Tuesday, 25 May 2010

Adventures in beer design (Part III). Getting technical…..Hello Sugar!

This bit is a bit technical…so if you don’t want to read it I’ll understand.

Last time I talked about how gravity is a measure of sugar concentration and how that is related to alcohol. This time I’ll explain where the sugar comes from and how I’m going to control it to fit in with my beer design.

For the purposes of designing my beer I’m going to start with the final gravity. I’ve decided that it should be 1012 – 1014. Let’s say 1012 for the sake of argument. This should provide a reasonable mouthfeel but not make it too sickly sweet. There are a number of ways to control the final gravity.

The first is controlling the types of sugars that you convert during mashing by managing the mash temperature. (Mashing is basically the process by which starch in the malt is converted into sugars and is done by mixing milled malt (grist) with water…more on that later). As a general rule, temperatures over 65-66⁰C result in a sugar profile with more dextrinous sugars. The yeast cannot ferment these and so they remain in the beer.

The second is the choice of yeast. Some yeasts are high attenuating and some low attenuating. To explain it a different way some yeasts are well hard and will eat everything ignoring the rising alcohol levels (which, by the way, is one of their waste products). Others are a bit more sensitive and once they have eaten their fill they object to sitting in their own waste products and stop playing – basically they go to sleep. I have a particular yeast that tends to attenuate down to around 1012 on a good day – not the hardest yeast on the market but nor is it the softest.

The final way is to control the temperature at the end of fermentation. By cooling the beer quickly the yeast will stop fermenting. The drawback to this method is that unless you remove the yeast from the beer completely by filtering then when the beer warms up the yeast is likely to start fermenting again. Seeing as some of my beer is destined for cask and is unfiltered then this is probably not the best method.

Cool….that’s final gravity sorted. Now for original gravity(OG). First I’ll decide on the ABV (alcohol by volume). It’s certainly not going to be at the 140/- level of almost 9% mentioned in my last blog. Just to re-iterate, I want my beer to refreshing and flavourful and more-ish. Anything too strong in the alcohol department may mean that although people would love to have more they’re incapable of asking for it or unable to get up and walk to the fridge. Nope, it’s going to be a “small” beer – relative to the good old 19th century days of course. I reckon I aim for 4.4% ABV. So, I know I want a final gravity (FG) of 1012 and an alcohol of 4.4%. I plug that into the calculation (OG-FG) x 0.129 = ABV, do a bit of jiggling about and hey presto! I need an OG of 1046.

So far so good, but where do I get all the sugar to get this OG of 1046. Well, the sugars come from the malt. Rather than me boring you to death about malt and mashing here is a link to an excellent website that explains it all rather more entertainingly than I can.


Read it? Ok, you’ll be a malt expert by now. What it doesn’t explain is how brewers calculate how much malt they need to get the desired gravity. This may be a bit boring but bear with me if you really want to understand beer design. Otherwise feel free to go back to reading Hello magazine.

Each malt has a theoretical extract – that is the theoretical amount of sugar that you can extract from the malt. This varies according to the type of malt and the malting processes used. However, as an example, pale malt may have a theoretical extract of 300 l⁰/kg (litre degrees per kilogram). That is, 1 kg of malt will provide 300⁰ (degrees) of extract (sugar) in 1 litre of water. So if I want to brew 20 litres of beer starting with an original gravity of 1046 I need 20 litres x 46⁰ (for some reason you subtract 1000 from the OG) = 920 l⁰ (litre degrees). Therefore the amount of malt I would need is 920 l⁰/300 l⁰ per Kg = 3.06 Kg of pale malt. Simples!

Oh if only it was so! Actually I need to take into account a few other factors. Brewing equipment isn’t perfect and often the actual extract doesn’t match the theoretical extract. This is often determined by the type of kit and the process used and will vary from brewery to brewery. The efficiency of the brewery in extracting sugar is determined by trial. Some, more modern breweries, may have efficiencies over 100% but most small brewers are around the 80% mark. So, say the efficiency of the brewing kit is 80%, then I need to adjust my calcs. Instead of 920 l⁰ I need 920 x (1/0.8) = 1150. The amount of malt is then 1150/300 = 3.83 Kg.
The second factor I need to consider is if I am going to use more than one malt. For example I may decide for reasons of colour and/or taste that I want to add a small amount of crystal malt, say 4%. Crystal malt has an extract value around 260 l⁰/Kg. Therefore the amount of crystal malt required is (4% x 1150)/260 = 0.18 kg. The amount of pale malt will be (96% x 1150)/300 = 3.68 Kg.

Sooooo…just to summarise...I'm aiming for a 4.4% beer with an original gravity of 1046 and a final gravity of 1012. I guess the next decision is the type of malts to use……I’ll save that for the next blog.

Thursday, 13 May 2010

Adventures in beer design (Part II)…..do you realise the gravity of the situation?

I was looking at some old brewing data for Scotch Ales and was somewhat alarmed at the gravity of the beers. I mean this in the brewers sense of the word gravity rather than as in seriousness. However, these guys brewed at seriously high gravities.

I suppose I should try and explain the importance of gravity to brewing. Gravity, or more specifically, specific gravity, is a measure of the density of a liquid in comparison to the density of water. Brewers use this to measure the concentration of sugar in their worts. So what? Well…if you can measure the concentration of sugar then you have a fair idea how much alcohol you produce. You see yeast turns sugar into alcohol and as the sugar is turned into alcohol the gravity of the liquid falls. There are two main gravity measurements that brewers use. The first is Original Gravity, that is the concentration of sugar before the yeast goes into action. The second is Final Gravity, that is the concentration of sugar after the yeast has finished fermenting. From these two figures we can estimate the amount of alcohol produced using a formula that someone cleverer than me made up.

