Tuesday, 19 August 2014

Mind your IBUs

This is just a quick note to explain what an IBU is and how to work out how many of them your homebrew's got. It's also the 100th post on this blog. What a milestone!

IBU stands for International Bittering Units and the bitterness of a beer can be quantified and expressed in IBUs. One IBU is the same as one milligram of isomerised alpha acid per litre of beer.

The proper way to work out the bitterness of a beer is by analysing a sample in a laboratory but if, like me, you don't have a spectrophotometer, then you can make do with using a figure calculated from the hop additions.

It's convenient to use brewing software that does this for you but it's just as easy to work it out for yourself. Here's how:

Each hop addition adds bitterness to the beer and the bitterness from all the additions can simply be added together to give the total bitterness. To work out how much bitterness any given hop addition provides, you just do the following:
  1. Multiply the grams added by the alpha acid percentage of the hop. This gives you a total amount of alpha acid available from that addition. (in grams)
  2. Multiply this by the utilisation rate, which is the percentage that gets isomerised. I use 26% for 60 minute additions and 5% for 0 minute additions. This gives you a total amount of isomerised alpha acid. (still in grams)
  3. Multiply this figure by 1000 to get milligrams and divide by the batch size to get a per litre figure. This is now your IBU figure for that particular addition.
For example, if you add 15g of a 12%aa hop at 60 minutes, then you get:
  1. 12% of 15g is 1.8g
  2. 26% of 1.8g is 0.468g
  3. 0.468g x 1000 / 26l = 18 mg/l or 18 IBUs.
Repeat for each hop addition and add them all together to get the total. This could get pretty tedious so instead of doing the sums each time, I've put it all in a spreadsheet which works it out automatically. All I have to do is alter the alpha acid percentages and the weights. The beauty of this is that you can fiddle around with your own utilisation rates.

A few brewers, such as Marble, are starting to cut out the middle hop additions and add the majority of the hops at flameout, making up any remaining bitterness with a small addition at the start of the boil.

According to the Tinseth numbers, which most of the brewing software use as default, flameout additions don't contribute any bitterness. In reality this isn't the case though. I've spoken to one brewer, who does have a spectrophotometer, who says they get 10-14% utilisation from flameout hops. Another pro brewer suggested 4-5% is a good ballpark figure to use. I suspect that for normal homebrew kit, with a 15-20 minute hop stand, a figure somewhere in between is going to be right.

It's important to remember that the utilisation percentages are approximate and will vary a lot depending on the kit you use but the above figures are good enough to get started. If you're adding a big flameout addition and are using a generic brewing calculator to work out the IBUs, then be careful, because the chances are your beer could end up more bitter than expected.

 The only way the flameout hops add no significant bitterness is if you cool the wort down to below 80C before adding them, which means little isomerisation takes place. This is what some brewers do, with great success. It's just another way of doing things but as ever, it's probably best to get brewing and see what works for you.

Brew 17 - Vienna IPA

5.9% IPA

Brew date 27/6/14

This was my entry for The Great British Homebrew Challenge 2014, a competition run jointly by Thornbridge Brewery and Waitrose. The winning entry would see their recipe scaled up and brewed by Thornbridge and stocked in Waitrose stores nationwide. Quite a prize!

The first major hurdle with competitions is deciding what to enter, so I thought hard about what kind of beer might have a chance of success. I figured the beer would have to appeal to a wide cross-section of drinkers and therefore be commercially attractive. So no rhubarb and marmite-infused saisons then. I thought it should also be at least a bit different to any of Thornbridge's current offerings.

I narrowed it down to two possibles that appealed to me; a Belgian golden ale or an IPA made with Vienna malt. As I had never used Belgian yeast before, I opted for the Vienna IPA as a safe choice because I could just use WLP001 yeast and hopefully hit the numbers pretty well.

I wanted to make it quite full-bodied, not too dry and quite dark in colour for an IPA, with a complex flavour so I added a bit of biscuit malt and some caramalt. I decided upon using Columbus, Citra and Ahtanum hops as I thought they would create a good range of taste and aroma, from dank through to floral. A pale ale water profile was used, high in sulphates to keep the bitterness from becoming too harsh.

Again, I went for just three hop additions; at 60 minutes, 0 minutes and a dry hop. The bittering addition was a small amount of Columbus and the big 0 minute addition was 1/3 Columbus and 2/3 Citra, providing about 60% of the IBUs.

I'd been a bit disappointed not to hit the numbers very well when making my last beer, so I put some considerable effort into researching brewhouse efficiency and attenuation rates and such things. It turned out that to end up with a 5.9% ABV beer I would need to collect 32 litres of wort with a pre-boil gravity of 1.046. There should then be 26 litres left in the kettle after the boil is complete, with an original gravity (OG) of 1.057. This should then ferment down to 1.012, giving a 5.9% beer. Quite a tall order!

Happily, this brew behaved itself impeccably and hit every number spot on. Seeing the hydrometer bobbing about at 1.057 after hours of toil was a very nice sight. The pH of the mash was even 5.2, exactly as it should be. It was as though the stars had aligned and everything fell into place.

