Crosslinked polyvinylpyrrolidone PVPP reduces turbidity active polyphenols

In order to ensure the clarifying effect and stability of the beer, the turbidity should be reduced first after fermentation and post-ripening. The clear and transparent appearance of beer through post-fermentation clarification, colloidal and microbial stabilization is an important factor in the popularity of beer once it is launched.

The challenges of beer clarification

Polyphenols in beer

After initial clarification, the appearance of the beer cannot be maintained for long. To demonstrate the stability of turbidity, the beer needs to be clear and transparent all the way from the brewery to the consumer. However, beer turbidity and its chemical composition are very complex. Many substances cause the formation of abiotic turbidity (colloidal turbidity).

Among them, one of the most important abiotic turbidity is caused by the reaction of proteins and polyphenols brought into the brewing process by raw materials such as hops. Currently, we are focusing on how low-molecular weight polyphenols form cross-links with proteins through weak intermolecular interactions, such as hydrogen bonds, to further optimize the brewing process.

In this process, we need to consider the overall shelf life of the product, which covers various working conditions during the transport process, and also take into account the potential impact of many external factors such as stirring operations, temperature changes and direct sunlight.

The above factors may have adverse effects on the clarity and flavor stability of beer.

The biggest threat to lasting clarification

Beer turbidity

Colloidal turbidities are formed during low-temperature fermentation and ripening and are usually effectively removed during subsequent clarification or filtration processes. However, once the protein and polyphenol content exceeds a certain limit, even after filtration, they will continue to react and affect the taste of beer.

When we talk about polyphenols, we often classify them based on their ability to form complexes with proteins (i.e., tannin reaction capacity). Among them, as one of the most representative tannin polyphenols, the tannin reaction ability of proanthocyanidins is gradually enhanced with the deepening of polymerization degree. In addition, oxidation has a significant effect on this type of reaction, the higher the degree of oxidation, the more reactive polyphenols.

Tannin reactions can create permanent turbidity, so this must be avoided!

Currently, there are a variety of methods to prevent the formation of turbidity, but since abiotic turbidity is mainly caused by the reaction between polyphenols and proteins, modern stabilization methods focus on removing these reactive substances (at least one of them) in order to fundamentally solve the turbidity problem.

Although a variety of methods can be used to remove active proteins from turbidity, such as adsorption, precipitation, and enzyme addition, there is currently only one main method for reducing active polyphenols in turbidity – the use of polyethylpyrrolidone (PVPP).

solution

The adsorbent PVPP was used to remove polyphenols

As a crosslinked polymer of PVP, PVPP inherits the excellent performance of PVP which is widely used in medicine and other fields. Through the cross-linking reaction, PVPP molecules are insoluble, ensuring that they can be completely removed after performing their role in removing turbidity, maintaining the purity of the product.

PVPP has a large surface area, which enables it to bind tightly to polyphenols that easily form turbidity through strong hydrogen bonds. In the process of beer production, PVPP particles can effectively adsorb and remove these polyphenols to ensure the stability of beer turbidity.

Although traditional PVPP is a single-use material, renewable PVPP options are available today. In a specific PVPP filter, the particles are retained and, after adsorption of the polyphenols, washed with caustic alkali to remove the adsorbed polyphenols.