The End Of Sulphur In Wine? PCT On The Horizon

Ξ April 26th, 2012 | → 14 Comments | ∇ A Day at a Time, Technology, Wine News |

Just when it seemed the debate over the use of sulfites in wine couldn’t get any more acrimonious, along comes a promising new technology which threatens to bring peace.
Though dried fruits typically contain 10 times the sulphur dioxide (SO2) found in wine and SO2 levels in fruit juices frequently equal or exceed it, our most holy fermented grape juice remains a special case. After all, no one spends $10,000 on a bottle of fruit juice unless it is fermented. Now, whether conventional, sustainable, organic, biodynamic, or ‘natural’, winemaking employs sulfites on a sliding scale, driven in large measure by health concerns, both of the body (at high levels sulphur can have deleterious health effects) and of the planet (sulphur is a petrochemical product). Or perhaps I should say by the perceived dual health concerns. As often as an expression of an earnest environmentalism, bad faith, opportunistic and commercial, informs the choice, the position a winery, a critic or consumer may take on the use of sulfites and SO2. Why bad faith? Well, let’s just say that neither a natural wine booster traveling 5000 miles through the ionized upper-troposphere to a tasting, or an industrial winemaker re-wiring his pesticide sprayer to run on solar-charged batteries are models of consistency.
But were I writing a website dedicated not to the wine industry but to that of dried fruits and juices, not to mention dehydrated potatoes, vegetables or even pancake syrups, I should likely have a post or two dedicated to this nearly omnipresent preservative. And I would just as likely be discussing this new technology.
It is called Pressure Change Technology (PCT) and was, as near as I can determine, first presented in the pages of a scientific journal, Chemical Engineering & Technology from 2007 (subscription only). Titled The Effect of a New Pressure Change Technology (PCT) on Microorganisms: An Innovate (sic) Concept for Food Safety, the abstract reads,
“A new pressure change technology (PCT) for a non-thermal inactivation of microorganisms in liquid food and pharmaceuticals is described. This technology was applied to food-relevant microorganisms and was capable of reducing the organisms up to 7.5?log. The influence of process parameters (type of gas, pressure, and temperature) was investigated with the help of physiological changes of microorganisms. The results of this pressure change technology are shown and discussed.”
Just thank the lord I am not discussing that paper. A more layman-friendly press release from the Internet Journal of Viticulture and Enology caught my eye last week.
“Pressure Change Technology (PCT) is a low cost process with minimum energy use that has potential with further development and validation to be of significant commercial benefit to wine producers by providing them an alternative to the use of sulphur dioxide in the winemaking process.”
The company referenced in the full press release is PreserveWine. From their site,
“PCT is a novel non-thermal technique that involves charging a liquid product with pressure and an inert gas [N and Ar - Admin] and then rapidly releasing the pressure. The sudden pressure release causes microbial cell walls to rupture, inactivating microorganisms. This has been demonstrated on a small pilot scale batch process; in the current project PreserveWine the PCT process will scientifically validated. A further objective is the development and scale-up into a continuous in-line pre-industrial demonstrator to test the PCT with wine and other liquid foods.”
The objectives to be achieved are the following,
- Repeated validation of the process to reduce microbial loading in wine by at least log10 5 and protect wine from chemical and biological oxidation.
– Enhanced organoleptic quality (aroma and taste) of wine when compared to ’sulphited wine’ wines when assed by a trained taste panel.
– Pilot scale demonstration of our PCT system capable of being integrated into a commercial winemaking process line, at flexible design for optional application at various processing stages, with a throughput of 120 L/h
– Full HACCP and GMP compliance
– Provide data to scale up to industrial capacity of 1.2 m3/h at energy costs of 40% to comparable thermal processes, ensuring a potential market share of 1% of the wine holdings in Europe.”

Two wineries have been the site of preliminary research: Château Guiraud, a well known French producer of fine sweet wines located in Sauternes, a short distance from Bordeaux; and Tenute Del Vallarino, a producer of still and sparkling wines in the Piedmont region of Italy. As is well known, SO2 acts in wine as both an anti-microbial – ‘bound’ sulphur – and a color preservative – ‘free’ sulphur – for white wines. ‘Bound’ sulphur inhibits bacterial growth, while ‘free’ sulphur reacts with oxygen to prevent oxidation. One can easily understand Château Guiraud’s concern, inasmuch as sweet wines contain very high amounts of sulphur. Tenute Del Vallarino produces white wines.
The project was begun in December, 2010 and results will be published on November 30th of this year, 2012.
Many questions remain unanswered, of course. Though PCT is scaleable and is said to both low in cost and energy use, whether this new technology will be embraced by wine purists, or endorsed by Demeter and from within the organic wine movement, remains to be seen. Personally, I wish PreserveWine great success.
Ken Payton, Admin
For further reading:
See the very detailed PDF. It includes photos and diagrams of the process. Allergens In Wine: What Lies Ahead?
New EU rules for ‘Organic Wine’ agreed
Do EU organic rules for wine leave glass half empty?
Sulphites in wine


