Three additional papers have directly looked at the role of dry hopping and its implications on the pH of beer. A 2019 BrewingScience paper found that each dry hop dosage would result in a consistent increase in pH of 0.03 for every 100 g/hl of hops used. In 2016, Dr. John Paul Maye led a study that determined dry hopping at a rate of 100 g/hl would raise the pH of beer 0.036.

Maye’s results also align with a 2018 paper that also found a linear increase of 0.036 pH increase per 100 grams of dry hops used. Below is a chart from Maye’s work when testing beer pH after dry hopping with Cascade up to 2 pounds per barrel (cited above).

I reached out to Dr. John Paul Maye to ask further questions regarding the increase in pH coming from dry hops. Maye explained to me that his team did a lot of work trying to isolate the compound(s) in hops responsible for the increase in pH, but they haven’t yet determined the exact cause. They did find that that the rise in pH is coming from something in the leaf material of the hop and not within the lupulin gland and is extremely water-soluble. Maye came to this determination because when they dry hopped samples with CO2 extracted spent hop material it would cause an increase in beer pH at the same rate as unextracted hops. Potentially, when dry hopping with Cryo hops which have had most of the vegetal material removed, you could experience a smaller increase in pH than what you would expect from T-90 pellets.

As mentioned previously, Maye’s research found that even though hazy IPAs (which have much higher dry hopping rates) had slightly lower pHs on average than west coast IPAs (with lower dry hopping rates). The reason could be that active fermentation dry hopping, sometimes done in hazy IPAs, is giving the active yeast a chance to absorb or metabolize the pH increasing compound(s) coming from the plant material of the hops. I also wonder if the higher gravities of NEIPAs as well as dry hopping rates above the 2 pounds per barrel (as studied in the chart above) are playing a role to help explain the west coast IPA to NEIPA pH differences.

Dry Hopping pH Calculator

Using the data from the above studies, I put together a draft calculator which can help estimate your final beer pH based on your dry hopping rates. Specifically, the calculator assumes that dry hopping at a rate of 100 g/hl (0.26 pounds per barrel) will increase beer pH by 0.025 units. Although some of the research described above found the increase to be closer to 0.036 units, I’ve found this is too high based on my experience and playing with the calculator. The figure I use is closer to what was found in the higher gravity sample from the 2014 Schmick paper. To use the calculator, enter your dry hop amount in grams, batch size in hectoliters, and the pH of the beer pre-dry hopping (post fermentation), and it will calculate an estimated pH increase. Feel free to play with the assumed pH increase rate to dial this into your actual results to more accurately predict future beers.

Does it Matter?

What matters most is how the beer tastes, right? What happens when the same dry hopped beer is left at the higher pH or lowered with a form of acid and put to a panel of tasters. Maye’s team did this and found that the tasting panel found the higher pH beers scored higher for bitterness marks as well as for overall enjoyment. Specifically, they lowered the pH of the dry hopped beers from a pH of 4.9 to 4.5 using sulfuric acid and the lower pH beers didn’t taste as good as the higher pH beers. The chosen method of acidification (sulfuric acid) could be the reason for the tasting preferences (I chose lactic acid in my tests).

There is not a lot of research that I could identify on the impact of manually lowering beer pH in heavily hopped beers pre-packaging and how this might translate to positive or negative sensory scores. Because of this, I had few of us at Sapwood taste two of our hoppy beers dosed with lactic acid after packaging.

First, we took our hazy 8.6% DIPA (Cryovolcano) that was dry hopped at 4.4 pounds per barrel (~16g/L) and took a final beer pH reading, which was 4.56. Using an eyedropper, I dropped in lactic acid until reaching a reading of 4.2. We did one blind triangle test and could identify the dosed beer out of the lineup. The consensus was the beer with the lower pH was slightly softer on the palate with more of a “hop compoundy” flavor. In contrast, the higher non-dosed pH beer finished with a little more of a green polyphenol-like bite with a lingering herbal quality. For me, the lower pH beer invited another drink sooner, and I preferred it out of the two, but I had a hard time deciding.

Moving to a 5.6% hop-forward beer dry hopped at a rate of 2.2 pounds per barrel (~8g/L), I again measured the final pH of one of our beers (Light and Beauty) reading 4.52. Using lactic acid, I dropped in enough to get the same 4.2 reading. Again, it was fairly obvious to pick out the lower pH beer, even more so in this lower ABV beer. The lower pH beer had less of an aromatic punch (although some of the aromatics could have been driven out while mixing in the lactic acid). Much like with Cryovolcano, the lower pH beer finished with less harshess/jaggedness. However, I think this time at the detriment of the beer. Here the higher pH beer was perceived to have more body and complexity to me, and the lower pH sample tasted a little flatter in flavor. In this case, I favored the higher pH beer.

