Microbiological stabilisation is one of the final critical steps before beer packaging. For non-pasteurised beers in particular, the challenge is twofold: controlling residual yeast and spoilage microorganisms that may affect shelf life, while preserving the desired sensory profile, freshness and brilliance.

Thermal pasteurisation has long been a reference method for ensuring the microbiological stability of beer. Today, with the growth of craft beer, low- and no-alcohol beers and increasing expectations regarding freshness and sensory quality, brewers are showing greater interest in alternatives that limit the product’s exposure to heat.

Cold membrane filtration provides such an alternative: a membrane physically retains targeted microorganisms before packaging, without applying thermal treatment to the beer. It is particularly relevant for breweries seeking to preserve product characteristics while achieving the required level of microbiological stability.

However, successful implementation involves much more than selecting a membrane. Clarification, prefiltration, filtration rating, differential pressure, microbiological validation, membrane integrity and control of CIP/SIP cycles all directly influence process performance.

Cold filtration or pasteurisation: two approaches to microbiological stabilisation

Pasteurisation and membrane filtration pursue the same general objective, but rely on fundamentally different mechanisms:

• Pasteurisation inactivates microorganisms through a controlled combination of time and temperature, generally monitored using Pasteurisation Units (PU).
• Cold filtration physically removes microorganisms from the beer using a membrane with defined retention characteristics.

	Cold filtration	Thermal pasteurisation
Mode of action	Physical retention of yeast and bacteria by a membrane barrier	Biological inactivation of microorganisms through heat
Aromatic profile	Helps preserve volatile hop compounds and the beer’s initial freshness	Thermal exposure may affect sensory characteristics
Energy requirements	No heating of the beer for stabilisation	Heating and cooling cycles required
Quality control	Microbiological performance can be supported by membrane integrity testing	Process monitored using Pasteurisation Units (PU)
Process position	Before packaging	Before or after packaging, depending on the process

Why choose cold filtration rather than pasteurisation?

1. Preserve the sensory profile of the beer
   One of the main advantages of cold filtration is the absence of thermal treatment. Microorganisms are separated mechanically, limiting the beer’s exposure to heat and helping preserve key product characteristics: aromatic profile, freshness, colour, bitterness and overall sensory quality. This is particularly relevant for beers where aromatic expression is a key product characteristic.
   
2. Control microbiological stability
   Final filtration is designed to retain residual yeast and spoilage microorganisms that could lead to refermentation, acidification, sensory defects or product changes during storage. Unlike pasteurisation, which inactivates microorganisms, the membrane acts as a physical barrier. For critical microbiological applications, membrane selection should therefore be based on documented retention performance rather than solely on a nominal micron rating.
   
3. Maintain the desired clarity and brilliance
   Filtration also contributes to achieving and maintaining the clarity and brilliance expected for beer styles where these characteristics are required. The objective is not, however, to make every beer perfectly clear. A bright lager and an intentionally hazy beer obviously require different levels of clarification. The filtration train should therefore be adapted to the desired visual profile while achieving the required level of microbiological stability.
   
4. Reduce operating costs
   By avoiding thermal treatment (heating and subsequent cooling of the beer), cold filtration can reduce energy and water requirements. Combined with correctly sized prefiltration, it can also help extend membrane service life and minimise beer losses, contributing to optimised overall process costs.

An effective cold filtration strategy starts before the membrane

A final membrane should not be used as a clarification filter. After fermentation and maturation, beer may still contain yeast, hop particles, proteins and various colloidal fractions. Sending this load directly to a fine membrane can result in premature fouling.

The sequence is typically:
high load → fouling → increased ΔP → reduced flow rate → shorter filtration cycles

An effective cold filtration process therefore relies on progressively reducing the contaminant load:
Matured beer → Clarification → Prefiltration → Final membrane → Packaging

Stage	Function	Global Filter solutions
Clarification	Reduce yeast, suspended solids and particles	PP / HFPP / FG / HFFG depending on the process
Prefiltration	Protect the membrane and optimise its service life	PP-Series / HFPP-Series
Final filtration	Achieve the required microbiological retention	PES membranes according to application requirements
Gases and utilities	Minimise the risk of recontamination	Hydrophobic PTFE / polysulfone membranes & hydrophilic PES membranes

How can recontamination be prevented after final beer filtration?

This is a critical consideration when cold filtration replaces thermal treatment. Even a high-performance membrane cannot compensate for contamination occurring downstream of the filter. Microbiological control must therefore continue all the way to final package closure:
Membrane → Pipework → Valves → Filler → Bottle / Can / Keg

Hygienic line design, sanitation procedures and filling conditions are therefore inseparable from the performance of the final filtration stage.

CO₂, air and vents: integrating utilities into the filtration strategy

Gases used in breweries can also represent a potential contamination route. CO₂, process air and fermentation or bright beer tank vents should therefore be included in the overall process assessment.

Global Filter offers hydrophobic PTFE and polysulfone membranes for gas and vent filtration. Water used for certain washing or rinsing operations should also be considered as part of the overall filtration strategy.

Oxygen control is equally important. After fermentation, oxygen pick-up during filtration or packaging can quickly affect the sensory stability of the beer. Filter vessel purging, connections and start-up procedures should therefore be carefully controlled to minimise increases in dissolved oxygen.

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Correctly designed and sized, cold filtration can therefore provide a genuine alternative to pasteurisation for breweries seeking to produce non-pasteurised beers while controlling microbiological stability and preserving their sensory profile.

Are you considering reducing or eliminating pasteurisation, or looking to optimise an existing cold filtration process? Have your filtration process assessed by our specialists.