A measurement of phenolic content of grapes describes grape potential. It characterizes grape maturation, block to block variation, and variation between vintages. It is an important part of describing raw material coming into a winery and is often the first indication that a wine lot may have poor color, high or low tannin or unripe seeds.

Grape Water Content

Clients have best results sampling directly from the vineyard rather than from picking bins. Sampling mechanically harvested fruit from gondolas or sampling direct from a fermenter does not give reliable results. 

The panel consists of a wine-like extract of the grapes followed by HPLC analysis. The panel is designed for red grapes and the extraction process is intended to mimic red wine fermentation.  Reported compounds include total, monomeric and polymeric anthocyanins, tannin, catechin and quercetin glycosides. Two ratios are also reported: the catechin/tannin ratio and polymeric anthocyanins/tannin ratio. 

Grape Maturity

The phenolic panel for grapes measures critical parts of the grape ripening process. Anthocyanin synthesis and degradation, seed ripening, tannin concentration due to dehydration, changes in tannin extractability and tannin modification can all be followed by a periodic sampling program.

Raw Materials Description

A measure of Brix, TA and pH is not enough to fully understand grapes arriving at the winery. Phenolic composition along with other grape analytical tools such as grape water content can provide winemakers with the information they need to make initial decisions such as streaming, water adds and saignées as well as a heads up about potential problems in color or seed ripeness. 

Vineyard Variation

Grape phenolics are some of the most sensitive indicators for evaluating variation within vineyards or differences between vineyards. Soil variation and management differences may directly affect phenolic composition or may do so indirectly through changes in vine vigor. This information incorporated into a vineyard information system is proving to be a potent tool for identifying vineyard potential as well as vineyard problems and their potential causes. 

Experiments

Vineyard trials are an essential part of continual improvement in the vineyard. A measurement of phenolic compounds is an essential part of evaluating the effects of changing production practices in red grapes. Phenolic composition responds to changes in irrigation, ground management, canopy management, yields and spray materials.

Want deeper insight into grape potential and vineyard performance?

ETS Labs' phenolic panel delivers a detailed profile of grape maturity, color potential, and tannin structure—critical data for informed winemaking and vineyard decisions. Reach out to learn how our advanced analytics can help optimize your harvest strategy and improve wine quality from the ground up.

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