|The same, and yet not the same.|
A worthy question! Let's try the exact same beer dispensed with CO2 and "on cask" side by side and drink critically!
The subject: Cloverland Resinator India Red Ale. Here's the recipe. I must note that this particular half of the ten-gallon batch was the beneficiary of extra dry hops - another ounce each of Centennial and Amarillo (yay PNW hops!).
After quality time with the dry hops, this half of the batch was split into quarters and racked to separate kegs. One was carbonated to approximately 2 volumes and pushed with CO2 gas through a Perl faucet; the other was very lightly carbonated (approx. 0.5 vols) and pumped through a Pullman beer engine. Both kegs were at cellar temp (56 F on a sunny January Sunday in beautiful St. Paul) and evaluated by yours truly ... the water crackers were delicious.
Looks: Clear, golden-red hue with an off-white bead.
Smells: Sticky, resiny, juicy, bright hops - dried ginger, pine, orange & grapefruit, citrus peel. Hops totally dominant. Higher, more pronounced aroma overall.
Tastes: Like Portland OR. Bitterness is quite enhanced; if I didn't know they were the same beer, I would have guessed at least 50% more IBUs than beer engine pour. Hops from front to back - abundant ginger/citrus/pine in fore- and aftertaste, herbal bitter whack in the back half, dry finish with lingering hops.
Texture: Lighter, brighter, positively prickly by comparison even though it's not very highly carbonated.
Looks: Same golden-red color; frothy, off-white head. Clear with a couple dry hop floaties.
Smells: Same hop aromatics as CO2 but lower intensity - the malt's nutty, biscuit, fruit, caramel, and toffee nuances can be discerned - lighter caramel malts & a suggestion of the fermentation show. More balanced. More complex. As I sit and write, I find that the engine-poured pint retains much more hop aroma as it sits, which makes sense - the escaping gas is scrubbing the bouquet from the CO2-poured beer.
Tastes: Like Kent UK - not just because of the lower CO2 level, but also because the primo Maris Otter base malt can express itself. Earthier hop character - pine and ginger more pronounced, citrus less so. Malt and hop flavors in something closer to a balance, with rounded, softer, more unobstructed pine & nutty biscuit. Hop flavor seems fresher - tastes like how cones smell, reminiscent of a fresh- or wet-hopped ale. Much higher hop flavor in the finish vs. CO2, but less in the front. Longer finish overall.
Texture: Creamy, fuller-bodied vs. CO2, yet easier to drink fast.
... and then my wife walked in and I was made to share. Here are her comments:
"It's like a tongue-coater [the beer engine pour] versus a tongue-stabber [the CO2 pour]. The beer engine one is like hop honey, it's viscous ... it's like beer candy. Obviously meant for savoring ... it makes you appreciate it. The CO2 one is like hop lightning, it leaves the palate much faster. It's more refreshing."
Both are good, and quite different.
CO2 definitely gets points for intensity. The beer engine shows me a more multifaceted pint and seems more reflective of the ingredients - the "cask" treatment lets more (and more of the) subtle flavors and aromas shine through, while they're covered up in the CO2-dispensed beer, which only allowed the darkest of malts to peek through the hops. While the CO2 pour had higher hop character overall, the hop flavor at the finish of the taste was actually stronger and seemed fresher in the beer engine pour.
And then of course there's the question of what you're in the mood for: CO2 seems to be a better route for hopapocalyptic bombastic lupulin brutality; the beer engine seems more egalitarian in its treatment of all the ingredients (say, if you're using expensive base malt in an IPA and want to taste it ...), and might lend itself better to the contemplative nursing of multiple pints over the course of an evening.
CONCLUSION OF THE CONCLUSION:
I like beer a lot; if you're still reading, then you probably do too.