20 November 2010

How our senses help us decide what we eat

Senses help us select our food.
So, this is a blog post about the importance of sensory criteria for selecting food, which was inspired by a day of cooking up goods for the holidays.

What makes people choose the foods that they do? This question may seem obvious to yourself--after all, you know what you like--but this is a question posed by food industry scientists ask themselves day in and day out.

The science of food selection can get crazy complex when you think of the huge variety of foods that you find at your corner grocery store. Food scientists must continually find new "niches" for products to be placed in the marketplace.

How do they do it? The same question can be asked of musicians who endlessly produce new songs that the radio blares as latest hits, but using the same 12 musical notes. Only, in the case of food, scientists only have five notes, or tastes, the "Five-Taste Stimuli":

-savory (umami - think MSG, mushrooms, tomatoes, broth)

Taste rates high in the evaluation for selection from consumers. As it happens, the sensation is produced when the food comes into contact with cilia (tiny hairs) on gustatory cells, which make up around 10,000 taste buds (depending on age; people lose them as they age).

By itself, taste isn't all that complex, but then food is mixed with other sensory criteria:

-touch (texture, mouthfeel)
-hearing (yes, the sound of food)

Sight has to do with the presentation or appearance of the food. When we first look at food, we are in a sense already "eating it" with our eyes: judging for shape and color, ripeness or rottenness, smoothness or crunchiness, well-cooked or burnt.

Visual signals, mixed up with several other stimuli, instantly tell your brain whether or not you're ready to eat that grilled chicken breast or let it brown a little longer, or whether to eat that banana or wait until it turns from green to yellow (but not to black).

Smell is a wholly vital part of what it is to create food -- and I would argue that any good food scientist is also an expert at using volatile molecules from food to reach our olfactory epithelium. Flavor, in fact, is around 75 percent smell.

In the olfactory epithelium, which is inside the nasal cavity, is where volatile molecules will act on between 10 to 20 million olfactory cells. These cells can pick up between 2,000 to 4,000 different odors. A few experts are so well trained, they can distinguish closer to 10,000 -- an extremely keen sense of smell.

Touch is a sense that we use for picking our foods because it allows us to pick up on texture, astringency, consistency and temperature. Generally, with food, we start our touch evaluations with our fingers and then as the food moves toward our lips, next is the mouthfeel.

Mouthfeel of a food can tell us a lot more: a smooth texture may mean more fat content, which is more desirable to our energy-seeking brains. It also tells us whether that steak is tender or chewy, dry or moist, if the soda pop is bubbly or flat, if the vegetables are crispy or rubbery, if citrus fruits or vinegar is astringent.

Of course, touch inside the mouth also determines a food's temperature and spiciness. Heat and cold are picked up by the taste buds. The sensation of spiciness, like the one caused by capsaicin in hot peppers, is caused by irritating nerves.

A sense of hearing might not seem as important in food selection, but most of us evaluate food all the time with sound without even realizing it. We like to hear the snap of a celery stick, the crackle of potato chips, the pop of popcorn.

The sounds give clues about whether a food is fresh or sufficiently cooked. Think also of the sound a watermelon makes when you tap it to make sure it's fresh, or the sound stir-fry makes when it's sizzling.

So, back to how food scientists use all these sensory criteria: With the five-taste stimuli and other sensory signals (as in music with 12 notes, beats and rhythms), food scientists can continue creating thousands of foods that flood our grocery stores annually.

Each and every satisfying food can be appreciated for its particular complexity of visual presentation, flavor aroma, texture and sound -- they are what makes us love to eat.


Brown, A. 2000. Understanding Food: Principles and Preparation. Wadsworth: Belmont, CA.

No comments: