All things change over time. Historically, stout might have been a type of porter, but that might not be true today.
One reference for change in beer tradition is the existing Style Guidelines. These guidelines are not important because they define a particular historical style, but because they attempt to both exemplify historical standards and capture modern innovation in a single stroke. They are intensely debated precisely because they attempt to coalesce a modern understanding of beer with a historical one.
The style guidelines for stout and porter seem to imply at least a few distinctions between stout and porter that make it hard to call stout a type of porter in the modern age.
I feel obligated to go over the style guidelines in some depth, mostly because they are the basis of so much of our modern understanding and expectation of beer. I don’t share Ronald’s view that the BJCP is rubbish because they don’t cite sources — if they cited sources, it would be much more difficult for the guidelines to be living documents. I’ll leave the rest of that discussion for another day.
My original intent was to run over the various commonality between Porter and Stout and perhaps highlight some of the differences that the BJCP makes clear. As I did this, I found myself wanting a visual reference of the various components of these beers. I broke open Photoshop and made this:
(Available at desktop resolution for a 23″ monitor, 1900×1200, from my Flickr stream.)
It should be noted that “lighter” obviously doesn’t mean “light” for this series of beers, but “sweet” most certainly means that — sweet stout can be cloying for some drinkers due to the presence of lactose, an unfermentable sugar. Other items of note that are clear from examining this and reading the BJCP guidelines follow:
Every stout recommends the use of unmalted grains, particularly roasted barley.
Every stout recommends the use of unmalted grains, particularly roasted barley, but the only porter that allows this use is the robust porter, and the guidelines state that this is merely an optional addition, not an integral part of the style. The online recipes I found confirm that the presence of roasted barley in porter is fairly random.
- The grain bills for stouts seem to contain a lower percentage of pale malt than the grain bills for porters, with the exception of traditional Brown Porter recipes. Stouts tend to contain more adjuncts, chocolate, wheat, oatmeal, and caramel malts than their porter brethren.
- Most of this data reflects the ancestry of these beers according to Pattinson’s historical observation that Stouts were heavy Porters: Stouts mostly have higher bitterness levels, higher or similar alcohol content, darker color, and heavier mouthfeel, but maintain similar overall malt and hop bills, producing similar overall impressions of the final product. There are some outliers, but in general, a brown porter with extra pale malt might easily be a dry stout, a sweet stout (with lactose added), or an American stout. Similarly, a robust porter with a higher gravity looks very much like a Foreign Extra Stout or an American Stout. Baltic Porter is the only real outlier with it’s relatively low BU:GU ratio and lack of unmalted grains.
One man’s robust porter might be another man’s American stout.
There is an incredible amount of variance within a given style that isn’t well represented in this graphic. I tried to represent IBU levels with gradients, but ABV range was more difficult, and range of ingredient levels seemed impossible. I’ll examine this more in the next section when we look at modern porters and stouts and my impressions of them, but for now, it’s worthwhile to say that one man’s robust porter might be another man’s American stout.
- The styles that we refer to as stout and porter, as a whole, are extremely diverse, and there is a lot of bleed between the two. I’ll get into this more when I investigate specific beers. For now, it is enough to mention that some porters will qualify as stouts (particularly dry robust porters with small amounts of roasted barley in the recipe), and some stouts will qualify as porters. Additionally, there are many beers that are clearly not porters according to the style guidelines, but are definitely stouts, and vice versa.
The style guidelines for stout and porter seem to imply at least a few distinctions between stout and porter that make it hard to call stout a type of porter in the modern age. The ubiquitous presence of unmalted grains in stouts, their generally higher gravity ranges, reduced pale malt presence, and the higher average bitterness and mouthfeel of stouts all imply that calling a porter a type of stout is at worst confusing and at best meaningless to the modern drinker.
Designing a porter recipe and making it into a stout recipe is no longer a matter of simply taking first-runnings off the wort and fermenting that, increasing the total grain bill of the recipe, or reducing the amount of wort extracted from a given grain bill. Crafting a style-fitting stout recipe requires much different attention to malt bill and hop profile than crafting a style-fitting Porter recipe. As such, I think it is safe to say that the style guidelines define stouts and porters differently, and it is not sufficient or useful to qualify one as a type of the other.