Monday, 8 September 2008

The roastiness of Porter and Stout

I've been thinking a lot about roast. What was the relative roastiness of Porter and Stout?

My thoughts were prompted by comments on my assertion that Porter was roastier than Stout, based on the percentage of black malt in the grist. As Lachlan so rightly pointed out, allowance should also be made for the relative strength of the worts and the presence of brown malt.

So here's a relative roastiness calculation for various Porter and Stouts. The calulation is simple:

og of wort * %age of black malt * 1200 (EBC colour) +
og of wort * %age of black malt * 180 (EBC colour)
= roast quotient.

By this method, 1877 Reid Rg Porter is the roastiest, with a quotient of almost 9,000. The least roasty is 1851 Barclay Porter TT Porter with a quotient of just under 6,000.

Is this a fair method?

I've just thought of a method of checking this calculation. By comparing my 1914 Whitbread Porter and SSS. I know the brown and black malt content of both.


B. said...

Ron, are you trying to adjust for the total amounts of brown and black malts in the grists and the relative roastiness of those malts? If so,I think you may want to remove the "10" part of the gravities when carrying out this calculation. Comparing 1058 to 1094 only equates to a 3.4% increase in grain bill, 58 to 94 a 62% increase

For the 1877 Reid Rg Porter:

Then scaling down by 100,000 would yield more approachable numbers.

The full results for the 1877 table would then be:
Rg: 4.92
Crs: 3.40
S: 4.19
SS: 5.06
SSS: 5.90

Still, these numbers are very close and the relative roastiness of Brown and Black malts is a big variable. At the current assumption (black being 6.6 times roastier) the Rg does not have the most roast. If the ratio is made roughly 14:1 then the Rg becomes just as roasty as the SSS.

Ron Pattinson said...

b, thanks very much for your input. It makes a lot of sense. Maybe I should have used pounds per barrel OG?

I'm not sure how quantifiable "roastiness" is, but a rough estimation is still useful.

Numbers below 10 are good, too. EAsier to take in.

Good contribution.

Kristen England said...
This comment has been removed by the author.
B. said...

I like numbers, so it's no problem. Simply going with grain weights would make the calculations simpler, yeah.

Some calculated measure of roastiness certainly is interesting to have. Even with the uncertainty about comparing different grains I would have taken this approach myself, for whatever it's worth.

Kristen England said...

The big problem is that we are trying to put numbers to perceptions. Think a schwarzbier. Most are hella darker looking than tasting yes?

Don't make the mistake in thinking black malt is that roasty.

Ive brewed a ton with both brown and black malt. Ive found that a beer with 6% black malt will be no were near as roasty tasting as one with 2% black and 8% brown malt.

I think its more complicated than it looks for sure. Brown malt lends a big drying character to the flavor of the beer that makes the dark roasty flavors really jump out.

I also think there is a threshold in which you need to hit before a beer actually tastes really roasty. Percentages are great but the actual amount is much more imporant. I brewed the same beer with the same percentages of both brown (10%) and black malt (2%). The first had an OG of around 10P and the second was 20P. THe first had a very pleasant character reminiscent of Fullers London Porter. The second wasn't harsh but it was much more sharp and roasty.

Point short, we need to take the actual amounts of these things into the equation and not just the percentages. Meaning I think the amount of roastiness is not a linear curve but rather logarithmic with the gravitity being more important than the actual percentages. THis is true to a point and I think it will change based on every malt.

Also, the darkness in EBC (L) of a grain doesn't implicitly imply its more 'roasty'. The type and preparation of the malt are the most important things again. Husked vs dehusked black malt is a great example.

I can run a simple test. Use different amounts of black, brown, chocolate, Roast barley and have people indicate which is more roasty. Then do the same thing with a combination. Very simple and should give us a good range to work with. Of course this is subjective but thats what 'roasty' means right?

Anonymous said...

That you could never hope to quantify such a concept as 'roastiness' notwithstanding, I reckon this is an interesting theoretical exercise.


- You absolutely have to do what b. says. A SG of 1.000 is your 'zero' point - i.e. contains no malt.

- I'm not sure if you have such data, but it would be far more accurate if you used colour data from the period in question. The 1200EBC and 180EBC I grabbed are for modern malts, and not even from the same maltster.

- I suspect the 'truth' would lie somewhere between this estimate and your % of grist approach. Perhaps you could introduce some kind of scaling by absolute pale malt content? What I'm getting at is that a 1.040 beer with 100kg of black malt is likely to taste 'roastier' than a 1.100 beer with 100kg of black malt (for the same batch size).

- There are SO MANY other considerations here (beer age, water content, yeast strain, hopping...) that I don't think you could ever come up with anything close to accurate. But like I said, it's a fun exercise. I wonder if you could measure whatever it is that causes roastiness (carbonised somethingorother?) in a lab? That wouldn't help for 19th century beers much though...

Anonymous said...

Or you could brew them all and we could test for ourselves!

Anonymous said...