Jean Hoefliger ferments more than half of the wine he makes for Alpha Omega Winery in-barrel. The Swiss-born winemaker, who has been with Napa Valley’s Alpha Omega since it opened in 2001, runs 600 to 700 barrel fermentations each year. Hoefliger doesn’t inoculate, and he says he doesn’t worry when individual fermentations shut down and stay dormant until the spring. He plans on most fermentations taking six to eight months to complete.

One barrel of his 2011 Chardonnay stuck and did not finish until the first lots of 2012 Sauvignon Blanc had arrived at the winery. “There is a risk in making such fermentations,” Hoefliger says.

While Hoefliger acknowledges the risk, he says the slow, native fermentations are key to his style. And to make sure primary fermentation is a success, he needs a healthy, natural environment for the yeast, which dictates that his barrels be as clean as possible.

Keep them clean and sanitary
The right barrel-washing protocol complements a winemaker’s style and helps minimize the risk for microbial contamination. Yet for the seemingly simple proposition of cleaning a barrel, suppliers offer a wide range of equipment, and many in the industry have different opinions about the best approach.

Hoefliger gives each of his barrels a hot water, high-pressure rinse followed by cold water and ozonated water. He says the heat from the initial rinse “opens the pores” in the barrel interior, allowing ozone to penetrate. He likes ozone because it has a short half-life and poses less of a risk to the cellar’s microbial population, which Hoefliger relies on to ferment his wine. “I can’t really hurt that natural environment,” he says.

Following the ozone rinse, cellar workers gas each barrel with sulfur dioxide and insert a paper cup in the bunghole for storage. Hoefliger says he hasn’t had any major issues with Brettanomyces or lactobacillus, and he maintains a robust population of helpful microbes.

Janet Myers, the general manager and director of winemaking at Franciscan Estate and Mount Veeder Winery, both also located in the Napa Valley, says she uses a warm water rinse followed by high-pressure hot water and an ozone rinse.

Myers says ozone has proved effective in keeping Brettanomyces in check. “We’ve never had a big Brett problem, but we know it’s there, and we’re keeping it at bay.”

She says Franciscan operates a Tom Beard barrel-washing line that was just retrofitted to include an ozone station powered with a McClain ozone generator. Myers says she looked at steam sanitation but decided ozone is effective and came with the least amount of risk for her barrel system and crew.

New interest in steaming barrels
Tom Beard, the founder and lead designer of the Tom Beard Co., which is part of P&L Specialties in Petaluma, Calif., says winery clients have shown an increased interest in steam cleaning.

Beard developed a two-barrel steam unit that the company released last year. The machine is similar to the company’s line of automated barrel-washing equipment. A forklift driver can place two barrels on a rack on top of the machine. The barrels slide onto rollers so a worker can spin them into a position with bungs above a nozzle.

Once the barrels are in place, a worker can set the desired steam cycle, and the nozzle rises up into the barrel and injects steam. The nozzle is equipped to seal the bung and create a vacuum effect on the barrel. When the steam hits the cool air inside the barrel, the air expands rapidly. As the air cools, it pulls the barrel in on itself.

Following the steam treatment, the machine lowers the nozzle head to equalize pressure and then gives barrels a rinse of water. Beard says a winemaker can opt to run ozone through the machine for that final rinse or run warm water and then switch to an ozone generator for a water and ozone rinse.

For general barrel cleaning, Beard says effective washing depends on heat, flow and impingement. The water needs to be hot, and Beard says he used to always recommend 180ºF, although water at 160º can still be effective. Beard says it’s hard to dislodge tartrates at temperatures lower than that.

In recent years, as more clients looked to reduce their water use, Beard says he focused on increasing pressure while reducing water flow. But at a certain point, “You may just be rearranging the crud” in the barrel, he says. Adequate water flow ensures good “sheeting action” that rinses out the inside of a barrel. Six gallons per minute at 250 psi provides enough water and pressure to provide effective cleaning, he says.

