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Laboratory Filtration Tools for Beer Quality Control

Learn how different grades of filters stack up in various American Society of Brewing Chemists (ASBC) methods to ensure the consistency and safety of your beer. Key tests include removing turbidity from wort, removing carbon dioxide from finished beer, and removing yeast cells after fermentation, as well as microbiological testing using membrane filters to detect spoilage organisms.

Cytiva (Sponsored) May 13, 2025 - 10 min read

Laboratory Filtration Tools for Beer Quality Control Primary Image

Filter Papers for Use in the Beer Industry

Here we explore how three grades of Cytiva filters, Whatman™ filter paper Grades 2V, 597½, and 2555½, performed in three tests:

Removal of turbidity from wort (Malt-4)
Removal of CO₂ from finished beer for quality-control purposes (Beer-1,D)
Removal of yeast cells after fermentation (Beer-8)

All tests were performed according to the ASBC methods presented in Table 1. The Biotechnology School at Jiangnan University in Jiangsu, China, performed all testing.

The filters used in the tests were 320 mm in diameter and prepleated with 16 pleats (Figure 1).

Figure 1. A Prepleated Whatman Filter Paper

Wort Filtration

The quality of a wort batch depends on the quality of the malt used to produce it. By measuring wort filtration speed and turbidity, you can determine whether the malt used to produce the wort is leading to a desirable end-product. It can also help you quantify a tolerance range for quality control of the end-product consistency.

Measuring filtration speed also helps you understand the malt’s contribution to fermentable extract, pH, color, viscosity, and nitrogen content¹. In addition, you need a clear wort sample to support later photometric testing. Gravity filtration with a suitable filter paper helps achieve all these objectives.

In the lab, they prepared two batches of malt to support the testing of the filtration step for method ASBC Malt-4. To isolate the wort, they removed the spent grain by prefiltering the malt using a coarse filter bag. They then adjusted the wort in the filtrate to a turbidity level of 10 nephelometric turbidity units (NTU) before they measured the base turbidity.

The lab filtered a 150 ml sample of wort using gravity through Whatman filter paper Grade 2V, 597½, or 2555½. The lab measured the turbidity pre- and post-filtration and calculated the percent reduction. They also recorded the filtration times.

They repeated this process for a total of three samples. The results for the two prefiltered wort batches are provided in Table 2.

Although the Grade 2V filter paper was superior for turbidity removal, filtration time was much longer than with the other two papers, up to 413 seconds for a 120 ml sample compared to 83 seconds and 52 seconds for Grades 597½ and 2555½, respectively. The 597½ grade paper performed better when the starting material was more turbid, and Grade 2555½ performed better when initial turbidity was low.

Filter selection ultimately depends on how much time you have to perform the test and how clear you need the sample to be. Table 2 and the filtration times should help you make an informed choice with respect to these parameters.

CO₂ Removal before Further Testing

During fermentation, CO₂ is produced and dissolves into the solution. When a QC lab prepares a sample of this solution for analysis, this dissolved CO₂ may lead to inaccurate results in tests such as total acid determination. Therefore, the CO₂ content needs to be minimized before testing. One method for achieving this is to pass the beer sample through an appropriate paper filter using gravity filtration.

The amount of CO₂ in beer is expressed as mg/ml and is derived from the following formula.

\[ \frac{C \times (V - V_0) \times 44}{10} \times \frac{V_1 + 1}{V_1} \]

Where:
C = concentration (M) of HCl standard
V₀ = volume of HCl (ml) required to adjust pH in a water blank to 3.9
V₁ = sample volume (ml)
V = volume of HCl (ml) required to adjust pH of the sample to 3.9

Per ASBC method Beer-1,D, the lab chilled a 4 ml sample of beer to 39°F (4°C), then filtered it using gravity through Whatman Grade 2V, 597½, or 2555½ filters and transferred it to a conical flask. They added 1 ml of a 10 M stock of NaOH to the beer and mixed thoroughly. They then transferred a 10 ml sample of this mixture to a fresh beaker and added 20 ml of distilled water. The mixture was then titrated against 0.5 M HCl, with the volume required to reduce the pH to 3.9 recorded. They repeated the measurement with 50 ml of unfiltered beer and then with 50 ml of water as a blank control.

They measured the amount of CO₂ in unfiltered and filtered beer samples, then calculated the amount and percentage of CO₂ removed. They repeated this process for a total of three samples.

Results for CO₂ removal are given in Table 3. The Grade 2V paper showed the highest efficiency in removing CO₂ from the beer, indicating its suitability for this analysis.

Removal of Yeast Cells after Fermentation

Measuring the total acidity of the final brewed beer requires removing any remaining yeast cells. Gravity filtration can easily achieve this separation of particulate matter from the liquid sample.

The lab prepared a typical fermentation broth containing yeast cells suspended in solution. To test this broth for acidity per ASBC method Beer-8, the yeast-cell content needs to be removed. The lab estimated the initial number of suspended yeast cells using a cell-counting chamber. They then filtered samples of 150 ml of this suspension by gravity through one of the three filter paper grades, and the resulting filtrate was subjected to serial dilution.

They plated the resulting samples on YPD agar plates to determine the number of viable yeast cells not retained by the filter. They used the difference between the two counts to determine filtration efficiency. This process was repeated for a total of three samples.

Table 4 provides results for yeast-cell removal from fermentation broth. All three papers performed well in the test, removing greater than 99.5 percent of suspended yeast cells. Whatman Grade 2V filter paper achieved 99.99 percent removal.

Microbiology

The ASBC also provides guidelines recommending membrane filters for microbial detection and enumeration. Although the antibacterial qualities of hops reduce the growth of most microorganisms, some bacterial strains can reproduce and spoil the beer’s flavor and appearance.

The most common method for determining the presence of these bacteria is to filter samples throughout the brewing process, plate them, and then incubate them in an anaerobic environment. This method, commonly known as the membrane filter (MF) technique, allows for the precise and accurate quantification of microorganisms in a liquid sample.

The ASBC recommends using the MF technique as a reliable method for detecting and enumerating spoilage organisms. The most used filters are 47 mm membrane filters with a 0.45 µm pore size, which is effective for retaining bacteria such as Lactobacillus, Pediococcus, and other beer spoilage microbes. For yeast and mold detection, a slightly larger pore size (e.g., 0.8 µm) may be used.

The ASBC also provides guidance on the type of hardware and filtration setup required for effective microbiological testing. Standard setups include

sterile disposable or autoclavable reusable funnels, typically 100–250 ml
membrane filter holders for 47 mm membranes
a vacuum filtration system

Disposable systems offer convenience and reduce the risk of cross-contamination, while reusable systems may be more economical for laboratories processing a high number of samples. Proper selection of filter pore size, material, and compatible filtration hardware is essential for test sensitivity and accuracy.

We offer a wide range of filters and hardware for microbiological QC testing. To learn more about our brewing QC solutions, visit Cytiva Life Sciences. To request a sample or speak with a product specialist visit cytiva.com.

References

Kühbeck F, Back W, Krottenthaler M. “Influence of Lauter Turbidity on Wort Composition, Fermentation Performance and Beer Quality—A Review.” Journal of the Institute of Brewing. 2006;112(3):215-221. doi:10.1002/j.2050-0416.2006.tb00716.x

Laboratory Filtration Tools for Beer Quality Control