A. Have you ever wondered why grapefruit juice is often served in small glasses? It is because most people like to drink it only in small doses, as they find it somewhat bitter. 8Naringin, a natural chemical found in grapefruit, has a bitter taste. Although some people like that bitterness, there are other people who want nothing to do with it. 12So juice companies often decide to use grapefruit with lower naringin content, despite the fact that naringin has antioxidant properties that can help prevent cancer and arteriosclerosis.
B. A New Jersey biotech company, the Linguagen Corporation, has found a way to eliminate the bitter taste in grapefruit juice. In a taste test, the company had participants drink grapefruit juice from two different sets of white paper cups, labeled 304 and 305. Each participant drank from one cup and then the other, cleansing their palates between tastings with water and a soda cracker. Even the smallest sip from the 304 cups was determined to have the bitter taste commonly associated with grapefruit. The 305 cups were found to be different, however. They still had the sour taste of citrus, but the bitter taste of naringin was gone. The 305 batch had been treated with adenosine monophosphate, also called AMP, 1a compound that blocks the bitter taste in foods without affecting the nutrition value of those foods.
C. Taste research has become commonplace these days. Food biologists are researching all five basic tastes：sweet, bitter, sour, salty and umami a Japanese term referring to savoriness. 2-13Food biologists are especially interested in bitterness, because there are thousands of bitter-tasting natural compounds that are not currently used as foods. Biologists view these bitter foods as an untapped potential food source for our future needs. Some bitter foods, such as grapefruit and cruciferous vegetables such as cabbage, kale, broccoli, and cauliflower are nutritious despite，and sometimes because of, their bitter-tasting components. Over time, many people have acquired a taste for bitter foods.
D. 3It is important to note that people taste bitterness at different levels. These variances appear to be mostly genetic. 9About three-fourths of people are sensitive to the taste of the bitter compounds phenylthiocarbamide and 6-n-propylthiouracil. Those people who are sensitive to phenylthiocarbamide seem to be less likely than others to eat cruciferous vegetables, according to Stephen Wooding, a geneticist at the University of Utah. Some people, known as supertasters, are especially sensitive to 6-n-propylthiouracil because they have an unusually high number of taste buds. 10-11It is not unusual for supertasters to avoid all kinds of bitter-tasting foods and drinks, including some vegetables, coffee, and dark chocolate. Supertasters, possibly because of their taste proclivities, tend to be thin. They also tend to be less fond of alcoholic drinks, which are often slightly bitter. A research study found that super tasters consume alcoholic beverages, on average, only two to three times a week, compared with five or six times for the average tasters.
E. 4In describing a taste bud, each taste bud contains a small group of receptors that capture the taste molecules. These taste molecules are known as tastants. When a person tastes something bitter, the receptors relay a signal through proteins called G proteins. These G proteins are involved in the perception of bitterness, sweetness, and umami, and were identified and labeled in the 1990s by Linguagen founder Robert Margolskee at the Mount Sinai School of Medicine in New York. This G protein is known as gustducin and it triggers a cascade of chemical reactions that lead to ion changes within the cell. As this happens, the brain gets a signal that the person is eating something bitter.
F. In 2000, a group of researchers identified some 30 different kinds of genes that code for bitter-taste receptors. No matter which tastant enters the mouth or which receptor it attaches to, bitterness always tastes the same. 5The only things that vary are the intensity of the bitterness and the ways our sense of taste identifies the flavor.
G. After determining how the taste mechanism works, scientists started to research how to interfere with it. As Margolskee noted, AMP contains no bitterness of its own, however, when it is added to foods, it attaches to bitter taste receptors. 6-14As effective as it is, it has been determined that AMP cannot block every type of bitter taste, probably because it does not attach itself to all 30 of the bitter-taste receptors. As a result, researchers continue to look for other bitter blockers, using a technology called high-throughput screening.
H. 7Taste researchers are excited about the idea that compounds like AMP will eventually make processed foods healthier. For example, a single cup of Campbell's chicken noodle soup contains 850 milligrams of sodium chloride (table salt) , more than a third of the recommended daily allowance. All the salt in the soup masks the bitterness created in the canning process. Part of the salt that is currently used in the soup could be replaced by a different kind of salt, potassium chloride, which tends to be scarce in some diets. Potassium chloride has a bitter aftertaste that could be easily eliminated with a dose of AMP. Bitter blockers could a lobe used to take the bitterness out of things like children's cough syrup and they can also be used to reduce the bitterness which is frequent in other drugs and medications.