14 Responses to ' The End Of Sulphur In Wine? PCT On The Horizon '

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  1. John Skupny said,

    on April 27th, 2012 at 8:26 am

    (sulphur is a petrochemical product

    Can you qualify that statement, I understood that sulphur is a naturally occurring compound that is available in different forms – I didn’t think ‘petrochemical’ had anything to do with it. Please advise.

  2. Admin, Ken Payton said,

    on April 27th, 2012 at 8:33 am

    Hi John. I’ve added a link from Shell Global to the phrase ‘petrochemical product’. Cheers.

  3. Gordon Armstrong said,

    on April 27th, 2012 at 9:59 am

    Ken, while sulphur may come from several sources, the dusting sulphur used on my organic wine grapes is 100% a mined product.


  4. Jim Peck said,

    on April 27th, 2012 at 10:10 am

    This is not new technology. This was looked at when I was at Gallo some 20 years ago. It was not adopted because it required a lot of energy and could not be adapted to our volumes.

  5. Admin, Ken Payton said,

    on April 27th, 2012 at 10:11 am

    Thank you for the comment, Gordon. The specs of the PCT process concentrate on eliminating sulphur use the winery, whether its origin be petrochemical or mined. But your point is well taken. Cheers.

  6. Admin, Ken Payton said,

    on April 27th, 2012 at 10:18 am

    Hi Jim. Thank you for the comment. My sense is that both energy use and volumes have been addressed in the PreserveWine tech, otherwise it is difficult to understand why the EU would be investing in the development of PCT. At the bottom of the post you’ll find linked a fairly detailed PDF that might shed light on this matter. Cheers.

  7. Joel Burt said,

    on April 27th, 2012 at 12:11 pm

    Cool article! I think you may be a bit confused on the properties of bound vs free SO2 though. Bound SO2 is not antimicrobial and is bound to phenolics, sugars, actetaldehyde, etc. You might have meant molecular SO2, which is antimicrobial and is a portion of the FSO2 (the other portion is bisulfite which is not anti microbial) and is pH dependent. Also, SO2 can bleach color; but does keep the wine from turning brown.

  8. Admin, Ken Payton said,

    on April 27th, 2012 at 12:18 pm

    Hi Joel. Thank you for the comment and clarification. I will more closely re-read Ron Jackson and my Jan/Feb, 2009 issue of Practical Winery & Vineyard Journal! Always hitting the books. Take care.

  9. Per-BKWine said,

    on April 29th, 2012 at 1:21 am

    This sounds quite similar to ‘flash detente’ (by Pera) or Delta Extractys although they are not used to reduce microbiological activity but rather increase extraction.

  10. Admin, Ken Payton said,

    on April 29th, 2012 at 7:48 am

    Hi Per. Thank you for the info. I’ve placed your link in the comment section below. Cheers.

  11. on April 29th, 2012 at 12:48 pm

    Good article but it should be pointed out that by no means is anti-bacterial the only reason we use SO2 in wines. Most importantly, SO2 is a good reducing agent which protects the goodies in wine from air oxidation. As such, it also acts as an anti-browning agent especially in white wines. Most of the “Organic” wines I’ve tasted were spoiled — not so much by bacterial growth but by simple air oxidation. Air kills unprotected table wine in a hurry!

  12. Admin, Ken Payton said,

    on April 29th, 2012 at 12:56 pm

    Thank you for your important observation. Cheers, Richard.

  13. Mark Buckley said,

    on April 30th, 2012 at 11:38 am

    This looks like an interesting way of reducing microbes prior to bottling, but I agree with Richard Peterson’s comment on additional benefits of SO2 in protecting from oxidation. Other technologies that are being looked at are Infrared which is being used in waste treatment plants and testing is going on in using this on wine. I believe it originated in South Africa.

  14. Admin, Ken Payton said,

    on April 30th, 2012 at 12:23 pm

    Thank you for the comment, Mark. True, I only briefly mention SO2’s anti-oxidative role in wine near the end of my post. That is for a simple reason. PreserveWine’s presentation has chosen to focus largely on PCT’s anti-microbial fix, though they clearly indicate oxidation is also minimized in some measure. Cheers.

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