Author: Malcolm Frazer

Brewers who are serious about making the best beer possible know that good brewing water is key, and getting good brewing water often requires adjusting its chemistry with minerals and acid. Shown to effect enzymatic activity during the mash as well as clarity, aroma, and flavor of the finished beer, mash pH is a component most water conscious homebrewers pay attention to. In a recent conversation with Colin Kaminski, co-author of Water: A Comprehensive Guide for Brewer’s and Brewmaster at Downtown Joe’s, the topic turned to the potential impact differing pH levels of the wort during the boil have on things like hop utilization, perception of bitterness quality, and extraction of aromatic compounds.

This isn’t a new idea, though it seems far less focused on by homebrewers than other aspects of water chemistry. In my research, I found many in the brewing world accept a positive correlation exists between boil pH and hop utilization, increases in the former leading to improvements in the latter, and that it also leads to greater extraction of aroma compounds that remain in the finished beer.

Pretty great, right? Simply increase the pH of the wort pre-boil to get killer hop character. Except that’s not all there is to it. As Chris Colby discusses in a 2014 article on Beer & Wine Journal, a higher boil pH is purported to increase the risk tannin extraction from kettle hops, which are known to produce what many describe as a harsh bitterness.

So says the hard science, but what of the practical? Curious whether the average beer taster would be able tell the difference, I designed an xBmt to test it out!

| PURPOSE |

To evaluate the differences between 2 IPAs of the same recipe where one had a boil pH of 5.12 and the other a boil pH of 5.45.

| METHODS |

Much gratitude to Love2Brew for sponsoring this xBmt by hooking me up with a couple MACC IPA kits, a recipe designed by our own Ray Found that I was excited to try. I did make a small change by adding a touch more Magnum at 60 minutes to increase both the bitterness and plant matter in the wort, as these are both components said to be impacted by boil pH.

The night before brewing, I pitched 2 packs of WLP001 California Ale Yeast into a single large starter that would later be split between the two batches.

As my strike water was heating, I weighed and milled my grain with the help of an always willing volunteer.

I chose to perform separate mashes for each kit, both using the batch sparge method, staggering them by about 20 minutes. Thanks to BeerSmith, I hit the same mash temperature for both batches.

Each wort was collected in its own kettle following a 60 minute rest and both were at 5.45 pH. Based on conversations with brewing water experts Martin Brungard, John Palmer, and Colin Kaminski, I opted to adjust only one of the batches using phosphoric acid since it is essentially flavorless and wouldn’t contribute any minerals that might otherwise impact the variable being tested. Adding 2.5 mL of 77% phosphoric acid to the low boil pH wort brought it down to 5.12 pH.

Both batches were then boiled for 60 minutes with hops added per Ray’s recipe.

At the completion of each 60 minute boil, I quickly chilled the wort to my target fermentation temperature.

Hydrometer measurements following each boil confirmed both reached the same 1.066 OG.

I transferred each batch to its own conical fermentor controlled to 66°F/19°C then split the starter evenly between them.

Signs of fermentation were evident the following morning and both batches appeared to proceed similarly. As I usually do, I ramped the temperature a bit a few days into fermentation to ensure complete attenuation. Dry hops were added and left for a few days before I returned to measure FG since fermentation activity had ceased. I was surprised to discover the first observable difference.

This difference remained over multiple hydrometer measurements. Prior to packaging, I also took pH readings of both beers and found, perhaps expectedly, the high boil pH beer has slightly higher pH than the low boil pH sample.

The beers were then cold crashed, fined with gelatin, then kegged. After about a week on gas in my keezer, the beers were carbonated, clear, and ready for evaluation.

| RESULTS |

A total of 42 people participated in this xBmt, each blindly served 1 sample of the lower boil pH beer and 2 samples of the higher boil pH beer in different colored opaque cups then asked to select the unique sample. While 20 tasters (p<0.05) would have had to accurately identify the low boil pH sample as being different in order to reach statistical significance, only 15 (p=0.43) did so, suggesting they were unable to reliably distinguish an IPA made with a 5.12 boil pH from the same IPA with a 5.45 boil pH.

Since the results failed to achieve significance, any correct responses on the triangle test may very well have been by random chance, thereby invalidating any further data collected. However, given the moderate sample size, I thought it’d be interesting to share some of the information gleaned from the comparative analysis completed by only those participants who accurately identified the unique sample. Of the 15 participants who accurately chose the unique sample in the triangle test, 8 reported a preference for the low boil pH sample, 5 liked the high boil pH beer more, and 2 had no preference despite noticing a difference. While some of these tasters seemed to provide descriptions consistent with expectations in follow-up conversations, the level of convergence was not drastic.

My Impressions: When I initially tried these beers directly out of the fermentors, I was certain I detected differences, all of which aligned perfectly with what I knew I should have detected– stronger aroma and more assertive bitterness in the high boil pH beer. Then I laughed at myself– of course I tasted what I expected, I knew what had been done to the beers and exactly what to look for. I slightly preferred the higher boil pH beer as I perceived the bitterness as more assertive yet not overly harsh. The difference maker for me was the hoppier aroma in the high boil pH beer, as achieving that initial burst of hop aroma is often elusive for IPA brewers. As for Ray’s MACC IPA recipe, it was quite nice and well designed, especially the hop bill. I typically make drier IPA, but this was a nice change. With the impression of sweetness without being cloying, likely from the dose of Honey Malt, and heaps of classic American hop character, this is a recipe up any IPA lovers alley and was well received by the xBmt participants.

| DISCUSSION |

The pH scale is logarithmic rather than linear in nature, meaning a difference of 3 pH (10³ H+) is substantially greater than a difference of 1 pH (10 H+). It’s for this reason brewers tend to mind seemingly small variances in pH, for example, the commonly accepted “ideal” mash pH range of 5.2 – 5.6, as this translates to a relatively large ionic difference. The aforementioned range is similar when it comes boil pH, hence the decision to do a comparison between a low of 5.12 pH and a high of 5.45 pH. Despite the seemingly small 0.33 pH difference, which amounts to just over 2 times the H+ ion concentration, I fully expected these beers to be easily distinguishable by a panel of arguably well qualified tasters, the high boil pH sample possessing perhaps more hop character with a harsher bitterness than the low boil pH beer. Curiously, that’s not what happened, tasters could not reliably tell them apart.

During the data collection session, I was amazed as many of the people I would have bet on correctly identifying the unique sample walked away stumped. From early on, it was clear most people struggled on the triangle test. However, comments from a few of the correct respondents following completion of the survey did seem to align quite well with expectations, with descriptions of the high boil pH beer as being “more hoppy” and “biting” while others perceived the low boil pH beer have less bitterness or aroma. Of course, these are commonly used descriptors, and given the results of this xBmt, it’s possible their consistency with what I expected is mere coincidence. Either way, I’ll continue to pay attention to my boil pH and look forward to further investigations on the topic.

Is the pH of your boiling wort something you’ve taken into consideration? Please share your experience in the comments section below!

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