ON Saturday evening on the lawn at the Capay Organic farm, 90 miles north of San Francisco, Ann C. Noble addressed about 100 people gathered around tables bearing glasses of red slurry.

''Write down whatever comes to mind, even if it sounds ridiculous,'' said Ms. Noble, a food scientist. ''We don't have words for tomatoes yet.''

Ms. Noble, best known for creating the Wine Aroma Wheel, a brightly colored disc with aromatic descriptions to help people characterize wines, was trying to develop a similar vocabulary in the first sensory evaluation of heirloom tomatoes.

Volunteers diced and ladled five heirloom varieties into wine glasses (leaving room for headspace so the tomatoes could breathe, of course). A petri dish topped each glass to capture the tomatoes' fleeting scent.

Ms. Noble, professor emerita at the University of California, Davis, said the rules were simple. Close your eyes. Don't talk. Turn off the background music. Smell before you taste. Each tester was given a comment sheet that included suggestions from Ms. Noble for tasting notes, like melon, apple, cinnamon, coffee and pumpkin.

''With the first one you're likely to say, 'Oh God, it smells like a tomato -- how will I kill the next half hour?' '' she said. ''But that's O.K. It takes time. And just think -- you might come up with the perfect word no one has ever used to describe that note.''

With that, she set the tasters free.

They swarmed around the tables, dipping noses deep into glasses, swirling the tomato slurries as if they were wine. Comments were whispered: ''vanilla.'' ''Carrot.'' ''This is like broccoli.'' ''This one's more green.''

Thaddeus Barsotti, the operations manager of Capay Organic, said he came up with the idea for the tasting because he was frustrated at not knowing how to describe his tomatoes when people asked him about them at the farmer's market.

''I thought it'd be cool,'' he said, ''to take tomatoes and put them in front of people and say, 'How does this taste to you?' ''

As it turned out, there are a lot of ways to characterize a tomato. One, later revealed as a Brandywine, received some of the sharpest descriptions, like a ''musty'' odor reminiscent of ''smelly feet.'' (A more forgiving participant described it as ''ripe, like chocolate.'') Ms. Noble asserted that it smelled ''like Fritos.''

''It does,'' she said, as her companions raised their glasses to take a whiff. ''It's like just-fried potato chips.''

Some notes said as much about the person writing them as they did about the tomato. ''My grandmother's Avon bath powder,'' wrote one person about No. 5 (Yellow Brandywine). No. 4 -- Evergreen -- was described as ''acrylic paint on muslin,'' ''milkweed pod,'' ''peeled bark of willow,'' ''stagnant pond,'' and ''like jeans you've been playing football in on the grass.''

The tasting was organized by the farm and the Yolo County chapter of the organization Slow Food.

Several guests complained that the night's tomato bounty wasn't quite ripe enough; a rainy March had delayed planting, and the tomatoes were not as luscious as they had hoped. But that didn't stop people from eating them.

''I think there's something addictive about tomatoes. I mean, they're in the tobacco family,'' said Trini Campbell, an owner of Riverdog Farm nearby.

Addictive or not, it seems unlikely that tomato tastings will take off in the way wine tastings have.

''The rate-limiting variable in tomatoes is the range of flavor,'' said Ms. Noble. ''It's kind of like we're just tasting pinots.''

But Georgeanne Brennan, a leader of the Slow Food chapter who coordinated the event, still hopes for more.

''They'll never look at tomatoes the same way again,'' she said of the night's guests. ''Their lives will have been changed.''

Photos: A FLEETING SCENT -- Ann C. Noble sniffs a glassful of slurried heirloom tomato, a Marvel Stripe, at a tasting at the Capay Organic farm in California. The array of tomatoes, above. (Photographs by Peter DaSilva for The New York Times)