Author: Ray Found

In the story of beer’s history, a critical advantageous development came in the way of boiling the wort, as it effectively killed off any potentially harmful pathogens prior to fermentation, which then reduced the pH and created alcohol, working in concert to reduce the risk yet further. When hops were eventually introduced, beer not only took on a new flavor profile but overall product stability improved as well, to the point it was essentially safe for consumption indefinitely, preserving the “just boiled” and therefore safe water. In effect, brewing allowed for the preservation of both the Autumn grain harvest as well as a cache of potable (by way of being boiled) water for later consumption, reserve, or transport.

But what else is happening in the boil? Besides the obvious evaporative concentration of non-volatile compounds, boiling rapidly isomerizes alpha-acids found in hops, lending beer its characteristic bitterness. Furthermore, long duration boils or boiling a portion of the wort down to a syrup are methods heralded by some brewers as ways to increase malt character based on the hypothesis that in addition to concentration effects, Maillard reactions and, controversially, caramelization may be induced where the surface of the kettle meets the wort.

Boil vigor is a variable I hadn’t considered much until a couple things made me rethink my position. First, soon after the Picobrew Zymatic was introduced, I learned it doesn’t technically boil wort but rather holds it at 207°F/97.2°C for a set duration of a nominal “boil” step. This sort of countered what I understood about the importance of boiling and made me wonder how beer made with a not-quite-boil might differ from one made under more normal boiling conditions.

Then, in a quest for precise variable control when brewing xBmt beers, I upgraded to 20 gallon kettles that allowed for ample room to run simultaneous boils at full blast rather than carefully modulating the gas valves to maintain equal boiloff rates. It worked, I reliably hit the same post-boil volumes when brewing side-by-side batches, but due to increased BTUs from running my burners wide open, my boiloff rate jumped from about 1.5 gallons per hour to over 2.5 gallons per hour– it turns out physics is not suspended for the purposes of brewing. I became curious if this increased boil vigor in some way impacted the quality of my beer, perhaps intensifying the bitterness from excess isomerization or changing the malt character due to Maillard reactions, so I designed an xBmt to find out!

| PURPOSE |

To evaluate the differences between a beer where the wort was boiled with minimal vigor and one where the wort was boiled with extreme vigor.

| METHODS |

I went with one of my favorite recipes for this xBmt, one that is pretty evenly balanced between hop and malt characters.

Make America Amber Again

Recipe Details Batch Size Boil Time IBU SRM Est. OG Est. FG ABV 5.5 gal 60 min 56.8 IBUs 14.8 SRM 1.054 1.011 5.6 % Actuals 1.054 1.015 5.2 % Fermentables Name Amount % Pale Ale Malt, Northwestern (Great Western) 7.25 lbs 62.37 Munich I (Weyermann) 2.5 lbs 21.51 Caramel/Crystal Malt - 40L 1 lbs 8.6 Crystal 15, 2-Row, (Great Western) 8 oz 4.3 Pale Chocolate Malt 6 oz 3.23 Hops Name Amount Time Use Form Alpha % Magnum 10 g 60 min Boil Pellet 12.1 Cascade 55 g 15 min Boil Pellet 9.3 Amarillo 37 g 15 min Boil Pellet 7.7 Centennial(mine) 20 g 15 min Boil Pellet 11.1 Yeast Name Lab Attenuation Temperature San Diego Super Yeast (WLP090) White Labs 80% 65°F - 68°F Notes Water Profile: Amber Balanced in Bru’n Water Spreadsheet

Given my work travel schedule, I wasn’t able to make starters in time for this brew day, so instead I bought 4 packs of WLP090 San Diego Super Yeast, 2 for each batch. The night before brewing, I collected RO water for a 10 gallon batch sparge batch, opting to split the wort post-mash in order to keep things as equal as possible. The water was then adjusted to loosely match the Amber Balanced profile in Bru’n water.

The next day, while my strike water was heating up, I weighed out and milled the grain.

With the strike water to the right temperature, I mashed in to hit my target mash temperature right on the nose.

Following the 60 minute mash rest, I collected the first runnings then followed that up with a quick batch sparge.

I collected slightly less than 16 gallons/60 liters of wort that I stirred to ensure homogeneity before using gravity to transfer equal amounts from one kettle to another, each ultimately ending up with just shy of 8 gallons/30 liters.

I lit the flame under both kettles at the same time, one with the gas valve wide open and the other with the valve at roughly half-throttle, then waited for each to come to a boil. Unsurprisingly, the full-throttle batch reached a boil first, after which I set the timer to see how much longer the weak boil wort would take. I observed bubbling atop the second batch about 15 minutes later and adjusted the valve to maintain but a gentle simmer before setting the boil timer.

