Harvest, maceration and seed tannin extraction


In the previous blog entry, we discussed how different winemaking techniques impact wine sensory properties and phenolic contents. It’s interesting to see how variations in winemaking techniques can interact with variations in viticultural decisions. As we pointed out previously, harvesting decisions play a key role in fruit and wine quality. Federico Casassa recently made an interesting argument on balancing maceration and seed maturity at harvest with respect to seed tannin extraction in the September 2016 issue of Wines & Vines.    

Tradeoffs and considerations for delayed harvest

Winemakers often attempt to reduce extraction of seed tannin, which is believed to cause wine bitterness due to its high flavan-3-ol content. Delayed harvest can lead to lower seed tannin levels. It also hikes fruit Brix levels. There is concern that heightened Brix measures might cause high ethanol levels, which then undermines the seed tannin reduction impact of delayed harvest.

Furthermore, winemaking techniques such as maceration also impact phenolic contents. How should we think about the right balance between harvest dates and techniques like maceration in terms of regulating tannin extraction?

The authors experimented with relatively early harvest scenarios compared to common practice in California. The “early harvest” scenario is defined as 20.35º ± 0.16º Brix, and the “late harvest” scenario is defined as 24.91º ± 0.46º Brix.


The experiment yielded rather striking results. Independent of winemaking methods, grapes with late harvest dates showed lower seed tannin concentration. However, both late harvest date and warm weather increased overall tannin extraction into wine for both seed and fruit tannins. Surprisingly, ethanol levels didn’t seem to have any significant impact on tannin extraction. Overall, fruit with later harvest date showed more positive flavor and aroma profiles and sensory properties.

Maceration had the effect of increasing tannin extraction. However, this effect was independent of harvesting decisions. Interestingly, extended maceration increased seed tannin relative to fruit tannin extraction.

Where do we go from here?

It’s key to understand the impact of both harvesting decisions and winemaking methods on tannin extraction in order to find the right balance. The lack of impact due to ethanol levels effectively increases the importance of harvesting decisions in driving fruit and wine quality. It should also be noted that the results may be most applicable to early ripening varieties like Pinot Noir and Merlot.

Fruition Sciences offers a full suite of products addressing a variety of vine health monitoring needs to enhance fruit and wine quality. Our Dualex Signature product provides detailed nitrogen accumulation profile so that vineyards can apply fertilizer where it’s needed and track adverse effect of saline irrigation on nutrient uptake. Our Physiocap product helps growers identify where dry biomass accumulates in your vineyard to improve pruning decisions. Our Multiplex Map helps vineyards optimize harvesting decisions based on areas of uniform fruit coloration.

Posted by Vintage Report

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