Fascinating facts about filtration

By a cunning bit of arranging I was able to be in Nottingham the same day as some IBD lectures at an inferior Midlands based institution. The first one was about filtration by Rod White, formerly of Molson Coors.

It was based on a survey of large brewers, as it's felt there's still a lack of knowledge about beer filterability. It basically took as a starting point that beta-glucanase was used so obviously it was based on the experiences of industrial brewers as craft brewers would never use exogenous enzymes. Beta-glucanase generally makes filtration one and a half to two times as efficient but some breweries get by fine without using it.

Xylanases usually make a smaller improvement (15-30%) but may help in problems years. Arabinoxylans are present at levels six times greater than beta-glucans but are difficult to measure.

A university based study showed that xylanases worked best to improve filterability.

A lot of variations are found between breweries with brewhouse turbidity ranging from 3-70 EBC. Up to 25% of brewhouse haze is carbohydrate not protein.

Copper finings improve filterability by 25%.

Lowering the loading and reducing raking in the lauter tun can improve performance by 25-50%.

Removing solids (by e.g. adding isinglass to Conditioning Tank) also helps.

Yeast derived material could be a big factor. German brewers measure starch and glycogen and give it an iodine value. Glycogen can be an indication of filtration problems caused by yeast. Are flocculins breaking from the yeast cells and clogging filters?

Beer that spent a week longer sitting on yeast before filtration certainly had poorer filterability. Yeast generation number also affects it.

Ale and lager yeasts also show differences, but dried yeasts were much more filterable. Cultured yeast had much more particles present (trub, etc.).

Brewers can have problems with processing aids. Antifoams in Fermenting Vessel can clog cross flow filter membranes over time, though this is not a problem with kieselguhr filters. Single shot PVPP may also cause problems with cross flow. Tannnic acid can be a great help but can cause problems if added immediately upstream of filtration.

Classic British ale brewing is good for filterability. In a practical, not a moral sense obviously. Mash tuns give good quality wort and as mentioned previously copper and isinglass finings help.

If there are filtration problems it is worth looking at using xylanases rather than just increasing the amount of beta-glucanase used.

Problems can begin in the brewhouse: mill settings and raking will affect filterability. Mash filters are potentially worse.

Roasted grains lead to fine particles that will block 0.5 micron pores. Brown coloured ales are generally fine though.