Ξ October 28th, 2008 | → 3 Comments | ∇ A Day at a Time, Interviews, Technology, Wine News, Wineries |
For what follows I strongly recommend reading a piece I wrote in June entitled Cleaning Wine Barrels With Ultrasound. It chronicled that important innovation in barrels cleaning technology, ultrasonics, developed by Cavitus,
“the leading proprietary systems developer and solutions provider of high-power ultrasonics applications for liquid-phase food and beverage processing.”
As I have written in the June post, ultrasound as a cleaning technology for wine barrels had come to my attention in a November/December, ‘07 article of Practical Winery and Vineyard. Days before I was to leave for the Wine Blogger’s Conference in Santa Rosa I received an email from one of the principle authors of the article, Andrew Yap, Cavitus’ Director of Oenology and Industry Marketing. He was to be in Napa visiting wineries interested in participating in barrel cleaning trials with Cavitus’ HPU Beta Prototype.
Among the reasons for winery interest, let’s call it excitement, was a 2008 paper he co-authored, Inactivation of Brettanomyces/Dekkera in wine barrels by high power ultrasound published in The Australian and New Zealand Wine Industry Journal, available for download from the Cavitus site or to read below.
In this wide-ranging, three-part interview Andrew Yap discusses both the published paper and the HPU Beta Prototype.
I interviewed him Sunday, October 26th, at his hotel in Napa.
Admin Perhaps we might begin with an overview of your recent paper. And a few details of your methodology.
Andrew Yap Yes. Essentially, what we wanted to show is that Brettanomyces can be killed in wine, or in liquid, or in media. But, of course, in a 225L barrel brett is not only on the surface of the wood but also in the sub-layers, in the pores. And we looked at killing brett that already existed in barrels. So we got lots of infected barrels from wineries and looked at the effect of high power ultrasound (HPU). But it was really difficult to find brett in the barrels, it’s like finding a needle in a haystack. We did locate brett cells in various parts of the barrels, but the thing is, once you’ve sonicated the barrel and you want to go back and see whether the brett has been killed and you obtain a plaque next to where you originally drilled, where you found live cells, that plaque may not contain any cells. What does that tell you? Does that mean the ultrasound killed those cells? Or that they weren’t there in the first instance?
So what we had to do was then actually inoculate pieces of wood, six centimeters by six centimeters, normal size staves cut into those dimensions, and suspend them into a broth culture of brettanomyces cells for five to seven days until we could detect the cells throughout the staves. What we did then with the staves, in one of the trials, we put the staves in a holder and then put the holder into the barrel so that it is midway between top and bottom. In another trial we nailed these staves opposite the bung hole.
In these two different trials, the first using high pressure hot water (HPHW), and the second using HPU, to see and compare the effects. Now, I must tell you that with these blocks of wood when using the HPHW or HPU we have to insure that the effects don’t come from the sides but that the effect come only from the front, through the wood. We had to seal the sides with parafilm and a thick rubber band around the sides so that you don’t get any of the effects of HPU or heat. And when we then drilled pieces of the stave blocks we drilled into the center so as to stay away from the sides. Any brett cells killed would be only from the energy coming through the block. I want to emphasize that.
One of the great advantages of your technique, high powered ultrasonics, over high pressure hot water is the depth at which the brett may be killed in wood. Now, the HPHW is effective to a depth of approx. 2 millimeters, if I’ve read your paper correctly, while HPU reaches to a depth of four millimeters.
AY Now, having said that, it could kill cells below 4mm, from 4mm to 12-14mm. You are probably aware that wine travels about 8mm through the barrel wood. That’s average. With the ultrasound we actually see water going as far as 14mm. And wherever there is water, cavitation bubbles are formed. Where they are formed and when they implode, energy is released. Any cells up to 14mm deep, wherever there’s liquid, the micro-organisms are likely to be killed.
Why did we do it up to 4mm only? Because this is an initial, very early trial. But the University of Adelaide is continuing to look at isolating cells at 8mm to 12mm, or deeper.
