A Rapid Method to Quantify Phenolic Compounds in Red Wine Fermentations is Now Available On-Line

[Photo features Dr. Roger Boulton in his lab, being interviewed by a German television crew with regard to The Skogerson-Boulton Model.}

The Department of Viticulture and Enology is excited to announce the launch of a website that allows researchers and winemakers to rapidly determine phenolic compounds during red wine fermentations. The predictive method was developed by Kirsten Skogerson (M.S. 2006) and Professor Roger Boulton, and is based on more than 400 samples analyzed during the 2006 Australian harvest. Given free access to this model, winemakers can now evaluate phenolic parameters in their wines rapidly and easily.

Phenolic compounds play key roles in the color, color stability, astringency and mouthfeel of red wines. The goal of this research was to develop a simple tool that would allow nearly instantaneous prediction of phenolic compound classes (anthocyanins, tannins, polymeric pigments and total phenols) in red wine at all stages of fermentation. Currently, the most widely used methods for quantifying color and tannin extraction in red wine fermentations require significant amounts of time for sample preparation and analysis, or significant cost and delayed results if a contract lab is used.

This model allows a winemaker or researcher to use UV-vis spectroscopy to predict phenolic compound classes as determined by the Harbertson-Adams assay. The Harbertson-Adams assay is a colorimetric assay that was developed by Professor Doug Adams and Dr Jim Harbertson. This assay measures anthocyanins, polymeric pigments, tannin and iron-reactive phenols. Due to the robust nature of the assay and low equipment and reagent costs, it has found wide acceptance in research settings as well as in the wine industry today. However, its application to large sample sets requires dedicated lab personnel and significant time.

The predictive ability of the present model is strongest for anthocyanins (17% predictive error), iron-reactive phenolics (18%), and non-tannin iron-reactive phenolics (18%). Total tannin is also well predicted (34% predictive error), as are total polymeric pigments (31%). Further testing with grapes from other regions and seasons should be undertaken.

This research has provided an elementary tool for the rapid determination of phenolic compounds in red wine fermentations that will have immediate application in industry and research. Minimal training requirements, low cost of the equipment needed, and simple sample preparation make the Skogerson-Boulton method ideal for industry applications. The spreadsheet which incorporates the model can be found at http://boulton.ucdavis.edu/uv-vis/index.htm .