Heriot-Watt Brewing and Distilling course

[Twostage]

Oh I’m planning on doing so, but realising that I’ve some weeks to go before I can give a coherent view on it. Some of the articles on wort boiling are at the level where I don’t understand the terms being used, and I have to read them in short sessions as otherwise I just feel cross eyed. One of the reasons I’m not posting at the moment is that I’m not drinking - well I’ve had 2 units ( a whisky and a small glass of fizz) in the last 7 weeks so far, and I felt bad about even that. So it’s a bit difficult looking at all the yummy things you are all drinking in the ‘what are you drinking’ threads !

I'd call 2 units in 7 weeks as complete abstinence (pressed post too fast).

I'm really hoping there isn't compelling science against a 30 min boil as I'm into the routine of 30 min mash and 30 min boil (plus I've dipped my toe in the water of no chill).

 

[Ross1974]

Definitely following this one " for the science ".

Ready to start my second batch, so I'll be posting up tonight on that one.

 

[DocAnna]

Some of you will know I’ve been a bit quiet and away from the forum. Lots of reasons, some of which have been purely time related and the intensity of the HW course. I’m going to try to provide some catch up and updates here. The module I’ve been doing this semester is on boiling and fermentation, so far covering wort boiling, hops and this last week has been all about yeast. In theory this next week is called a ‘consolidation week’ however then amount of learning material in week 5 has been much more than the previous weeks, and I think is intended as 2 week’s worth. It’s been eye opening, made me appreciate I knew far less about boiling, hops and fermentation than I thought I knew, and is going to take a lot of thinking about for how it will inform my own brewing.

I’ve not been brewing myself for quite a while now, in part the time issue, in part because I wasn’t drinking at all for a couple of months (ok some tiny lapses but pretty much). However as this thread is on the HW course, to mention that this module is biology and chemistry based rather than the maths and engineering of last year. It has demonstrated to me that I’m far more comfortable with maths and engineering than I am chemistry - which feels like a very long list of chemical names. The biology part is ok though, reassuringly given my job really! I’m not going to be able to summarise everything here so will try to bring what I’ve learnt into other discussions. There are some headline takeaways though.

• Length and vigour of the boil is important, but not all the functions of the boil require the same conditions all the way through. The length of boil required will depend significantly on the type of base grain, amount of roasted malts used, pH, and vigour of the boil.
• It is vitally important for an initial rapid cooling after the boil to below 80 deg to avoid hot side oxidation - and yes this is a well recognised issue (That was an eye opener - hot side oxidation does exist!)
• Oxygenation prior to pitching is not a yes no answer, and too much will reduce the final alcohol level and change flavour profiles.
• Oxygenation prior to pitching dried yeast isn’t necessarily a good thing
• Oxygenation is important if using liquid yeast or reusing yeast from a previous batch
• Acid washing of yeast prior to pitching has a strict schedule of how to use if at all, is strictly 1 to 2 hours prior to pitching, and you mustn’t store acid washed yeast. Though all bets are off on this if it’s a whirlpool hopped beer.
• Hop extracts and modified hops are a good thing and not cheating, though the hops that are light strike proof do seem a bit artificial to me.
• Dried yeast viability at room temperature drops a whole lot faster than at fridge temperature - so dried yeasts should be kept fridged too.
• Rehydrate your dried yeasts if you can do so with the right hygiene precautions, don’t if you can’t . Rehydration at highest temp (35 deg C) for ale yeasts reduces cell damage than if using pitching temp liquid - yep that’s an odd one, turns out it’s to do with the different forms of the yeast cell membrane at temperatures and dried.

There’s lots and lots more, stuff I need to think about including the impact of re circulation late in the boil, of the impact of stirring and all the stuff about yeast strain. Oh and the SG dropping to target is not even close to when fermentation is done. Phew, head hurts a bit with all this.

