San Rafael, Calif.—Although aqueous ozone is commonly used in the cellar as a sanitizer, a few companies are seeking to expand its role in winemaking.

Some see it as an effective foliar treatment for crops, and another firm is touting a process that uses gaseous ozone to eliminate the use of sulfur dioxide in winemaking.

Ozone is an allotrope of oxygen with one more atom than the far more prevalent and breathable O₂. The extra atom makes ozone a powerful oxidizing agent, and this property is what has made it such a popular sanitizer. Ozone is used in water treatment, food storage and distribution and several other industries.

Ernie Wilmink is the founder of AgriOzein, a company based in Lindsay, Neb., that produces ozone generators designed to provide disease and pest control in vineyards. Wilmink’s firm builds sprayer units equipped with ozone generators at a factory in Wakeeney, Kan.

Less spraying in the vineyard
When Wilmink spoke to Wines & Vines about his ozone systems, he said he had just sold his 49th spray unit in the United States. Wilmink is looking to convince growers to make the switch to ozone, arguing they’ll save money by using smaller amounts of chemicals and treating their grapes with something that doesn’t leave any residue. Growers in the Midwest have become proponents of ozone as a vineyard tool, since summer rains and humidity in the region require a much more frequent rate of spray application to keep pests and disease in check.

Wilmink’s standard “turn-key” ozone sprayer rig costs just under $25,000. The unit comes with a 100-gallon tank, and the application rate is typically 30-35 gallons per acre. To ensure the ozone application is effective, Wilmink said the water needs to  have at least 750 mV of oxidation-reduction potential. He said most of his clients measure this with a handheld probe.

Wilmink said ozone appears to offer growers more benefits than just reduced chemical use. He said clients who have been using his system for years say their vines are healthier overall and appear to be in better balance and producing grapes of higher quality.

In the Russian River Valley, John Bacigalupi, the owner and president of Bacigalupi Vineyards, is the first California grower to purchase one of Wilmink’s ozone generators.

Bacigalupi rigged the unit onto a sprayer he already owned, though he had yet to use it when he spoke to Wines & Vines in early July. He’s hoping ozone will reduce chemical costs and usage while keeping his Pinot Noir and Chardonnay grapes free of Botrytis, powdery mildew and other vineyard ailments common in California’s cooler regions. He said he sees potential in ozone because it is so oxidative it destroys the cell walls of microbes. Such a basic, almost elemental, anti-microbial effect is something that Bacigalupi believes won’t engender a resistance that the agricultural industry is seeing with chemicals like glyphosate. 

A generator on the sprayer powers the ozone generator as well, and it also runs a circulation system that incorporates the ozone gas into water from the tank. Wilmink said he’s worked with a few clients to customize an existing spray rig to accommodate an ozone system.

Eliminating sulfur dioxide?
The Italian company Purovino just recently began offerings its services in the United States. Joe Hajost is the U.S. licensed sales representative for the company he says is working with 12 wineries in Italy and treated 220,000 tons of fruit there in 2013.

Developed by the PC Engineering firm and professor Fabio Mencarelli at Tuscia University, Purovino is a patented post-harvest treatment for grapes. After being collected into vented bins, grapes are loaded into cold storage containers that Purovino delivers to its winery clients. The grapes then undergo 14 to 20 hours of fumigation with a proprietary ozone gas treatment to send the grapes’ natural oxidative mechanisms into overdrive. “It’s kind of an oxidation on steroids kind of thing,” Hajost said while delivering a presentation about the process at the MyEnologist lab in Napa, Calif.

Once the ozone treatment is done, Hajost said a winemaker can just apply his or her normal crush protocol to the grapes, aside from one key difference: “You never have to add SO₂,” he said.

In comparative winemaking trials, wines made from grapes treated with the Purovino process had higher levels of polyphenols and anthocyanins and similar levels of VA, but while the control wine had 17 ppm of free sulfur dioxide, the Purovino wine had 1 ppm. Total sulfur in the control wine was 25 ppm, and the Purovino wine had 5 ppm.  

The Purovino process does tend to boost Brix levels by a few degrees, resulting in higher alcohol levels. The Montepulciano wine made with Purovino treated grapes had an alcohol level of 13.89%, while the control wine had an alcohol level of 13.16%.

Depending on the amount of fruit needing treatment, the cost of the Purovino process can range from $250 to $325 per ton. Hajost said the treatment cost includes the bins, generators and container. He said the company might be able to use a client’s cold storage room, depending on the setup.

In April, Purovino staff presented a seminar about their technology along with Steve Reynolds, the owner and winemaker of Reynolds Family Winery, at a joint meeting of the Napa Valley and Sonoma Valley technical groups of winemakers. Reynolds has been conducting trials with the Purovino process.