At the conclusion of each 60 minute boil, I quickly chilled them to just above my groundwater temperature. I observed a rather drastic difference in remaining wort volume demonstrating the impact boil vigor has on boil rate. In this case, the strong boil batch had lost 1.25 gallons/4.7 liters more to boiloff than the batch boiled gently.

Since the purpose of this xBmt was evaluate the impact boil vigor has on flavor development, I topped off the strong boiled batch with distilled water to eliminate wort concentration and hence OG as a factor.

A hydrometer measurement showing both worts at the same OG was validating and, presuming all that was lost during the boil was pure water, suggested the distilled water addition left both with a similar mineral profile.

I proceeded with racking the same amount of wort from either batch to separate fermentors.

After a couple hours in my cool chamber with both worts stabilized at my desired fermentation temperature of 66°F/19°F, I pitched 2 packs of WLP090 San Diego Super yeast into each batch. Both beers were fermenting actively by the next day and moved along at a seemingly similar pace. Once signs of activity were gone, I took hydrometer measurements that showed both beers had attenuated to an identical FG.

The beers were then cold crashed and kegged.

The filled kegs were placed in my cold keezer and burst carbonated overnight before I reduced the gas to serving pressure. After another few days of conditioning, I pulled samples and was unable to discern a difference in color, clarity, or head retention.

| RESULTS |

A total of 21 people of varying levels of experience participated in this xBmt. Each participant was served 1 sample of the weak boil beer and 2 samples of the strong boil beer then asked to identify the one that was unique. While 12 tasters (p<0.05) would have had to correctly identify the unique sample in order to reach statistical significance, only 11 (p=0.56) picked the odd-beer-out, indicating participants in this xBmt were not able to reliably distinguish a beer produced using a weak boil from one where the wort was boiled very vigorously.

While not very scientifically sound, this is only beer and hence it’s possible some might adapt these findings to fit their beliefs. For them as well as those with a curious itch, I figured I’d share the potentially meaningless preference data. Of the 11 tasters who happened to select the unique sample, 5 reported preferring the weak boil beer while 6 endorsed the strong boil beer as the one they liked more.

My Impressions: I never perceived a distinct difference between these beers, and in fact, didn’t choose the unique sample in any of the “blind” triangle tests I attempted. When sampling side-by-side and not at all blind, likely buoyed by bias, I picked up a certain je ne sais qois difference between the beers. While I’m notoriously bad at turning taste bud reports into prose, I couldn’t even convince myself of just what the difference was, so I’m taking this perception with a mighty large grain of salt.

| DISCUSSION |

Boil vigor of wort is known to have an impact on the amount of water that ends up being evaporated off, which is naturally going to impact wort density– more vigorous boils will result in higher OG than less vigorous boils, all else being equal. The observational data from this xBmt certainly backs this up with the strong boil batch resulting in nearly 1.25 gallons/4.7 liters less wort than the weak boil batch. The linear relationship between wort density and color notwithstanding, many brewers believe a strong boil is key to producing the toasty and rich flavors brought on by Maillard and caramelization reactions, which is also said to impact color. However, this xBmt did not demonstrate such differences to be reliably apparent, as neither the visual observations nor the tasting panel provided strong evidence to suggest differences beyond evaporation were present.

Interestingly, participants in this xBmt were unable to reliably distinguish the strong boil beer from the weak boil beer, both of which appeared to share an identical color, suggesting the biggest impact of boil vigor may simply be to boiloff rate. While it’s certainly possible Maillard and caramelization reactions aren’t occurring at the temperatures and duration we boil wort for, I can’t help but wonder if the opposite might be true, that both beers actually possessed those characteristics.

Of course, boiling wort serves more than just the purpose of condensing wort, it also aids in the volatilization of SMM/DMS and isomerization of hop alpha acids. Based on the results of this xBmt and my personal experience with these beers, I suspect even a weak boil is sufficient enough for these reactions to take place, as there’s basically no temperature change as a function of boil vigor.

In the end, while this single result shouldn’t be viewed as proof boil vigor doesn’t matter at all, it’s my opinion it definitely belongs well down the list of things to worry about when trying to create the perfect beer. I’ll continue to boil vigorously for the sake of repeatability and consistency, as this is an important aspect of xBmts, but for those who can only achieve a weak boil, it’s nice to know it likely has minimal impact on beer quality.

If you have any thoughts on this xBmt, please share them in the comments section below!

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