exBEERiment | Impact Alpha Acetolactate Decarboxylase (ALDC) At Dry Hop Has On A West Coast Pils

Author: Jordan Folks

Diacetyl is a chemical compound produced during fermentation that’s often described as contributing a buttered popcorn characteristic and slick mouthfeel to beer. While the BJCP contends it’s appropriate in small quantities in certain styles, diacetyl is widely viewed as an off-flavor that’s to be avoided at all costs. Every yeast used by brewers can produce diacetyl, though some strains are more apt to do so, especially when fermenting in certain conditions, namely the cooler environments commonly associated with lagers.

Belonging to the vicinal diketone (VDK) chemical group, diacetyl is formed when alpha acetolactate (ɑ-acetolactate) produced during fermentation is oxidized, resulting in the tell-tale buttery aroma and flavor. While certain processes can be used to reduce the chances of diacetyl production, a relatively new product called Alpha Acetolactate Decarboxylase (ALDC), which gets added to the beer at yeast pitch, promises to “prevent the formation of diacetyl by breaking down the precursor, alpha acetolactate, as it is formed during fermentation – converting it quickly and directly into acetoin.”

I absolutely despise diacetyl and consider it the bane of my brewing existence. While I typically employ methods that result undetectable levels of diacetyl, I recently had an issue with hop creep, a phenomenon associated with dry hopping where enzymes restart fermentation of residual sugars, leading to additional alpha acetolactate production, thus increasing the risk of post-fermentation diacetyl formation. ALDC offers a compelling solution by continuously breaking down alpha acetolactate at all points in the brewing process, including dry hopping. Curious how this unique enzyme might impact a heavily dry hopped West Coast Pilsner, I designed an xBmt to test it out for myself.

| PURPOSE |

To evaluate the differences between a West Coast Pilsner that received a dose of ALDC at dry hop and one that received no ALDC.

| METHODS |

Seeing as my issue with hop creep was occurring primarily on my heavily dry hopped beers, I went with a nice West Coast Pilsner recipe for this xBmt. Big thanks to F.H. Steinbart for hooking me up with the malt for this batch!

Light My Way

After collecting the full volume of water for two 5 gallon/19 liter batches, adjusting each to the same mineral profile, and getting them heating up, I milled the grain.

With each batch of water properly heated, I incorporated the grains and set the controllers to maintain the same 146°F/63°C mash temperature.

During the mash rests, I weighed out the kettle hop additions.

The worts were boiled for 60 minutes with hops added at the times listed in the recipe. Once complete, and following the 10 minute hopstand, I quickly chilled the worts before taking refractometer readings showing they were at the same target OG.

After transferring identical volumes of wort from either batch to sanitized fermentation kegs, I pitched two pouches of Imperial Yeast L13 Global into each one.

Following two weeks of fermenting at 57°F/14°, I added the dry hop charges to both batches then dosed one with the recommended amount of ALDC.

The beers were left alone for 24 hours, at which point I took hydrometer measurements showing they were both at a similar FG.

Next, I cold crashed the beers overnight then transferred them under pressure to CO2 purged serving kegs that were placed on gas in my keezer. After 3 weeks of cold conditioning, they were carbonated, clear, and ready for evaluation.

| RESULTS |

A total of 25 people of varying levels of experience participated in this xBmt. Each participant was served 2 samples of beer where no ALDC was added at dry hop and 1 sample of the beer dosed with ALDC at dry hop in different colored opaque cups then asked to identify the unique sample. In order to reach statistical significance, 13 tasters (p<0.05) would have had to accurately identify the unique sample, which is precisely how many did (p=0.04), indicating participants in this xBmt were able to reliably distinguish a West Coast Pils that was dosed with ALDC at the point of dry hopping from one that was not treated with ALDC.

The 13 participants who made the accurate selection on the triangle test were instructed to complete a brief preference survey comparing only the beers that were different. A total of 7 tasters reported preferring the beer dosed with ALDC at dry hop, 2 said they liked the beer made without any ALDC, 1 had no preference despite noticing a difference, and 3 reported perceiving no difference between the beers.

My Impressions: Out of the 5 semi-blind triangle tests I attempted, I correctly identified the odd-beer-out every time. While I perceived the beer dosed with ALDC as being exactly as I’d designed it to be, which is to say saturated with hops and clean on the palate, I detected a slight butter note in both the aroma and flavor of the batch that received no ALDC. It wasn’t a diacetyl bomb by any means, but I definitely preferred the batch dosed with ALDC at dry hop.

| DISCUSSION |

With very rare exception, the buttery characteristics associated with diacetyl is considered to be a flaw in beer, hence brewers employ myriad techniques for ensuring its absence. A modern chemical prophylactic is ALDC, which typically gets added at yeast pitch, though has the ability to mitigate diacetyl formation at any point in the brewing process. Indeed, tasters in this xBmt were able to reliably distinguish a West Coast Pils that was dosed with ALDC at the point of dry hopping from one that was not treated with ALDC.

Without lab testing, it’s impossible to know what the actual difference in diacetyl levels between these beers was, or if there even was one. However, given how tightly controlled this xBmt was, the fact a decent number of tasters could both tell them apart and reported preferring the ALDC dosed beer suggests it had some positive impact.

I happen to be quite sensitive to diacetyl, so I’m willing to do whatever is needed to ensure it is not present in my beers, and lately that has involved the use of ALDC. While I’m sure there are times this addition isn’t necessary, considering its price and ease of use, I have no qualms relying on it as a prophylactic in every beer I brew just to be sure. These results validate this sentiment for me, especially since I was rather easily able to tell these beers apart and preferred the one dosed with ALDC.

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

Support Brülosophy In Style!

Follow Brülosophy on:

FACEBOOK   |   TWITTER   |   INSTAGRAM

If you enjoy this stuff and feel compelled to support Brulosophy.com, please check out the Support page for details on how you can very easily do so. Thanks!