Home Wine Business Editorial Expert Editorial Expert Editorial: Alcohol-Free Wine Presents Challenges in Filtration and Quality Assurance

Expert Editorial: Alcohol-Free Wine Presents Challenges in Filtration and Quality Assurance

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The production of non-alcoholic wines presents a particular challenge for producers, since it differs considerably from the classic winemaking process.

By Dr. Ilona Schneider and Felix Marzolph, MBA

Non-alcoholic (NA) versions of typically alcoholic beverages are becoming more and more popular. In addition to alcohol-free beer, the fan base for NA wines and sparkling wines has also seen an increase. While the market share for these wines is still less than one percent, NA sparkling wine already has a five-percent share of the market, according to German wine manufacturing magazine Der Deutsche Weinbau—and the trend is rising. The production of non-alcoholic variants presents a particular challenge for producers, since it differs considerably from the classic winemaking process. The wines are also different products in terms of sensory experience.

Alcohol-free wine is defined as a beverage with a maximum of 0.5 percent alcohol by volume. In wine, however, alcohol is an essential protective factor against harmful microorganisms, such as yeasts and bacteria. For non-alcoholic variants, this means the beverage will be susceptible to such microorganisms and therefore constantly run the risk of becoming unstable. As a result, filtration has a distinctly important task: maintaining the microbiological stability of alcohol-free wine until bottling and beyond.

Filterability and bacterial load in the production process

Both the filterability and the microbiological properties of alcohol-free wines were examined as part of two separate master theses, by Sven Horter (Hochschule Geisenheim University) and Felix Marzolph (Weincampus Neustadt). The objective of these scientific papers was to determine the filter index and total bacterial count of different alcohol-free wines. In addition, the two papers examined which filtration steps would ensure microbiological stability.

The production and filtration system test consisted of eight steps: from the tanker, to the dealcoholization process and subsequent tank storage, then to the filtration process with crossflow storage filtration (CFF), intermediate tank storage and two-stage fine and final filtration.

Process for industrial production of alcohol-free wines [Eaton Filtration]
Process for industrial production of alcohol-free wines [Eaton Filtration]

Samples were taken from the tanker and again after passing through the dealcoholization system, after CFF and after the two-stage cartridge filtration. Samples were then analyzed. To identify the filterability 0.85 gallons (3.2 liters) of the respective wine were added to the device’s storage container and filtered using a 0.45-μm flat filter membrane (test membrane) at a constant pressure of 14.5 psi (1.0 bar). Based on the measured filtrate quantities, the wine was then classified as “easy to filter” with a filter index value of ≥3,000 mL, “average filterability” with a filter index value of 2,500-2,999 mL, or “difficult to filter” with a filter index <2,500 mL.

The microbiological tests of the samples were carried out in a laboratory using membrane filtration. Each sample was filtered using a 0.45-µm flat filter membrane under sterile conditions and then incubated on different culture media in agar plates. The growth of microorganisms that could contaminate the wine was counted after a defined incubation period of five days at a temperature of 81°F (27°C). 

Initially, four different wines with a volume of 6,600 gallons (25,000 liters) each were analyzed: a German red wine, a German white wine, a Spanish Merlot and a Spanish Cabernet Sauvignon. 

Sampling point

German
red wine

German
white wine

Filter index [ml]

Cell count
[CFU/
ml]

Filter index [ml]

Cell count
[CFU/
ml]

Tanker

622

> 100

3,000

> 200

After dealcohol-
ization

200

> 200

693

> 200

After CFF

3,000

> 200

3,000

> 200

After two-stage cartridge filtration

3,000

0

3,000

0

 

Sampling point

Spanish
Merlot

Spanish
Cabernet Sauvignon

Filter index [ml]

Cell count
[CFU/
ml]

Filter index [ml]

Cell count
[CFU/
ml]

Tanker

927

> 200

450

50

After dealcohol-
ization

323

> 200

250

> 200

After CFF

675

> 200

638

> 200

After two-stage cartridge filtration

3,000

0

3,000

0

Tab. 1: Results of the filter index measurements and the total cell count. Comments: CFU: colony-forming units; > 100: more than 100 CFU/ml; > 200: CFU/ml no longer countable, overgrown

This revealed that three of the four wines were already classified as “difficult to filter” following the initial sampling from the tanker. Only the German white wine achieved a filter index of 3,000 mL and was therefore “easy to filter.” 

