what about the swirling?

Don’t worry, swirling wasn’t invented just to make you spill wine on yourself. Swirling and aerating exposes wine to oxygen, which is actually good just before tasting. The actions lead to evaporation. In this case, undesirable compounds like sulfites, sulfides, and ethanol typically evaporate first. These substances can make wine smell rotten or taste too alcoholic. Exposing the wine to oxygen before sipping helps to decrease these bitter notes.

Conclude (AKA Talk About it Pompously)

This is when you leverage what you know about wine tasting to have a grounded discussion instead of indiscriminately spewing impressive adjectives.

Let’s go back to the cherry-tobacco-dirt wine we started with. Now you can explain to your friends that its brilliant ruby color is a result of grape skin compounds called anthocyanins. You can tell them you’re not just swirling your glass to look cool, but to get rid of sulfides and other potentially bitter compounds. Explain that the dark cherry flavor is probably a result of esters reacting with acids in the wine. And that dirt smell? Let’s call it earthy and chalk it up to just the right amount of the organosulfur compounds.

Every glass of wine is full of science. Chemical reactions in every step of the winemaking process work in unison to produce the magical liquid set before you. Even if your palate needs work, appreciating the scientific wonder in wine is the first step toward becoming a true connoisseur.