Wort is up to temperature and I’m passed the hot-break so time for bittering hops. 15g of Magnum will be boiled for 60mins giving me about 23 IBUs in 21 litres of wort.
Hazelwood Brewday
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Forgot pictures but I added 33g of Fuggles and half a protofloc tablet at 15 minutes. At flameout I cooled the wort through my plate chiller to 78F where it’s now resting to allow the gunk to settle out before transferring the wort to the fermenter.
It does look like I’m brewing a stronger version of my regular bitter but I don’t mind that and I may just have learned something about my own process (effect of recirculation flow rate on mash efficiency). I’m going to be brewing another batch of Summer Breeze and will set the flow rate the same as today to see if the results are repeatable.
It does look like I’m brewing a stronger version of my regular bitter but I don’t mind that and I may just have learned something about my own process (effect of recirculation flow rate on mash efficiency). I’m going to be brewing another batch of Summer Breeze and will set the flow rate the same as today to see if the results are repeatable.
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To finish the story on this brew, the gravity ended up at 1048 and is 2 points up on my target OG. This pushed my brew house efficiency on this beer from 74% to 77% and may push the ABV from 4.46% to 4.73% depending on the performance of the yeast. Speaking of yeast I used one pack of MJ M36 Liberty Bell, pitched at 75F (24C), sprinkled dry onto my wort, and will ferment at 20C.
Checked my fermentation cabinet this morning and all is well. The hypnotic tapping of the bubble trap is a wonderful thing. You can keep your whale song, I’d rather listen to my beer!
The little fella peering round the corner left of the shelf is the temperature data logger for the fermentation cabinet.
Checked my fermentation cabinet this morning and all is well. The hypnotic tapping of the bubble trap is a wonderful thing. You can keep your whale song, I’d rather listen to my beer!
The little fella peering round the corner left of the shelf is the temperature data logger for the fermentation cabinet.
I’m now planning my next batch of Summer Breeze and having accepted my own challenge to get more hop flavour and aroma from my current (V2) recipe, I’ve been doing a bit of reading. I’m not (yet?) wanting to pressure ferment or do closed transfers. I do accept these may well have an impact but I first want to make changes in my existing process before I start introducing even more variables. So here goes…
We know hop flavours and aromas, of the fruity kind, are linked to hop essential oils and Linalool/Geraniol are more prized than some of the others but hop Thiols (sulphur compounds) are increasingly recognised as contributing more bang for your buck. Thiols are found in malt and in hops and they exist in two broad forms; free Thiols which are immediately available for us to use and bound Thiols or “thiol precursors” which are bound up within a more complex compound and need to be pulled out. These have been found to be up to 1,000 times more abundant than free thiols.
The enemy of Thiols is thiol oxidase which is an enzyme that breaks down Thiols. Thiol oxidase is also in the malt and is activated by oxygen - the more oxygen the more thiol oxidase so less thiol and less of the fruity hop aroma/flavour in your beer. I think this is the science behind minimising hot-side aeration.
With all that now said:
We know hop flavours and aromas, of the fruity kind, are linked to hop essential oils and Linalool/Geraniol are more prized than some of the others but hop Thiols (sulphur compounds) are increasingly recognised as contributing more bang for your buck. Thiols are found in malt and in hops and they exist in two broad forms; free Thiols which are immediately available for us to use and bound Thiols or “thiol precursors” which are bound up within a more complex compound and need to be pulled out. These have been found to be up to 1,000 times more abundant than free thiols.
The enemy of Thiols is thiol oxidase which is an enzyme that breaks down Thiols. Thiol oxidase is also in the malt and is activated by oxygen - the more oxygen the more thiol oxidase so less thiol and less of the fruity hop aroma/flavour in your beer. I think this is the science behind minimising hot-side aeration.
With all that now said:
- I want to maximise the extraction of Thiols (I should also say there are many Thiols and different ones contribute different aromas/flavours, also that some Thiols enhance others by lowering the taste threshold which all starts to get a bit complicated, and that different hops have different Thiols in varying proportions).
- I want in particular to free up the bound Thiols (remember these are far more abundant but not accessible in their bound form).
- Having got all these Thiols I want to keep them in my beer!
I’ve noted a few process changes I want to try that I hope will increase hop aroma and flavour…
Hot-side Aeration
When mashing I will turn down the flow rate on my recirculation pump. This takes hot wort from the bottom of my boil kettle and sprays it on the top of the malt. This has never given me any problems - except maybe it has without my knowing. The relatively fine spray has to be one of the best ways to aerate the wort I can think of other than pumping oxygen through an aeration stone! I turned down the flow to a dribble on my last brew and also saw an increase in efficiency - I have no idea if this was a fluke but I’ll be doing it again and will look to confirm any efficiency improvement. If it does, I have another area to research! For now my aim is to reduce hot-side aeration.
