SAN FRANCISCO - This city is a short stagger from the nation's winemaking heart, a geography lesson not lost on the chemists flocking here this week with scientific papers and theories on how to take some of the guesswork out of grape growing and winemaking.

The occasion is the 232nd annual meeting of the American Chemical Society and several of the attendees spent Sunday afternoon extolling the virtues of making better wine through chemistry ¡ª even as some organic vintners complain the technology is being used to mass market wine that all tastes the same.

The wine scientists aim to bring the same chemical analysis used in chemical plants, oil refineries and pharmaceutical factories to make wine manufacturing more efficient, consistent and, of course, more profitable as the industry continues to enjoy burgeoning sales.

Last year, U.S. retail wine sales totaled $26 billion, a 5 percent increase over 2004 and California winemakers produced nearly two-thirds of the 703 million gallons sold, according to the San Francisco-based Wine Institute.

Many winemakers are now dabbling with high-tech chemical analysis to streamline the yearlong wine making process and squeeze more money out of the grape. For now, chemical analysis is largely being used to make harvest decisions ¡ª but others are using high technology equipment to tweak the grape juice while it ferments.

Cleary said the Modesto-based winery is using a laboratory process called chromatography that chemically separates grape into its component parts, such as the molecules responsible for aroma, taste and feel. That analysis can be used to make the decision to harvest when these particular molecules reach their highest concentration levels, Cleary said.

"It takes good grapes to make good wine and we're trying to improve our predictions of when to harvest," Cleary said.

Scientists don't fully understand the delicate mix of compounds that emerge during fermentation and why they create such pleasing sensations for wine drinkers. So chemists are trying to isolate chemicals that produce desirable fragrances and flavors.

Scientific analysis is now also being used to uncover the chemicals that give wines their taste, aroma and texture. Those tests help vintners monitor the wine as it ferments, enabling them to make subtle changes.

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