Taste: Surprising Stories and Science About Why Food Tastes Good (16 page)

From The Tomato Project website: hos.ufl.edu/kleeweb/flavorresearch.html

My fiancé, Roger, hates fresh tomatoes; I can’t imagine life without them. It’s really difficult for him to articulate what he doesn’t like about the tomato. His answer, “There’s a certain flavor . . . ,” is accompanied by a scrunched-up face. Yet he adores foods made from cooked tomatoes: pasta sauce, tomato soup, ketchup. The difference between the two is that the cooking (or processing) of tomatoes flashes off the volatile aroma compounds in the tomatoes that Roger finds objectionable. Cooked tomatoes don’t have those green, grassy, earthy top notes, defined as compounds with low molecular weight that are really sensitive to heat. Top notes are the aromas you detect most strongly in a food. Because they are light, they evaporate quickly. This phenomenon explains why freshly squeezed orange juice savors better than pasteurized. The low molecular weight volatiles in the juice are lost from the heat of pasteurization. They are the compounds that give it that fresh flavor.

The background notes in tomatoes withstand cooking because they’re heavier. The weight of these molecules makes them less sensitive to heat. I don’t know if it’s the trans-2-hexanal, the β-ionone, or the 3-methylbutanol that offends Roger. All I know is that four to five minutes in a sauté pan are enough to get rid of it.

Now, let me recommend a real-world experiment that my father—not a scientist—taught me at age five. In the middle of August, go to the best grocery store or farmers’ market in your neighborhood. Find an heirloom tomato that’s heavy for its size, plump, full of juice, but not mushy. When you get home, put a paper towel in the neck of your shirt as a bib. Lean over the sink, wash the tomato. Sprinkle it with sea salt. Then, holding it like an apple, sink your teeth in. See if you can detect the phenylacetaldehyde. No? Good. Now forget about volatiles and enjoy one of Mother Nature’s most perfect foods.

YOU WILL NEED

Masking tape and marker

2 glass measuring cups

2 whole lemons for each person tasting

Juicer

A medium bowl

Plastic wrap

A small nonreactive saucepan

Saltine crackers for cleansing your palate

DIRECTIONS

1. Using masking tape, label the glass measuring cups. Measuring cup 1: Fresh Juice. Measuring cup 2: Boiled Juice.

2. Juice all the lemons into the bowl.

3. Pour the juice into the measuring cups until you have separated it into two equal parts.

4. Cover the measuring cup labeled “Fresh Juice” with plastic wrap and put it in the refrigerator.

5. Pour the remaining juice into the saucepan. Heat on high until the juice starts to boil. Boil on medium-high heat for 3 minutes.

6. Remove the juice from the heat and pour into glass measuring cup labeled “Boiled Juice.”

7. Chill the boiled juice to the same temperature as the fresh cup, about 2 hours. Make sure the two cups are the same temperature.

TASTE

8. Taste the fresh juice first.

9. Eat a cracker and drink some water to cleanse your palate.

10. Taste the boiled juice second.

OBSERVE

1. When you taste the fresh juice, you will experience two—perhaps three—Basic Tastes. You’ll definitely taste sweet and sour (mostly sour) with perhaps a tiny bit of bitter, depending on the lemon and how much of the pith and rind you squeezed.

2. After you’ve noticed the tastes, focus on the aromas. Freshly squeezed lemon juice has some brilliant, crisp, sharp aroma top notes that give it its signature flavor.

3. When you taste the boiled juice, you’ll notice the same basic tastes. But when you focus on the smell in the boiled juice, you’ll notice that something’s missing. It’s not as aromatic as the fresh juice. This is because boiling the juice liberated the lighter compounds and they evaporated off into the air. The resulting juice thus contains fewer aroma compounds.

4. The process of boiling juice is similar to what happens when juice (or any liquid) is pasteurized, a process that uses heat to kill bacteria. It allows juice to stay fresher longer. The heat kills dangerous microbes as well as lovely, subtle aromatic top notes. Next time you taste a glass of orange juice at a restaurant, see if you can detect those subtle top notes, which might indicate whether the restaurant is squeezing its own juice. Or not!

YOU WILL NEED

1 bottle of nectar-like juice such as pear, peach, or mango, at room temperature

3 glasses or plastic cups with matching lids

A roll of plastic wrap (if you are using glasses)

1 stick butter, brought to room temperature naturally (do not melt using heat!)

1 jar peanut butter, at room temperature

Sampling spoons and cups

3 bendable straws for each person tasting

Paper and pens or pencils

DIRECTIONS

PREPARE THE STIMULI

1. Pour ½ cup juice into one of the glasses. Cover the top tightly with plastic wrap or a snap-on lid.

2. Put 2 tablespoons butter into one of the remaining glasses. Cover the top tightly with plastic wrap or a snap-on lid.

3. Put 2 tablespoons peanut butter into the last glass. Cover the top tightly with plastic wrap or a snap-on lid.

4. Set the glasses aside for about an hour so that the volatile aromas of the juice, butter, and peanut butter fill the empty space in the glass. This empty space is called the headspace.

Set the remaining juice, butter, and peanut butter out so that they are easily accessible for sampling but out of smelling range of the covered glasses.

SMELL AND DISCUSS

• Using the short end of a straw, the first person should puncture the plastic wrap or lid with it, but do not let the straw touch the aroma stimulus. Make sure it stays in the headspace. You want to sample the air, not the food or drink.

• Close the lips around the straw and breathe in and out. This is the retronasal smell, or mouth-smell, of the stimulus. Allow each taster to mouth-smell the samples (using clean straws, if they want).

• Now, smell the stimuli as you normally would, using your nostrils.

• Finally, taste the stimuli.

• Discuss your experience.

This is an ongoing training exercise that will take you a few weeks, maybe even months, to master.

YOU WILL NEED

10 to 15 spices and herbs that you use on a regular basis
⁶

Masking tape

Marker

Paper

DIRECTIONS

1. Using masking tape, put the names of the ingredients on the bottoms of the containers.

2. Cover the container labels with paper so that you can’t tell what’s what.

3. Quiz yourself by randomly picking up a jar, opening it, and smelling. Try to identify the contents without looking at the name. (
It’s best to do this with a partner, as the temptation to cheat will be overwhelming! You will not learn if you look at the name of the spice first and sniff second. You must sniff first and guess second.
)

4. At first, identifying spices by smell will be extraordinarily hard. You’d think you’d know the smell of ingredients you use regularly! The problem is that you’re never forced to identify them without other contextual clues.

5. If you find this difficult, ask yourself this series of questions:

a. Is this is an ingredient you use regularly? If no, you’re in trouble! If yes, proceed.

b. Is this a familiar smell? Yes or no?

c. If it’s familiar, try to associate the smell with some emotion it provokes. For example, is it something you cook with often or not? If yes, that helps. If no, that gives you a clue as well. Is this something you’ve smelled at your mother’s house? Friends’ houses? That Indian restaurant down the street?

d. Try to identify what category this ingredient belongs to. Does it smell citrus-y, musky, grassy, or warm? If you can identify the category of aroma, that will help narrow it down.

e. What do you think it is? Take a guess before you look at the name. This is the only way you’ll learn!