Here is the first tasting of my Imperial Sourdough Neo-Kvass. I should have done it sooner than 6 weeks after bottling, but for the first month or so after bottling they tasted nearly identical. The sourdough version is on the left, the control (fermented with bread yeast) is on the right. If you want to compare the flavors in this tasting to my first batch of Kvass, here are the tasting notes for it.
Bread Yeast Kvass
Appearance – Murky orange brown, with a small white head. I imagine this is how most beers looked before the industrial revolution, (poor flocculating yeast, darker/poorly modified malt, etc...)
Smell – Prominent toasty/bready, with a secondary fruitiness (pear/cantaloupe). There is also a creaminess too it that is very interesting, much like a milk/cream stout.
Taste – Mild toasted flavor with a light tartness. There is just a hint of coffee grounds in the finish. Just barely enough hops to counter the light residual sweetness.
Mouthfeel – Medium/light body with moderate carbonation, it might be a little better with a milder carbonation.
Drinkability & Notes – I think toasting fresh bread makes for a better Kvass than the stale bread I used the first time, and on this scale it wasn't that much more effort. It is a very drinkable and refreshing beer, certainly proof that low gravity beers can be loaded with interesting flavors.
Appearance – The beer looks nearly identical to its “clean” brother, but the bugs clearly have been at work giving it noticeably greater carbonation which leads to better head retention.
Smell – More doughy rather bready/toasty. If anything the yeast character is more subdued than the other one, it does not have much in the way of fruitiness. A very light minerally/metallic aroma comes out as it warms, reminiscent of iron.
Taste – Certainly more lactic tartness than the clean version, but the sourness is still pretty subdued. The malt character is more assertive than in the nose, here the toast comes out. It does not taste metallic.
Mouthfeel – A bit lighter in the mouth and spritzier than the bread yeast version, but not to the point of over-carbonation.
Drinkability & Notes – After a month in the bottle these two beers were practically indistinguishable, now the sourdough character is starting to show itself. I am amazed by how truly little distinct character I have gotten from pitching a sourdough starter into a batch of beer. It may be that if I tried this again with the same starter I would get much different results because it is getting more of a sour character as time goes on. Certainly proof that it is possible to make a drinkable beer with a sourdough starter as I have heard some American settlers did in the mid-1800s.