Oxidation - a new friend

Hi all,

Having previously chalked up 30 or so full extract and partial mash BIAB brews without ever falling prey to the curse or oxidation, I've given an unwelcome home to this menace in all of the half dozen or so of my first ever batches of all grain. While I'm one to enjoy working my way through a problem, I'm drawing a blank on the cause and it's tempting me to return to extract and partial BIABs right now. I'd be hugely grateful for any opinions on the following (and most recent) process that's also given me a duff batch of bland wet cardboard flavoured IPA:

Brew - Nelson Sauvin Single Hop IPA. 23 litre/6 gal target fermentation volume, 6.6kg/14.6lb base malt, IBU 52, EBC 14, OG 1.064, FG 1.013, RO/DI water adjusted for mineral balance and pH according to Martin Brungard's Brew'n water spreadsheet.

Process:
1. Mill my own grain while producing DO/RI water
2. Heat required adjusted DO/RI water in 37 litre/10 gal stainless steel boil pot, begin mash using 50 litre/13 gal stainless steel insulated mash tun with drainage spigot. Stir a couple of times during mash.
3. Heat required volume of adjusted DO/RI sparge water while mashing.
4. Batch sparge using high-temp food grade silicon tubing to 30 litre/8 gal plastic carboy until 27 litres/7 gal of wort obtained.
5. Transfer from 30 litre/8 gal plastic carboy via spigot to 37 litre/10 gal stainless steel boil pot using same high-temp food grade silicon tubing.
6. Bring to boil and add copper hops.
7. Add flavour hops and protofloc for last 15 mins.
8. Add aroma hops at flame out and cool to pitching temp (22 degrees C) using copper coil immersion cooler over approx 15 min.
9. Transfer to 30 litre/8 gal plastic carboy via spigot and high-temp food grade silicon tubing and pitch yeast (Nottingham, dry).
9a. (addendum) Aerate wort using plasterer's whisk attached to electric drill.
10. Primary fermentation until max FG obtained (5 days at peak temp 22C/72F day 2, 20C/68F remaining period)
11. Transfer to second 30 litre/8 gal plastic carboy via spigot and high-temp food grade silicon tubing and mix in priming dextrose.
12. Rack to brown glass swing-top bottles using racking cane.

I gave up on transferring to a second 30 litre/8 gal plastic carboy for a 10 day secondary fermentation on the suspicion that O2 in the headspace or the extended period in an O2 permeable HDPE container may be the cause but this did not solve the issue. I also moved to the use of high-temp food grade silicon tubing but to no avail. I'm also very careful to avoid any unnecessary splashing during liquid transfer.

The result - when sampled up to bottling on day 5, it was all you'd expect. After four weeks in the bottle, there are no pronounced flavours, only the stale oxidation. The was equally noticeable but easier to monitor when I was using a secondary fermentation. After the primary, the green beer tasted as you'd expect but, after the secondary, there was a noticeable reduction in expected flavours at the expense of an increase in the stale oxidation taste. After a few weeks in the bottle, there was only the stale oxidation taste.

So here I am. At a loss but hoping you can help. All advice truly welcome.

D

I am new but I just want to ask, why are you transferring to the carboy before the boil, why not directly to the Kettle then boil?

There really isn't anything in the procedures described that scream oxidation. A couple of fine points, though....

Is the main difference between AG process and the BIAB is the use of the carboy as a wort receiver? I would look very carefully at how much foaming is occurring during the two transfers. Basically, anywhere you see foaming in uncarbonated beer or wort, you're seeing oxygenation occur. Eliminate all sources of this.

Silicon tubing is usually very large in diameter. Is it staying full during each transfer? It needs to or is simply a cascading oxygenation device. The surface area of wort is exponentially expanded inside tubing and as it twists along can uptake a lot of air.

How vigorously and how often are you stirring during the mash? This should be very gentle and usually isn't necessary.

When you batch sparge, are you stirring the grain while adding water, or waiting until the grain bed is covered before stirring? The latter is mess likely to be a source of oxidation.

When racking for bottling, just pour the boiling sugar solution into the plastic carboy first, then syphon in on top of it. Use a bottling arm with the valve removed to make sure the beer flows smoothly all the way to the bottom. Often tubing curls and makes a small fountain.

It takes a LOT of effort to create hot side aeration in a way that is perceptible. But, if your process is adding it incrementally, it can show up. A very vigorous boil will help strip some O2 from hot wort. Paler beers are more susceptible to HSA because the melanoidin-O2 bonds are fewer and weaker. An equally aerated black beer is far less likely to show HSA.

Hot side aeration is huge. Especially for homebrewers. If your getting cardboard inside of 4 weeks then it is Hot side aeration.

RickS said:

I am new but I just want to ask, why are you transferring to the carboy before the boil, why not directly to the Kettle then boil?

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Thanks, RickS. The carboy is the only graduated container I have but I will mark the SS boiling pot for the next batch and see if this helps...

