Track down the Issue (Oxidation?)

[ryantollefson]

Argh...

This is supposed to be a Sculpin clone (light colored IPA). First pic & second pic are the same recipe, same overall BIAB method, both fermented in SS Brewtech stainless fermenter, both temp controlled, both kegged (starsan & CO2 purge), with only minor changes in process... can you help me track down what went wrong?

The 2nd batch is much darker color, really lacks in hop aroma (& flavor), and after 2 months I've still not finished the keg (strongest sign of an issue right there ). I don't notice a cardboard flavor, but it does seem really dull (esp. for an IPA).

Differences that I can remember:

• 2nd batch, never changed to an airlock, just left the blow-off tube in place
  • blow-off tube is silicone (read somewhere that silicone is actually pretty O2 permeable, not sure if that would matter)
• 2nd batch double milled the grain for BIAB, 1st batch single milled it & used DME to hit OG numbers. 2nd batch hit numbers without DME
• 2nd batch I didn't leave the starter on the stir plate quite as long & I noticed fermentation wasn't quite as vigorous
• 2nd batch, a few days after dry-hopping I used a sanitized stainless spoon to try to rouse the hops (had read this somewhere)
  • I ended up leaving the 2nd batch in the fermenter about 1.5 weeks longer than the first before transferring to the keg (to let it clear more)
• 2nd batch I used silicone tubing to transfer to keg (oops, I left my vinyl tubing in a bucket of starsan for about a month - it looked cloudy & weird, so I didn't trust it)

Stirring the hops, transfer with silicone, leaving silicone blow-off tube, something else? What do you think?

Thanks,
-Ryan

 

[Dcioni]

My vote is stirring the wort/beer in the fermenter w the spoon causing oxidation. I don’t think silicone vs vinyl could be that significant tbh.

Also maybe (but I’d guess less significant) leaving it in fermenter for longer caused more yeast to fall out/flocc—potentially reducing the haze and making it appear darker too?

 

[ryantollefson]

My vote is stirring the wort/beer in the fermenter w the spoon causing oxidation...

Could be; I was really careful not to splash, but still...

Also maybe (but I’d guess less significant) leaving it in fermenter for longer caused more yeast to fall out/flocc—potentially reducing the haze and making it appear darker too?

Possible - the first was a little (not bad, but a little) cloudy, but it had good flavor/aroma. The 2nd batch is really dull for flavor/aroma.

 

[beermanpete]

The color difference could be due to the apperant lower mash efficiency and subsequent additon of the DME. How much DME did you add?

 

[ryantollefson]

The color difference could be due to the apperant lower mash efficiency and subsequent additon of the DME. How much DME did you add?

I'm not sure... probably 1/4 - 1/3 lbs. I added until I hit the pre-boil number I was looking for.

Just to be clear... I added on the lighter color (1st) batch, not the 2nd batch.

You think lighter color could be because of lower efficiency + DME?

 

[beermanpete]

Yes, I was thinking the DME could lighten the color. However, the small amount you added does not seem like it would be enough to change the color so much. Did you boil the wort on the second batch more vigouroulsy or for a longer time?

 

[ryantollefson]

Yes, I was thinking the DME could lighten the color. However, the small amount you added does not seem like it would be enough to change the color so much. Did you boil the wort on the second batch more vigouroulsy or for a longer time?

No, both were a 60 min. boil. If there was a difference in boil rate is was minimal.

 

[ESBrewer]

For sure it's not the silicone tube. I would guess it is oxidation caused by stirring operation (or more likely just opening the fermentor at a stage when there was not enough co2 production to drive the oxygen out). Did you dry hop in primary or secondary and was there a lot of head space in the fermentor? Or then DME, or longer time in fermentor -> yeast autolysis?. Frankly, I don't have enough experience, I'm just speculating.

 

[couchsending]

Lifting the lid and stirring did it for sure. Do you pressure transfer with your SS conical? If so this is what I’ve started doing and have been really really happy with the amount of time that really punchy aroma is lasting.

When i add the DH addition I will add the pressure transfer piece and fill the headspace with CO2 and purge a few times, then fill until it starts to escape out the PRV. I have a small, spare CO2 tank that I will leave it hooked up to. Just be sure to make sure you shut the Co2 all the way off as it’ll drain your tank in a heartbeat. You can hit with a burst here and there as you’re dry hopping and cold crashing (if you’re doing that in primary). Also make sure your transfer line is purged. I used to fill the transfer line with beer, let it sit for 10 minutes to absorb the O2 then drain that but I’ve found it better to just leave the last 5-10 PSI in the keg, hook up the ball lock and let that last bit of Co2 in the tank purge the line and just hook it up to the conical as it’s starting to wind down. The silicon tubing definitely makes no difference whatsoever.

