Issue link: http://winesandvines.uberflip.com/i/137110
GRAPEGROWING Sensory assessment—The tasting of berries in the vineyard for fruit grading is not new. However, formalized berry sensory assessment (BSA) is relatively new and now used in some assessment schemes.25 There has been little research to support its use. BSA was positively correlated with juice composition/wine score,14,15,23,28 but in most cases only a few out of 20 or so attributes were correlated with wine score such as flesh maturity, astringency of pulp and skin, seed and skin color. Yield The majority of vineyards producing premium wine tend to have low yield (tons per hectare), so it is assumed by some that low yield is indicative of good quality. Many wine companies use yield as a criterion for fruit grading even though the weight of experimental evidence indicates that yield is not a reliable predictor of quality.8 This proposition is supported by some benchmarking studies that found yield and wine composition/score not correlated.6,26 Measures —From Our Table To Yours— Family Winemakers of California Tasting AUGUST 17 1-6 Trade; 3-6 Public AUGUST 18 1-5 Trade Only Festival Pavilion Fort Mason Center San Francisco Meet California's fascinating family-owned wineries, hear their stories, taste their wines, share with your family and friends. To attend visit: www.familywinemakers.org 54 p racti c al w i ne ry & v i n e yard J U LY 20 13 of vine balance are much more valid for fruit grading than yield alone. Can we do better? Precision viticulture techniques have been available for some time. It is puzzling why they have not been adopted more widely in vineyard assessment to provide a greater degree of objectivity. Aerial imagery, including normalized difference vegetation index (NDVI) or PCD, has demonstrated a strong relationship between vine "vigor" and wine composition, particularly phenolics, across multiple sites and vintages.2,12,13,19,21 NDVI maps that are sensitive to the variations of vertical leaf area index and gap fraction of the canopy can now be created by ground-based devices.7 Point and shoot near-infrared spectroscopy combined with GPS can generate fruit composition maps and quality potential zones.21 A recent paper described on-the-go sensing of berry anthocyanin concentration by a Multiplex fluorescence-based non-contact handheld sensor.3 Even if this technology is not able to replace the standard vineyard assessment by scoring of vine attributes, at the very least it could be used to identify zones within a vineyard block to permit more accurate and representative sampling. Conclusions Until such time that fruit grading is based solely on chemical measures of the fruit before or soon after crushing, vineyard assessment schemes will continue to be required for fruit streaming. Research shows that there is merit in assessing vineyard characteristics prior to harvest to get an indication of potential fruit attributes. However, for the purpose of streaming and grading fruit this assessment needs to be undertaken with a high level of accuracy and the results properly interpreted. Only then do you have some meaningful indication of the potential inherent in a batch of grapes. Many of the grading schemes currently in use do not adequately measure, count or sample within the vineyard to draw a reliable conclusion about fruit quality. For this reason, there is a need for an improved vineyard assessment scheme for fruit grading that has a greater degree of objectivity than the current schemes and that is transparent to growers. PWV This text was edited from first publication in the May 2013 Australian & New Zealand Grapegrower & Winemaker with permission of the publisher, Winetitles.