(Original Gravity – Final Gravity) x 0.129 = % Alcohol by Vol (ABV)

Here’s an example for a Scotch Ale from my old friend W H Roberts. This is a 19th century 140/- Scotch Ale.

Original Gravity = 1130.75
Final Gravity = 1061
Therefore the calculated ABV is a whopping 8.99%!! According to the literature the actual ABV was 8.86% so not a million miles away.

The other thing to note in this beer is the level of attenuation. What’s attenuation I hear you ask? Attenuation is the degree to which the yeast has managed to convert sugars to alcohol. Why is it important? (I wish you’d stop asking awkward questions). It’s important because it determines the amount of residual (unfermented) sugar remaining in the beer. This will affect the sweetness and the mouthfeel of the beer. A large amount of unfermented sugar (low attenuation) will result in a sweet tasting beer with a full mouthfeel. Conversely a beer that has been attenuated to high degree may be thin and unbalanced. The beer above has a very high level of unfermented sugar in it – not only did it start off with a lot of sugar in the first place (OG of 1130) but the level of attenuation was only 53.36% i.e. just over half the sugar was fermented. Attenuation is a funny thing and without going into the details there are two possible methods of determining it. One is called apparent attenuation and the other is called real attenuation. Let me know if you want to know more!!

Ok, so much for a 19th century Scotch Ale – high in alcohol and high in unfermented sugar, probably not to today’s drinker’s taste but hopefully it has given you an idea of how Original Gravity, Final Gravity and Alcohol content link together.

Next time I’ll talk explain how it all applies to my beer design.

Friday, 7 May 2010

Adventures in beer design Part I

Time to start designing beer number two. Where do you start when designing beer? First of all I need to decide what sort of style I want to make and how I want it to taste. I have few guiding principles – I want the beer to be refreshing and to have drinkability. That is, I want it to be more-ish but at the same time I want it to express the characteristics of the style of beer I am making. i.e. it needs to have flavour. So, basically, I want to produce a beer that refreshing but flavourful, is based on a style and can express the key characteristics of that style. Secondly I want the beer to be something that is unusual – that may be in terms of the style, name or a story behind the beer.

The first beer I produced, California Common, was all about a style that is seldom seen in the UK. It was a steam beer and was light in style. This time I think I will do something closer to home and am looking at brewing a Scottish ale. I’m a bit of a geek when it comes to brewing history and its influence on beer styles and the beers we have today. Edinburgh was once one of the UK’s great brewing centres and boasted numerous breweries. Delving into my brewing books and doing a bit of on-line research I see that Scottish beer had a distinct style. I won’t bore you with details of the how and why, but to summarise, it was malty and not very heavily hopped.

As with most beer styles the lines can be somewhat blurred and it can be difficult to categorize. However, for the sake of simplicity, I have decided to split Scottish ales into three sub-categories.

The first one is strong Scotch Ale which is typically high in alcohol. This can sometimes be called “Wee Heavy” and has an ABV (alcohol by volume) of around 6% and upwards. Hmm…I think I can rule this one out as the level of alcohol will mean that people will not be able to have more than a few before their legs give way! Also, I seem to remember drinking this in the form of a 90 shilling (the shilling system is a whole other story!) and it was quite sickly sweet.

The second is also Scotch Ale (just to confuse matters) but is of a much lower strength (below 4%). These were popular in the mid to late twentieth century and had widespread distribution in both Scotland and the North-East of England. Funnily enough, towards the latter end of the 20th Century this style was more popular in North-East England than in Scotland. Not sure if any of these exist anymore but I remember McEwan’s Scotch and I used to brew Whitbread Best Scotch at Castle Eden brewery. I guess this was a bastardisation of the strong Scotch Ales mentioned above and the strength was reduced for whatever reason. However, it seems to have been a very popular style amongst the miners and workers. This would suggest that it was a refreshing and sessionable beer. A possibility I think but I’m a bit concerned that a) it may be remembered as a kegged cheap beer and b) it may be confused with strong Scotch Ale.

The third category, I have designated as Scottish Ale (as opposed to Scotch) and further split into light, heavy and export (or 60/-, 70/- and 80/-, where “/-“ means shilling). These are well recognised in Scotland and there are huge variations from brewer to brewer. Commonly available on both keg and cask I don’t think these would be unusual.

Ok….so nothing is standing out and grabbing my attention. Once more I delve into the brewing books looking for inspiration and lo and behold – I think I’ve got it! You’ll have to forgive me for being a wee bit cagey about all the details but I have no idea who is reading this and don’t want to give too much away at this early stage but in a book about Scottish Beer published in 1847, the author talks about a “small beer” in Edinburgh which is “clear and very brisk, and, consequently, very agreeable to the palate.” This sounds encouraging in terms of a description.

So….how about I use this for inspiration and brew a Scottish Small Beer that has many of the characteristics of typical Scottish Ales (maltiness, low hopping rates) but has the qualities mentioned in the book(clear, brisk and very agreeable to the palate). It fits for a Scottish style beer that is brewed at somewhere between 3.5 – 4.5% ABV. Now we can get down to designing the actual product………….