Removing sulfite compounds from wine

A U.S.-based wine purification company came to Purolite with a concept to remove sulfite (So2) at the point of use (time the wine will be consumed) for both red and white wine. In this way, the sulfite benefits to the wine would be maintained, while the negative health and taste characteristics would be eliminated.

Sulfites develop naturally in wine when sulfur dioxide and water mix in during the fermentation process in wine making, and are normally in the range of 10 – 14 ppb. Additionally, sulfite can be added to wine as a preservative to extend the bottle’s shelf life, raising the levels to around 20 – 200 ppm on average. This is done by both commercial producers as well as home bottlers.

It is interesting to note that sulfite-free wine is not actually sulfite free. Sulfite free wine indicates that the producer does not add extra sulfites to the wine in the bottling process, but still contains the naturally occurring sulfites. It is interesting to note that even “Sulfite Free” wine may have to use a “Contains Sulfites” notice on the wine label if the naturally occurring sulfite level is not < 10 ppm.

Sulfites have anti-microbial properties, making them beneficial and desirable to have (and keep) in the wine. Without them, wine would oxidize very quickly or turn to vinegar.

Many people note that they are sensitive to the sulfites in wine, and sulfite was identified as an allergen by the U.S. FDA. However, sulfite sensitivity is not the only reason to want to remove the sulfite from wine before consumption. Removing the sulfites before drinking helps to remove the sulfite-based bitter aromatic compounds, enhancing the natural flavor of the wine.

The company’s concept was to take wine back to its natural state by removing excess sulfite, while keeping the natural levels. To accomplish this, they needed an amine base resin with a high affinity for the sulfur compound and would remove the sulfite. When wine would pass through a specially designed resin-filled filter, the compound would be removed without affecting its taste or color.

The filter concept consisted of a small pod containing several grams of resin designed for use on a bottle of wine. However, in addition to wine bottles, the company wanted a solution for individual wine glasses as well that would be cost effective, use less resin and not alter the product design or effectiveness.

Although there are several companies that could provide a standard resin, the resin is not purified below 25 ppb and could not be used for a commercialized product intended for food applications.

To solve the overall problem, Purolite provided a polymethacrylate resin with an immobilized sulfur-attracting compound that underwent a proprietary cleaning procedure. This procedure purified the resin and compound to the lowest (and cleanest) in the industry—eliminating any concern for chemical leaching into the filtered wine. Additionally, Purolite obtained an official food contact approval certificate for the resin to address any customer concerns.

Next, Purolite tested different solutions to accommodate the wine glass option and developed a solution by using an inert resin mixed with the active resin that maintained effectiveness and help reduce cost.

The process development, experimentation and regulatory compliance work took about 1.5 years, but the final resin-based solution enables the company to proceed to market with a safe, consistently effective product without undergoing scrutiny for chemical additives.

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