A mound of roasted coffee beans promise delicious flavor.

Creating Flavors

Flavor arises as much from psychology as from physiology. The brain constructs flavor, which is not a sense but a mixture. It is commonly said that flavor is equal to taste plus smell, but as your next meal will convince you, there is much more to flavor.

Shepherd and Spence have pointed out that almost all of the senses are involved in flavor. You might consider influences such as heating (but not too much), cooling (but not too much), expectations, color, texture (which involves more than touch, as chewing gum manufacturers can attest) and early experience, or you might think of others. Which makes more sense to you, the old “flavor = taste + smell + touch” or the flavor pyramid of food professionals?

Why, then, do we always locate flavor in the mouth, when in fact it’s mostly smell (even if the exact proportion is hard to pin down) and other senses? Spence writes that this is an attentional quirk called oral capture. We are familiar with visual capture from watching ventriloquism, when the ventroloquist’s voice seems to issue from the mouth of a dummy.

To understand why this attentional quirk occurs requires a deeper dive into the work of the late Anne Treisman, to decide whether flavor represents an illusory conjunction (I don’t think so) or the greater likelihood that some features of our experience, like taste, are more salient than others even if it defies logic?

We lack an intuitive list of food smells, other than yummy and yucky. But tastes are different.

We readily identify sweet, sour, salty, and bitter tastes and maybe umami.  How about kokumi? You might throw in fat and calcium and chemesthesis. There may be others

If you are interested in more about this, here’s taste expert Linda Bartoshuk.

It’s worth a moment’s thought to consider why some flavors are good and some are bad. It’s not a matter of sensory transduction but of hedonic preferences that originate in the brain. It’s pretty clear that “yumminess” is assigned to tastes and smells by the orbitofrontal cortex (or see this site). Yuckiness may be more complicated, but you can find clues here, there and yonder. Some tastes, smells, and flavors are good or bad depending on circumstances. Integrating all of this sensory and hedonic information may occur in the insula (called the Isle of Reil when I was an undergrad).

One of the bright ideas for enhancing flavor, the century-old Maillard reaction, in tasty use for over a million years before it was named, may have led to leaps in brain evolution. Some researchers believe that applying heat to food–cooking–was a driving force behind our brain evolution. Perhaps Wrangham thought of it first; some tie it to our discovery of using fire. The idea seems to have caught on, though others remain skeptical.

A cup of coffee with cream on a saucer

BIO: Papillae, taste buds, and receptor cells get mixed up a lot in the media. There are taste buds all around the mouth, and taste receptors in a lot of other places in the body, including our breathing passages and intestines.

You may already have it straight in your mind, but just as an FYI I thought I’d add more, though it’s hardly rocket science.

The taste buds are not classified by taste sensitivity. Only the taste receptors–the actual transducers–are specialized according to the kind of taste they sense. There’s a good illustration here.

The papillae are the bumps on the tongue. There are three kinds that carry taste buds and one kind, filiform papillae, that carry only touch receptor cells.

So papillae carry the taste buds, which are supporting structures for the actual taste receptor cells.

Taste receptors and taste buds are scattered all over the tongue except for the middle. The old idea that regions of the tongue are specialized for different tastes turned out to be a myth. Each part of the tongue has receptors for all of our principal tastes. However, different tastes are mapped onto different sets of neurons in the brain! You can find a summary here. The intermediary substances that keep our tastes straight are called semaphorins.

Interesting, isn’t it, why we like molecules that other people can’t stand? In the summertime, some folks  enjoy the smell of skunks, and they have a zooful of bliss waiting for them every year.

Psychologists have been working to find the secret of odor preferences for decades. What’s clear so far is that we classify odors mainly according to their pleasantness, and that pleasantness is multidimensional. The smell of bleach is really of sodium hypochlorite, and chlorine is used in several hygienic applications. So maybe we sometimes associate bleach with cleanliness? That illustrates one major approach to odor hedonics, saying that our liking for smells arises from their association with pleasant objects, and outcomes like health.

Experience doesn’t strike all of us the same way, of course, thanks to differences in heredity.

Another approach says that it’s molecular size that determines pleasantness. (Which approach is right? You decide; I just dropped by to borrow the hedge clippers. Some isonitriles are small and some flower fragrances are larger. Skunk thiol is sort of medium. Does that persuade?)

Sometimes we like bacterial smells–The earth! The sea!–and sometimes we don’t.

Body odors are often unpleasant if they belong to other people, but the one we call B.O. not only supports a thriving industry in deodorants and antiperspirants but is sometimes attractive, especially if you can find a bacteria donor. But underneath the odors may lurk health risks, though some folks just think they smell bad.

So do we like perfumes because they’re cover-ups? Then why are gasoline perfumes on the market? Or baby-smell perfumes? (Men seem to prefer bacon.)

Just a final note to warn against taking smells too uncritically. That chlorine smell isn’t always so hygienic.

PSYCHO: Food preferences are among the more intriguing kinds of attitudes we have, partly genetic (research here) and partly learned. Genetic influences are a two-way path, oddly enough. The learning can be of several kinds, too. We learn conditioned taste aversions by classical (Pavlovian, respondent) conditioning, as Garcia found. We adopt cultural biases (WARNING: contains disturbing images) mainly by observational learning. Some preferences and avoidances are surely examples of operant conditioning, while others may arise from the mere exposure effect to food ingredients in the amniotic fluid that surrounds a fetus. Infants share some preferences and there may be a sensitive period in infancy for the formation of food preferences, but the relative strength of all of these influences has yet to be identified.

People used to say that we could trust the “wisdom of the body“, following the famous physiologist Walter Cannon. That doesn’t work. Can we trust the wisdom of repugnance? How much do genes control?

Sometimes it’s a good idea to break away from genes and learning, perhaps: Try something new.

Or try eating your popcorn with chopsticks.

Our eating is immersed in psychological currents. Children may largely inherit a tendency toward picky eating, sometimes as supertasters, but both the onset and duration of the disorder are influenced heavily by the behavior of a child’s parents.

SOCIAL: Bacon and eggs seem to go together to make breakfast. But what about “tofu with fish and rice soaked in soy sauce”? It can be hard to find a Western breakfast in Tokyo outside of the major hotels.

A lot of research is going into flavor pairings, and it relies to some extent on cultural comparisons. On the one hand, researchers stress the pairing of foods that share some of the same flavors. You can try it yourself here or there. Flavor chemists try to predict tasty combinations, and in the case of strawberries and coriander*, it may have worked.

On the other hand, there’s Indian food. A lot of people find it irresistible, and there’s an interesting reason for that. In many cuisines, food flavors overlap; but Indian foods each have flavors that stand alone. You can see how it works in this interactive map. Interestingly, this characteristic may reflect a basic difference between Asian and Western preferences!

And third, food pairings can affect how the ingredients are absorbed. I haven’t taken time to track down the evidence on suggestions like these, but they remind us that ultimately the greatest pairing of a food is with longer life. A food’s contribution to our health seems to be the reason we tolerate bitter tastes in food; in fact, the healthier a food proves to be, the more palatable it becomes**.

What ingredient would make a wedding cake perfect? Prince Harry’s pastry chef favored elderflower.

Finally, there are pairings to avoid. Someone mentioned durian in another posting, and a website in Malaysia suggests that durian should not be eaten with any of these.

*Coriander is the same plant as cilantro. (The seeds are coriander and the leaves are cilantro.) Some folks think cilantro divides humans into two kinds, but some of us have changed.

**For example, when the body is depleted of sodium, salt becomes more palatable. It’s also true that the more we are exposed to any new food, the better we will like it. Exposure involves more than just eating.

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