"We start with the current vintage wines, so we're judging potential at this stage, but as expected the quality is terrific. We already have a number of gold medals that will be in contention for the trophies," he said.

Tuesday marked the first of three days of judging the more than 500 wines from nine countries in this year's competition, which will be tasted by three international and three Australian riesling experts.

Belsham said that althoughriesling used to be overshadowed by chardonnays and sauvignon blancs, the white grape variety was increasing in popularity.

"One of the misconceptions about riesling is it's monostylistic and it's not at all. She is the queen of white wines because she can be the little floral example, she can be the elegant example, she can be the little black dress, she can be fully velvet-robed and everything in between," he said.

"That's why it's such a great wine style to judge because you're not looking for the definitive riesling – there's a riesling for every occasion."

The challenge, returning   for the 15th year, is the largest of its kind in the southern hemisphere, and the second-largest in the world.

Challenge chairman Ken Helm said that what sets it apart from other wine shows werethe seminars, master classes on grape growing and winemaking that formed part of the week-long event.

"We're not just a wine show. The seminars and the master classes are just something thatno other show had done, and a lot of other shows nationally are now copying it. They say the greatest accolade is to be copied," he said.

The public also has the chance to taste all of the judged wines on Saturday from 11am-4pm at the trade and consumer tasting event at Albert Hall.

"I don't think anyone will get through the whole 500. We have difficulties ourselves, we have to use seven judges and two associates to get through them all over a four-day period," Helm said.