Hot-side Aeration
When mashing I will turn down the flow rate on my recirculation pump. This takes hot wort from the bottom of my boil kettle and sprays it on the top of the malt. This has never given me any problems - except maybe it has without my knowing. The relatively fine spray has to be one of the best ways to aerate the wort I can think of other than pumping oxygen through an aeration stone! I turned down the flow to a dribble on my last brew and also saw an increase in efficiency - I have no idea if this was a fluke but I’ll be doing it again and will look to confirm any efficiency improvement. If it does, I have another area to research! For now my aim is to reduce hot-side aeration.
Copper and Iron Ions
I noted that Thiol Oxidase breaks down Thiol. It also happens that copper absorbs Thiol and both copper and iron ions are present in your wort and pro-oxidative leading to beer becoming oxidised over time. (If you use a copper CFC it may be possible you’re adding additional copper ions to your wort?).
Alpha-acids have been shown to “complex” metal ions in the mash, removing the oxygen. A dose of 1g/litre of high alpha-acid hops in the mash is all that’s required. I’ll therefore be putting a dose of hops in the mash. I’m not sure how this might affect IBUs - mash temps are low for isomerisation but are those alpha-acids still there when the wort is brought to the boil or have they been somehow “consumed” while dealing with the metal ions?
I noted that Thiol Oxidase breaks down Thiol. It also happens that copper absorbs Thiol and both copper and iron ions are present in your wort and pro-oxidative leading to beer becoming oxidised over time. (If you use a copper CFC it may be possible you’re adding additional copper ions to your wort?).
Alpha-acids have been shown to “complex” metal ions in the mash, removing the oxygen. A dose of 1g/litre of high alpha-acid hops in the mash is all that’s required. I’ll therefore be putting a dose of hops in the mash. I’m not sure how this might affect IBUs - mash temps are low for isomerisation but are those alpha-acids still there when the wort is brought to the boil or have they been somehow “consumed” while dealing with the metal ions?
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Thiol precursors
Thiols are what I want in my beer and hops have two forms of Thiols; free Thiols and bound Thiols (precursors). The free Thiols are immediately available and extracted through dry-hopping but they are highly volatile and drift off easily - more on this shortly.
The Thiols in Thiol precursors need to be “cleaved” and this is done by beta-lyase which is produced by yeast during primary fermentation but the precursors need to be already in your wort. This is where hot-side hopping comes in and the whirlpool in particular. Thiol precursors are non-volatile and stick around even at higher temperatures. Interestingly, the Thiol precursors most likely to give you tropical fruity aroma/flavour are the least volatile, floral Thiol precursors are more volatile, woody Thiol precursors are most volatile. This means a whirlpool at close to boiling, say 95C, will give the most fruity precursors (85C favours floral and 75C favours woody).
I already have a fairly heavily hopped whirlpool but from this I’m going to raise the temperature of my whirlpool to 95C.
Thiols are what I want in my beer and hops have two forms of Thiols; free Thiols and bound Thiols (precursors). The free Thiols are immediately available and extracted through dry-hopping but they are highly volatile and drift off easily - more on this shortly.
The Thiols in Thiol precursors need to be “cleaved” and this is done by beta-lyase which is produced by yeast during primary fermentation but the precursors need to be already in your wort. This is where hot-side hopping comes in and the whirlpool in particular. Thiol precursors are non-volatile and stick around even at higher temperatures. Interestingly, the Thiol precursors most likely to give you tropical fruity aroma/flavour are the least volatile, floral Thiol precursors are more volatile, woody Thiol precursors are most volatile. This means a whirlpool at close to boiling, say 95C, will give the most fruity precursors (85C favours floral and 75C favours woody).
I already have a fairly heavily hopped whirlpool but from this I’m going to raise the temperature of my whirlpool to 95C.
Fermentation
So now if the research is correct, I will have reduced Thiol-eating oxidase, I’ve reduced pro-oxidative metal ions (not eliminated, some are needed by the yeast), and I’ve loaded my wort with tropical fruity Thiol precursors ready for the yeast to cleave the Thiols.
Thiols are cleaved through bio-transformation using a yeast derived enzyme called beta-lyase. The Thiols are extremely volatile and will drift off at warmer temperatures far more easily than at lower temperatures. This means that fermentation should be at the lower temperature range in order to hold on to those Thiols. It also appears that higher pitch rates and yeast nutrients will help here.
During primary fermentation some of those Thiols will have drifted off so dry hopping after primary fermentation is beneficial but you need to use a hop that’s high in free Thiols.
Pellet hops are more mucky than leaf but do allow for greater surface-area contact with the wort and are less likely to introduce oxygen (caught in all the gaps around and between leaves).