Although this is just a couple of samples and only using lactic acid (tartaric acid could be another option to experiment with), it was interesting to taste how adjusting the final pH could impact the beer. Perhaps lowering the pH to just 4.4 in the lower ABV (or even higher) beer would have been a better sweet spot. Practically speaking, I also wonder if reducing the pH pre-packaging in a big, heavily dry hopped DIPA might allow for slightly higher dry hopping rates because the acid seemed to help lower the green-polyphenol finish a bit.

Shelf Stability and High Beer pH

There is some concern with beers that finished higher in pH and its microbiological stability. Beer is generally not the greatest environment for most microorganisms to take hold as beer is usually has acid with pH’s ranging from pH 3.8 to 4.7, lower than most bacteria can tolerate for growth. Most heavily hopped beers should have less bacteria-related problems (mainly from gram-positive bacteria or lactic acid bacteria). The reason is that the minimum concentration of hop acids needed to inhibit most gram-positive bacteria is coming from the high hopping rates. Examples of gram-negative bacteria of the genera Pectinatus and Megasphaera that could potentially still emerge, but lower pH and increased alcohol helps to inhibit them. So, the enormous amount of hops used in higher finishing pH NEIPAs should help to inhibit lactic acid bacteria anyways.

Head Retention and Beer pH

A paper that looked at how dry hopping impacts head retention and found that as the pH increased in beer the head retention decreased. In the paper, Cascade hops were used for dry hopping at dosage rates of 0.5, 1, 1.5, 2, 2.5 lbs./bbl and measured for foam stability. As the dosage of Cascade increased, foam stability decreased as the pH increased. In addition, the longer Cascade hops sat in the beer during dry hopping, the more the foam stability was reduced. This decrease in stability was slight after two days of dry hopping, then accelerated on day three, and continued to slowly decrease until day eight. Ultimately, long term dry hopping can have a negative impact on head retention. Another point in favor of shorter short dry hop times.

Using the NIBEM test for beer foam, a 2019 BrewingSciencepaper (also referenced above for pH increases from dry hopping) found a reduction in foam stability at higher dry hopping rates with T-90 pellets. Specifically, the authors found a definite drop in foam stability with an average of 91 seconds less. The result is likely attributed to foam positive proteins interacting with the hop derived polyphenols and the vegetative matter in the hops pulling out foam positive iso-alpha-acids losses during the dry hop. Also, dry hops contain foam negative waxes, hop oils, and lipids that can impact head retention.

Beer pH and Ester Production

What about beer pH and its impact on ester production? Although less of a concern when making clean (non-soured) hoppy beers, it’s interesting to learn how pH can impact fermentation. The Journal of Bioscience and Bioengineering tested three different beers fermented each with a different starting pH (3.0, 5.0, and 7.0). As the starting pH increased, so did the esters formed during fermentation. The beer fermented at a pH of 7.0 resulted in the highest ester concentration with a 13% increase in total acetate esters and a 7% increase in total ethyl ester production compared to the control (5.0 pH beer). On the other hand, the beer fermented at a low 3.0 pH resulted in an 18% decrease in total ester concentration. Not entirely useful information when making NEIPAs, but still interesting!

Beer pH and Haze Stability

It appears that both the pH of wort (no alcohol present) and beer can impact the haze levels in your beer. A 2003 Journal of the American Society of Brewing Chemists paper determined that the pH of beer can significantly impact the protein-polyphenol interactions leading to haze. The authors found that the highest haze intensity increased over seven-fold as the pH increased. S pecifically, with no alcohol present, the maximum haze was found in a pH range of 5.0-5.5. With alcohol present, the pH range where the most turbidity was found decreased. With an ABV of 6%, the pH range with the most haze potential was 4.5-5.0, and with an ABV of 12%, the pH with the most haze potential was 4.5.

To me, this suggests that day one dry hopping could potentially lead to more haze in part because post-boil beer pH (generally around 5.0-5.2) falls nicely into the range the paper above determined has the highest haze potential from protein-polyphenol interactions. It’s interesting then to experiment with small day-one dry hop charges to encourage haze stability (if this is what you are after). This small initial dry hop dose might not contribute much to the aroma of the beer as I would expect most of the compounds (especially the less-polar hydrocarbons) would be removed during fermentation. Still, a small amount of the fruiter and more polar monoterpene alcohols may remain.

I’m curious if any of you are tracking pH throughout the processes? Are you making any adjustments to the pH pre-packaging? If so, how and why?!

Key Findings