While inside a barrel, the washer head on Tom Beard machines moves up and down while also spinning 360º. Beard says the “heart of the whole system” is the washer’s multiple needle points of high pressure; hot water provides coverage to the entirety of the barrel.

Total sanitation is difficult
Proper cleaning is essential to any program to keep barrels sanitary, says Ken Fugelsang, a professor emeritus with Fresno State University who spent 40 years teaching at the school and researching a wide variety of subjects related to winemaking.

Barrels need regular cleaning to ensure microbial contamination is kept to minimal levels. Completely sanitizing barrels, however, is a challenge because oak has a natural waxy component that repels water, and it’s difficult to reach microbes deep inside the wood’s vascular elements, Fugelsang says.

For something close to full sanitation, Fugelsang says he has recommended filling a barrel with a mixture of water and sodium percarbonate and letting it sit overnight. But this method is time consuming and requires quite a bit of water.

He says steam is a good option because of the hot temperature and its penetrative capabilities, but he conceded generating steam in sufficient quantities requires a lot of electricity—and at more than 200º, steam poses a significant scalding risk to workers.

Fugelsang says ozone is great for use in a closed system such as a final rinse for hoses and pumps or a bottling line, but he doesn’t think it’s as effective when used on barrels. When aqueous ozone is blasted into a barrel, Fugelsang says much of it immediately outgases out of solution, and its short half-life renders it even less effective. “On smooth surfaces its activity as a sterilant is very feasible,” he says. “For a brief spray and go, it’s not going to be efficient at all.”

Fugelsang adds that before he retired he had been interested in pursuing some research into sanitizing barrels with ozone gas, which could be far more effective but is more of a health risk than aqueous ozone.

Effective as both a gas and liquid
John McClain, the founder and president of McClain Ozone, says through years of analysis as well as trial and error he has determined proper protocols for effective and efficient ozone use.

He says a few competing ozone companies may give their clients vague estimates of “a couple of minutes” for sanitizing barrels. But without knowing exactly how much ozone is in the water stream, a winemaker could be using far too little ozone or way too much. McClain says ozone is such an effective sanitizing agent that contact time is not as important as the correct dose amount. “Essentially, if you kill everything there is no half-life,” he says. “We have a much better understanding now of timing vs. sanitation.”

McClain started his Napa, Calif.-based company in 1994. “The problem that came up immediately was barrel sanitation,” he says.

After some tinkering and experimentation, McClain says his portable ozone generators proved effective at treating barrels for Brett and acetobacter contamination. From there, more winemakers started using the equipment on tanks, hoses and bottling lines as well as using gaseous ozone to clear rooms of airborne organisms.

Today, McClain Ozone has distributors on every major wine-producing continent. Wine still accounts for half his total business, but breweries are becoming more interested in ozone, and Southwest Airlines purchased 80 of McClain’s generators to sanitize the drinking water system and other equipment on their planes.

He says his generators, which start at $5,900, can put out a range of 2-10 ppm ozone. A more powerful system is going to cost more, but McClain says they’re still popular with smaller wineries because a more potent ozone dose means shorter rinse times and using less water.

Because it’s such a robust oxidizer, ozone can’t be used with some materials like rubber, so it may not work with a winery’s barrel-washing equipment.

One winemaker in the Central Coast worked with McClain and Gamajet Cleaning Systems Inc. to build a custom spray nozzle that shoots ozone at high pressure, enabling the winemaker to clean and sanitize simultaneously.

McClain’s generators can be equipped to produce gaseous ozone, which McClain says isn’t any more dangerous than sulfur dioxide. He says ozone gas is more effective for barrel storage than sulfur dioxide. While sulfur is effective at preventing microbial growth, ozone flat out kills critters. Sulfur dioxide also lingers inside a barrel, McClain says, while ozone gas degrades to pure oxygen.