My changes here will be to add a proportion of my dry hops on day 0 to maximise bio-transformation of the dry hops (remember bio-transformation will also release all those Thiols from the precursors) and ferment at a cooler temperature (say 18C). I will add the rest of my dry hops around day 7 with a little sugar to create a CO2 blanket and drive out O2 from the head-space. Then fit a CO2 ballon and move the fermenter to a cool shelf in the brew-shed at 12C to capture those free Thiols from dry-hopping.
So now if the research is correct, I will have reduced Thiol-eating oxidase, I’ve reduced pro-oxidative metal ions (not eliminated, some are needed by the yeast), and I’ve loaded my wort with tropical fruity Thiol precursors ready for the yeast to cleave the Thiols.
Thiols are cleaved through bio-transformation using a yeast derived enzyme called beta-lyase. The Thiols are extremely volatile and will drift off at warmer temperatures far more easily than at lower temperatures. This means that fermentation should be at the lower temperature range in order to hold on to those Thiols. It also appears that higher pitch rates and yeast nutrients will help here.
During primary fermentation some of those Thiols will have drifted off so dry hopping after primary fermentation is beneficial but you need to use a hop that’s high in free Thiols.
Pellet hops are more mucky than leaf but do allow for greater surface-area contact with the wort and are less likely to introduce oxygen (caught in all the gaps around and between leaves).
My changes here will be to add a proportion of my dry hops on day 0 to maximise bio-transformation of the dry hops (remember bio-transformation will also release all those Thiols from the precursors) and ferment at a cooler temperature (say 18C). I will add the rest of my dry hops around day 7 with a little sugar to create a CO2 blanket and drive out O2 from the head-space. Then fit a CO2 ballon and move the fermenter to a cool shelf in the brew-shed at 12C to capture those free Thiols from dry-hopping.
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So that’s the plan. I was going to brew this tomorrow but decided to wait until I receive some yeast nutrient I’ve ordered so it might be a couple of days later. I’ll post the brew-day for anyone with an interest in all this lunacy. 
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While reading this last bit (some excellent info hb cheers ) I had a dooh moment when I realised I bought 500g of yeast nutrient and forgot to add it to my last brew. 
And I thought everything went to plan, ah well.
And I thought everything went to plan, ah well.
Releasing the bound Thiols sounds like an old Dr Who plot line, but this is all very intriguing. I do though think a hop stand over 80 is going to lose a lot of the aroma compounds due to volatility and isomerisation of the alpha acids which apparently is more of a problem for home brewers due to more surface area to volume compared to commercial set ups. However, Scott Janish has a bit in his New IPA book on this. Hop stand at 85 C retained more linalool than at 95 or 75 C. Flavour differences 95 C: citrus, spicy, esters; 85 floral and herby. 75 lowest in categories other than woody. Oxygen added at whirlpool or chilling through aeration releases more of the 'green onion taste thiol' apparently as well.
It does make me wonder whether 90-85 C might be the sweet spot for a hop stand which is higher than I expected, either that or add some at 90 then some at 80 C?
Anna
It does make me wonder whether 90-85 C might be the sweet spot for a hop stand which is higher than I expected, either that or add some at 90 then some at 80 C?
Anna
Nice work there - That's almost identical to my solution but I made a spiral rather than a ring, and I put 2mm holes instead of needle holes, so that I could re-circulate through it without the holes immediately blocking up with weeny bits of crud
Really appreciating the detailed notes, Mr H :hat:
So much to learn here. Many, many thanks for sharing
So much to learn here. Many, many thanks for sharing
The whirlpool is more about capturing those precursors. The aroma in theory is locked in the precursors which are non-volatile (Thiol is volatile when released during fermentation). The linalool I’m interested in is added in the first dry hop at day zero of fermentation and should be bio-transformed (some at least) into citronellol.
Your point about isomerisation is well made. I need to think about that.
So that’s the plan. I was going to brew this tomorrow but decided to wait until I receive some yeast nutrient I’ve ordered so it might be a couple of days later. I’ll post the brew-day for anyone with an interest in all this lunacy.
If you have a Wilko close by?!
https://www.wilko.com/en-uk/wilko-yeast-nutrient-50g/p/0022654
We do but I have some on order so I’m happy to wait a day or two, in part because I also have some Citra pellet hops coming with it. I only have leaf at the moment.
My head hurts! 
I’ve thought about it. I already account for isomerisation of whirlpool hops. I just need to make an adjustment for the higher temperature. That’s easy enough
Let’s see if all this makes any difference whatever. If it does, I’ll tell you what you need to do!My head hurts!
Let’s see if all this makes any difference whatever. If it does, I’ll tell you what you need to do!
Yes please!
