Filtration problem

[S.Foster]

Observation(s):
Recently, without any process changes, beautiful post fermentations to under go cold crashing have gone from almost clear beer (slightly hazy) to highly turbid beer (almost muddy looking) to the point of making filtration impossible.

Details:
Fermentis US-05 yeast (have experienced no prior flocculating problems (do not repitch)). No excessive dissovled B-glucans or gels to be found chemically, 70micron pads (97 pads in the plate and frame), 30degree F, 4.8% abv. beer, Some ice crystals found floating throughtout the beer but not in a visual "slushy" form (beer still looks visually liquid), we typically us a flow rate of 6.0 - 7.0 BBL per hour, pH of the beer is within normal post fermentation range, all prior wort production was visually clear and free of particulate matter reaching the kettle, hot break was good and cold break was good, used hot side finings. Have tested non-crashed beers through the filter and they filter as expected for cold crashed beers. Is it possible that the beer is partially freezing and the ice crystals are blinding the filter? There is virtually no build-up particulate matter on the pads and only colour has been deposited on them.

Possibility:
It appears that ice is the culprit but looking for more input from more minds.


Looking for additional thoughts

[TL Services]

My first thought on this is a difference in the malt you're using. I have seen similar problems many times with new season's malt which has a higher than normal level of low molecular weight proteins. Essentially it is the same mechanism as a 'chill haze' but the lower molecular weight proteins are highly soluble so don't come out of solution as readily with copper finings and the wort cold break isn't noticeably poor either.

They form part of the group of so-called 'sensitive proteins' which have a high level of proline and which react with polyphenols to produce haze/turbidity (the reaction is hastened by high levels of dissolved oxygen, as an aside).

However when rapidly chilled to very low temperatures the resultant protein-polyphenol complex becomes insoluble, forming a visible haze (sometimes extremely dense) and causing filtration problems.

To check this, try taking a sample of your beer that's causing the problem and warming it; nothing complex, just take a clear glass/bottle, fill it with the beer and stand it in reasonably hot water for a while. If what you're seeing is as described above, then the material will resolubilise once it warms up.

I would repeat that the mechanism is basically the same as chill haze formation, but the nature of the proteins involved make the haze material more soluble that usual, hence it doesn't appear until the beer is subjected to very low temperatures, as you're doing.

Some years ago we did an enormous body of work into this issue, which seemed to happen most years and without any process/material changes (ie. same regimes, same raw materials, etc.). It was only once we started analysing the 'problem' wort for protein spectra that we found very high levels of low-weight proteins when compared to 'non problem' wort.

[S.Foster]

Kwlsd

Thank you. You are exactly right. We are using Simpsons and MCI's malts. Your suggested experiment performed as exactly as you said it would and the results were spot on. Cheers!

[S.Foster]

Kwlsd

Do you have any recommended reading for further reference on this subject and other English specific and/or related materials?

I current reference the following books:
1. Brewing: Science and Practice
2. Handbook of Brewing
3. Technology Brewing and Malting
4. Handbook of Brewing- Processes, Technology and Markets

[TL Services]

Online:

http://web.foodscience.cornell.edu/siebert/FoodSci608/lock/reprints/hazemod.pdf

I'd suggest talking to your copper finings supplier as most of the bigger companies will have met this sort of problem and - hopefully - should be able to recommend a suitable finings to reduce the level of sensitive proteins.

Also worth discussing with your malt supplier as this is something they need to be aware of.

Depending on the exact nature of the haze complex, these can drop out of suspension given a maturation stand of a few days (especially if there's a high level of material). Alternatively/additionally an auxiliary finings can be used.

As the haze material is a protein-polyphenol complex, PVPP can be effective as this reduces the polyphenol level. This can be used as a one-shot addition prior to filtration or by adding into your filter powder.

Dissolved oxygen control - especially post-fermentation - is critical as oxygen increases the formation of the haze complex. The same complex is involved with 'age-related' haze in bottled beers and that, in itself, will become more evident if someone stores their beer in the fridge prior to drinking.