By Lindsay Doi

UMPQUA VALLEY, Ore. -- Wine connoisseurs may talk about "tasting the soil" and minerality in fine wines, but geologists say that's simply not possible, as minerals from vineyard soils aren't present in finished wine.

Winemakers here in the Umpqua Valley say soil and climate make all the difference, even if science says that minerals from the soil don't influence taste. Geologists say tests show that the concentration of minerals in wine is below the threshold of human taste and smell and it doesn't come from vineyard soil at all. Still, many winemakers assert that the soil lays the foundation for a fine wine.

Winemakers say climate is also a major factor, as the topography of a vineyard influences the amount of sunlight and heat an individual plant receives. While scientists are still unclear about how geology and soil chemistry affect grape growing, some winemakers say it's an inexplicable process that is key to the unique taste of each bottle of wine.

Vineyard owners say soils must be matched to particular grape varieties, as different textures, like gritty sandstone or smooth clay, yield different characteristics in fruit. And with more types of soil than other wine growing regions, Umpqua Valley wineries are hoping to capitalize on their "terroir."

Still, scientists say it's all a matter of personal opinion as to which soils make better wines. One scientist even conducted a study with the same grapes grown on two different soils and found taste testers split 50-50 on which wine tasted better.