Californian winemakers are turning to hi-tech chemistry to choose optimum grape picking times, according to a Gallo Family Vineyards executive.

Michael Cleary, senior manager of grape and wine chemistry at Gallo told the annual American Chemical Society meeting in San Francisco that spectroscopy and chromatography will be used more commonly in its wine-making.

Spectroscopy is the study of the make-up of matter based on the light it emits, while chromatography involves chemically separating mixtures into their component parts.

Resulting molecular data can help identify and evaluate aroma, colour, taste and palate feel of grapes and their juice. When tests show beneficial molecules are at their highest concentrations, grapes are ready for harvest.