Author: Phil Rusher

One of the most common methods for carbonating beer, particularly among newer homebrewers, is bottle conditioning whereby controlled refermentation occurs in the package. Typically, brewers blend a specific amount of priming sugar with the fermented beer, transfer it to bottles, then seal those bottles such that the CO2 produced during the conditioning process gets absorbed into the beer, thus carbonating it. A tight seal is also necessary to prevent oxygen from entering the vessel and potentially ruining the beer.

Brewers who rely on bottle conditioning have a few options when it comes to sealing their filled bottles, the most popular being crown caps, which get crimped over the lip of the bottle to form an airtight seal. As a one-and-done product, crown caps typically get tossed once removed from the bottle. An arguably more economical alternative is swing-top bottles, which are also referred to as Grolsch-style, flip-top, and keeper bottles. Instead of a cap being crimped in place, the seal on a swing top bottle is achieved with a rubber gasket affixed to a porcelain stopper that is held in place by hinged wires.

Both crown caps and swing tops are successfully used by many brewers, though opinions abound as to which is better at retaining CO2 while resisting oxygen ingress. While I don’t tend to bottle condition much these days, I was curious whether either sealing method would lead to a noticeable difference and put it to the test.

| PURPOSE |

To evaluate the differences between bottle conditioned beers packaged in either crown cap or flip-top bottles.

| METHODS |

The recipe for this xBmt was somewhat inspired by the much beloved American classic, Sierra Nevada Pale Ale, which is famously bottle conditioned.

Pocono Pale Ale

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 52.2 IBUs 6.0 SRM 1.057 1.012 6.0 % Actuals 1.057 1.009 6.4 % Fermentables Name Amount % Mecca Grade Lamonta: Pale American Barley Malt 11 lbs 89.8 Mecca Grade Rimrock: Vienna-style Rye Malt 1 lbs 8.16 Mecca Grade Opal 44: Toasted Toffee Barley Malt 4 oz 2.04 Hops Name Amount Time Use Form Alpha % Pahto HBC 682 5 g 60 min Boil Pellet 15 Summit 5 g 60 min Boil Pellet 15 Centennial Hop Hash 28 g 10 min Boil Pellet 32 Yeast Name Lab Attenuation Temperature Flagship (A07) Imperial Yeast 75% 60°F - 72°F Notes Water Profile: Ca 156 | Mg 0 | Na 25 | SO4 156 | Cl 63 Download Download this recipe's BeerXML file

A day prior to brewing, I made a single large yeast starter of Imperial Yeast A07 Flagship.

Later that evening, I weighed out and milled the grain in preparation for the following morning.

On brew day, I heated the previously collected RO water to my desired profile then mashed in to achieve my desired temperature.

While waiting on the mash, I prepped the kettle hop additions.

When the 60 minute mash rest was complete, I collected the sweet wort then proceeded with a 60 minute boil with hops added at the times stated in the recipe.

When the boil was finished, I quickly chilled the wort with my IC then took a hydrometer measurement confirming it was at my intended OG.

The wort was then racked to a 60 liter/16 gallon Speidel fermenter.

The filled fermenter was placed in my chamber and left alone for a couple hours to allow the wort to finish chilling to my desired 66°F/19°C fermentation temperature. Once there, I pitched the entire yeast starter.

After 9 days, no signs of activity were present so I took a hydrometer measurement confirming FG had been reached.

At this point, I proceeded with packaging by first adding 4 conditioning tablets to each of the 12 oz amber bottles. In order to reduce potential extraneous variables, I then racked the beer directly from the fermenter into each bottle, alternating between crown cap and swing-top just to be sure.

The filled bottles were placed on a shelf in my dining room that maintains a consistent 68°F/20°C. After 3 weeks of conditioning, I moved the bottles to my fridge for a 3 week chilling and clearing period before serving them to tasters.

| RESULTS |

A total of 21 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of beer from a crown cap bottle and 1 sample of beer from a swing-top bottle in different colored opaque cups then asked to identify the unique sample. While 12 tasters (p<0.05) would have had to accurately identify the unique sample in order to reach statistical significance, only 7 did (p=0.58), indicating participants in this xBmt were unable to reliably distinguish an American Pale Ale conditioned in a crown cap bottle from one conditioned in a swing-top bottle.

My Impressions: Out of the 10 triangle tests I attempted, I ended up picking the odd-beer-out 8 times, which is arguably quite consistent. While the beers smelled and tasted identical, I noticed the one from the swing-top bottle was ever so slightly less fizzy than the beer packaged in a crown cap bottle. The difference wasn’t drastic at all, and there’s no doubt my performance was biased by my awareness of the variable.

| DISCUSSION |

Bottle conditioning is often the first carbonation method utilized by new homebrewers because it requires less equipment and has a lower associated cost. Some commercial breweries also choose to bottle condition, with some claiming it contributes higher quality carbonation and foam to beer. While crown cap bottles are most popular, swing-top bottles also get used fairly regularly, and some have developed a belief one is better than the other. The fact tasters in this xBmt were unable to tell apart a Pale Ale conditioned in either a crown cap or swing-top bottle suggests the type of seal did not have a noticeable impact.

These findings seem to indicate crown caps and swing-tops can be used to achieve the same ends with neither being any better or worse than the other. With respect to my own triangle tests, I can’t help but wonder the extent to which time in the bottle may have contributed to my performance, as I did my trials over a week after tasters. It seems plausible that some gas may have escaped the swing-top seal in that time, thus reducing the perceptible fizz just enough for my biased tongue to notice. Or perhaps the explanation has to do with one complaint I’ve heard about swing tops– the rubber gaskets aren’t always uniform between bottles, which can lead to poor seals. Regardless, the difference was slight, which the fact exactly 1/3 of tasters picked the unique sample supports, and neither showed signs of oxidation.

As I imagine is the case for most homebrewers, I started off bottle conditioning in crown cap bottles because that’s what came with my kit. The few times I used swing-top bottles worked out just fine, I didn’t perceive it as having any noticeable impact. I keg the large majority of my beer these days, but if I was going to bottle, I wouldn’t shy away from swing-tops for standard beers, as they provide an element of convenience. For beers I plan to age for awhile, I might go with crown caps to eliminate the concern of rubber gaskets drying out or not being seated properly.

If you have any thoughts about this xBmt, please do not hesitate to share in the comments section below!

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