Effect of harvest timing on chemical and sensory characteristics of Chardonnay (2015)

Emily Pelton

Veritas Vineyard & Winery



Purpose: To compare characteristics of chardonnay harvested based on acid levels versus density. Methods: Chardonnay was harvested from the same vineyard; the control lot based on a density of 1095, the trial lot based on a pH of 3.3.  Lots were processed, fermented, and aged identically post-harvest. The control lot was acidulated to the same pH as the trial lot and trial lot was chaptalized to the same specific gravity as the control lot. Results: There was a significant sensory difference (p<0.05) between the trial and control with a preference for the trial group. Discussion: Being able to see how a single focused maturation variable will impact finished wine is a valuable tool for winemakers when considering harvest options. Conclusion: Picking chardonnay based on specific gravity versus picking based on acid levels will result in different characteristics being present in the resultant finished wine.

Presented on January 20th 2016 at King Family Vineyards


Stylistic Goals of Chardonnay



This experiment was designed to determine whether there is an increased balance of flavor and structure in Chardonnay when it is harvested based on acid and chapitalized, or whether it is harvested on brix and acidulated.


“Trial” refers to the early pick, and “Control” refers to late pick.  Chardonnay was harvested from the same uniform block at two harvest dates one based upon the ideal pH and TA (8/24/16), and the other based on ideal brix and physiological maturity (9/6/15).  The specific gravities at harvest were 1076 and 1095 respectively. All fruit was harvested in bins.

The fruit was whole cluster pressed  after sorting with the addition of 50ppm SO2 and 1.6 mL/hL Cinfree enzyme to the press tray.  The was juice settled for 48 hours.  Both the early pick and the late pick were fermented in stainless steel tanks with an inoculation of  20 g/hL CY3079 using 25 g/hL Go Ferm rehydration nutrients. Fermentation was started on 8/28/16 and 9/9/16 respectively. The early pick was chaptalized with 3.2 kg/hL sucrose on 8/27/16. The late pick was acidulated with 0.5 g/L tartaric acid on 9/12/16. When each lot had completed AF, it was pressed (program 9), settled, and racked to barrel (Ana Selection F MT 2013). Both lots were stored and treated identically throughout ageing.


Laboratory testing was performed both after AF (Figure 1.) and prior to being tasted at the sensory session (Figure 2.). In this experiment labs were done to confirm consistency between trial and control in terms of pH and TA. Measurements of sugar content in a post-fermentation test are meaningless as they are now a function of yeast performance. Chapitalization was calculated based on brix measurements of post press, pre-fermentation juice.


(Figure 1). - Post Fermentation Lab Results: TA (g/100mL); TSO2, FSO2 (mg/L)


(Figure 2.) – Pre Sensory Session Lab Results: TA, VA (g/100mL); Gluc+Fruc, Malic (mg/100mL); FSO2, TSO2 (mg/L); Alcohol %V/V


Triangle taste tests showed a significant difference between trial and control (p<0.05). Of those that correctly identified the difference between trial and control (n=22) 31.8% preferred the control and 59.1% preferred the trial, and 9.1% had no preference.

Descriptive analysis (below) performed by Enartis/Vinquiry indicate a preference for the trial wine as well:


Trial (Early Pick) 


Pale yellow. CO2 bubbles. Hazy.



Creamy, orange creamsicle, citrus, estery, sweet, good intensity, aromatic floral, vanilla, yeasty, oxidized, seems like end of alcoholic fermentation, aldehydic, bruised apple, banana, bitter orange, some oak aromas, cream, vanilla, pastry, somewhat stale.



Round, a bit short, creamy finish, volume okay, light wine, acidic but okay. Orange skin, orange creamsicle, yeasty, vanilla, slightly stale citrus flavors. Lacks structure.



Citrusy, estery white that is slightly tart and lacks body and structure.


Control (Late Pick)


More gold in the yellow hues - more oxidized. Cloudy. CO2.



Closed, a bit reduced, nutty and some spice, cut apple (aldehydes), seems evolved, nutty and toasty, yeasty, less expressive, less fresh, crushed almond.



Leaner and seemingly more acidic, some notes of evolution (not fresh) and with burning sensation on palate (alcohol?), oxidized, aldehydic, not balanced



Seems more evolved, has burning sensation on palate, not balanced, not really round, not creamy. Both wines showed aldehydic character, which made it somewhat difficult to differentiate the two. Nevertheless, there seemed to be a large difference between the two wines and the preference here was for the first wine (Early) as the body was more balanced, not burning and round and creamy.



Traditionally, harvest dates are chosen based on a combination of maturation indicators. The winemaker will take consideration of these and other factors to choose the ideal time for harvest. However, it is important to be aware of how the wine can be impacted as each maturation aspect is balanced in consideration of weather and other objective influences.

In this case we were able to see that the chardonnay that was picked based on ideal pH and TA was preferable to the chardonnay picked based solely on ideal sugar content. However, it is important to note that while the trial group was considered preferable to the control, descriptive analysis indicates that perhaps both wines would benefit from a collective balance of character. In practical terms this shows that the winemaker’s chosen maturation characteristics is paramount to any single indicator. Also, that this balance will have long term effects on the outcome of the finished wine.

Along with demonstrating what effects certain single parameters will have on wine, this experiment shows the importance of accurate data collection and analysis prior to harvest.



Picking chardonnay on two separate dates each based on specific maturity indicators produces two unique wines with individual character strengths. The importance of each indicator should be considered with respect to the desired traits of the finished wine. 






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