For all of the wines, the filter index fell significantly, to values between 200 and 693 mL, following dealcoholization. The CFF allowed the two German wines to attain a filter index of 3,000 mL, while the index value of the Spanish wines increased only slightly and remained “difficult to filter.” It was only through the combination of depth filter cartridges and downstream membrane filter cartridges that all wine batches could achieve a filter index of 3,000 mL and be classified as “easy to filter.”

Notably, during the microbiological tests, high (>100 CFU/mL) to very high (>200 CFU/mL) microbiological loads were observed in three of the wines when they were delivered to the tank. Only the Spanish Cabernet Sauvignon demonstrated a lower cell count of 50 CFU/mL. After dealcoholization, all of the wines were subject to very high loads of >200 CFU/mL. It was only following the two-stage cartridge filtration that the microbiological load of all the wines could be reduced to the sterile range of 0 CFU/mL, meaning no yeast or bacteria that could contaminate the beverages could be re-introduced.

Confirmation trial

In a further test using 6,600 gallons (25,000 liters) each of a Spanish Merlot, French Chardonnay and European rosé, the microbiological results with regard to bacterial load were confirmed. Although the load for the Chardonnay and the rosé decreased after dealcoholization, they still exhibited high values of >100 CFU/mL. For the Merlot, the load was very high throughout the entire production process. It was only following the two-stage cartridge filtration that the colony-forming units were reduced to zero, allowing for a sterile bottling process of the alcohol-free wines.

Sampling point

Spanish
Merlot

French
Chardonnay

European
Rosé

Tanker

> 200

> 200

> 200

After dealcoholization

> 200

> 100

> 100

After CFF

> 200

> 100

> 100

After two-stage cartridge filtration

0

0

0

Tab. 2: Results of identifying the total cell count. Comments: All values in CFU/ml; CFU: colony-forming units;
>100: more than 100 CFU/ml; >200: CFU/ml no longer countable, overgrown

Two-stage fine and final filtration

As the test results show, the production process of alcohol-free wine is a particular challenge in terms of filterability and microbiological stability. The removal of the alcohol significantly reduces filterability — even the German white wine delivered as “easy to filter” only achieved an index value of >700 mL once the alcohol had been removed. A wine that is difficult to filter can easily become a cost factor for producers. 

The more difficult the wine is to filter, the easier it is for the membrane filter cartridges to become clogged. This then leads to more frequent cleaning or filter replacement. During this time, machines are at a standstill and bottling is delayed.

In addition, the non-alcoholic wine loses its protection against microorganisms that could contaminate the beverage. A contamination value of >200 CFU/mL indicates a very high bacterial load. This was detected in a large number of samples. Manufacturers must set in place especially stringent sanitary requirements for filtration systems if the alcohol is missing as an inhibitor. This is the only way a microbiologically stable NA wine can be bottled to prevent the secondary fermentation and sensory changes caused by microbiological activity within filled bottles.

This series of tests has shown that the CFF process was unable to achieve sterile levels in any sample. In terms of filterability, CFF proved helpful for some of the samples, but was not sufficient for all of the wines analyzed. 

It was only possible to obtain sterile wines following two-stage fine and final filtration using depth and membrane filter cartridges. The depth filter cartridges retained the majority of the particles and microorganisms, while the downstream membrane filter cartridges, so-called “police filters,” ensure microbiological stability. This two-stage fine and final filtration is absolutely essential for the production process of alcohol-free wines. It is the only way to ensure the microbiological quality and sustainable marketability of the alcohol-free beverage, and therefore to offer quality assurance of the highest level.

_______________________________________________________

Dr. Ilona Schneider, Eaton Filtration
Dr. Ilona Schneider, Eaton Filtration

Dr. Ilona Schneider, enologist, brings more than 25 years of experience in enology and beverage treatment. She most recently works as a product manager for beverage treatment for Eaton Technologies GmbH in the wine filtration business. [email protected]

 

Felix Marzolph. MBA; Eaton Filtration
Felix Marzolph. MBA; Eaton Filtration

 

 

Felix Marzolph, MBA, brings over 10 years of experience in winemaking and wine production in various technical roles where most recently he works as a sales manager for Eaton Technologies GmbH in the wine filtration business. [email protected]

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