GiESCO 2019 banner
IVES 9 IVES Conference Series 9 GiESCO 9 GiESCO 2019 9 Climate change 9 Evaluation of vineyards, fruit and wine affected by wild fire smoke

Evaluation of vineyards, fruit and wine affected by wild fire smoke

Abstract

Context and purpose of study ‐ Wineries may randomly reject fruit from vineyards near wild fires exposed to smoke. It is difficult to determine if fruit has been compromised in quality when exposed to smoke, and whether or not smoke taint flavors will result when fruit is fermented into wine. Phenolic smoke compounds bind with sugars in the fruit with enzymes (glycosyltransferases) and are then hydrolyzed during maturation, wine making and even in a taster’s mouth. Testing the fruit for volatile phenols and glycosides is both expensive and not completely predictive as standards are not well defined for damage based on smoke chemical content. Micro‐vinification even with partially ripened fruit is an inexpensive and fairly accurate method to quickly determine if fruit has a potential smoke taint problem. Wines can then be tasted for the presence of off flavors. Developing standards based on volatile phenolic and glycocide concentrations to predict whether fruit is affected by smoke and how wine will taste when vinified would be very helpful for accepting or rejecting fruit from affected areas.

Materials and methods ‐ Following wild fire smoke exposure, fruit was sampled and micro‐vinified during veraison and again 2 weeks before harvest from 13 Cabernet sauvignon vineyards in a transect 25 km across Lake County, California. A control vineyard unexposed to wildfire smoke was sampled outside of the area. Sub samples from each vineyard were analyzed immediately for guaiacol and 4‐methyl guaiacol. 19 liter wine lots were then microvinified, stabilized and bottled for each vineyard for both sampling dates. The wine was analyzed for volatile phenols and glycoside compounds (guaiacol and 4‐methyl guaiacol, methyl cresol, 4‐methyl syringol, o‐cresol, p‐cresol, syringol, syringol gentiobioside, methyl syringol gentiobioside, phenol rutinoside, cresol rutinoside, guiaocol rutinoside and methyl guaiacol rutinoside). A 14 member tasting panel evaluated the wines for smoke flavors. Panel members were able to detect off flavors in both sample sets, and tainted wines were highly correlated with elevated concentrations of volatile phenols and glycosides. GIS data of vineyard proximity to the fire, elevation, temperature and wind direction and speed were used to conduct multivariate analysis of factors affecting wine smoke compound chemicals and flavor impacts on wine.

Results ‐ Not all wines were affected; in this study, 6µ/l guaiacol was the threshold of detection for off flavors in wine by most tasters. Off flavors were much stronger in the wines made from riper fruit, as were the concentration of smoke compounds, by as much as six fold compared to unfermented fruit. Wind direction and speed, proximity to active fires, and temperature are the factors that are most highly correlated to smoke damage to fruit near wildfires. The control wine sample had no off flavors and no volatile phenols were detected. By contrast, some sites close to the edge of fires and immediately downwind were very heavily affected, and contained high levels of smoke taint compounds. This study will help to better understand when vineyards are most at risk to wild fire smoke damage, and how micro‐vinification may be a reliable and quick way to predict fermentation outcomes before harvest in vineyards affected by wildfire smoke.

DOI:

Publication date: June 19, 2020

Issue: GiESCO 2019

Type: Article

Authors

Glenn MCGOURTY (1), Michael I. JONES (1), Anita OBERHOLSTER (2), Ryan KEIFFER (1)

(1) University of California Cooperative Extension Mendocino County, 890 North Bush Street, Ukiah, Ca. 95482
(2) University of California Davis Department of Viticulture and Enology, Davis,California, 95616

Contact the author

Keywords

Wild fire smoke, smoke taint in wine, volatile phenols, glycocides , guaiacol, 4‐methyl guaiacol

Tags

GiESCO 2019 | IVES Conference Series

Citation

Related articles…

Influence of temperature and light on vegetative growth and bud fruitfulness of grapevine cv. Semillon

Aim: To investigate the effects of different levels of temperature and light intensity on grapevine vegetative growth and bud fruitfulness, which includes the number and size of inflorescence primordia in primary buds.

Prototype development for the recovery of wine aromas from fermentation gases

Dealcoholised beverages are trendy. But this market segment is slowed down by flavour losses during dealcoholisation and by the reduced perception of flavours in the absence of alcohol.

The influence of initial phenolic content on the outcome of pinot noir wine microoxygenation

Over the years, microoxygenation (MOX) has become a popular vinification technique to improve wine sensory qualities. However, among the impacting factors reported

Leaf elemental composition in a replicated hybrid grape progeny grown in distinct climates

The elemental composition (the ionome) of grape leaves is an important indicator of nutritional
health, but its genetic architecture has received limited scientific attention. In this study, we
analyzed the leaf ionome of 131 interspecific F1 hybrid progeny from a Vitis rupestris (♀) X Vitis
riparia (♂) cross. The progeny were replicated in New York, South Dakota, Southwest Missouri ad Central Missouri, and the concentration of 20 elements were measured in their leaves at
three different phenological stages during the growing season. In leaves collected at the apical node at anthesis, elemental concentrations correlated in a consistent manner (p < 0.05) across all four geographic locations. In subsequent phenological stages, elemental ratios in the apical-node leaves remained consistent across the South Dakota and New York sites, but not across the Missouri sites. In leaves collected at the basal and middle nodes, correlations varied greatly across all locations.

Effect of drought on grapevine wood fungal pathogen communities using a metatranscriptomics approach

Crops are facing increasing biotic and abiotic stress pressures due to global changes. However, trade-off mechanisms between these stresses and the underlying physiological processes are still poorly understood, especially in perennial crop species. To better understand these trade-offs, we studied the effect of drought on grapevine (Vitis vinifera) physiology and esca-related wood fungal communities. Esca is a vascular disease caused by a community of wood-infecting pathogenic fungi, and characterized by trunk necrosis, leaf scorch symptoms, yield losses, and mortality.