A Big Fat Italian Dinner

The Scapucino dinner table, laden with a huge variety of rich and colorful Italian dishes, looks sumptuous. The enticing aroma of herb-rich pasta sauce dominates the feast and fills the air. It is Papa Scapucino's birthday, and Mama Scapucino always prepares a meal to remember. The celebration is about to begin, but unfortunately no one has much of an appetite.

The timing of this special meal is simply dreadful. The entire family is suffering from a terrible cold, and with noses stuffed solid, the aroma of food can travel no farther than to their nostrils, where thick mucus blocks further entry.

Without the scent of food, appetite lacks stimulation. As enticing as the feast looks, the Scapucinos just don't feel hungry. The family eats their wonderful birthday dinner without enjoying a bite.

The Marriage of Taste and Smell

Taste and smell are as closely tied as fitness and health. Even though tasting and smelling organs are located in different places in our heads, when we are ingesting foods, the messages traveling through the nerve systems of both organs arrive in the same area of the brain. The two sets of signals combine into a single perception—flavor. The tasting organs alone can't do the job. When our noses are plugged, we don't perceive flavor.

The Tasting Organs

Everyone knows that our tasting organs are on our tongue. Look at yours in the mirror. Those little bumps that you see on the top and along the sides are clusters of tiny taste buds. The bumps are called papillae; each contains one to 15 taste buds. There are tiny pores on the surface of the taste buds through which flavor chemicals in food pass to come in contact with taste receptor cells that connect to nerves.

No one knows exactly how we taste food, but somehow chemical changes in the taste receptors stimulate nerve endings, which send an instant message to the brain.

In 1864, when scientists first presented the concept of how we taste things, they identified four flavors that we perceive: sweet, sour, salty, and bitter. Different taste cells have the responsibility for each of these basic flavors. They affect each other and work together in harmony like the four voices in a barbershop quartet. They send a single message to the brain about the overall flavor of that delicious chocolate bar that you happen to be nibbling on.

In addition to the four basic flavors, food scientists in the mid-1980s developed a strong argument in favor of a fifth flavor, umami. It's a Japanese word that means “deliciousness.” Umami is a natural flavor in most foods and is also the flavor of the food enhancer MSG (monosodium glutamate). You can experience this basic flavor yourself by sprinkling a few grains of MSG on your tongue. Don't expect anything “delicious.” Most flavor scientists, like those at the Monell Chemical Senses Center in Philadelphia, now accept these five basic flavors.

In addition to these five, we cannot ignore other flavors that are not primary flavors in the strict sense, but that we clearly perceive. Think of such tastes as pungent (like hot chili); metallic (like licking a metal baking pan); and astringent (like unripe apples). Flavor scientists have yet to figure out how to deal with these.

The flavors of foods come from a large number of chemical compounds. When these compounds are combined in a certain ratio, such as one sweet to five sour, you perceive flavor. In tomato it is a combination of sweet, sour, and salty, and a little umami (without umami, there would be a less intense tomato flavor). The ratios are different in ripe and unripe tomatoes, and in a beefsteak and a cherry tomato. When the balance of sweet, sour, salty, and umami is perfect for our taste, we have a yummy tomato.

The Smelling Organs

We perceive smell, a process called olfaction, a little differently. The smelling organs in the nose perceive the volatile gases associated with food, not the liquid component that our taste buds do. The idea of smelling is simple. Gases drift into our noses and we identify them. But how? That's anything but simple.

Think of each volatile gas molecule as having a certain shape—like a door key. Now think of our smelling organs as having a huge number of different-shaped keyholes. When a gas molecule finds a keyhole it snugly fits into, you have contact. The nerve tethered to that keyhole sends a message to the brain, and the smell is identified. If it's a familiar smell, like popcorn, the ID is instant. If it's not familiar, like elephant dung, your brain sends out a command to search the data bank that is your brain.

We have pretty good smelling organs, although most animals have noses hundreds to even a million times more sensitive. Physiologist R.W.A. Linden from King's College in London believes that we can identify some 2,000 odors but only about 200 tastes. Most of these odors are a combination of volatile (readily evaporated) oils working together to give a specific smell. But taste and smell have other functions in life besides bringing forth the pleasures of eating. They alert us to the dangers of spoiled and poisonous foods, fire, and gas leaks. They provide us with such delights as the scent of a pine forest, a jasmine flower, or the salty sea. They also help us attract and stimulate sexual partners.

Like optical illusions that fool your eyes, tastes and odors can also fool our senses. An utterly delicious Asian tropical fruit called durian smells exactly like a ripe tropical sewer. And what about Limburger cheese? It smells like a forgotten bag of dirty gym socks, yet it's a full-flavored delight to eat. The wonderful ability of our olfactory system to desensitize itself allows us to get over the smell.

Try this. Have some trusting friends close their eyes and hold their noses. Give one of them bits of onion to chew, and the other, bits of apple. Ask them what they're eating. Without sight and smell, only the onion's bite might give your trick away.

And for the Scapucino family…there is always next year. Mama is already planning a feast that will be heavy on the garlic, just in case!

Vocabulary

Limburger:
A soft white cheese with a very strong odor and flavor.
desensitize:
To stop reacting to stimuli
olfaction:
The sense of smell.

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  1. What kind of properties are the flavors sweet, sour, salty, bitter, and umami?
    Answer: Sweet, sour, salty, bitter, and umami are physical properties.
  2. To complete this part of the activity, print out and use a copy of the chart titled “Properties of Food” (PDF file). You can use your memory of each food to help you with your description. Or you may want to gather samples of each food to help you with your description. Describe the flavors of a banana, a chocolate chip cookie, cheddar cheese, and a lemon using the words “sweet,” “sour,” “salty,” “bitter,” and “umami.” Describe the appearance of each food. Describe the texture of each food. Study your chart after you have filled it in. Then answer the three questions beneath the chart.
    Answer: Answers on the chart will vary but could include the following connections. Banana: sweet; yellow; soft. Chocolate chip cookie: sweet, salty, umami; light brown and dark brown; crispy or chewy. Piece of cheddar cheese: salty, umami; bright orange; smooth, creamy. Lemon slice: sour; yellow; moist and granular. Students may answer that the chart does give enough information for someone to guess what each kind of food is. The additional information that might be needed could include more in-depth descriptions of the color and texture of the food. Students might suggest that mass, density, and volume could be listed for each food.

Activity

  1. What kind of properties are the flavors sweet, sour, salty, bitter, and umami?
    Answer: Sweet, sour, salty, bitter, and umami are physical properties.
  2. To complete this part of the activity, print out and use a copy of the chart titled “Properties of Food” (PDF file). You can use your memory of each food to help you with your description. Or you may want to gather samples of each food to help you with your description. Describe the flavors of a banana, a chocolate chip cookie, cheddar cheese, and a lemon using the words “sweet,” “sour,” “salty,” “bitter,” and “umami.” Describe the appearance of each food. Describe the texture of each food. Study your chart after you have filled it in. Then answer the three questions beneath the chart.
    Answer: Answers on the chart will vary but could include the following connections. Banana: sweet; yellow; soft. Chocolate chip cookie: sweet, salty, umami; light brown and dark brown; crispy or chewy. Piece of cheddar cheese: salty, umami; bright orange; smooth, creamy. Lemon slice: sour; yellow; moist and granular. Students may answer that the chart does give enough information for someone to guess what each kind of food is. The additional information that might be needed could include more in-depth descriptions of the color and texture of the food. Students might suggest that mass, density, and volume could be listed for each food.