 

[Twostage]

Some of you will know I’ve been a but quiet and away from the forum. Lots of reasons, some of which have been purely time related and the intensity of the HW course. I’m going to try to provide some catch up and updates here. The module I’ve been doing this semester is on boiling and fermentation, so far covering wort boiling, hops and this last week has been all about yeast. In theory this next week is called a ‘consolidation week’ however then amount of learning material in week 5 has been much more than the previous weeks, and I think is intended as 2 week’s worth. It’s been eye opening, made me appreciate I knew far less about boiling, hops and fermentation than I thought I knew, and is going to take a lot of thinking about for how it will inform my own brewing.

I’ve not been brewing myself for quite a while now, in part the time issue, in part because I wasn’t drinking at all for a couple of months (ok some tiny lapses but pretty much). However as this thread is on the HW course, to mention that this module is biology and chemistry based rather than the maths and engineering of last year. It has demonstrated to me that I’m far more comfortable with maths and engineering than I am chemistry - which feels like a very long list of chemical names. The biology part is ok though, reassuringly given my job really! I’m not going to be able to summarise everything here so will try to bring what I’ve learnt into other discussions. There are some headline takeaways though.

• Length and vigour of the boil is important, but not all the functions of the boil require the same conditions all the way through. The length of boil required will depend significantly on the type of base grain, amount of roasted malts used, pH, and vigour of the boil.
• It is vitally important for an initial rapid cooling after the boil to below 80 deg to avoid hot side oxidation - and yes this is a well recognised issue (That was an eye opener - hot side oxidation does exist!)
• Oxygenation prior to pitching is not a yes no answer, and too much will reduce the final alcohol level and change flavour profiles.
• Oxygenation prior to pitching dried yeast isn’t necessarily a good thing
• Oxygenation is important if using liquid yeast or reusing yeast from a previous batch
• Acid washing of yeast prior to pitching has a strict schedule of how to use if at all, is strictly 1 to 2 hours prior to pitching, and you mustn’t store acid washed yeast. Though all bets are off on this if it’s a whirlpool hopped beer.
• Hop extracts and modified hops are a good thing and not cheating, though the hops that are light strike proof do seem a bit artificial to me.
• Dried yeast viability at room temperature drops a whole lot faster than at fridge temperature - so dried yeasts should be kept fridged too.
• Rehydrate your dried yeasts if you can do so with the right hygiene precautions, don’t if you can’t . Rehydration at highest temp (35 deg C) for ale yeasts reduces cell damage than if using pitching temp liquid - yep that’s an odd one, turns out it’s to do with the different forms of the yeast cell membrane at temperatures and dried.

There’s lots and lots more, stuff I need to think about including the impact of re circulation late in the boil, of the impact of stirring and all the stuff about yeast strain. Oh and the SG dropping to target is not even close to when fermentation is done. Phew, head hurts a bit with all this.

Lot of interesting stuff there and a few teasers . Re: the hop extracts bit I'd been thinking recently about trying it as there seems to have been some recent innovations. I was coming at it from the reduced wastage/less trub angle.

 

[Ross1974]

• It is vitally important for an initial rapid cooling after the boil to below 80 deg to avoid hot side oxidation - and yes this is a well recognised issue (That was an eye opener - hot side oxidation does exist!)

So no chill is out then? Hmm.... I better get my immersion cooler out then. Weird thought though. The last brew i did, which was a hefeweizen, was not chilled but ledt in the fermenter to cool overnight prior to pitching. It was much better than the previous brew, which ended up down the toilet, and it was quick chilled.
My next IPA, which im just preparing, was going to no chill too. But now I am wondering if its the right thing to do.

Great updates though. Still "enjoying" it?

 

[DocAnna]

So no chill is out then? Hmm.... I better get my immersion cooler out then. Weird thought though. The last brew i did, which was a hefeweizen, was not chilled but ledt in the fermenter to cool overnight prior to pitching. It was much better than the previous brew, which ended up down the toilet, and it was quick chilled.
My next IPA, which im just preparing, was going to no chill too. But now I am wondering if its the right thing to do.