I bottled with 100g of dextrose, enough to get a carbonation of about 2.4 vols. After two weeks it was lovely and fizzy and tasting delicious. This beer definitely has the best hop aroma out of any I've made, with the Ahtanum quite prominent. The Columbus and the Citra seem to play very nicely together as well. I'm really pleased with how it turned out and hopefully the judges think so too. Fingers crossed!

Edit: They did think so! 

Brew 15 - Propaganda (2)

6.3% Black IPA

Brewday 11/5/14

A bit of a belated post here. Just continuing the theme of writing up notes on my last few brews, to get up to date. It's fair to say that my most successful brew up until this point had been Propaganda, my black IPA, so I decided to have a crack at another one.

I tweeted that I was trying to plan a black IPA and didn't know whether to use any crystal malt. I received a few replies and among the people responding was James Kemp, or JK, formerly of Fullers, Thornbridge and Buxton breweries, who knows a thing or two about black IPAs to say the least.

The answer to my question by the way, was yes. About 5% crystal malt will help to darken the colour a bit, limiting the amount of Carafa III needed and would also help to support the massive dry-hopping needed. JK also very helpfully supplied me with some further advice regarding water manipulation and hop schedules. Thanks mate!

The grain bill I ended up with looked like this:

Maris Otter 5000g (69.4%), Munich 1000g 13.9%), Crystal 120EBC 350g (4.9%), Carafa Special III 325g (4.5%), Chocolate Malt 175g (2.4%), Wheat Malt 350g (4.9%)
The important thing was to use about 5% medium crystal and to limit the Carafa to the 4.5% region, to minimise the roasted flavours. I didn't add the Carafa at the end but instead mixed the whole lot in together. 


I decided to use a single hop, Citra, with a single bittering addition of 28g at 60 minutes and a flameout addition of 175g. JK said that the 0 minute additions do add bitterness and suggested using 4-5% utilisation when working it out. With such a large amount being used, the effect is substantial and with this brew, over half the bitterness is added after flameout.

Unfortunately, when took a gravity reading, it was only 1.060. I'd been hoping to make a beer nearer the 7% mark, so it was nowhere near. In hindsight, all I could think of was that I'd not broken up the grain properly when mashing in and had left some doughballs behind. I went and bought a big stainless mash paddle for next time.

I carried on and the ferment finished at 1.012, making the finished beer 6.3%. I dry hopped with 200g of Citra pellets, which makes a rate of about 9grams per litre.

I had been gradually cutting down on the carbonation over the last few brews but probably went too far with this one and should have gone for a bit more. It eventually got to the point where it was just about carbed enough but the beer still needed swirling round in the glass to get a decent head. I'd try to get it a bit fizzier next time.

Overall, I was pleased with the end result, which was definitely black and had a really good hop aroma. I'd use some other hops next time, probably Columbus, Citra and Nelson and of course try to iron out some of the little mistakes I made. As always, I learnt a lot though, which is the main thing!

Wednesday, 13 August 2014

Brew 16 - The Beer That Went Clear

5.0% American Pale Ale

Brewday 31 May 2014

There were a lot of firsts in the making of this beer. It was the first time I'd cold crashed with a fridge, the first time I'd fined with gelatin and the first time I'd done proper water manipulation. I obtained a set of mini-scales to weigh the salts on, as can be seen below:

There was no special plan for the beer, it was just an exercise in trying out some new techniques more than anything, so I decided a 5.0% pale ale would be just fine for this.

Grain Amt (g) Amt (%)
Maris Otter Low Colour 4600 92.0
Caramalt 250 5.0
0 0.0
0 0.0
0 0.0
0 0.0
Torrified Wheat 150 3.0
Total 5000

Time 60 10 0 Dry Total
Hops Citra Citra Citra T90
Alpha (%) 14.0 14.0 12.8
Amount (g) 7 125 125 257.0
Amt / L 0.3 0.0 5.0 5.4
Total AA (g) 0.98 0 17.5
Gravity 1.052 1.052
Utilisation 0.26 0.05 0
IBU (mg/L) 10.2 0.0 35.0 0.0 45.2

Sorry for the poor layout. The recipe is copied from the spreadsheet I use. I'll try to find a better way of displaying them in the future. The lower table shows three hop additions; 7g at 60 mins, 125g at 0 mins and a 125g dry hop.

The last few beers had had a fair bit of "craft haze" about them so I paid a lot of attention to technique during this brew, with the aim of trying to get it clearer. I recirculated the first runnings for longer and went out and bought a second-hand fridge off ebay halfway through, which was useful as I could now cold-crash properly. This, combined with using gelatin as a fining agent, worked wonders and resulted in the clearest beer I'd ever made.

Unfermented wort

Before cold crash
After cold crash
I took a case along to my mate Dan's 40th birthday party, where it went down very well. Having a dedicated brew fridge is really useful and I now don't know how I managed without one for so long!

Open for business...

Okay, it's been a very long time since the last post here - ever since we discovered that Untappd is a much better way of sharing beer reviews in fact. Still, I haven't been updating the homebrew posts either, which is remiss of me.

From now on, this blog will mainly be a log of my home brewing journey and general musings on the subject. I've updated the pages at the top of the blog to reflect this.

The lack of posts doesn't mean I haven't been brewing - far from it. Well, actually Ruth and I have been renovating an old house so that takes up most of our time. I've still been managing to do at least one brew a month though, so not too bad.