Application of sprinkler cooling within the bunch zone during ripening of Cabernet Sauvignon berries to reduce the impact of high temperature

Abstract

Background and Aim: High temperature stress has been linked to detrimental effects on berry composition during ripening. This study aimed to assess the impact of an evaporative cooling system located inside the grapevine canopy to mitigate extreme temperature effects on grape berry composition during ripening. Methods and Results: During three seasons (2012 to 2015), an intra-canopy sprinkler system at the bunch zone was tested on Cabernet Sauvignon vines. The system cyclically sprayed (20 s/10 min) for an air temperature above 38°C, cooling the air inside the canopy by 3 to 5°C. This is in agreement with an air cooling simulation model. The relative humidity in the canopy also increased in the sprinkler-cooled canopy. No differences were detected in TSS, although sugar per berry was significantly higher in treated vines because of increased berry mass. There was a tendency for higher anthocyanins and phenolic substances per berry in cooled berries measured from two seasons and higher concentration of anthocyanins in wine from cooled fruit measured only in one season. We define indices that can be used to assess the efficiency of sprinkler cooling and to demonstrate the high efficiency of intra-canopy sprinklers compared to other systems. Conclusion: Despite cooling operating only over a small duration of the ripening period, the increased berry mass indicates that high temperature, even for a short period, has a profound effect on berry growth. Other berry compositional properties and wine, however, were not impacted. Significance of Study: This research demonstrates the potential of an efficient intra-canopy sprinkler system to reduce heat stress during ripening.

Uptake and Glycosylation of Smoke-Derived Volatile Phenols by Cabernet Sauvignon Grapes and Their Subsequent Fate during Winemaking

“…Control and smoke-exposed vines were separated by at least one buffer vine. In-canopy misting treatments involved the continuous application of fine (65 µm) water droplets to the bunch zone of six adjacent vines, using a purpose-built sprinkler system (comprising two CoolNet Pro "tee" configuration sprinklers (Netafim Australia, Adelaide, SA, Australia) per vine, suspended 30 cm above the cordon, each delivering water at a rate of 11 L/h) supplied with mains water pumped from a 1000 L plastic tank, as described previously [22].…”

“…A recent study used in-canopy sprinklers to mitigate the effects of heat stress in Cabernet Sauvignon berries during ripening, by spraying water within the bunch zone (for 20 s/10 min when air temperature exceeded 38 • C) to cool the vine microclimate by 3-5 • C [22]. Attempts to "wash" grapevines/fruit following exposure to smoke (using water, 5% aqueous ethanol or milk) did not reduce the guaiacol concentration of grapes or juice [23,24], which might reflect rapid diffusion of smoke-derived volatile phenols into berries.…”

Classification of Smoke Contaminated Cabernet Sauvignon Berries and Leaves Based on Chemical Fingerprinting and Machine Learning Algorithms

“…Smoke treatments were applied (approximately seven days post-véraison, the period grapes are thought to be most susceptible to smoke contamination [ 10 ]) using a purpose-built smoke tent ( Figure 1 a,b) and experimental conditions reported previously [ 4 , 61 ]: low and high-density smoke treatments were achieved by burning different fuel loads (i.e., ~1.5 and 5 kg of barley straw, respectively). In-canopy misting was evaluated as a method for mitigating the uptake of smoke-derived volatile phenols by grapes and involved the continuous application of fine water droplets (65 µm) to the grapevine bunch zone using a purpose-built sprinkler system (delivering water at 11 L/h), as previously described [ 62 ]. Each treatment was applied to six vines from three adjacent panels, except the HS treatment, which comprised only five vines, with treatments separated by at least one buffer vine.…”

Field practices for adapting Mediterranean viticulture to climate change

“…The application of sprinklers as a cooling system can have a positive impact on grape growth and composition (Kliewer and Schultz 1973, Keller 2010a, Caravia et al 2017). Kliewer and Schultz (1973) reported interesting results in three cultivars after sprinkling the whole canopy when the air temperature was above 30ºC.…”

“…Berry composition showed higher levels of titratable acidity and malate, lower pH, and increased coloration in the sprinkled grapes. Caravia et al (2017) utilized an intra-sprinkler system at the cluster zone when air temperature was above 38ºC, which cooled the air inside the canopy by 3 to 5°C. They reported increments in berry mass without differences in sugar content and a tendency for higher anthocyanin and phenolic compound contents per berry in the cooled treatments compared to the un-sprinkled ones.…”