Great updates though. Still "enjoying" it?

Thank you, yes still enjoying it - not quite so much for the two ‘hop weeks’ which were heavy on the chemistry side. I strongly suspect the no chill method at home brew scale is fine on two counts, that the initial cooling is really quite quick, and if not disturbing it after the boil that the risks of oxidation are reduced. Another consideration is that the lack of rapid cooling increases DMS levels after the boil -which in a Hefeweizen may be desirable.

 

[Twostage]

So no chill is out then? Hmm.... I better get my immersion cooler out then. Weird thought though. The last brew i did, which was a hefeweizen, was not chilled but ledt in the fermenter to cool overnight prior to pitching. It was much better than the previous brew, which ended up down the toilet, and it was quick chilled.
My next IPA, which im just preparing, was going to no chill too. But now I am wondering if its the right thing to do.

Great updates though. Still "enjoying" it?

I'm a no chiller too. Perhaps I should let DocAnna answer but maybe it depends on what rapid means. I would guess large commercial volumes would take a lot of chill action to get below 80 where small volumes we brew would naturally drop in a similar time.

 

[Twostage]

I really must type faster (or shorter posts) lol

 

[Ross1974]

Great stuff. Loving the updates. Be good to see what the science actually says vs years of luck and experience

 

[Agentgonzo]

The length of boil required will depend significantly on the type of base grain, amount of roasted malts used, pH, and vigour of the boil.

This isn't surprising TBH, but would also explain why some people get such different results. Boil vigour varies enormously from what I have witnessed and isn't often quoted by those on differing sides of the religious war.

I've heard boil off rates as low as 4% in an hour, and as high as 25% in an hour. Not surprising that 30 min / 60 min boil results vary wildly. Also ph.

 

[Agentgonzo]

Oxygenation prior to pitching dried yeast isn’t necessarily a good thing

Interesting. It would be good to know more.

Dried yeast viability at room temperature drops a whole lot faster than at fridge temperature - so dried yeasts should be kept fridged too.

Which I think is what most home brewers do. But no idea how long it's sat on a shelf in a shop before it gets to you.

 

[Agentgonzo]

It is vitally important for an initial rapid cooling after the boil to below 80 deg to avoid hot side oxidation

So no chill is out then

I'm now wildly guessing, but no chill cubes generally get filled to the brim and sealed. So I wonder whether "no chill (in cubes)" works because this particular method excludes the oxygen, and if you did a no chill in an open (enough) vessel, then you'd hit problems?

 

[Northern_Brewer]

Interesting. It would be good to know more.

Not oxygenating dried yeast is a well-known thing, the way dried yeast are prepared maximises sterols which are needed for new cell membrane and hence cell division, and making sterols is what you need the oxygen for. So the typical dried yeast have enough sterols for 3 cell divisions or so, and they typically manage 3-4 divisions in a typical homebrew fermentation so they don't really need any more sterols, and hence oxygen.

The other thing with oxygen is that individual strains vary hugely in how much they need of it, again contributing to the "no right answer" dilemma.

Which I think is what most home brewers do. But no idea how long it's sat on a shelf in a shop before it gets to you.

To put shelf-lives in perspective, I had some dry bread yeast sat at the back of a cupboard at ambient for nearly 20 years and it was still maybe 30-40 % effective at raising bread. Didn't bother doing a full viability test on it, but you're looking at a half-life of over a decade in that case, even at ambient.

The other thing with eg acid washing is that at homebrew scale, you're as likely to add as many contaminants through the extra fiddling with the yeast, as you wash out of it, so it's generally counterproductive at our scale.

 

[Agentgonzo]

Not oxygenating dried yeast is a well-known thing, the way dried yeast are prepared maximises sterols which are needed for new cell membrane and hence cell division, and making sterols is what you need the oxygen for. So the typical dried yeast have enough sterols for 3 cell divisions or so, and they typically manage 3-4 divisions in a typical homebrew fermentation so they don't really need any more sterols, and hence oxygen.

