John Thull, Geoffrey Anderson* and Matthew Clark
*Unitech Scientific LLC, 12026 Centralia Road, Suite H, Hawaiian Gardens, CA 90716
(geoff@unitechscientific.com)

Proper fruit ripeness is a primary quality predictor in winemaking. A simple, portable meter to monitor both fruit sugar and acid in the vineyard could provide this timely, important information. The PAL-BX/ACID 2 combo meter from ATAGO-USA is evaluated for utility as a tool to monitor preharvest ripeness of winegrapes. Grape sugar is measured by digital refractometry directly from juice and total acid, by conductivity following 50-fold dilution. The evaluation, performed within the University of Minnesota Grape Breeding program, included several varieties of Vitis vinifera and hybrid grape. Brix and acid changes were tracked over a two-month period prior to harvest. The meter was easy to use and produced repeatable results. Acidity is expressed as tartaric acid equivalents (g/L) and when combined with sugar (Brix) measurements, the meter offers a rapid, in-field analysis of fruit ripeness that is useful to optimize harvest timing. The interpretation of acid conductivity versus titratable acidity data is discussed.

Funding Support: University of Minnesota Grape Breeding Program