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Interpolation of wine grape quality indicators (Anthocyanin and Brix) and development of differential harvest attachment

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  071097.(doi:10.13031/2013.22971)
Authors:   Balaji Sethuramasamyraja, Sivakumar Sachidhanantham, Matthew Yen, Robert Wample
Keywords:   Precision Agriculture, Precision Viticulture, Differential Harvesting, Anthocyanin, Brix, Wine grapes, Cabernet Sauvignon

Measurement of quality and segregation of wine grapes during harvest is a growing need for producers and wineries alike. The commonly used quality indicators for wine grapes are anthocyanin (mg/g) and brix (degrees) contents. Geo-referenced field samples of wine grapes were measured for anthocyanin and brix using a portable near-infrared (NIR) spectrometer. Data was collected from 437 sampling points in a 45 acre block of vineyard in the Central Valley of California. The quality indicators were subject to geo-spatial modeling for the distribution of the spatial variability of wine quality across the field. Subsequently, the anthocyanin dataset was utilized to produce a quality zone map of ‘high’ and ‘low’ for the vineyard while the brix dataset was utilized to determine the timing of the harvest. The anthocyanin concentration used to differentiate between high and low quality was above or below 0.87 mg anthocyanin/g fruit respectively. Based on this quality map, a modified commercial mechanical grape harvester was utilized for segregation of wine grapes on-the-go. Three 40 tons lots of wine grapes representing the standard (average) field blend, high anthocyanin and low anthocyanin were differentially harvested. These wine grapes were fermented separately were subjected to analytical and taste panel analysis.

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