"Oh boy," said one of my fellow judges with just a wee bit of wryness in his voice, "we get to judge the Minnesota White Table Wine and Minnesota Red Table Wine categories."

I couldn't bite my tongue because I needed it for tasting 90 wines that day. But I kept quiet, fairly certain that the wines would put the kibosh on my cohort's lighthearted snark.

And they did, providing some of the highlights at last week's Riverside International Wine Competition in Temecula, Calif., a wonderful proving ground for U.S. wines not from the West Coast. (We tasted some obscure varietals called noble, carlos and diamond, with wildly varying results; more below.)

Chankaska Creek in Kasota, Minn. (near St. Peter), nabbed a gold for its 2011 Marquette Reserve and a silver for its 2012 "Petite Colline" white blend. Carlos Creek Winery in Alexandria also received two medals, a silver for its 2011 Marquette and a bronze for its 2011 Frontenac.

Perhaps as important, those judges — two Californians and a Bostonian — came away impressed, as did a few other judges who stopped by and sampled.

You need an open mind — and a great palate — to judge a competition like this. In the sweepstakes round for sparkling wines, we took awhile to discern that one we particularly liked was from California rather than France. It turned out to be a $10 bottle from Barefoot, the eventual sweepstakes champ.

When we encountered an unfamiliar grape, out came a smartphone for some research. I was able to serve as the "expert" on the Minnesota portions, which were not necessarily wines made here, but varietals and blends using one of the four grapes developed by the University of Minnesota: marquette and frontenac on the red side, plus the white la crescent and frontenac gris.

The judging works like this: We sample all the wines in the flight, then write down gold, silver, bronze or no medal. When everyone's finished, we share our grades and award a medal (or not) based on the average, with one exception: If two of us vote "no medal," that's what it gets. If the average falls in between two grades (two silver, two bronze), we discuss it and go up or down.

When we had a flight of concords, many of them tasted like the best Welch's grape juice ever — but didn't seem like wine (no acidity or tannins). So while they were delectable, we ultimately couldn't justify giving them medals as wines.

We had some delicious cabernet sauvignons from the Finger Lakes, a few excellent Bordeaux blends (meritages) from Virginia, some very nice vidals and vignoles and some truly wretched Florida wines made from a red grape called noble. Quite the misnomer there.

On the other hand, the lone diamond was a jewel, a clean, focused effort from New York's Goose Watch Winery. Another double-gold wine provided even more good news in the Minnesota White category: The Diamond Mine "Island Mama" is a blend of the cold-hardy la crescent, brianna and frontenac blanc (the latter, a mutation that just popped up in the vineyard).

Minnesota still has a long way to go in growing the right grapes in the right places and vinifying them well. But it's a mighty fine sign when these tundra-bred grapes are even mutating into something tasty.

Follow Bill Ward on Twitter: @billward4