 

[Die_Beerery]

Oxidation for sure.

“The deleterious effects of oxygen uptake at any point in the brewing cycle is well documented. The only exception to this is the oxygen introduced at the start of the fermentation. It is true that there is a considerable variation among beer drinkers both with respect to their ability to detect oxidized flavors, and with respect totheir acceptance of these notes. Yet the track record is clear in both amateur and commercial brewing: Consistently successful brewers are invariably the ones who operate low oxygen systems. For most of the twentieth century, attention was focused on oxidation occurring after the end of the fermentation-so-called cold side aeration (CSA). Concerns about CSA are well founded since there are a number of relevant mechanisms, all of which are destructive to beer flavor.”

CSA is all over in any brewing texts and a simple google search will yield countless results. However George lays it out well here:

“Methods for such optimization are covered in, for example, in the references by Bamforth (1999) and Fix (1998). Following C. D. Dalgliesch (1977), it is useful to characterize staling in terms of three basic stages:

• Stage A is the period of stable, “brewery-fresh” flavor.

• Stage B is a transition period in which a multitude of new flavor sensations can be detected.

• Stage C products are the classic flavor tones involved in beer staling.”

He goes on to list an overview of the stages, the highlights of them being:

“Stage A beer is pristine in flavor. During stage B, Dalgliesch described a decline in hop aroma, a decline in hop bitterness,an increase in “ribes aroma” (or sometimes “catty” flavor), and an increase in sweet, toffee-like, or caramel tones. The terms ribes (or currant) and catty are widely used in the United Kingdom and Scandinavia to recall overripe or spoiled fruit or vegetables. Some tasters cite a “black currant” tone (Hardwick, 1978). In truth, these terms describe a wide spectrum of negative flavors developed when beer is in stage B. Toffee or caramel flavors can come from many sources, but those associated with staling will invariably have unattractive cloying notes. These effects are enhanced by residual diacetyl and also by excess heat treatment of wort. Finally, stage C products range from papery or leathery to sherry- or vinegar-like notes.”


Taken from here
http://www.********************/brewing-methods/cold-fermentation-and-spunding-results/

 

[ryantollefson]

...Did you dry hop in primary or secondary and was there a lot of head space in the fermentor? Or then DME, or longer time in fermentor -> yeast autolysis?. Frankly, I don't have enough experience, I'm just speculating.

No secondary, only Primary. 2nd batch was in the fermenter 1.5-2 weeks longer than first batch.

Lifting the lid and stirring did it for sure. Do you pressure transfer with your SS conical? If so this is what I’ve started doing and have been really really happy with the amount of time that really punchy aroma is lasting...

Just thinking more, and reading the responses, that's what I'm leaning toward. No, no pressurized transfers - also, it's a brew-bucket, not a conical (not that it should really matter for this).

 

[ryantollefson]

Oxidation for sure.

That's what I'm thinking too.

As for everyone saying don't worry about the silicone tubing...

Just some food for thought:

It was also no surprise that the rate at which oxygen transfers through carboy closures made of materials known to be extremely oxygen permeable, silicone being a prime example, can be very significant, while carboy closures made of dense, low-porosity, low-permeability materials have oxygen transfer rates that are essentially negligible. It was also not surprising that air locks made of thin, relatively oxygen permeable materials and based on water-trap designs permitted the transfer of small, but significant, amounts of oxygen. Oxygen dissolves in and moves through water, especially when the water is stirred.

http://www.mocon.com/assets/documents/PPS_Article_highq.pdf

 

[couchsending]

No secondary, only Primary. 2nd batch was in the fermenter 1.5-2 weeks longer than first batch.


Just thinking more, and reading the responses, that's what I'm leaning toward. No, no pressurized transfers - also, it's a brew-bucket, not a conical (not that it should really matter for this).

They do make a pressure transfer option for the brew bucket lids, was actually looking at it today. It’s a little spendy and you have to buy a specific drill bit but it can be done.

 

[PADave]

They do make a pressure transfer option for the brew bucket lids, was actually looking at it today. It’s a little spendy and you have to buy a specific drill bit but it can be done.

Or just rig up your own setup. You don't need their option to do a pressure transfer with the brew bucket.

 

[PADave]

Taking the lid off and stirring is what did it. Keep that fermenter sealed up!