Thursday, February 13, 2014

Scottish Stout Tasting – Body & Mouthfeel

The mouthfeel of beers is one of the more complex aspects of brewing. I often see it simplified as final gravity equals body. Sure mashing toward the upper-end of the saccharification range results in more alpha amylase activity, which produces a higher proportion of unfermentable dextrins, which in turn leaves both a higher final gravity and a thicker body. However, this is not the same as using a lower attenuating yeast strain, which will leave a higher percentage of fermentable sugars behind. Assuming identical original and final gravities, a hotter mash will produce a beer with more body, while a less attenuative yeast will produce a beer with more residual sweetness.

Carbohydrates aren’t the only source of body in beer however. Proteins from the malt and glycerol from the brewer's yeast are also options for enhancing body. Beta glucans, a type of soluble fiber, gets a “maybe.” While grains that contain beta glucans (like oats) tend to create a silky body, there hasn’t been enough study yet (to my knowledge) to conclusively state that beta glucans are the source.

Carbonation plays a tricky role. In a beer that has a thick body already, I find that higher carbonation wrecks the mouthfeel. There are few things more disappointing than an over-carbonated imperial stout for example. However, for a beer that is thin, higher carbonation can actually improve the body by distracting from the watery mouthfeel. Think gueuze or Berliner weisse. Tannins from oak play a similar role, a small amount can enhance body, while excess leave a rough dryness.

Scottish Stout, next to a dying fire.All this is to say that despite a relatively high final gravity (1.017), and moderate-low carbonation, the body on my second batch of Scottish stout didn’t reach quite where I wanted it. Could it be excessive oak tannins? Or was it the lack of protein from the highly-modified Maris Otter? Or maybe my expectations are too high for a beer that is only 5.4% ABV? Otherwise it is a very enjoyable beer, and hopefully I’ll get just a bit closer next time.

90/- Scottish Stout #2

Appearance – The head is a stout-appropriate tan, and wonderfully dense, sticky, and lasting. The body is black, with only a hint of ruby at the bottom where the light can make it through. Held at an angle the beer looks to have dropped pretty clear in the keg.

Smell – The nose is lightly roasted coffee to start. Nothing reads burnt or charcoal (although the fireplace is adding a hint of smoke). There is a deeper maltiness behind the roasted barley that you wouldn’t have in say an Irish Dry Stout, toasted bread and toffee. Otherwise it’s clean without much identifiable character from the yeast or hops.

Taste – Starts out malty and rounded, distinctly Scottish to me. The finish is long and blends caramel and coffee, lingering and evolving for a few seconds after each sip. It isn’t a rich black coffee, more a Frappuccino - mellow and inviting, but not especially complex in terms of roast. Hop bitterness is low, but it doesn’t come across overly sweet thanks to the roasted barley and toasted oak.

Mouthfeel – The carbonation is perfect, very light, nothing to disrupt the body. Sadly the body itself is underwhelming. Not thin or watery by any means, but not substantial enough for the flavors.

Drinkability & Notes – Perfect beer to drink on a snow day. Loads of flavor, without too much alcohol. Begs for another sip each time. Maybe next time I’ll add 10-15% flaked oats or rye to enhance the body. Otherwise, just about there!


  1. There is some research which has shown little impact of dextrins on beer thickness/body unless they are very high. Alcohol content also plays a big part in body. As you said it's a complicated part of beer.

    If you are inclined have a look at the article The Mouthfeel of Beer A Review by Langstaff and Lewis. It is available on the internet.

  2. Hello,

    Sorry if this is a dumb question. When you say 'I’ll add 10-15% flaked oats or rye to enhance the body', does this mean you calculate what 10-15% of the current grain bill is and add it ON TOP of what you currently have, or do take away the 10-15% of the current grain bill and substitute with the flaked oats?

    Also, I have found that flaked oats kills the head of my beer. Would you use flaked barley instead? If not, what are your reasons? TIA

  3. To avoid boosting the OG by 10-15%, I would reduce the amount of base malt (Maris Otter in this case) and replace it with an equal amount of flaked grain.

    Thanks. Found the study - although it is 20 years old, so not sure if anything newer has changed things. Concerning dextrins, the issue is that there seems to be something about attenuation that affects the mouthfeel of a beer in my experience.

    Here is one summary they present of a study that covered most of the bases:

    "Langstaff et al. performed physical and chemical analyses on a set of commercial beers which had previously been used to characterize the sensory attributes of mouthfeel. The instrumental measurements were correlated with the sensory attributes. Dissolved CO2 was significantly correlated with the sensory perceptions of foam volume and total CO2. Several parameters (polyphenol, fermentable sugars, chloride and glycerol) were strongly correlated with the fullness terms of density and viscosity and with the afterfeel terms of oily mouthcoat and stickiness but were poorly correlated with astringency. Instrumental viscosity and glycerol correlated at a higher level of significance with the fullness terms, including sensory viscosity, than were beer B-glucan and megalosaccharides. Alcohol was weakly correlated with the fullness and afterfeel terms but highly correlated with present gravity, original gravity and real extract."

  4. I've used the first running boil down trick a few times to good effect, yielding some decent melanoidin formation. I'd be concerned of doing it with highly kilned/roasted malts. Perhaps getting burnt flavors or astringency? I could see steeping the dark stuff in a separate pot and blend it back in after you pull the first running?

  5. From my experiences with this batch and the previous one, the formation of burnt flavors wasn't an issue during the boiling-down. All the concentrated boil does is speed up what normally happens during the boil, and plenty of strong stouts get long boils without issue.