Looking at Graham Wheeler's "Beer Engine" I see the default alpha acid values he sets for his hops are much less than the ones from my local homebrew shop. For example, he has Goldings at 5.7, and Fuggles at 4.9. Mine are 7.5 and 5.26 respectively.
Secondly, even using the values he supplies, the Engine doesn't give the same EBU values as in his book "Brew Your Own Real Ale At Home". His Eldridge Pope "Thomas Hardy's Country Bitter", for example, uses 38g of Fuggles and 32g of Goldings for the full boil time of 2 hours. According to the Engine, at the AA values set in it for these hops, this will give 40 EBUs in the finished beer. The recipe in the book states the bitterness as 27 EBU. A significant difference!
This has totally confused me and, before I start my next AG brew, it would be very much appreciated if someone could explain what's going on, please.
Guy
Alpha acid and EBU values
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guypettigrew
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Graham
Re: Alpha acid and EBU values
You obviously have a first edition. There are a couple of issues. In that book I used a fixed hop utilisation of 20% irrespective of the beer being brewed. This is low, but was deliberately done to compensate for the poor quality of hops available in (all but about a handful of) home brewing shops twenty years ago. They were usually packed in ordinary polythene bags, not airtight, stored on shelves in the main area of the shop, at ambient temperature and under fluorescent light. The actual alpha-acid content was not usually specified in those days either. I had little confidence in the hops available to the average home brewer then.
I still think that a fixed percentage utilisation is as good as, if not better than, the popular utilisation prediction formula, but these days I would use 25-27%. - 25% for a typical beer and 27% for a more highly hopped beer.
Another issue is that I assumed 10% wort loss due to hop absorption and for stuff that gets left behind after all the syphoning and transferring that takes place. This was done to ensure that novice brewers achieved or even exceeded the target gravity of the beer at the specified volume. It was rather too generous though. In the second edition I reduced the wort loss to a more reasonable 5%, and in the third edition I abandoned the wort loss all together.
In reality, wort loss should be taken into account, because if you lose wort you also lose bitterness. However, it is a highly variable parameter; different people's set-ups have different dead spaces, some people sparge their hops and some people do not. Some people boil their hops in a bag and give them a squeeze afterwards - others do not. With the advent of brewing software, people have a habit of shoving the figures into their favourite software and then wondering why the figures don't tally. As far as I am aware, none of the current brewing software, including my own, compensates the bitterness for wort loss and they give errors because of it. However, those errors are transparent, so nobody notices.
Go into BeerEngine defaults and turn off boil time compensation and gravity compensation, and then set base utilisation to 20%.
If you use 26.3 litres as target volume, to account for the 10% wort loss, then it will match the recipes in the first edition. The Fuggles are 4.5% in the first edition, not 4.9%.
Like I said, I probably would not do it that way today
I still think that a fixed percentage utilisation is as good as, if not better than, the popular utilisation prediction formula, but these days I would use 25-27%. - 25% for a typical beer and 27% for a more highly hopped beer.
Another issue is that I assumed 10% wort loss due to hop absorption and for stuff that gets left behind after all the syphoning and transferring that takes place. This was done to ensure that novice brewers achieved or even exceeded the target gravity of the beer at the specified volume. It was rather too generous though. In the second edition I reduced the wort loss to a more reasonable 5%, and in the third edition I abandoned the wort loss all together.
In reality, wort loss should be taken into account, because if you lose wort you also lose bitterness. However, it is a highly variable parameter; different people's set-ups have different dead spaces, some people sparge their hops and some people do not. Some people boil their hops in a bag and give them a squeeze afterwards - others do not. With the advent of brewing software, people have a habit of shoving the figures into their favourite software and then wondering why the figures don't tally. As far as I am aware, none of the current brewing software, including my own, compensates the bitterness for wort loss and they give errors because of it. However, those errors are transparent, so nobody notices.
Go into BeerEngine defaults and turn off boil time compensation and gravity compensation, and then set base utilisation to 20%.
If you use 26.3 litres as target volume, to account for the 10% wort loss, then it will match the recipes in the first edition. The Fuggles are 4.5% in the first edition, not 4.9%.
Like I said, I probably would not do it that way today
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guypettigrew
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Re: Alpha acid and EBU values
Hi Graham
Many thanks for the helpful reply. Yes, my copy of your book is from 1993. A genuine first edition!
It's many years since I've made beer and I well remember hops being in plastic bags. Discovering they are now vacuum packed in foil, with the alpha acid value printed on them, was a very pleasant surprise.
So, from what you've told me, is it right to stay with the EBU values and the percentages of the different hops in your recipes, plug in the alpha acid values on the hop packets, and then allow the Engine to calculate the weights of hops to be used?
Thanks.
Guy
Many thanks for the helpful reply. Yes, my copy of your book is from 1993. A genuine first edition!
It's many years since I've made beer and I well remember hops being in plastic bags. Discovering they are now vacuum packed in foil, with the alpha acid value printed on them, was a very pleasant surprise.
So, from what you've told me, is it right to stay with the EBU values and the percentages of the different hops in your recipes, plug in the alpha acid values on the hop packets, and then allow the Engine to calculate the weights of hops to be used?
Thanks.
Guy