Many people can't stomach the taste of nutrient-rich Brussels sprouts or protein-packed tofu, but now scientists are seeking to fool our senses into believing they taste and smell more like mouth-watering steak or yummy chocolate.
This new field is a combination of genomics - the hunt for genes that turn "on" or "off" under certain conditions - with the age-old science of flavor and fragrance enhancement. It's a high-tech version of something chefs and perfumemakers have done for generations: find out what tickles our senses, bottle it, and sell it.
To this end, scientists are filling in the missing links between our nose, taste buds, and brain. If successful, they could turn tofu into steak, make medicines taste better (without the spoonful of sugar), or create salty and sugary additives without the unhealthful side effects.
"The goal is not to manipulate genes, but to use clever chemistry to fool those genes into doing something slightly different," says Charles Zuker, professor of biology at the University of California, San Diego, and an investigator at the Howard Hughes Medical Institute. "Just find a molecule that blocks the receptor for that taste, like a lock and a key. I gum up the lock, and the key won't fit. It lets you mimic the taste of wonderful wine or the smell of a rose."
So far, researchers have identified about 370 genes that are responsible for the 10,000 or so odors we humans can identify. These genes are activated when exposed to a toxic whiff of ammonia or the inviting aroma of wildflowers, and then they send chemical messages to the brain. Each smell activates a unique combination of these smell-receptor genes.
Our taste system is more simple. We only have five basic tastes: sweet, sour, salty, bitter, and umami (Japanese for savory) that are controlled by only two genes, a finding reported two years ago by Dr. Zuker and colleagues in the journal Cell.
Last March, Zuker and a group at Harvard Medical School in Boston found a group of chemical receptors - proteins on the surface of cells in the mouth - responsible for the bitter taste.
Other researchers are exploring the taste connection between mothers and children. Gary Beauchamp, director of the Monell Chemical Senses Center, a Philadelphia-based private research institute, has discovered that infants whose mothers drank carrot juice while pregnant were more likely to drink carrot juice after birth. He's also found that breast-fed babies are open to tasting a wider variety of flavors than bottle-fed babies, precisely because what a mother eats is reflected in her milk. "The infant is being programmed to be familiar and like flavors that reflect the best judgment of what his mother thinks is nutritious," he says.
Dr. Beauchamp notes that some bitter foods, such as dark-green vegetables, contain alkaloids that are toxic in high quantities. Our aversion to bitter tasting foods is an important evolutionary warning sign. Over time, however, much of the toxic properties of our vegetables have been bred out, while the taste remains. Being able to make these healthful, yet bitter vegetables taste good "would be a real breakthrough," Beauchamp says.
While basic research continues to better our understanding of smell and taste, one company is pushing forward to develop consumer products based on these taste- and smell-receptor genes.
Senomyx, a San Diego biotech firm, has filed for patents on 245 of the 370 smell genes in the past eight months. It is using technology to screen hundreds of thousands of molecular compounds to see which ones activate these smell genes and therefore could be either enhanced or blocked. They are doing the same with the simpler human taste system.
"We can test 10,000 compounds a week against the receptors," says Mark Zoller, Senomyx vice president of research. "Our ultimate goal is to have the molecular code of every odor."
Last month, Senomyx signed an agreement with Kraft Foods to develop consumer foods using these new compounds.
Despite the advances, a steak-like tofu may be several years away, according to industry experts. Even then, the final arbiter is our own individual sense of taste and smell, one that varies from person to person.
"You have to have the human element," says Gene Grabowski, a spokesman for the Grocery Manufacturers Association, a food industry group based in Washington, D.C. "You have to have human tasting. Biotechnology enables us to speed up the pace of experimentation and increase the variety. It doesn't change the fact that we have human beings designing food."
(c) Copyright 2001. The Christian Science Publishing Society