Have you heard from various wineries just how wide spread brett is? I know that in the secondary market it is very common. Alot of wineries will sell brett infected or at least questionable barrels to unsuspecting customers.
AY That is a problem. We’ve done alot of surveys of the cleanliness of barrels sold second-hand by large wineries to the smaller wineries. The barrels that are sold to the smaller wineries of boutique wineries are chockablock full of tartrates and, as you can imagine, obviously brett as well if they have been infected. In fact, most of the larger wineries sell their barrels after they are three to four years old. In a sense they get rid of their brett problem, really, by passing them on to the secondary market.
In terms of how wide-spread? You really need to be in the industry and know the people to get the message. If you are a winemaker and I came along and asked you, “Do you have a brett problem?” “Nah. I don’t have a brett problem.” (laughter) They don’t want to reveal it.
And I’ve been in the wine industry long enough, I’ve been in the wine industry for about 30 years, I am still involved in teaching at the University of Aukland, teaching wine science students doing a post-graduate course. And I know alot of people in the Australian wine industry, in the New Zealand wine industry, here in the US, and once you know them well enough they will discuss the problem with you. In fact, the reason they would want to tell you about a brett problem is in order to possibly get an angle as to how you can assist them. As a result of that, brett is very wide-spread. It’s extremely wide-spread.
In fact, in a previous paper I already stated that Pascal Chatonnet who is this French researcher, probably the best known brett researcher in the world, he stated more than 10 or 15 years ago the model for a brett infected wines you’d find on the supermarket shelves, were you to go collect them and assess them, was only around 28%. Two years ago when he did the same survey for a big conference at which he was invited to speak, he revealed that about 70% of wine on the supermarket shelves have got 4-ep taint, brett taint.
Was this in France or world-wide?
AY World-wide, world-wide. A random sample. Now it is possible of that 70% alot of them will be below the detectable threshold. But when you put it through a machine you’ll find the taint compound. But many people without a sensitivity to it will not be able to pick up the brett taint, even above the threshold.
Of course, in France brett is often used to produce a particular style. Provence, for example.
AY It’s absolutely crazy! I think one of your most famous winemakers here suggested that adding a bit of brett taint will give a wine a funkiness, a particular style, I think that was a big mistake. Now the American wine companies recognize that. They try to avoid brett at any cost.
I know you’re running a series of pilot tests in Australia, and of course, here. That’s the reason you’re in Napa, California.
AY Yes. We’ve done three trials already with our Beta Prototype system. We did it with a very large wine company in Australia, in the Barossa Valley and a medium size family company. [All but one of the wineries have not authorized the release of their names-Admin] Now why did we choose those two companies? Because they’re always in the forefront of technology and they like to look at new innovations. They’re trialing new things all the time, very much like many of the companies I’m working with here.
So we finished that in September. Our machine next went to New Zealand and just finished a trial with a very big company. The machine now being flown here, it is on the way to California. With regard to the trials they were all very successful. The winemakers liked what they saw with respect to what the ultrasound could do to clean the barrels.
Our first trial here in California will be in one of the big wineries in the Monterey wine region.
Oh! That’s near where I work.
AY Yes, it’s one of your biggest. In fact, if you want to come and look at the trial you are welcome to attend. The winemaker has said he would allow outside people to visit.
This would be Constellation’s Gonzales Winery?
AY Yes. I don’t know whether you know the general manager, Hugh Reimers?
Yes, I know of him. I wrote a recent piece about the new solar installation being assembled at the Gonzales Winery.
Is Hugh Reimers a colleague of yours?
AY He was my student! (laughs) That tells my age, doesn’t it? I taught him at Roseworthy Agricultural College. It is very well known for the oenology degree that it taught.
Hugh was one of the top students. In fact, there are quite a number of Roseworthy graduates in the industry here. Yesterday when I went to a winery I met one of the winemakers there, she’s from Australia, from Western Australia. I’m not sure where she studied.
What happened to the Roseworthy program was it got absorbed into the University of Adelaide’s when the two institutions merged. That was in 1990. I taught at the university up until 2002.
End of Pt 1.