High-Power Ultrasound in Enology: Is the Outcome of This Technique Dependent on Grape Variety?

The disruptive effect exerted by high-power ultrasound (US) on grape cell walls is established as the reason behind the chromatic, aromatic and mouthfeel improvement that this treatment causes in red wines. Given the biochemical differences that exist between the cell walls of different grape varieties, this paper investigates whether the effect of the application of US in a winery may vary according to the grape variety treated. Wines were elaborated with Monastrell, Syrah and Cabernet Sauvignon grapes, applying a sonication treatment to the crushed grapes using industrial-scale equipment. The results showed a clear varietal effect. The wines made with sonicated Syrah and Cabernet Sauvignon grapes showed an important increase in the values of color intensity and concentration of phenolic compounds, and these increases were higher than those observed when sonication was applied to Monastrell crushed grapes, whereas Monastrell wines presented the highest concentration in different families of polysaccharides. These findings correlate with the differences in the composition and structure of their cell walls since those of Monastrell grapes presented biochemical characteristics associated with a greater rigidity and firmness of the structures.

A New Approach to the Reduction of Alcohol Content in Red Wines: The Use of High-Power Ultrasounds.

BACKGROUND: To obtain wines with a lower percentage of alcohol, the simplest approach would be an earlier harvest of the grapes. However, this has implications for the wine composition and quality, due to the lack of phenolic maturity that these grapes may present. A technological innovation that could help in this situation could be the use of ultrasound in wineries. METHODS: Grapes were harvested with two different ripening levels (25.4 °Brix and 29 °Brix), transported to the winery, and vinified. Also, a large-scale high-power ultrasound system was used to treat part of the less mature grapes just after crushing. These grapes were also vinified. The three different vinifications were skin-macerated for 7 days. The wine aroma compounds and physicochemical, chromatic, and sensory characteristics were analyzed at the time of bottling. RESULTS: The wine made with the ultrasound-treated grapes showed very similar characteristics to the wine made with the more mature grapes, especially regarding total phenol and tannin content, but with an alcohol content 15% lower than the latter. CONCLUSIONS: The results indicate that this technology could be applied to grapes to favor the extraction of grape phenolic compounds, even when grape phenolic maturity is not complete, allowing the production of quality wines with a reduced alcohol content.