Expert Editorial: Regular Cleaning and Passivation of Stainless Steel Tanks Results in Better Wine



To maintain wanted neutrality, stainless steel tanks need to be correctly cleaned. This is one job finest remaining to the professionals.

By the Astro Pak workforce

For millennia, winemaking has been as considerably an art as a science. Even after the renowned enologist Emile Peynaud initiated the modernization of the business in the 1960s, winemaking was about lowering the unknowns and allowing artistry prosper. Not only did Peynaud drive for applying only the most effective grapes when entirely ripe, he was also an advocate of using stainless metal. 

In the 1960s, Chateau Haut Brion switched to stainless steel fermentation vats. [Astro Pak]
In the 1960s, Chateau Haut Brion switched to stainless steel fermentation vats. [Astro Pak]

The two features are connected. Tradition known as for chateaux to harvest their grapes ahead of they have been entirely ripened to get benefit of their significant acidity, which acts as a preservative against spoilage in aged oak vats. By switching to stainless steel fermentation vats (as Chateau Haut Brion did in 1961), wineries shortly identified they could use thoroughly ripened grapes for richer, rounder flavors, with stabilized temperatures throughout fermentation, amid other strengths. 

No Additional Flavors

On the surface of every single stainless steel tank is a pretty slender (close to 1-millionth the diameter of a human hair) layer of hugely steady metallic atoms that do not easily corrode or rust. This passive layer, sometimes referred to as the passive movie, is accountable for providing corrosion resistance. Due to the fact of this chemically nonreactive layer, ageing wine in stainless steel provides almost nothing to the taste. Advocates of growing older in stainless metal preserve that this allows for the total expression of the assortment and the environmental problems in which the grape is developed. 

Stainless Steel Composition [Astro Pak]
Stainless Metal Composition [Astro Pak]

Having said that, to manage that preferred neutrality, stainless steel tanks must be thoroughly cleaned. Further, the passive layer must be taken care of and improved so that it can continue to protect both the tank and the wine ageing in it. Passivation” is a chemical therapy for stainless steel and other alloys that boosts the ability of the taken care of surfaces to resist corrosion.

At initial, cleansing would seem rather easy, but undertaking it incorrectly can hurt the metal, shortening its lifespan and (potentially) incorporate undesired flavor to the wine. On most surfaces and in most purposes, a thorough cleaning with bleach and tap water would be appropriate. However, as winemakers know, the chlorine in bleach is the principal ingredient that leads to cork taint in the wine. As a final result, it’s just not applied in wineries. This avoidance also negates the corrosive character of chlorine when it comes in get hold of with stainless metal factors. 

What’s not as properly identified is that municipal faucet water also is made up of chlorides that could in the same way attack the passive layer with the identical benefits. Utilizing purified water and a suitable detergent avoids that chance. But even this is only element of the remedy. 

When uncovered to air, stainless metal the natural way oxidizes at the metallic surface area, producing a chemically resistant oxide movie. However, environmental contaminants and free iron are nonetheless current close to the surface. Scientific tests have revealed that this normally developing oxide film has a 1-to-1 ratio of chromium to iron. This floor does not provide most corrosion resistance, furthermore it might continue to have contaminants that may possibly alter a wine’s taste profile. 

The acidity in wine also has an adverse effect on the steel’s skill to maintain its passivity, as it lessens the performance of its self-healing house. Clearly, it demands to be strengthened as much as doable. This is in which the procedure of passivation comes in. 

Creating Safety

A chemical passivation therapy cuts down the sum of free iron on the metal’s area, allowing for a thicker, much more resistant passive layer which is greater capable to resist wine’s acidity and guarantee that the steel will not interact with the wine as it’s fermenting and maturing. 

A knowledgeable service provider will use surface active agents to break the water barrier and clean the actual surface of the metal, removing any contaminants that may be present. [Astro Pak]
A proficient services provider will use floor lively brokers to break the h2o barrier and clear the actual surface area of the metallic, eradicating any contaminants that may well be current. [Astro Pak]

For most effective success, this is not a do-it-you task. In excess of-the-counter chemistry does not reach the same chromium-to-iron ratio that a chemical cleaning and passivation supplier can. Furthermore, doing an in-household passivation raises various worries, which include: 

  • What are the risks to personnel and gear?
  • Is this the most effective use of accessible manpower?
  • How is the high-quality of the passive layer calculated?

That final worry also applies to cleanliness: How is the high-quality of the cleaning process measured? 

The method of flipping a tank can get times and extensive cleaning. Nonetheless, few wineries are in a position to doc the performance of the method. In point, cleaning goods themselves can pose a potential contamination hazard if made use of improperly or not carefully flushed. This is in addition to the fining brokers and preservatives utilized throughout the winemaking process. The latter can comprise excess sulfur dioxide (SO2), which can corrode a tank’s surface area. Not only can this minimize the useful existence of the tank and associated plumbing, but it opens up the chance of free of charge iron interacting with the wine. If this occurs, the tank might have to have to be more carefully cleaned and handled (working with a wide range of extra intense measures) and then passivated to restore its sleek, chemically neutral surface.

Making sure that one’s facility is compliant with recent Fantastic Producing Tactics (cGMP) and recent Good Documentation Methods (cGDP) is a full-time occupation in itself. Retaining specialist-level and up-to-day awareness for verifying and documenting the success or failure of a sanitary cleaning and passivation process, on leading of one’s other day-to-day tasks in the winemaking sector, might not be a realistic expectation. 

Interact the Industry experts

Thanks to the comprehensive get in touch with time involving the wine and the tank, it is absolutely important that the tanks are cared for. Contamination can upset the sensitive balance of aromas and preferences.

Professionals know the details of cleaning and compliance and can tailor the procedure to the specific configuration and circumstances of the winemaking operation. [Astro Pak]
Gurus know the aspects of cleansing and compliance and can tailor the treatment to the precise configuration and instances of the winemaking operation. [Astro Pak]

Fortunately, there are industry experts who know the details of cleansing and compliance and can tailor the process to the unique configuration and situations of the winemaking operation. A proficient provider provider will use area energetic brokers to break the h2o barrier and cleanse the actual surface area of the metallic, eradicating any contaminants that may be present. This could involve biofilms that frequently kind as a outcome of the malolactic fermentation process. 

As soon as all cleaning remedies are entirely flushed away, the passive layer will be enhanced to make it resilient and dependable to guarantee the stainless metal is steady from wine batch to wine batch. The very last stage is sanitization of the steel, followed by yet another extensive rinse to eliminate all chemical substances from the vat. All strategies must be documented to establish compliance with business and regulatory specifications.

Like any preventive maintenance, sanitary cleansing and passivation is ideal performed on a typical, scheduled basis. A proactive system that takes into account the particulars of your operation allows you emphasis on what you do ideal — creating fantastic bottles of wine.


Astro Pak provides significant purity, precision cleaning providers for approach piping, products and tanks to the food and beverage business. It companies a large assortment of purchasers from little to Fortune 100 corporations, with cleansing and sanitization services that involve pre-operational and servicing cleaning to clear away rust/rouge, organic and natural contamination and bioburden working with procedures and options that are safer for both equally method machines and staff. Astro Pak’s qualified and committed crews deliver tailored methods, faster turnaround and reduced general price tag.