Since being green-lit in 2019, high-powered, low-frequency ultrasound has become one of the most promising technological developments in winemaking. Its ability to effectively ‘age’ wine in minutes stands to revolutionize traditional production, which is facing many challenges, including a warming planet.
Now, a team from the University of Castilla-La Mancha and the University of Murcia in Spain has for the first time put the spotlight on the increasingly popular pink drop, rosé, to see if ultrasound – so far predominantly used in red wine production – could have similar benefits.
Ultrasound, or sonication, has mainly been used during red wine production to reduce maceration time. A necessary part of extracting a red’s hue, as well as its flavor compounds and tannins, the maceration stage of soaking the juice with the skins and seeds prior to fermentation can take anywhere from a few hours to days, or even weeks.
Ultrasound’s ability to speed up cellular breakdown, as well as promote certain chemical reactions and structural changes in wine that mirror the effects of aging it, means it can develop the sensory properties in just minutes.
“The application of ultrasound was primarily designed for reducing maceration time in red winemaking,” said corresponding author of the study Encarna Gomez Plaza, a professor at the University of Murcia, Spain. “However, experiences with white wines showed that the aroma fraction could be increased by sonicating crushed grapes. Therefore, we decided to study the effect of ultrasound in rosé wines, something which has not been done before.”
While rosé doesn’t have a lengthy maceration stage, the longer it is, the higher the risk of oxidation of certain compounds that will give the wine a bitter, unpleasant taste. Ultrasound, which encourages the breakdown of the grape skin cells, speeds up the natural process while removing that oxidation window.
For this study, the researchers had three groups of Monastrell grapes; a control with no maceration time, one that underwent four hours of maceration, and one that only had sonication treatment before moving onto the next stage of the process.
At the end of production, a blind test by a panel trained in sensory evaluation of wine rated the grapes subjected to ultrasound as superior in aroma and flavor.
“Sonication gave rise to wines with intense red berry and flowery odors, with scores higher than those of wine from macerated grapes,” noted the authors.
In 2019, the International Organisation of Vine and Wine (OIV) permitted the use of ultrasound on grape compounds during pre-fermentation maceration. The aims set out in the guidelines state that it’s to boost concentration of phenolic compounds (which affect taste, color and texture) and other grape compounds, reduce maceration time, limit the release of tannins present in the seeds and to accelerate the grape processing.
As well as improving the quality of the wine produced, the process also mitigates the effect of climate change. In the face of increased temperatures or heatwaves, vines will shut up shop, conserving water that would usually go into the fruit, slowing the ripening process.
As demand for wine across the globe grows, ultrasound treatment is being viewed as a way to ‘cheat’ nature to provide good quality wine despite the challenges faced by the industry.
“We want to increase our knowledge on the effect of ultrasound in wineries,” Gomez Plaza said. “We are researching how to solve problems that sometimes appear during winemaking and the chemistry behind this behavior.”
The research was published in the Journal of the Science of Food and Agriculture.
Source: Society of Chemical Industry via phys.org
