One group of Riesling enthusiasts has set out to change the perception that all Riesling wines are sweet.In 2007, Dan Berger, Coke Roth and Jim Trezise assembled at a wine event and began to talk about the problem with Riesling. “Consumers walk into a store,” said Berger, a wine writer in Santa Rosa, Calif. “They liked the last Riesling they had, so they pick up a bottle, wondering if it’s dry or sweet. They can’t…