Sugar loading dynamics in California: varietals & vintage effects?

The graph below shows the average sugar loading of 250 blocks of Californian Cabernet Sauvignon. It is based on more than 2 500 analyses of sugar quantity per berry, from véraison to harvest, during the 2016 vintage (Figure 1)

grape sugar loading

Figure 1: time variations of sugar per berry in California vineyard in 2016 (Cabernet Sauvignon)

What can we learn from that data?

  • the average rate of loading during the first phase is 5 mg/berry/day
  • the duration of active sugar loading is about 36 days
  • the average date for the end of active sugar loading is the 26th of August
  • the average Brix at the end of sugar loading is 21 °Brix (or 12,1 %vol.)

Comparison of the last 8 vintages

The graph below (Figure 2) shows the average Brix at sugar loading stop vs the average date of sugar loading end for Cabernet Sauvignon from 2009 to 2016.grape brix sugar

Figure 2: Brix when sugar loading ends over the period 2009-2016 in California (Cabernet sauvignon)

The Cabernet Sauvignon is very sensitive to vintage effect, from the point of view of its sugar loading:

  • we can distinguish “early” vintages like 2014, 2015 & 2016 with sugar loading stop at the end of August from “late” vintages like 2010 or 2011 when Cabernet Sauvignon has loaded sugar until the end of September or beginning of October.
  • the average Brix at sugar loading stop ids also vintage dependent: ranging from 20 to 22 °Brix.

The parameters that can mainly explain these variations between vintages are:

  • Temperature
  • Vine water deficit
  • Balance Leaf Area vs Yield
  • Nitrogen deficit


Comparison with other varietals

Does Cabernet Sauvignon load sugar differently from other varieties like Merlot, Syrah or Sauvignon blanc? The graph below (Figure 3) presents the average sugar loading of 500 blocks of Californian Cabernet Sauvignon, Merlot, Syrah, and Sauvignon blanc during the 2016 vintage.

Sugar per berry

Figure 3: dynamics of sugar loading for different varietals in California, 2016

What can we learn from that data?

The table below summarize the main findings characterizing sugar loading profile analysis

Sugar loading

Table 1: 2016 dynamics during sugar loading for 4 varietals

Fruition Sciences has partnered with Vivelys and ETS Lab to help you better time your harvest! 

With Dyostem analysis, you will monitor berry volume variations along active sugar accumulation from veraison to picking. This key information about ripening dynamic will help you refine your picking decision on top of classically measured fruit parameters. Contact us to learn more about it.

Posted by Nicolas Bernard

Agronomy engineer and Oenologue from the French National Institute of Agronomy at Montpellier (France), Nicolas Bernard has been working since 2001 on understanding the relationships between ecophysiology of the vine and grapes and wines quality.
Co-founder of the Sferis company in 2002, he has developed some tools like Xilem© (vine water status measurement) and Dyostem (grape quality analysis). He has also been working as a consultant in Europe and South America for irrigation management, grape characterization, and picking dates strategies.
Since 2008 and the merge of Sferis and Oenodev companies, Nicolas is in charge of the Vine Solutions at Vivelys (Oeneo group)

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