Lesson 6 - Process Aids and Additions
This lesson discusses the function of process aids and how they improve colloidal stability. It also explores filter aids, post-fermentation additions, and the use of deaerated water as tools to enable a brewer to meet their final pack beer quality specifications.
Enzymes
Proteolytic enzymes include papain (derived from papaya), bromelain (derived from pineapple), ficin (derived from figs), and enzymes from Bacillus subtilis. We use these enzymes to break down the proteins that can cause haze formation.
Papain is supplied in liquid form and is commonly used at a dose rate of 0.5-4 g/hL. It is usually added during maturation and can survive pasteurisation where values of less than 20 PU are used.
One pasteurisation unit (PU) is the microorganism death that occurs in a product held at 60°C (140°F) for 1 minute. We can estimate the total number of PU for a particular pasteurisation process for beer using:
PU = t × 1.393 (T−60)
where T is the temperature in degrees Celsius and t is the time in minutes at which the beer is held at that temperature.
A standard range for beer pasteurisation is between 12-30 PU.
Papain breaks proteins down with little discretion. This means that foam proteins are affected as well, which causes foam stability issues in the final pack. For this reason, even though it is a cheap stabilisation product, papain is no longer a popular chill proofing choice.
Proline specific enzymes (PSE) also called prolyl endopeptidases (PEP) can also be used for stabilisation. PSE catalyses hydrolysis of proteins at proline residues. Haze active proteins are high in proline, so PSE reduces the likelihood of haze formation. Foam active proteins are generally lower in proline so PSE has little effect on foam stability. PSE works slower than process aids that adsorb haze-active material so is dosed into cooled wort at the start of fermentation to give it time to complete its work. The suggested dose rate is 1-3 g/hL depending on the proportion of malt in the grist and the gravity of the wort (hence wort protein level). Studies have shown that PSE can produce a stabilisation comparable with PVPP / Silica Gel. However, it is still not used as widely as other stabilisation products. Brewers Clarex® is an example of commercially used PSE.
As PSE is added to cooled wort, it degrades protein throughout fermentation. As a result, we can reduce the length of cold maturation. The following benefits are claimed for PSE use:
- Shorter cold maturation – haze forming proteins are degraded during fermentation.
- Warmer cold maturation temperature.
- Filtration is easier – less solid material makes it to the filter.
- Reduced waste – significantly smaller tank bottoms in maturation.
- Energy savings – shorter and warmer cold maturation reduces refrigeration costs.
PSE can produce gluten-free (less than 20 mg/L gluten in most countries), or gluten-reduced beer.