Many thanks, Brewfun.

Yes, the main difference between my AG process and the BIAB is the use of the carboy as a wort receiver. Will be a variable I change next as I've been wondering if the O2 permeability of the HDPE container sky-rockets when holding c.60-70C wort.

An excellent point noted also on the silicon tubing. Now you encourage me to think about it, this is also a difference between the two processes. I'll add this to the next set of changes.

Aside from the above, stirring of the mash is gentle and I only stir during the batch sparge after the grain bed is covered. There's also no foaming anywhere in my process.

Will order some more grain and try a sensitive IPA this coming weekend or next.

I have no idea if fermentation temperature affects oxidation, but higher temperatures affect production of other undesirable compounds, so it seems reasonable that higher temperatures could increase oxidation products. In other words, your pitching temps are higher than what I use.

I chill to about 60F/20C, pitch, and hold at or below the bottom of the yeast's recommended range for about two weeks, then raise the temperature to the top of the recommended range for a week. Most of my dry hopping takes place in a well-purged keg. I've never detected oxidation in spite of some less-than-careful handling of hot wort. That doesn't mean I haven't had oxidation, only that I haven't detected it - my palate is not sensitive to some off flavors and I enjoy some flavors that would make a beer judge cringe.

Can anyone enlighten me on the relationship - if any - between fermentation temperature and oxidation? Could that be what's causing or increasing DJ's problem?

most oxidation problems occur after fermentation.  Hot side aeration is not a common problem but looking at your process, you could be getting some oxidative reactions.    Be sure eliminate splashing of worth when transferring above 80F/26C.  As brewfun advises, a vigorous boil will drive off much of the oxygen. 

Be sure to pitch the right amount of healthy yeast which will consume the oxygen and absorb some of the oxidative off flavors and precursors. Fermenting at stable temps within the speficied range allows the yeast to thrive and do their very best for your beer. 

Bottling should be the same for extract and all grain and though you didn't have problems with extract beers, be sure to "cap on foam" which drives out oxygen from the bottle.

When bottle conditioning, store your bottles between 70 and 75F for the required time and then chill them to storage terps as soon as possible.    Beer stored at 32C/90F will stale in a few weeks.  At 2C/35F it will lat months or a year.

Temperature cycling, it is believed, will accelerate staling.  So, a warm garage by day and cold by night can stale a beer faster than steady temps.

DJAllen said:

RickS said:

I am new but I just want to ask, why are you transferring to the carboy before the boil, why not directly to the Kettle then boil?

Click to expand...

Thanks, RickS. The carboy is the only graduated container I have but I will mark the SS boiling pot for the next batch and see if this helps...

Click to expand...

I have a piece of pipe (could be a stick) for a dipstick that I carved a notch into @ each gallon.  It's easier than trying to keep marks on my brew kettle.

Many thanks to all for the great advice given. I'll amend my next brew (hopefully next weekend) to reflect your suggestions and post an update.

In the mean time, I have added one more detail (point 9a) to my original post. I aerate my post-boil but cooled wort using plasterer's whisk attached to electric drill after the dry-pitched yeast has hydrated. I've always done this but maybe worth noting.

Thanks for the recent response, Jomebrew. I always, always over-pitch my yeast and I've invented a neat heating/cooling system for temp control +/-1C (not sure what that is in F). Just a shame I can't keep the bottled beer at 64F or less during the London summers.

I have another minority opinion. Don't aerate at all. Even with liquid yeasts.

But especially not with Nottingham.

DJAllen said:

In the mean time, I have added one more detail (point 9a) to my original post. I aerate my post-boil but cooled wort using plasterer's whisk attached to electric drill after the dry-pitched yeast has hydrated. I've always done this but maybe worth noting.

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DJ, I'm not sure this gets you the aeration you need. You wort will be mixed for sure, but aerated not so much.

grathan said:

I have another minority opinion. Don't aerate at all. Even with liquid yeasts.

But especially not with Nottingham.

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Thanks, Grathan. You're now the second person to make this comment and the first was one of the most experienced brewers I've ever met so I'd be crazy not to try. Will add to my amended technique for the Warrior/Citra IPA I brew next weekend. Fingers crossed that I'm not wasting another Saturday and £20 of ingredients.

DJ, I'm not sure this gets you the aeration you need. You wort will be mixed for sure, but aerated not so much.
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Are you sure, Baron? I am left with a fair few inches of froth on the top of my wort when I finish with the whisk so I thought it would be more than just a mix.

Get an aquarium pump with a diffuser stone.  Sanitize it well and let it run for about 20-30 minutes.  You'll get more then just a few inches of foam.  It will be a foot or more of foam.  This is aeration.  What you're doing is called stirring.  Stirring adds some oxygen, but not enough.

