Lesson 10 - Maturation and Finishing End of Unit SAQ

***The sales of your flagship brand have climbed significantly over the last six months, and there is a demand for shortening the cellar residence time. What measures can you make to reduce the maturation process time without compromising quality?

Response:

• Time in cellar

This is the time from the end of fermentation to the end of filtration. A brewer can influence the cellaring process by focusing on key elements that will speed up this duration whilst not compromising quality.

• Warm maturation (also known as flavour maturation)

At the end of fermentation, VDK (vicinal diketones) levels are elevated, in particular, diacetyl. This is an undesirable flavour in many beers, and the primary aim during this stage is the conversion of VDKs from α acetolactate in the beer and subsequent removal of VDKs by yeast. In an efficient operation, this process should take between 24-36 hours, also called the diacetyl rest. This is also dependant on good yeast handling practices in fermentation. Maintaining a higher temperature after fermentation, normally around 14-16 °C, and good hygienic practices to avoid microbiological activity (microorganisms can also produce diacetyl), will help to reduce the diacetyl rest.

• Cold maturation

This is the process to remove haze forming components to ensure long term colloidal stability. The most common cause of haze is cross-linked proteins and polyphenols (these precursors must be eliminated to reduce the risk of haze). An effective way to reduce these components is cold storage of -1 to -2 °C for 3-7 days. In optimum conditions, three days is adequate; a brewer may also want to add a process aid such as silica gel at this stage but can also add it during transfer to the filter pre-buffer tank.

• Centrifugation

This is a process to remove solid material from the beer, this includes yeast, cold break (protein and polyphenol complexes) and spent hop material, from the main bulk of beer during the transfer from fermenter to maturation tank. If a centrifuge is running inefficiently, solid material may pass through and not be removed effectively. This may settle out in the maturation vessel but may continue through to the filter. Loading on the filter should be reduced as much as possible to increase filter run lengths which again, would have a positive effect on cellaring duration.

• Process aids

These are beer clarity stabilisation treatments that target the removal of one or both of the haze precursors, protein and polyphenols. Selecting the right process aid can deliver a quality product in an acceptable process time. Reviewing the process aids may provide opportunities to reduce process time. The use of silica gel, for example, has many benefits, as well as being a very effective protein adsorbent; contact time to achieve this is very fast, e.g., 80% of adsorption is achieved in < 3 minutes between the silica and beer. Using a silica gel could also reduce cellaring time.

• Brewers Clarex

This is a proline-specific endopeptidase enzyme which can specifically degrade the proline-rich proteins which contribute to haze formation in beer. It is added to the fermenting beer and degrades protein continuously throughout fermentation. As a result, one of the major benefits is that it negates the need for a cold maturation phase; this means a shorter conditioning time as haze forming proteins are degraded during fermentation. Other benefits include no requirements for process aids such as silica gel, and lower energy demands due to no cold maturation phase. A brewer would also expect to see longer filtration runs due to not having to use pre-filter stabilisation products, therefore less solid build up on the filter bed.

Maintaining best practice throughout the cellaring of a beer will also pay dividends. Achieving the right processes first time will eliminate the need to re-work or blend, again saving time and cost, and helping to reduce overall process time.