Think You Know Citrus?

For nearly a century, UC Riverside has been creating Frankenstein-like citrus in its groves and laboratories -- all in an effort to build the tastiest, hardiest fruits.

Behold the dull, gold Chandler pummelos, the oversized ancestors of grapefruit, that are as big as a baby’s head; Gold Nugget mandarins, with Crayola-orange rinds and sides squashed flat; and Kaffir limes, looking like so many electric-green golf balls.

These are not your run-of-the-mill oranges from Ralphs.

The bags and bins of ripe fruit chilling in a low-slung building on a corner of UC Riverside’s leafy campus are the cream of the university’s 22-acre experimental citrus crop. And this weekend at Riverside’s annual Orange Blossom Festival, the university is sending six pickup trucks of the exotic fruit for the public to taste.

For three weeks, about 250 volunteers have been picking, soaping, rinsing, packing and cutting 30-odd varieties of rare, extraordinary and just plain delicious citrus in preparation for the festival.

Although the annual celebration will sprawl over 40 blocks in downtown Riverside and include live bands, a carnival and plenty of food, UC Riverside’s tasting booth is expected to be one of the crowd favorites. Over the last decade, citrus groupies have waited in lines for more than an hour to get their annual fix.

“Riverside has this absolutely wonderful, extensive citrus collection -- just world famous,” said Ottillia “Toots” Bier, a staff research associate with the university’s Citrus Variety Collection. “It’s a gee-whiz experience to see some of these different things.... Ever seen the look on someone’s face when they see a blood orange?”

The citrus tasting booth is one of the festival’s biggest draws because people “know that they can’t do this any other time of the year,” said Britta Wichers, director of marketing for the Orange Blossom Festival Assn. Wichers estimates that each year the booth serves 10,000 to 20,000 people.

The university’s Citrus Variety Collection has two trees each of about 900 citrus species, one of the most diverse assortments in the world.

Over the seasons, farmers and growers evaluate some of the most promising products to decide whether they’re worth planting and taking to market.

A best-selling citrus has to be seedless (or pretty darn close), easy to peel and have a bright, smooth rind, said Tracy Kahn, a curator of the collection. Above all, it should taste good.

Two star fruits developed at the university are the Oroblanco, a white grapefruit-acidless pummelo hybrid with pale yellow fruit and a surprisingly sweet taste, released in 1980; and the Gold Nugget mandarin, seedless and tangy, released six years ago.

In addition to carrying out breeding experiments to make the trees hardier and bear fruit longer, scientists are conducting dozens of research projects in the citrus groves along Martin Luther King Boulevard. Those include mapping citrus genomes and looking for creative ways to combat the crop-destroying glassy-winged sharpshooter, which looks like a cross between a grasshopper and a cockroach.

Although the Citrus Variety Collection has been in Riverside for nearly a century and was the forerunner of the university, the obscure research project rarely attracted public attention until the debut of its wildly popular tasting booth at the festival 11 years ago. In the booth’s first year, Bier had to pick extra fruit overnight by her car’s headlights and wash it in her bathtub to keep up with public demand.

Perhaps because Riverside was home to a booming turn-of-the-century citrus industry, residents have a special affinity for the fruit.

“There’s a lot of people whose relatives have worked, or parents or grandparents have worked, in the citrus industry,” curator Kahn said.

This year’s tasting selection will include a new, unreleased Ruby blood orange-pummelo hybrid not found in any supermarket. It’s being evaluated for commercial potential, and the fruit is so new it has no name.

True Vitamin C connoisseurs, Bier and others choose the roughly 35 tasting fruits for diversity, appearance, aroma and flavor.

Bob Ayres, a UC Riverside database director who was sudsing fruits Thursday while wearing one of the citrus-print vinyl aprons Bier made for volunteers, considers the tasting experience one of a kind.

“Where else can you do that?” he said.

People are just “amazed at the diversity,” Bier said. “Everyone thinks an orange is an orange.”

The 11th annual Orange Blossom Festival will feature live music, a parade and food in downtown Riverside from 10 a.m. to 8 p.m. Saturday and 10 a.m. to 7 p.m. Sunday. The citrus tasting booth will be at Mission Inn Avenue and Lemon Street. Festival admission is free of charge.