The Effect of Grape Yield and Size on Quality
The Matthews Laboratory at the UC Davis Department of Viticulture and Enology released an interesting graphic on the effect of grape yield and berry size on quality. Conventional wisdom asserts that the smaller the berries and yields, the higher quality. But the Matthews Laboratory declared,
“It’s not the destination, but the journey that matters.”
According to the study, vineyard management techniques and physical phenomena are the true reasons for quality levels; not simply berry and yield size. The graph illustrates the “sensory or fruit attribute payoffs” that results from the “journey” that grapes take during the growing season.
For example, small berries that develop in a well-shaded environment will have less color and less tannin. Without treatment, grapes will have more color and slightly more tannin. Grapes that are grown in a water deficient vineyard will have more color and more tannin.
Low yielding vines that are grown in a water deficient environment have less veggie and more fruit flavors. Cluster thinning in this situation has no effect on the grapes’ flavor profile. What I found most interesting was that low yielding vines that are pruned will have more veggie and less fruit flavors according to the graph.
This is a bit counterintuitive as I was under the impression that there was a more or less proportional relationship between pruning and quality. The data from the Matthews Laboratory suggests this is an overly simplistic view.
Comments & Reviews
January 17, 2007 | Daniel Rotlisberger
Good post. From the "viticultural" view, I can understand the outcome of this research. So much research and development has gone into new and improved trellis systems that maximize grape leaf sunlight interception (eg Vertical Shoot Positioning (VSP) systems). This increased sunlight interception by the leaves allows for the vine to properly mature a higher yield of fruit than the conventional "California Sprawl" systems. The vineyard owners/manager that implement a VSP type of trellis, and also thin the grapes excessively, will cause more "green" flavors in the grapes because of the decreased amount of fruit that the green flavors produced by normal leaf metabolic processes can be spread out over. This can be confirmed by the research of Chapman, D. M. et.al. "Sensory Attributes of Cabernet Sauvignon Wines Made from Vines with Different Crop Yields", in the American Journal of Enology and Viticulture (Volume 55, Number 4). Hope I did not go too of course on this post...
January 23, 2007 | Ben Bicais
Hi Socowineguy, thanks for mentioning that article, fascinating read. I was particularly struck by Chapman, Matthews, and Guinard’s conclusion that, “the way a given similar yield was achieved had an impact on the sensory results.” They go on to say that pruning leads to, “more astringent, more vegetal, and less fruity” characteristics. Cluster thinning, on the other hand, has “little effect on wine aromas.” All of this confirms that assuming a proportional relationship between lower yields and higher quality is far too basic a view.
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