The other thing with oxygen is that individual strains vary hugely in how much they need of it, again contributing to the "no right answer" dilemma.

Yeah. All of the above is why you don't _need_ to oxygenate wort with dried yeast, but doesn't say why oxygenating with dried yeast could be a _bad_ thing.

 

[Northern_Brewer]

Yeah. All of the above is why you don't _need_ to oxygenate wort with dried yeast, but doesn't say why oxygenating with dried yeast could be a _bad_ thing.

Well the devil makes work for idle oxygen - if there's oxygen in the wort then it will end up oxidising hop/malt compounds rather than going into yeast sterols. If it doesn't need to be there, you're better off without it.

 

[Agentgonzo]

Well the devil makes work for idle oxygen - if there's oxygen in the wort then it will end up oxidising hop/malt compounds rather than going into yeast sterols. If it doesn't need to be there, you're better off without it.

This is one of the things I've never fully understood (maybe Anna knows now, but I don't want to ask because this thread has turned into 100 questions ).

But as far as I understand it (again, may be wrong), the yeast uses up sterols when it multiplies/buds. At which point the mother/daughter cells would use to oxygen to build up sterols again. Essentially multiplying until all the oxygen/sterols are used up.

This is how we build starters and stir plates to continually oxygenate the wort to aid multiplication. So why is dried yeast suddenly different that it won't use up extra oxygen?

 

[DocAnna]

This is how we build starters and stir plates to continually oxygenate the wort to aid multiplication. So why is dried yeast suddenly different that it won't use up extra oxygen?

Yep that’s the problem. The dried yeast will use the extra oxygen, will create higher yeast cell mass, more of the sugars used to make and service yeast, less into alcohol, and create different flavour compounds. There’s some good graphs on this on the course. My take in this is that with oxygen yeast is doing it’s own thing, not ‘our thing’ that we put it there to do.

 

[Northern_Brewer]

But as far as I understand it (again, may be wrong), the yeast uses up sterols when it multiplies/buds. At which point the mother/daughter cells would use to oxygen to build up sterols again. Essentially multiplying until all the oxygen/sterols are used up.

I can't remember the exact numbers so don't quote me but say dried yeast have 16% of sterols in their membranes and they need at least 2%. In the absence of oxygen the first cell-cycle (as opposed to "brewing gyle") generation will have 8%, and the generation after that will have 4% and the one after that 2%.

All those generations will have >2% sterol in their membrane, so why should they invest resources in building the machinery to make more sterols? They're better off investing those resources in the pathways that make more DNA or whatever. So if they don't build that machinery, they won't make any sterols and won't use any oxygen. They only need to build that machinery (and hence use oxygen) once their sterol levels are in danger of dropping below 2%. Meanwhile the oxygen is busy staling the hops and malt.

It's hugely more complicated than this, but it's a reasonable first approximation.

This is how we build starters and stir plates to continually oxygenate the wort to aid multiplication.

Well, erm - the purpose of stir plates is more about keeping yeast in suspension and in contact with "fresh" wort than it is about oxygen....

 

[Agentgonzo]

Yep that’s the problem. The dried yeast will use the extra oxygen, will create higher yeast cell mass, more of the sugars used to make and service yeast, less into alcohol, and create different flavour compounds. There’s some good graphs on this on the course. My take in this is that with oxygen yeast is doing it’s own thing, not ‘our thing’ that we put it there to do.

That makes perfect sense - thank you .
Also @Northern_Brewer , makes perfect sense as well. Thank you both

 

[Wynne]

I'm a no chiller too. Perhaps I should let DocAnna answer but maybe it depends on what rapid means. I would guess large commercial volumes would take a lot of chill action to get below 80 where small volumes we brew would naturally drop in a similar time.

@Twostage I think you have hit the nail on the head here. I brew at a 17 barrel (ca. 2700 litre) brewery and the transfer from kettle to fermenter via a plate heat exchanger takes 90-120 minutes.