troubleshooting: weird off flavor

[powwowwow]

I'm contract brewing with a facility that will remain nameless. I've noticed a particular, unpleasant "house flavor" to many of their beers, and I'm trying to figure out where it's coming from in order to address it.

I would describe it as a sort of stale, sawdust-like character... maybe a little bit of hot-hair-dryer. It's not in the aroma, it's only in the flavor. It seems maybe similar to oxidation, but again more of a rough, sawdusty thing as opposed to cardboard. And it appears immediately, not over time.

What are some of the first things you would check into for the off flavor i'm describing?

[einhorn]

If it's in every beer, I would check quality/age/milling of the base malt.

[powwowwow]

advanced milling?

We order the base malt from BSG in advance of each batch. Most recently it was Weyermann pils. It might arrive 2 weeks ahead of the brew date. Storage conditions can be in the 80's to 90's and humid. It is milled the day before (in the same ambient conditions), and then we mash in on the morning of the following day. Could milling the day before be contributing to the problem?

Maybe milling the day before brewing, combined with heat, is oxidizing the beer before it's even brewed?

[Matt Dog]

No. Every brewery I have worked at mills in the night before w no problems. If that were it no one would by pre-milled malt.

[nateo]

Sounds like oxidation. Have you seen this?

http://www.asbcnet.org/meetings/proceedings/2012/AbstractsDetail.cfm?AbstractID=407

"Stale aldehydes, including Strecker and saturated and unsaturated aldehydes with chain lengths of C8–C10, are generated from degradation of amino acids and oxidation of lipids, which are typically associated with beer oxidation during storage. Some of these compounds, such as (E)-2-nonenal and (E,Z)-2,6-nonadienal, can cause a “sawdust” off-flavor in beer at concentrations as low as 0.1–0.3 ng/mL–l (ppb)."

[einhorn]

Have you tried all the contract beers that are being brewed here to see if they have the same profile? Also, maybe you are hyper-sensitive to these flavors - have others tasted the same results?

[ATB Consulting]

A few thoughts...

Wort clarity - better clarity will lower the amount of fatty acids (lipids) that can be oxidized. Look at wort after run off and again after knock out. A fast run off followed by a quick whirl pool could lead to this. Maybe the brew sheets will reveal the run off time and whirlpool durations?

Metal ions - To much Cu and FE in the water can catalyze oxidation. Take a look at the water analysis.

Melanoidins - if melanoidins become oxidized they may then react with higher alcohols which will increase oxidation. Take a look at their brewing process to determine if wort or runnings are being agitated. For example, I've seen some breweries pump to quickly which causes a lot of splashing.

Do you know the dissolved oxygen levels in the beer(s)?

Hope this helps!

[powwowwow]

malty1: thanks a bunch for your suggestions. I will check into the wort clarity and Cu/Fe levels. I'm not sure if I follow what you're saying about melanoidins. At which points in the brewing process can wort agitation be a problem? when recirculating the mash?

the beer is dosed with oxygen in line on the way to the fermenter, after passing through the heat exchanger. The brewery has no equipment for measuring dissolved oxygen levels in the finished wort. It's a source of anxiety for me.

[ATB Consulting]

malty1: thanks a bunch for your suggestions. I will check into the wort clarity and Cu/Fe levels. I'm not sure if I follow what you're saying about melanoidins. At which points in the brewing process can wort agitation be a problem? when recirculating the mash?

the beer is dosed with oxygen in line on the way to the fermenter, after passing through the heat exchanger. The brewery has no equipment for measuring dissolved oxygen levels in the finished wort. It's a source of anxiety for me.

Agitation during recirculation of the mash while lautering and/or running off can lead to the flavor you are describing.