Order from best to worst.
  1.  Use an oxygen bottle and pump it through a diffuser stone into your wort.  This takes mere seconds to reach the appropriate oxygen levels for your yeast.  You can get too much oxygen into your wort with this method.
  2.  Aquarium Pump and diffuser stone.  This takes 20-30 minutes, but it is impossible to get too much oxygen into your wort with this method.
  3.  Splashing back and forth as you pour your wort from one container to the other.  Does get some oxygen into your wort, but it isn't possible to get enough to support good yeast growth.
  4.  Some type of stirring method (which is what you're doing).  Does get some oxygen into your wort, but also it isn't possible to get enough to support good yeast growth.

Scott Ickes said:

  1.  Use an oxygen bottle and pump it through a diffuser stone into your wort.  This takes mere seconds to reach the appropriate oxygen levels for your yeast. You can get too much oxygen into your wort with this method.

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This has been hotly debated over time.
One camp says it's virtually impossible to over aerate.
Another camp says you should never use pure oxygen with a starter because it creates too much yeast production too fast resulting in unwanted esters and higher alcohol creating off flavors.
Hmmm.
I just took a reading on a German maibock. It's been 15 days in the fermenter and still gassing. Overshot my FG. Looking for 1.016. It's now at 1.014
I used pure oxygen with a stone. Also used a yeast starter.
Looks like you're on to something here Scott... 

grathan said:

I have another minority opinion. Don't aerate at all. Even with liquid yeasts.

But especially not with Nottingham.

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Regretfully, I am not in agreement with that opinion.

During lag phase, free oxygen is important for complete yeast budding, uptake of amino acids, full growth and proper cell wall structure. Though yeast doesn't require O2 to start fermenting, the resulting beer is not as good, either.

Again, this is regarding free O2. Readily available to the yeast and not bound to any other wort chemistry. The OP is reporting staling, which is different O2 pathways.

durrettd said:

Can anyone enlighten me on the relationship - if any - between fermentation temperature and oxidation? Could that be what's causing or increasing DJ's problem?

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Temperature fluctuations speed up oxidation. An important consideration in bottled beer storage. Beers can measure near zero at packaging, but show increased O2 levels over time as O2 bonds break within the finished beer and redox.

In the kettle, O2 bonding is sped up, but so is the breaking of those bonds. If a substantial amount of O2 makes it in and there is a fair amount of polyphenols, proteins, amino acids and very little melanoidin, then yes, HSA can persist and create staling later.

HSA is a huge discussion in home brewing, but really isn't the flavor destroying monster issue for home brewed beer that it's made out to be. Yeast is a great O2 scavenger, even long after fermentation. Beer that's left with healthy lees at packaging and stored reasonably, shows an almost 2x shelf life over filtered versions of the same beer.

EDIT: I think some research showing O2 pickup during the boil will be presented at the upcoming AHA conference. Their ASBC paper indicates this O2 is bonding with proteins and amino acids and can be a part of later staling. Their research showed that late O2 pickup isn't as influential in beer staling as currently thought (which contradicts about a dozen studies). The inference is better protein reduction (hot/cold break) and more complete use of amino acids by yeast are part of beer stability. Both have long been known, but this is a little more information on the pathway which has yet to be completely verified.

HSA has a lot of variables and is a complex reaction. It only takes a few really basic and often intuitive steps to avoid it, altogether.

brewfun said:

HSA has a lot of variables and is a complex reaction. It only takes a few really basic and often intuitive steps to avoid it, altogether.

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And I know I shall be kicking myself when I find out just what of the few really basic steps I should have been taking to avoid my oxidation nightmare....

brewfun said:

grathan said:

I have another minority opinion. Don't aerate at all. Even with liquid yeasts.

But especially not with Nottingham.

Click to expand...

Regretfully, I am not in agreement with that opinion.

During lag phase, free oxygen is important for complete yeast budding, uptake of amino acids, full growth and proper cell wall structure. Though yeast doesn't require O2 to start fermenting, the resulting beer is not as good, either.

Again, this is regarding free O2. Readily available to the yeast and not bound to any other wort chemistry. The OP is reporting staling, which is different O2 pathways.

Click to expand...

It is commonly said that dry yeast doesn't require oxygenation. I don't know the reasoning here, but let's assume the science is correct. By the same theory if you pitch liquid yeast that is also of a large quantity and heavily oxygenated, than that has to be a similar concept.


From my experiences my beers have improved since I have stopped basting them with pure O2. I use a 2L stirred starter on 1.050 batch ( I couldn't tell if this is overpitched by experts standards, but I am guessing that it may be )

My thoughts are that if your yeast pitch is oxygenated and is of large enough quanity, there will be very little growth and therefore very little oxygen consumption. And possibly this leftover o2 will end up hurting your batch. I know this is wild speculation and I unfortunately I don't have a dissolved o2 meter to prove it wrong. Texts also seem to imply that over-oxygenating will simply lead to excessive yeast growth and excessive fruity ester production as well as a diminished alcohol level.


Almost all of the texts about proper oxygenation level (6-8ppm) do not take into account oxygen levels of the pitched yeast and its addition to the aerated wort.