When asked about a hypothetical winemaker on the fence between ozone and steam, McClain—as one might guess—doesn’t see much room for debate. He says that when he started, winemakers were wrestling with Brett despite “steaming the hell out of everything.” Wood is hard to penetrate with heat, he says, and the steam can release the wood’s volatile flavor compounds. “Steam is very hard on oak,” he adds.

An effective means of delivering heat
Not so, says Glenn Caster, sales manager with ARS and the Pressure Washer Co. ARS’s standard model runs around $5,000 not including accessories. Caster says the dry, saturated steam condenses so quickly it doesn’t volatize any oak compounds. Caster says steam is a “vehicle that delivers” heat and does its job quite efficiently, penetrating into the pores on the inside of a barrel. “It deposits the heat right there where you want it to be.”

Once it comes into contact with the wood, the steam quickly condenses, melting tartrate crystals and displacing any residual wine, Caster says. The rapid condensation also draws a vacuum effect.

“The heads of a barrel actually go concave during that process,” Caster says. “We’re sucking water, wine, dead bacteria, tartrates—all being pulled to an imaginary center of the barrel—and then we do a final rinse and get all that gunk out.”

It’s the vacuum and penetrative capabilities that make steam a better choice for cleaning and sanitizing, Caster contends. He recommends wineries opt for a warm water rinse to clean out as much loose material as possible, followed by a steam treatment. The steam vacuum comes with the added perk of providing a simple leak test. If a barrel won’t draw a vacuum, it’s unsound—and likely a leaker.

He says ozone, while an effective killer, is only as good as where it can reach. “The problem with ozone is a practical problem,” he says. “It’s delivered with water, and it only goes where the water goes.”

And if a winemaker is using a system that can’t clean out the tartrates from a barrel, the ozone can’t be effective. “If they’re not completely removed, the ozone never touches the Brett,” he says.

For washing, Caster says he sells equipment from pressure washers that range from 3,000 to 4,000 psi to the Bitard or “Bordeaux barrel rinser.”

Caster says the Bitard is usually mounted in the ground, and workers roll barrels onto the nozzle for a hot water rinse or steam as well. After a barrel is treated with steam, a worker can roll it off the Bitard and bung it. “To me, it’s the entry-level tool for cleaning a barrel,” he says.

New technology
One technology that Fugelsang thinks has quite a bit of potential is the high-energy ultrasonic system developed by the Australian firm Cavitus. The company toured the California wine industry in 2010 to show off its system, and Fugelsang says what he saw at a demonstration was quite impressive.

He says he can’t speak to the system’s effectiveness against microbes, but it did seem to do a better job of cleaning. During the presentation, several barrels that had been washed with a traditional high-pressure system then received an ultrasonic treatment. “The goo that came out of (the barrels) was just really startling,” he says. Fugelsang described the material as a “viscous, almost black” mixture of water and phenolic material.

Andrew Yap helped develop the Cavitus system. He says in an email to Wines & Vines that the company failed to reach a deal with a U.S. distributor in 2010, but they’re still looking for a U.S. partner. Yap currently is heading up research and development for the firm Wine Industry Ultrasonics and is a visiting lecturer of wine science at the University of Auckland, Australia.

“All the data clearly show that HPU (high-powered ultrasonic) effectively and efficiently removes tartrates, yeast lees and biofilms and kills Brettanomyces on the surface and inside pores, cracks and joints of oak staves,” he says.

A mobile HPU unit has been serving the Australian industry since 2008, and one launched in Spain in 2010. Yap says there’s more interest in France, especially Bordeaux. He says HPU is the most effective cleaning and sanitizing process that also is the gentlest on the inside of the barrel.

While ultrasonics or some other technology could be the next big step forward for barrel cleaning, it seems the best bet so far is still with a thorough cleaning with hot water. After that, it depends on what best fits your budget, winery set up and winemaking style.