Sensory and chemical profiles of Cabernet Sauvignon wines exposed to different irrigation regimes during heatwaves

Abstract

Heatwaves, defined as three or more consecutive days above average historical maximum temperatures, are having a significant impact on agricultural crop yields and quality, especially in arid or semi-arid regions with reduced water availability during the growing season. In grapevine, excessive heat can lead to not only crop loss, but a reduction in quality of the berries and resulting wine. The primary means of mitigating damage due to heatwaves is by applying excess irrigation water prior to and during the heatwave event, thus promoting evaporative cooling by the plant and reducing soil temperatures in the rooting zone and surface.  California wine-growing regions, among others, face a future of
decreased water availability, combined with increases in heatwave incidence, frequency, and intensity. Thus, we will require a greater understanding of the effects of heatwaves and water use at different times during development on grapevine physiology, berry composition, and wine chemistry and quality. In this study we evaluated the impact of different pre-heat wave irrigation practices on vine physiology and berry composition across the 2019 growing season in a commercial Cabernet Sauvignon vineyard in the Northern Central Valley of California, USA (Lodi, CA). Differential irrigation treatments were applied only when a heat event took place and started one or two days before each heatwave and continued until the last day of the heat event. Three irrigation treatments were implemented: a control or baseline, which was exposed to deficit irrigation and held at 60% ET, a second treatment where the irrigation was double the baseline  (2x baseline ET), and third treatment with triple the amount of water of the baseline (3x baseline ET). Replicated wine lots were fermented from each treatment following a standard red wine fermentation protocol. A trained panel characterized  sensorially the aroma and flavor profiles of the wines. Moreover, the wines’ volatile and phenolic profiles were analyzed and correlated to the sensory. 

We found that plants were able to recover from physiological stress caused by heat events but had a negative impact on berry biochemical traits. Negative effects on berry chemistry resulted from over and underwatering during heat waves. The sensory results showed how the differences found in treatments from a physiological and berry chemistry perspective are translated to the wines’ sensory properties and chemical characteristics